physicsworld--2020-07-21--SNMMI Annual Meeting highlights nuclear medicine innovation - Physics World

The Society of Nuclear Medicine and Molecular Imaging ( SNMMI ) held its Annual Meeting last week .
Billed as the “ Virtual Edition ” and run over an interactive virtual platform , the event included live education sessions , scientific presentations , a virtual exhibit hall and several networking events .
Here are some highlights from the research presented at this year ’ s event .
Researchers from the University of California-Davis shared results from the first study using uEXPLORER to conduct total-body dynamic PET scans of cancer patients .
Developed and validated at UC-Davis , uEXPLORER is the @ @ @ @ @ @ @ ) , high-sensitivity PET/CT scanner being used commercially .
A total-body dynamic PET/CT scan of a patient with metastatic cancer generated high-quality diagnostic images that identified multiple metastases Dynamic 18F-FDG PET with tracer kinetic modelling has the potential to better detect lesions and assess cancer response to therapy , according to the researchers .
Unlike conventional PET scanners with limited axial field-of-view ( 15–30 cm ) , the uEXPLORER is capable of simultaneous dynamic imaging of widely separated lesions .
“ The focus of our study was to test the capability of uEXPLORER @ @ @ @ @ @ @ cancer , ” explained UC Davis ’ Guobao Wang .
“ Different kinetic parameters can be used in combination to understand the behaviour of both tumour metastases and organs-of-interest such as the spleen and bone marrow .
Thus , both tumour response and therapy side-effects can be assessed using the same scan.
” For the study , a patient with metastatic renal cell carcinoma was injected with the radiotracer 18F-FDG and scanned on the total-body scanner .
The researchers calculated static PET standardized uptake values ( SUVs ) and performed kinetic modelling for @ @ @ @ @ @ @ major organs and six identified metastases .
They calculated the glucose influx rate and used additional kinetic modelling to generate parametric images of the kinetic parameters .
The kinetic data were then used to explore tumour detection and characterization .
They note that parametric images of the FDG influx rate improved tumour contrast over SUV in general and led to improved lesion detection in the renal cortex , which has been historically challenging .
“ Total-body dynamic imaging and kinetic modelling enabled by total-body PET have the potential to change nuclear medicine into @ @ @ @ @ @ @ different aspects of tissue behaviour can be assessed in the same clinical setting – much like the information gained from different sequences in an MRI scan , ” said Ramsey Badawi , co-director of the EXPLORER Molecular Imaging Center .
A first-in-human study has demonstrated the safety and favourable pharmacokinetic and dosimetry profile of 64Cu-EB-RGD – a new , relatively long-lived PET tracer – in patients with glioblastomas .
The radiotracer delivered high-contrast diagnostic imaging in patients , visualizing tumours that express low or moderate levels of α β integrin with high sensitivity @ @ @ @ @ @ @ and two patients with recurrent glioblastoma who underwent whole-body 64Cu-EB-RGD PET/CT .
The new radiotracer has unique qualities , explained Jingjing Zhang , from Peking Union Medical College Hospital .
The peptide sequence Arg-Gly-Asp ( RGD ) specifically targets the cell surface receptor α β integrin , which is overexpressed in glioblastomas .
To slow clearance , Evans Blue dye , which reversibly binds to circulating albumin , is bound to RGD , significantly enhancing target accumulation and retention .
The addition of the 64Cu label provides persistent , high-contrast diagnostic images in @ @ @ @ @ @ @ ratios for target tumour lesions and normal brain tissue in seven sets of brain PET and PET/CT scans obtained over two consecutive days .
They also collected safety data ( such as vital signs and physical exams , for example ) for each participant , one and seven days after the scans .
64Cu-EB-RGD was well-tolerated , with no adverse effects seen immediately or up to one week after administration .
The mean effective dose of 64Cu-EB-RGD was similar to that of an 18F-FDG scan .
Injection of 64Cu-EB-RGD into patients with recurrent @ @ @ @ @ @ @ , with continuously increased tumour-to-background contrast over time .
As well as providing a future diagnostic tool , the researchers noted that 64Cu-EBRGD could also be a breakthrough targeted radiotherapy for glioblastoma patients .
“ 64Cu-labelled EB-RGD represents a viable model compound for therapeutic applications , since 177Lu , 90Y or 225Ac can be substituted for 64Cu , ” explained Deling Li of Beijing Tiantan Hospital .
“ We are currently studying the 177Lu homologue to treat glioblastoma and other α β integrin expressing cancers , including non-small cell lung , melanoma , @ @ @ @ @ @ @ build on the current wave of radiotherapies like 177Lu-DOTATATE.
” A molecular imaging approach that combines 18F-FDG PET and MRI can precisely identify the location of pain generators in chronic pain sufferers , according to a study from Stanford University School of Medicine .
The imaging data led to new management plans for 62 % of the study ’ s participants .
18F-FDG PET has the ability to accurately evaluate increased glucose metabolism that arises from acute or chronic pain generators , such as hypermetabolic inflamed tissues .
The researchers sought to develop @ @ @ @ @ @ @ localize sites of increased inflammation related to sources of pain .
The team imaged 65 patients with chronic pain , from the head to the feet , using the 18F-FDG PET/MRI protocol .
Principal investigator Sandip Biswal and colleagues used image analysis software to measure maximum standardized uptake values and target-to-background ratios .
They identified locations of increased 18F-FDG uptake and compared these to known locations of pain , finding increased uptake in muscle and nerves at the site of pain in 58 patients .
These imaging findings resulted in 36 significant modifications @ @ @ @ @ @ @ recommendation of new invasive procedures , and 16 mild modifications , such as ordering an additional diagnostic test .
The researchers recommend that a study of a large cohort of patients is conducted to validate their findings .
“ The results of this study show that better outcomes are possible for those suffering from chronic pain , ” said Biswal .
“ This clinical molecular imaging approach is addressing a tremendous unmet clinical need .
I am hopeful that this work will lay the groundwork for the birth of a new subspeciality in @ @ @ @ @ @ @ had limited success in the treatment of prostate cancer , due to a significantly immunosuppressive tumour microenvironment .
Now , a preclinical study conducted at the University of Wisconsin-Madison has shown that targeted radionuclide therapy creates a favourable tumour microenvironment in prostate cancer , which improves the effectiveness of immunotherapies .
“ Understanding this treatment dynamic , our goal was to demonstrate that systemically delivered targeted radionuclide therapy provides beneficial immunomodulatory effects that may enhance the response of prostate cancer to immunotherapies , ” said Reinier Hernandez .
The researchers administered the imaging @ @ @ @ @ @ @ and performed PET/CT scans 3 , 24 , 48 and 72 hr after injection .
Analysing radiotracer uptake in tumours and in healthy tissues allowed them to estimate the dosimetry for targeted radionuclide therapy using 90Y-NM600 .
They then gave groups of mice either a high or low dose of 90Y-NM600 , and monitored tumour growth and survival for 60 days .
PET/CT data revealed that 90Y-NM600 immunomodulates the prostate tumour microenvironment by modifying tumour-infiltrating lymphocyte populations , upregulating checkpoint molecules and promoting the release of pro-inflammatory cytokines .
The team found that @ @ @ @ @ @ @ tumour microenvironment were elicited at relatively low radiation doses without incurring systemic toxicity .
“ Our results provide a rationale for combining targeted radionuclide therapy with immunotherapies , which , so far , have proven ineffective in prostate cancer .
Improving immunotherapy in prostate cancer could bring about a potentially curative treatment alternative for advanced-stage patients , ” said Hernandez .
The researchers noted that the study also presents a paradigm change in targeted radionuclide therapy , where the maximum tolerable dose may not always be the most beneficial to patients .
“ @ @ @ @ @ @ @ that immunomodulation is best achieved with a relatively low radiation dose to the tumour which does not affect the normal immune system , ” Hernandez explained .

Total-body dynamic FDG PET imaging with uEXPLORER can monitor the spatiotemporal distribution of glucose concentration in metastatic tumours in the entire body. (Courtesy: G B Wang, M Parkih, L Nardo et al, University of California Davis)
The Society of Nuclear Medicine and Molecular Imaging (SNMMI) held its Annual Meeting last week. Billed as the “Virtual Edition” and run over an interactive virtual platform, the event included live education sessions, scientific presentations, a virtual exhibit hall and several networking events. Here are some highlights from the research presented at this year’s event.
Total-body dynamic PET successfully detects metastatic cancer
Researchers from the University of California-Davis shared results from the first study using uEXPLORER to conduct total-body dynamic PET scans of cancer patients. Developed and validated at UC-Davis, uEXPLORER is the first total-body (194 cm axial field-of-view), high-sensitivity PET/CT scanner being used commercially. A total-body dynamic PET/CT scan of a patient with metastatic cancer generated high-quality diagnostic images that identified multiple metastases
Dynamic 18F-FDG PET with tracer kinetic modelling has the potential to better detect lesions and assess cancer response to therapy, according to the researchers. Unlike conventional PET scanners with limited axial field-of-view (15–30 cm), the uEXPLORER is capable of simultaneous dynamic imaging of widely separated lesions.
“The focus of our study was to test the capability of uEXPLORER for kinetic modelling and parametric imaging of cancer,” explained UC Davis’ Guobao Wang. “Different kinetic parameters can be used in combination to understand the behaviour of both tumour metastases and organs-of-interest such as the spleen and bone marrow. Thus, both tumour response and therapy side-effects can be assessed using the same scan.”
For the study, a patient with metastatic renal cell carcinoma was injected with the radiotracer 18F-FDG and scanned on the total-body scanner. The researchers calculated static PET standardized uptake values (SUVs) and performed kinetic modelling for regional quantification in 16 regions-of-interest, including major organs and six identified metastases. They calculated the glucose influx rate and used additional kinetic modelling to generate parametric images of the kinetic parameters. The kinetic data were then used to explore tumour detection and characterization. They note that parametric images of the FDG influx rate improved tumour contrast over SUV in general and led to improved lesion detection in the renal cortex, which has been historically challenging.
“Total-body dynamic imaging and kinetic modelling enabled by total-body PET have the potential to change nuclear medicine into a multi-parametric imaging method, where many different aspects of tissue behaviour can be assessed in the same clinical setting – much like the information gained from different sequences in an MRI scan,” said Ramsey Badawi, co-director of the EXPLORER Molecular Imaging Center.
Novel PET radiotracer images malignant brain tumours
A first-in-human study has demonstrated the safety and favourable pharmacokinetic and dosimetry profile of 64Cu-EB-RGD – a new, relatively long-lived PET tracer – in patients with glioblastomas. The radiotracer delivered high-contrast diagnostic imaging in patients, visualizing tumours that express low or moderate levels of α v β 3 integrin with high sensitivity.
PET and MRI of a glioblastoma patient injected with 64Cu-NOTA-EB-RGD at different time points after injection. (Courtesy: Jingjing Zhang et al, Peking Union Medical College Hospital/Xiaoyuan Chen et al, Laboratory of Molecular Imaging and Nanomedicine, NIBIB/NIH)
The study included three healthy volunteers and two patients with recurrent glioblastoma who underwent whole-body 64Cu-EB-RGD PET/CT. The new radiotracer has unique qualities, explained Jingjing Zhang, from Peking Union Medical College Hospital. The peptide sequence Arg-Gly-Asp (RGD) specifically targets the cell surface receptor α v β 3 integrin, which is overexpressed in glioblastomas. To slow clearance, Evans Blue dye, which reversibly binds to circulating albumin, is bound to RGD, significantly enhancing target accumulation and retention. The addition of the 64Cu label provides persistent, high-contrast diagnostic images in glioblastoma patients.
The researchers calculated tumour-to-background ratios for target tumour lesions and normal brain tissue in seven sets of brain PET and PET/CT scans obtained over two consecutive days. They also collected safety data (such as vital signs and physical exams, for example) for each participant, one and seven days after the scans.
64Cu-EB-RGD was well-tolerated, with no adverse effects seen immediately or up to one week after administration. The mean effective dose of 64Cu-EB-RGD was similar to that of an 18F-FDG scan. Injection of 64Cu-EB-RGD into patients with recurrent glioblastoma generated high accumulation at the tumour, with continuously increased tumour-to-background contrast over time.
As well as providing a future diagnostic tool, the researchers noted that 64Cu-EBRGD could also be a breakthrough targeted radiotherapy for glioblastoma patients.
“64Cu-labelled EB-RGD represents a viable model compound for therapeutic applications, since 177Lu, 90Y or 225Ac can be substituted for 64Cu,” explained Deling Li of Beijing Tiantan Hospital. “We are currently studying the 177Lu homologue to treat glioblastoma and other α v β 3 integrin expressing cancers, including non-small cell lung, melanoma, renal and bone, and hope to build on the current wave of radiotherapies like 177Lu-DOTATATE.”
PET/MRI approach identifies chronic pain locations
A molecular imaging approach that combines 18F-FDG PET and MRI can precisely identify the location of pain generators in chronic pain sufferers, according to a study from Stanford University School of Medicine. The imaging data led to new management plans for 62% of the study’s participants.
18F-FDG PET has the ability to accurately evaluate increased glucose metabolism that arises from acute or chronic pain generators, such as hypermetabolic inflamed tissues. The researchers sought to develop a clinical 18F-FDG PET/MRI method to accurately localize sites of increased inflammation related to sources of pain.
Adult male with decades of right neck pain, discomfort and tightening following birth injury. Images shows abnormally elevated FDG uptake (white arrows) in the right neck at the greater occipital nerve. (Courtesy: P Cipriano et al, Stanford University)
The team imaged 65 patients with chronic pain, from the head to the feet, using the 18F-FDG PET/MRI protocol. Principal investigator Sandip Biswal and colleagues used image analysis software to measure maximum standardized uptake values and target-to-background ratios. They identified locations of increased 18F-FDG uptake and compared these to known locations of pain, finding increased uptake in muscle and nerves at the site of pain in 58 patients.
These imaging findings resulted in 36 significant modifications in management plans, such as the recommendation of new invasive procedures, and 16 mild modifications, such as ordering an additional diagnostic test.
The researchers recommend that a study of a large cohort of patients is conducted to validate their findings. “The results of this study show that better outcomes are possible for those suffering from chronic pain,” said Biswal. “This clinical molecular imaging approach is addressing a tremendous unmet clinical need. I am hopeful that this work will lay the groundwork for the birth of a new subspeciality in nuclear medicine and radiology.”
Targeted radionuclide therapy enhances immunotherapy response
Immunotherapy has had limited success in the treatment of prostate cancer, due to a significantly immunosuppressive tumour microenvironment. Now, a preclinical study conducted at the University of Wisconsin-Madison has shown that targeted radionuclide therapy creates a favourable tumour microenvironment in prostate cancer, which improves the effectiveness of immunotherapies.
“Understanding this treatment dynamic, our goal was to demonstrate that systemically delivered targeted radionuclide therapy provides beneficial immunomodulatory effects that may enhance the response of prostate cancer to immunotherapies,” said Reinier Hernandez.
PET/CT images showing uptake and retention of 86Y-NM600 (imaging agent) in immunocompetent mice bearing prostate tumours. The team used the PET data to estimate tumour dosimetry and prescribe an immunomodulatory injected activity of 90Y-NM600 (therapeutic agent). (Courtesy: R Hernandez et al, University of Wisconsin-Madison)
The researchers administered the imaging agent 86Y-NM600 to mice with prostate tumours and performed PET/CT scans 3, 24, 48 and 72 hr after injection. Analysing radiotracer uptake in tumours and in healthy tissues allowed them to estimate the dosimetry for targeted radionuclide therapy using 90Y-NM600. They then gave groups of mice either a high or low dose of 90Y-NM600, and monitored tumour growth and survival for 60 days.
PET/CT data revealed that 90Y-NM600 immunomodulates the prostate tumour microenvironment by modifying tumour-infiltrating lymphocyte populations, upregulating checkpoint molecules and promoting the release of pro-inflammatory cytokines. The team found that 90Y-NM600’s pro-inflammatory effects on the tumour microenvironment were elicited at relatively low radiation doses without incurring systemic toxicity.
“Our results provide a rationale for combining targeted radionuclide therapy with immunotherapies, which, so far, have proven ineffective in prostate cancer. Improving immunotherapy in prostate cancer could bring about a potentially curative treatment alternative for advanced-stage patients,” said Hernandez.
The researchers noted that the study also presents a paradigm change in targeted radionuclide therapy, where the maximum tolerable dose may not always be the most beneficial to patients. “A key finding of our work is that immunomodulation is best achieved with a relatively low radiation dose to the tumour which does not affect the normal immune system,” Hernandez explained.


physicsworld--2020-07-20--Quantum squeezing is achieved at room temperature - Physics World

An optomechanical device that adjusts – or “ squeezes ” – the uncertainties in the quantum properties of laser light has been developed by Nancy Aggarwal at the Massachusetts Institute of Technology and colleagues .
The team created their source of squeezed light using a mirror that oscillates under radiation pressure , but displays little thermal fluctuation , even at room temperature .
Their approach could soon be used to boost the performance of gravitational wave detectors .
When researchers make measurements on a laser signal , uncertainties arise from quantum fluctuations in the numbers of photons detected and the @ @ @ @ @ @ @ the detector .
The relationship between this pair of uncertainties is described by the uncertainty principle , which dictates that a decrease in uncertainty in photon number must be accompanied by an increase in uncertainty in timing and vice versa .
Reducing the uncertainty of one measurement at the expense of increasing the other can be advantageous in some experiments — and is called quantum squeezing .
Currently , squeezing light must be carried out at cryogenic temperatures to minimize thermal fluctuations – and this requires bulky experimental equipment .
Now Aggarwal ’ @ @ @ @ @ @ @ system involving two opposite-facing mirrors within a spherical cavity , housed in a vacuum chamber .
One of the mirrors has a radius of 1 cm and is permanently fixed in place , while the other is just 70 micron across and is supported by a moveable cantilever of about the same size .
When a laser is fired into the cavity , radiation pressure imparted by its photons forces the smaller mirror to oscillate .
This movement creates correlations between the number of photons hitting the mirror and the timings of those @ @ @ @ @ @ @ therefore , Aggarwal and colleagues could cause the cavity to squeeze light by adjusting the uncertainties in numbers and timing .
To avoid the need for cold temperatures , Aggarwal ’ s team constructed their oscillating mirror from alternating layers of gallium arsenide and aluminium gallium arsenide – both of which contain pure , highly ordered atomic structures .
Within this composite material , any heat-driven collisions between electrons were suppressed .
This meant that instead of jittering due to thermal fluctuations , the mirror ’ s motion was dominated by light-driven radiation @ @ @ @ @ @ @ this allowed the team to produce squeezed light at room temperatures , and at a broad range of frequencies ; demonstrating a reduction in quantum noise of 15 % compared with previous techniques .
Perhaps the most exciting potential application for the team ’ s device will be improvements to the LIGO and Virgo gravitational wave detectors , which require compact and stable setups , as well as constant operation at room temperatures .
Through future research , Aggarwal and her colleagues now hope to adapt their setup to work with all possible @ @ @ @ @ @ @ new system is described in Nature Physics .

Heating up: artistic representation of how light is squeezed at room temperature. (Courtesy: Christine Daniloff/MIT)
An optomechanical device that adjusts – or “squeezes” – the uncertainties in the quantum properties of laser light has been developed by Nancy Aggarwal at the Massachusetts Institute of Technology and colleagues. The team created their source of squeezed light using a mirror that oscillates under radiation pressure, but displays little thermal fluctuation, even at room temperature. Their approach could soon be used to boost the performance of gravitational wave detectors.
When researchers make measurements on a laser signal, uncertainties arise from quantum fluctuations in the numbers of photons detected and the times at which the photons arrive at the detector. The relationship between this pair of uncertainties is described by the uncertainty principle, which dictates that a decrease in uncertainty in photon number must be accompanied by an increase in uncertainty in timing and vice versa. Reducing the uncertainty of one measurement at the expense of increasing the other can be advantageous in some experiments — and is called quantum squeezing.
Currently, squeezing light must be carried out at cryogenic temperatures to minimize thermal fluctuations – and this requires bulky experimental equipment. Now Aggarwal’s team has created a room temperature system involving two opposite-facing mirrors within a spherical cavity, housed in a vacuum chamber. One of the mirrors has a radius of 1 cm and is permanently fixed in place, while the other is just 70 micron across and is supported by a moveable cantilever of about the same size.
Radiation pressure
When a laser is fired into the cavity, radiation pressure imparted by its photons forces the smaller mirror to oscillate. This movement creates correlations between the number of photons hitting the mirror and the timings of those photons. By fine-tuning their setup, therefore, Aggarwal and colleagues could cause the cavity to squeeze light by adjusting the uncertainties in numbers and timing.
To avoid the need for cold temperatures, Aggarwal’s team constructed their oscillating mirror from alternating layers of gallium arsenide and aluminium gallium arsenide – both of which contain pure, highly ordered atomic structures. Within this composite material, any heat-driven collisions between electrons were suppressed. This meant that instead of jittering due to thermal fluctuations, the mirror’s motion was dominated by light-driven radiation pressure. For the first time, this allowed the team to produce squeezed light at room temperatures, and at a broad range of frequencies; demonstrating a reduction in quantum noise of 15% compared with previous techniques.
Perhaps the most exciting potential application for the team’s device will be improvements to the LIGO and Virgo gravitational wave detectors, which require compact and stable setups, as well as constant operation at room temperatures. Through future research, Aggarwal and her colleagues now hope to adapt their setup to work with all possible wavelengths of incoming laser light.
The new system is described in Nature Physics.


physicsworld--2020-07-20--Space-based spectrometer enters neutron lifetime debate - Physics World

While protons remain stable for at least 1034 years outside the nucleus , a free neutron survives for just under 15 minutes before it decays .
The neutron ’ s precise lifetime is , however , a matter of some debate , as the two techniques commonly used to measure it have produced conflicting results of 880 and 888 seconds .
A team of researchers at the Johns Hopkins University Applied Physics Laboratory in the US led by Jack Wilson has now put forward a third , radically different technique that involves measuring the number of neutrons near a planet @ @ @ @ @ @ @ spectrometer on NASA ’ s MESSENGER spacecraft during flybys of Venus and Mercury in 2007 and 2008 , they calculated the neutron lifetime to be 780 +/- 90 seconds .
While this measurement has a large uncertainty , the researchers note that the MESSENGER instrument was never designed to perform studies of this type – meaning that a dedicated instrument on a future mission could produce a measurement with much higher precision .
The established techniques for measuring neutron lifetime are both laboratory-based .
In the first , known as the “ bottle @ @ @ @ @ @ @ or mechanical forces to confine low-energy neutrons in a trap .
They then count the number of particles remaining after a fixed period of time .
In the “ beam ” method , they count the number of decay products – protons , electrons and antineutrinos – from a beam of neutrons .
The eight-second discrepancy between the neutron lifetimes measured using the bottle and beam methods has important implications for fundamental physics .
For example , the neutron lifetime is a key parameter in studies of nucleosynthesis ( element formation ) in @ @ @ @ @ @ @ ( which has been blamed on unknown experimental errors ) is therefore key to understanding how our universe formed 13.8 billion years ago .
The MESSENGER spacecraft ’ s neutron spectrometer was designed to measure Mercury ’ s surface composition , and to determine whether the planet ’ s poles might contain water ice .
The instrument consisted of a 103 cube of borated plastic scintillator sandwiched between two 4-mm thick 100cm2 lithium-glass plates that are sensitive to neutrons created via the neutron capture reaction 6Li +n → 3H + 4He .
This @ @ @ @ @ @ @ ’ s atmosphere or surface , so in effect , MESSENGER ’ s spectrometer measured the rates at which neutrons “ leak out ” from the planet .
The number of neutrons detected depends on how long it takes the particles to “ fly up ” and reach the spacecraft ’ s neutron spectrometer .
Hence , the shorter the neutron ’ s lifetime , the fewer the neutrons that survive long enough to reach the detector .
Before MESSENGER entered Mercury ’ s orbit , it went through a series of flybys @ @ @ @ @ @ @ During the second Venus flyby , its neutron spectrometer was switched on to check that the instrument was working properly .
The data used in this study , which is published in Physical Review Research , were taken during this Venus encounter and during MESSENGER ’ s first flyby of Mercury .
Venus ’ atmosphere is both simple and relatively uniform , containing mainly carbon dioxide ( 96 % by volume ) and nitrogen ( most of the remainder ) .
Because MESSENGER made observations over a large range of heights above the @ @ @ @ @ @ @ were able to measure how the neutron flux changes with distance .
“ The basis of our measurements is a set of models of the neutron production , propagation and detection during these flybys that are modelled with different lifetimes , ” Wilson explains .
“ The shorter the neutron lifetime , the more rapidly the neutron counts decrease with altitude and the model that best fits the data gives us the lifetime.
” The researchers describe their spacecraft-based technique as being conceptually like a giant bottle experiment , one that uses Venus @ @ @ @ @ @ @ comparable to their lifetime .
However , they emphasize that its systematic uncertainties are completely different from those of previous measurements .
This , they argue , is potentially a big advantage , as the most likely cause of the disagreement between the beam and ( conventional ) bottle techniques is that one or both of them underestimated or missed a systematic error .
The work is a proof-of-principle demonstration that such an approach is at least possible , Wilson tells Physics World .
More progress might be made using other planetary neutron @ @ @ @ @ @ @ that the best path forward would be to design a dedicated instrument on a future mission optimized to measure neutron lifetime from orbit .
Venus , he adds , is a good candidate in this respect thanks to its thick atmosphere and large mass that effectively traps neutrons .
“ The main thing that held our measurement back was the short time MESSENGER spent at Venus ( roughly 45 minutes ) , ” he says .
“ If we could spend a longer time there , we could improve the statistics of the @ @ @ @ @ @ @ with using the data from this spacecraft .
”

Artist impression of MESSENGER spacecraft in orbit at Mercury. (Courtesy: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington)
While protons remain stable for at least 1034 years outside the nucleus, a free neutron survives for just under 15 minutes before it decays. The neutron’s precise lifetime is, however, a matter of some debate, as the two techniques commonly used to measure it have produced conflicting results of 880 and 888 seconds.
A team of researchers at the Johns Hopkins University Applied Physics Laboratory in the US led by Jack Wilson has now put forward a third, radically different technique that involves measuring the number of neutrons near a planet. Using data acquired by the neutron spectrometer on NASA’s MESSENGER spacecraft during flybys of Venus and Mercury in 2007 and 2008, they calculated the neutron lifetime to be 780 +/- 90 seconds. While this measurement has a large uncertainty, the researchers note that the MESSENGER instrument was never designed to perform studies of this type – meaning that a dedicated instrument on a future mission could produce a measurement with much higher precision.
Bottle and beam methods
The established techniques for measuring neutron lifetime are both laboratory-based. In the first, known as the “bottle” method, researchers use magnetic fields or mechanical forces to confine low-energy neutrons in a trap. They then count the number of particles remaining after a fixed period of time. In the “beam” method, they count the number of decay products – protons, electrons and antineutrinos – from a beam of neutrons.
The eight-second discrepancy between the neutron lifetimes measured using the bottle and beam methods has important implications for fundamental physics. For example, the neutron lifetime is a key parameter in studies of nucleosynthesis (element formation) in the Big Bang. Resolving this discrepancy (which has been blamed on unknown experimental errors) is therefore key to understanding how our universe formed 13.8 billion years ago.
The MESSENGER spacecraft’s neutron spectrometer was designed to measure Mercury’s surface composition, and to determine whether the planet’s poles might contain water ice. The instrument consisted of a 103 cube of borated plastic scintillator sandwiched between two 4-mm thick 100cm2 lithium-glass plates that are sensitive to neutrons created via the neutron capture reaction 6Li +n → 3H + 4He.
This reaction occurs when cosmic rays strike Mercury’s atmosphere or surface, so in effect, MESSENGER’s spectrometer measured the rates at which neutrons “leak out” from the planet. The number of neutrons detected depends on how long it takes the particles to “fly up” and reach the spacecraft’s neutron spectrometer. Hence, the shorter the neutron’s lifetime, the fewer the neutrons that survive long enough to reach the detector.
Venus flybys
Before MESSENGER entered Mercury’s orbit, it went through a series of flybys of Earth, Venus and Mercury. During the second Venus flyby, its neutron spectrometer was switched on to check that the instrument was working properly. The data used in this study, which is published in Physical Review Research, were taken during this Venus encounter and during MESSENGER’s first flyby of Mercury.
Venus’ atmosphere is both simple and relatively uniform, containing mainly carbon dioxide (96% by volume) and nitrogen (most of the remainder). Because MESSENGER made observations over a large range of heights above the planet’s surface, the researchers were able to measure how the neutron flux changes with distance.
“The basis of our measurements is a set of models of the neutron production, propagation and detection during these flybys that are modelled with different lifetimes,” Wilson explains. “The shorter the neutron lifetime, the more rapidly the neutron counts decrease with altitude and the model that best fits the data gives us the lifetime.”
A “giant bottle experiment”
The researchers describe their spacecraft-based technique as being conceptually like a giant bottle experiment, one that uses Venus’ gravity to confine neutrons for periods comparable to their lifetime. However, they emphasize that its systematic uncertainties are completely different from those of previous measurements. This, they argue, is potentially a big advantage, as the most likely cause of the disagreement between the beam and (conventional) bottle techniques is that one or both of them underestimated or missed a systematic error.
The work is a proof-of-principle demonstration that such an approach is at least possible, Wilson tells Physics World. More progress might be made using other planetary neutron spectrometer data sets, but he suggests that the best path forward would be to design a dedicated instrument on a future mission optimized to measure neutron lifetime from orbit. Venus, he adds, is a good candidate in this respect thanks to its thick atmosphere and large mass that effectively traps neutrons.
“The main thing that held our measurement back was the short time MESSENGER spent at Venus (roughly 45 minutes),” he says. “If we could spend a longer time there, we could improve the statistics of the measurement and avoid introducing the systematics associated with using the data from this spacecraft.”


physicsworld--2020-07-20--Fukushima may have scattered plutonium widely - Physics World

Tiny fragments of plutonium may have been carried more than 200 km by caesium particles released following the meltdown at the Fukushima Daiichi nuclear power plant in Japan in 2011 .
So says an international group of scientists that has made detailed studies of soil samples at sites close to the damaged reactors .
The researchers say the findings shed new light on conditions inside the sealed-off reactors and should aid the plant ’ s decommissioning .
The disaster at Fukushima occurred after a magnitude-9 earthquake struck off the north-east coast of Japan and sent a 14 m-high tsunami crashing @ @ @ @ @ @ @ With low-lying back-up generators knocked out , the site ’ s three operating reactors overheated and melted down .
At the same time , hot steam reacted with the zirconium cladding of the nuclear fuel , generating hydrogen gas that exploded when it escaped from containment .
Caesium is a volatile fission product created in nuclear fuel .
During the Fukushima meltdown , it combined with silica gas created when melting fuel and other reactor materials interacted with the concrete below the damaged reactor vessel .
The resulting glass particles , known as @ @ @ @ @ @ @ a few microns or tens of microns across .
Satoshi Utsunomiya and Eitaro Kurihara at Kyushu University and colleagues in Japan , Europe and the US analysed three such particles obtained from soil samples dug up at two sites within a few kilometres of the Fukushima plant .
They used a range of techniques to study the physical and chemical composition of these CsMPs , with the aim of establishing whether they contained any plutonium .
To date , plutonium from the accident has been detected as far as 50 km from the @ @ @ @ @ @ @ that this plutonium , like the caesium , was released after evaporating from the fuel .
But the new analysis instead points to some of it having escaped from the stricken plant in particulate form within fragments of fuel “ captured ” by the CsMPs .
Utsunomiya and colleagues used electron microscopy and synchrotron X-ray fluorescence to look inside the CsMPs .
Based on these data , they were able to map the distribution of various elements coming from materials within the damaged reactors – including iron from stainless steel , zirconium and @ @ @ @ @ @ @ from cooling water .
They also found uranium within one of the CsMPs , in the form of discrete uranium oxide particles less than 10 nm across .
However , the researchers were unable to find any traces of plutonium using these methods – probably due to interference from strontium , another fission product .
Instead , they turned to X-ray absorption .
To compensate for high levels of noise , they carried out the measurement at two different synchrotrons , transporting their roughly 20 µm diameter particle from Japan to be blasted @ @ @ @ @ @ @ the UK and the Swiss Light Source in Switzerland .
The researchers focused their attention on the three areas of the particle that generated the most fluorescence from uranium .
They failed to detect plutonium at two of these locations , but succeeded at the third , with absorption spectra produced at both synchrotrons indicating the element ’ s presence .
The low signal-to-noise ratio meant they couldn ’ t identify exactly which plutonium species were present , but the shape of the spectra told them that it probably existed as an oxide @ @ @ @ @ @ @ .
Utsunomiya and co-workers also used mass spectrometry to measure the relative abundance of different plutonium and uranium isotopes within the microparticles .
They found that three ratios – uranium-235 to uranium-238 , as well as plutonium-239 compared to both plutonium-240 and -242 – all agreed with calculations of the proportions that would have been present in the fuel at the time of the disaster .
This agreement , coupled with the fact that the measured amount of uranium-238 was nearly two orders of magnitude greater than would be the case if it @ @ @ @ @ @ @ , led them to conclude that the uranium and plutonium existed as discrete fuel particles within the CsMPs .
The researchers note that previous studies have shown that plutonium and caesium are distributed differently in the extended area around Fukushima , which suggests that not all CsMPs contain plutonium .
However , they say that the fact plutonium is found in some of these particles implies that it could have been transported as far afield as the caesium – up to 230 km from the Fukushima plant .
As regards any threat to @ @ @ @ @ @ @ of the emitted plutonium are comparable with global counts from nuclear weapons tests .
Such low concentrations , they say , “ may not have significant health effects ” , but they add that if the plutonium were ingested , the isotopes that make it up could yield quite high effective doses .
With radiation levels still too high for humans to enter the damaged reactors , the researchers argue that the fuel fragments they have uncovered provide precious direct information on what happened during the meltdown and the current state of the @ @ @ @ @ @ @ points out that the composition of the debris , just like that of normal nuclear fuel , varies on the very smallest scales .
This information , he says , will be vital when it comes to decommissioning the reactors safely , given the potential risk of inhaling dust particles containing uranium or plutonium .
The research is reported in Science of the Total Environment .

Explosive event: The upper side of the unit 3 reactor building at Fukushima Daiichi was damaged by a hydrogen explosion. This area housed the spent fuel pool and the fuel handling machines. (Courtesy: TEPCO)
Tiny fragments of plutonium may have been carried more than 200 km by caesium particles released following the meltdown at the Fukushima Daiichi nuclear power plant in Japan in 2011. So says an international group of scientists that has made detailed studies of soil samples at sites close to the damaged reactors. The researchers say the findings shed new light on conditions inside the sealed-off reactors and should aid the plant’s decommissioning.
The disaster at Fukushima occurred after a magnitude-9 earthquake struck off the north-east coast of Japan and sent a 14 m-high tsunami crashing over the plant’s seawalls. With low-lying back-up generators knocked out, the site’s three operating reactors overheated and melted down. At the same time, hot steam reacted with the zirconium cladding of the nuclear fuel, generating hydrogen gas that exploded when it escaped from containment.
Caesium is a volatile fission product created in nuclear fuel. During the Fukushima meltdown, it combined with silica gas created when melting fuel and other reactor materials interacted with the concrete below the damaged reactor vessel. The resulting glass particles, known as caesium-rich microparticles (CsMPs), measure a few microns or tens of microns across.
Satoshi Utsunomiya and Eitaro Kurihara at Kyushu University and colleagues in Japan, Europe and the US analysed three such particles obtained from soil samples dug up at two sites within a few kilometres of the Fukushima plant. They used a range of techniques to study the physical and chemical composition of these CsMPs, with the aim of establishing whether they contained any plutonium.
Mapping plutonium spread
To date, plutonium from the accident has been detected as far as 50 km from the damaged reactors. Researchers had previously thought that this plutonium, like the caesium, was released after evaporating from the fuel. But the new analysis instead points to some of it having escaped from the stricken plant in particulate form within fragments of fuel “captured” by the CsMPs.
Utsunomiya and colleagues used electron microscopy and synchrotron X-ray fluorescence to look inside the CsMPs. Based on these data, they were able to map the distribution of various elements coming from materials within the damaged reactors – including iron from stainless steel, zirconium and tin from the fuel cladding and zinc from cooling water. They also found uranium within one of the CsMPs, in the form of discrete uranium oxide particles less than 10 nm across.
However, the researchers were unable to find any traces of plutonium using these methods – probably due to interference from strontium, another fission product. Instead, they turned to X-ray absorption. To compensate for high levels of noise, they carried out the measurement at two different synchrotrons, transporting their roughly 20 µm diameter particle from Japan to be blasted with X-rays at the Diamond facility in the UK and the Swiss Light Source in Switzerland.
The researchers focused their attention on the three areas of the particle that generated the most fluorescence from uranium. They failed to detect plutonium at two of these locations, but succeeded at the third, with absorption spectra produced at both synchrotrons indicating the element’s presence. The low signal-to-noise ratio meant they couldn’t identify exactly which plutonium species were present, but the shape of the spectra told them that it probably existed as an oxide, rather than as a pure metal.
Utsunomiya and co-workers also used mass spectrometry to measure the relative abundance of different plutonium and uranium isotopes within the microparticles. They found that three ratios – uranium-235 to uranium-238, as well as plutonium-239 compared to both plutonium-240 and -242 – all agreed with calculations of the proportions that would have been present in the fuel at the time of the disaster. This agreement, coupled with the fact that the measured amount of uranium-238 was nearly two orders of magnitude greater than would be the case if it had simply evaporated from the melted fuel, led them to conclude that the uranium and plutonium existed as discrete fuel particles within the CsMPs.
Implications for decommissioning
The researchers note that previous studies have shown that plutonium and caesium are distributed differently in the extended area around Fukushima, which suggests that not all CsMPs contain plutonium. However, they say that the fact plutonium is found in some of these particles implies that it could have been transported as far afield as the caesium – up to 230 km from the Fukushima plant.
As regards any threat to health, they note that radioactivity levels of the emitted plutonium are comparable with global counts from nuclear weapons tests. Such low concentrations, they say, “may not have significant health effects”, but they add that if the plutonium were ingested, the isotopes that make it up could yield quite high effective doses.
With radiation levels still too high for humans to enter the damaged reactors, the researchers argue that the fuel fragments they have uncovered provide precious direct information on what happened during the meltdown and the current state of the fuel debris. In particular, Utsunomiya points out that the composition of the debris, just like that of normal nuclear fuel, varies on the very smallest scales. This information, he says, will be vital when it comes to decommissioning the reactors safely, given the potential risk of inhaling dust particles containing uranium or plutonium.
The research is reported in Science of the Total Environment.


physicsworld--2020-07-20--United Arab Emirates launches Hope mission to Mars - Physics World

The United Arab Emirates ( UAE ) has launched a spacecraft to Mars , making it the first Arab country to do so .
The uncrewed probe – called the Emirates Mars Mission or Hope – launched from Japan ’ s Tanegashima Space Center at 6:58 a.m. local time and has now begun a seven-month journey to the red planet .
Hope will spend at least two years in orbit around Mars with a possible further two-year extension .
Estimated to cost around $ 200m , Hope will orbit Mars between 20,000 and 43,000 km from the surface .
From @ @ @ @ @ @ @ , studying daily and seasonal changes in the climate as well as analysing hydrogen and oxygen in Mars ’ atmosphere and why the gases are being lost into space .
The mission carries three main instruments : two spectrometers – one operating in the infrared and the other in ultraviolet – and an imager that will study the lower atmosphere at visible and ultraviolet wavelengths .
A UAE-led Mars mission was first mooted in 2014 with the aim of arriving at Mars in 2021 – timed to coincide with the 50th anniversary of @ @ @ @ @ @ @ UK .
Funded by the UAE Space Agency , Hope is a collaboration between the Mohammed Bin Rashid Space Centre in Dubai , which will oversee the mission , and the Laboratory for Atmospheric and Space Physics ( LASP ) at the University of Colorado , Boulder , which built and tested most of the craft .
“ Hope will capture the ebbs and flows of weather on Mars to a degree that wasn ’ t possible before , ” says LASP director Daniel Baker .
“ It ’ s a showcase for @ @ @ @ @ @ @ international endeavour.
” Indeed , Hope is the first of three Mars craft that will be taking off this month .
China is planning to launch Tianwen-1 on 23 July .
This mission will consist of an orbiter , lander and rover and will , among other things , measure the water and ice content on Mars .
Then on 30 July , NASA is scheduled to launch Perseverance – a robotic rover to find signs of ancient , extinct life .
Perseverance will also release a small experimental helicopter called Ingenuity , @ @ @ @ @ @ @ the Martian atmosphere .

Hopes and dreams: the United Arab Emirates Mars mission – dubbed Hope – will study the Martian atmosphere including daily and seasonal changes in the climate. (Courtesy: MBRSC)
The United Arab Emirates (UAE) has launched a spacecraft to Mars, making it the first Arab country to do so. The uncrewed probe – called the Emirates Mars Mission or Hope – launched from Japan’s Tanegashima Space Center at 6:58 a.m. local time and has now begun a seven-month journey to the red planet. Hope will spend at least two years in orbit around Mars with a possible further two-year extension.
Estimated to cost around $200m, Hope will orbit Mars between 20,000 and 43,000 km from the surface. From there it will investigate the Martian atmosphere, studying daily and seasonal changes in the climate as well as analysing hydrogen and oxygen in Mars’ atmosphere and why the gases are being lost into space. The mission carries three main instruments: two spectrometers – one operating in the infrared and the other in ultraviolet – and an imager that will study the lower atmosphere at visible and ultraviolet wavelengths.
[Hope] is a showcase for how space exploration has become an increasingly international endeavour Daniel Baker
A UAE-led Mars mission was first mooted in 2014 with the aim of arriving at Mars in 2021 – timed to coincide with the 50th anniversary of the UAE’s independence from the UK. Funded by the UAE Space Agency, Hope is a collaboration between the Mohammed Bin Rashid Space Centre in Dubai, which will oversee the mission, and the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado, Boulder, which built and tested most of the craft. “Hope will capture the ebbs and flows of weather on Mars to a degree that wasn’t possible before,” says LASP director Daniel Baker. “It’s a showcase for how space exploration has become an increasingly international endeavour.”
Indeed, Hope is the first of three Mars craft that will be taking off this month. China is planning to launch Tianwen-1 on 23 July. This mission will consist of an orbiter, lander and rover and will, among other things, measure the water and ice content on Mars. Then on 30 July, NASA is scheduled to launch Perseverance – a robotic rover to find signs of ancient, extinct life. Perseverance will also release a small experimental helicopter called Ingenuity, which will attempt a short flight in the Martian atmosphere.


physicsworld--2020-07-20--Best in physics: multi-target tracking and carotid plaque evaluation - Physics World

The “ Best-in-Physics ” poster session at the American Association of Physicists in Medicine ( AAPM ) Annual Meeting highlights the top five abstracts in the imaging , therapy and multi-disciplinary science tracks .
In 2020 , however , as with many events this year , things were different .
This year ’ s annual meeting , held jointly with the Canadian Organization of Medical Physicists ( COMP ) , went virtual .
Instead of crowds gathering around the posters , presenters shared their research via talks presented on the meeting ’ s online portal .
Here is part one @ @ @ @ @ @ @ s top scoring studies at the 2020 Joint AAPM|COMP Virtual Meeting .
Look out for a second report later this week .
Paul Liu , from the ACRF Image X Institute at the University of Sydney , described the use of an MRI-Linac to simultaneously track the motion of two treatment targets .
“ There are many radiotherapy cases that involve simultaneous treatment of multiple targets , ” he said , citing examples such as locally advanced prostate or lung tumours , and oligometastases .
The challenge here is that both targets can @ @ @ @ @ @ @ , this is addressed by using large treatment margins , but this then confers extra dose to healthy tissue .
Liu explained that the improved imaging capabilities of an MRI-Linac can be used to localize multiple targets simultaneously .
Liu and collaborators used the Australian MRI-Linac , which has a 1T magnet and a 120-leaf multileaf collimator ( MLC ) , to track two spherical targets irradiated with a 6 MV conformal field .
They used a motion platform to test three sinusoidal motion traces , plus lung and prostate motion traces recorded @ @ @ @ @ @ @ via an extra pre-treatment aperture segmentation step , Liu explained .
An MLC tracking algorithm uses the target volumes , geometries and MLC positions from the treatment plan to divide the MLC aperture into two segments specific to each target .
During treatment , the team recorded 4 Hz cine MR images and used a template matching algorithm to calculate the motion of each target .
When motion was seen , rather than shift the entire MLC aperture , the leaf positions of each segment were calculated independently and then recombined into a @ @ @ @ @ @ @ both targets .
For sinusoidal motion , the team recorded a tracking latency between the targets and their corresponding apertures of 328 ms , comparable to single-target MLC tracking systems .
Liu noted that two-thirds of this time is related to the MRI step , potentially enabling latency reduction by using faster imaging and reconstruction techniques For lung motion traces , “ multi-target tracking does a good job overall in tracking both targets simultaneously , ” said Liu .
The geometric uncertainty – defined as the RMS error between the target and aperture @ @ @ @ @ @ @ 5.5 mm without tracking to 2.7 mm .
After correcting for latency , this error reduced further to 1.2 mm .
For prostate traces , the RMS error was reduced from 4.2 mm with no tracking to 1.4 mm with multi-target tracking .
Putting these findings into clinical context , simulations showed that in both cases , large margins of up to 7 mm were needed to maintain target coverage without tracking .
With multi-target tracking , 3 mm margins provided over 99 % coverage .
“ This is the first experimental demonstration @ @ @ @ @ @ @ an MRI-Linac , ” Liu concluded .
“ We showed that this technology can help reduce margin sizes in cases of differential motion.
” Carotid plaques within arteries are at risk of rupture , which can cause adverse health effects such as cognitive deficits or stroke .
But assessing plaque vulnerability – how likely it is to break off , travel to the brain and cause hypoxia – is difficult , as the mechanisms of plaque rupture are unknown and each plaque is unique in size , shape and composition .
“ Our @ @ @ @ @ @ @ we can noninvasively and inexpensively see the carotid plaque that can cause stroke or other harmful heath events , ” explained Catherine Steffel from the University of Wisconsin-Madison .
“ We want to give clinicians an inside look at which plaques are vulnerable.
” Steffel and colleagues are investigating the use of quantitative ultrasound imaging to noninvasively identify a plaque prone to rupture via its scattering structures .
Their goal was to define quantitative ultrasound parameters that can identify plaque composition and help assess its risk .
Steffel examined the effective scatterer diameter @ @ @ @ @ @ @ describes the frequency dependence of acoustic backscatter and has been used previously to examine other tissues .
She notes that her team ’ s previous studies on excised plaque showed that small ESD corresponded to calcified regions , while larger ESD was seen from lipid particles in plaque .
The researchers performed in vivo ultrasound imaging of carotid arteries in 52 patients scheduled for clinical removal of plaque .
Just over half of the participants displayed symptoms of stroke or transient ischemic attack and they had a median stenosis ( artery narrowing ) @ @ @ @ @ @ @ plaque was surgically removed , it was scored by a surgeon and assessed by a pathologist .
The team then compared the in vivo images with the surgical scores and histopathology assessment .
Analysis revealed weak correlations between ESD and surgical calcification rating , and between ESD and histopathology cholesterol/fibrinoid level .
Stronger correlations were seen between ESD and histopathology hemosiderin score .
Steffel explained that the hemosiderin scores are important for evaluating plaque composition as hemosiderin deposits are key markers of plaque vulnerability .
“ Our results for calcium and cholesterol/fibrinoid do @ @ @ @ @ @ @ because our parameters were computed for the entire plaque rather than a region-of-interest , ” said Steffel .
“ The hemosiderin findings intrigued us , as to our knowledge , this has not been studied previously.
” In particular , the team found that two parameters – the average ESD and standard deviation ESD – could differentiate between hemosiderin scores of 0 and 2 .
“ Overall , this work demonstrates that ESD parameters may help identify plaque composition and microstructure , providing a future clinical tool for assessing plaque vulnerability with noninvasive @ @ @ @ @ @ @ Steffel concluded .

Virtual conference: Speaker Paul Lui watches his own Best-in-Physics presentation on the online meeting platform. (Courtesy: Paul Liu)
The “Best-in-Physics” poster session at the American Association of Physicists in Medicine (AAPM) Annual Meeting highlights the top five abstracts in the imaging, therapy and multi-disciplinary science tracks. In 2020, however, as with many events this year, things were different.
This year’s annual meeting, held jointly with the Canadian Organization of Medical Physicists (COMP), went virtual. Instead of crowds gathering around the posters, presenters shared their research via talks presented on the meeting’s online portal. Here is part one of my selection from this year’s top scoring studies at the 2020 Joint AAPM|COMP Virtual Meeting. Look out for a second report later this week.
MRI-Linac enables simultaneous MLC tracking of two moving targets
Paul Liu, from the ACRF Image X Institute at the University of Sydney, described the use of an MRI-Linac to simultaneously track the motion of two treatment targets. “There are many radiotherapy cases that involve simultaneous treatment of multiple targets,” he said, citing examples such as locally advanced prostate or lung tumours, and oligometastases.
The challenge here is that both targets can move independently of each other. Currently, this is addressed by using large treatment margins, but this then confers extra dose to healthy tissue. Liu explained that the improved imaging capabilities of an MRI-Linac can be used to localize multiple targets simultaneously.
Liu and collaborators used the Australian MRI-Linac, which has a 1T magnet and a 120-leaf multileaf collimator (MLC), to track two spherical targets irradiated with a 6 MV conformal field. They used a motion platform to test three sinusoidal motion traces, plus lung and prostate motion traces recorded from patients.
Multi-target tracking is achieved via an extra pre-treatment aperture segmentation step, Liu explained. An MLC tracking algorithm uses the target volumes, geometries and MLC positions from the treatment plan to divide the MLC aperture into two segments specific to each target.
Multi-target tracking: the motion phantom driving two targets, MR images of the targets, the MLC leaf positions adjusted in response to the target motion, and EPID images acquired during treatment for analysis. (Courtesy: Paul Liu/ACRF Image X Institute)
During treatment, the team recorded 4 Hz cine MR images and used a template matching algorithm to calculate the motion of each target. When motion was seen, rather than shift the entire MLC aperture, the leaf positions of each segment were calculated independently and then recombined into a single MLC aperture encompassing the motion of both targets.
For sinusoidal motion, the team recorded a tracking latency between the targets and their corresponding apertures of 328 ms, comparable to single-target MLC tracking systems. Liu noted that two-thirds of this time is related to the MRI step, potentially enabling latency reduction by using faster imaging and reconstruction techniques
For lung motion traces, “multi-target tracking does a good job overall in tracking both targets simultaneously,” said Liu. The geometric uncertainty – defined as the RMS error between the target and aperture positions during treatment – was reduced from 5.5 mm without tracking to 2.7 mm. After correcting for latency, this error reduced further to 1.2 mm. For prostate traces, the RMS error was reduced from 4.2 mm with no tracking to 1.4 mm with multi-target tracking.
Putting these findings into clinical context, simulations showed that in both cases, large margins of up to 7 mm were needed to maintain target coverage without tracking. With multi-target tracking, 3 mm margins provided over 99% coverage.
“This is the first experimental demonstration of tracking two independent moving targets on an MRI-Linac,” Liu concluded. “We showed that this technology can help reduce margin sizes in cases of differential motion.”
Quantitative ultrasound evaluates plaque vulnerability
Carotid plaques within arteries are at risk of rupture, which can cause adverse health effects such as cognitive deficits or stroke. But assessing plaque vulnerability – how likely it is to break off, travel to the brain and cause hypoxia – is difficult, as the mechanisms of plaque rupture are unknown and each plaque is unique in size, shape and composition.
“Our research tries to improve the ways that we can noninvasively and inexpensively see the carotid plaque that can cause stroke or other harmful heath events,” explained Catherine Steffel from the University of Wisconsin-Madison. “We want to give clinicians an inside look at which plaques are vulnerable.”
Steffel and colleagues are investigating the use of quantitative ultrasound imaging to noninvasively identify a plaque prone to rupture via its scattering structures. Their goal was to define quantitative ultrasound parameters that can identify plaque composition and help assess its risk.
Steffel examined the effective scatterer diameter (ESD) – a parameter that describes the frequency dependence of acoustic backscatter and has been used previously to examine other tissues. She notes that her team’s previous studies on excised plaque showed that small ESD corresponded to calcified regions, while larger ESD was seen from lipid particles in plaque.
Parametric map showing the variation in ESD throughout plaque. This example shows a 70% stenosis in the right internal carotid artery of an asymptomatic patient. (Courtesy: Catherine Steffel)
The researchers performed in vivo ultrasound imaging of carotid arteries in 52 patients scheduled for clinical removal of plaque. Just over half of the participants displayed symptoms of stroke or transient ischemic attack and they had a median stenosis (artery narrowing) of about 74%. After the plaque was surgically removed, it was scored by a surgeon and assessed by a pathologist. The team then compared the in vivo images with the surgical scores and histopathology assessment.
Analysis revealed weak correlations between ESD and surgical calcification rating, and between ESD and histopathology cholesterol/fibrinoid level. Stronger correlations were seen between ESD and histopathology hemosiderin score. Steffel explained that the hemosiderin scores are important for evaluating plaque composition as hemosiderin deposits are key markers of plaque vulnerability.
“Our results for calcium and cholesterol/fibrinoid do not agree with previous literature, perhaps because our parameters were computed for the entire plaque rather than a region-of-interest,” said Steffel. “The hemosiderin findings intrigued us, as to our knowledge, this has not been studied previously.”
In particular, the team found that two parameters – the average ESD and standard deviation ESD – could differentiate between hemosiderin scores of 0 and 2. “Overall, this work demonstrates that ESD parameters may help identify plaque composition and microstructure, providing a future clinical tool for assessing plaque vulnerability with noninvasive, relatively inexpensive ultrasound imaging,” Steffel concluded.


physicsworld--2020-07-17--Human hair soaks up oil spills, shortlist for astronomy photography contest, what if the Trinity tes

Human hair soaks up oil spills, shortlist for astronomy photography contest, what if the Trinity test had failed? - Physics World

Have you ever thought about how much human hair is cut and thrown away every day around the world , and wondered if something useful could be done with this renewable resource ?
Beyond making wigs – which is a major industry in itself – Megan Murray and colleagues at the University of Technology Sydney have found that human hair and dog fur are extremely good at soaking up oil spills on roads and other hard surfaces .
“ Dog fur in particular was surprisingly good at oil-spill clean-up , and felted mats from human hair and fur were very @ @ @ @ @ @ @ spills , ” says Murray .
Although synthetic materials are readily available for soaking up oil , they are not biodegradable .
As a result , the Australian researchers have tested several natural materials including peat moss – which was not as good as human hair .
They report their results in Environments .
The shortlist for the Insight Investment Astronomy Photographer of the Year 2020 competition has been announced and includes some fantastic images of the sky .
My favourite is a photo of polar stratospheric clouds above a snow landscape in @ @ @ @ @ @ @ .
He says the clouds “ are something I have been searching for for many years and had seen only in photographs until that day ” .
The winners will be announced on 10 September and the shortlisted works will be exhibited at the National Maritime Museum in London starting in October .
This week marks the 75th anniversary of the Trinity test and on his blog Restricted Data , Alex Wellerstein asks what would have happened if that first test of a nuclear weapon had failed ?
He considers three different types @ @ @ @ @ @ @ the military and political implications .

Hair cleansers: a felted dog fur mat (left) and loose human hair deployed on a porous surface. (Courtesy: Megan Murray, Soeren Poulsen and Brad Murray/Environments)
Have you ever thought about how much human hair is cut and thrown away every day around the world, and wondered if something useful could be done with this renewable resource? Beyond making wigs – which is a major industry in itself – Megan Murray and colleagues at the University of Technology Sydney have found that human hair and dog fur are extremely good at soaking up oil spills on roads and other hard surfaces.
“Dog fur in particular was surprisingly good at oil-spill clean-up, and felted mats from human hair and fur were very easy to apply and remove from the spills,” says Murray. Although synthetic materials are readily available for soaking up oil, they are not biodegradable. As a result, the Australian researchers have tested several natural materials including peat moss – which was not as good as human hair. They report their results in Environments.
The shortlist for the Insight Investment Astronomy Photographer of the Year 2020 competition has been announced and includes some fantastic images of the sky. My favourite is a photo of polar stratospheric clouds above a snow landscape in Finland that was taken by Thomas Kast. He says the clouds “are something I have been searching for for many years and had seen only in photographs until that day”.
The winners will be announced on 10 September and the shortlisted works will be exhibited at the National Maritime Museum in London starting in October.
This week marks the 75th anniversary of the Trinity test and on his blog Restricted Data, Alex Wellerstein asks what would have happened if that first test of a nuclear weapon had failed? He considers three different types of failure and looks at some of the military and political implications.


physicsworld--2020-07-17--Planet Nine: is it a planet, a primordial black hole or something else entirely? - Physics World

Planet Nine is a hypothetical world in the far reaches of our solar system .
Proposed in 2016 by Caltech @ @ @ @ @ Batygin , its existence would explain the unusual orbits of certain Kuiper belt objects ( @ @ @ @ @ we completely sure that Planet Nine in fact a planet ?
A paper in September @ @ @ @ @ could instead be explained by the presence of a primordial black hole smaller than your @ @ @ @ @ the bottom of this mystery , there have been recent proposals to send fleets of @ @ @ @ @ region of this mysterious object .
In the July episode of Physics World Stories Andrew @ @ @ @ @ the mystery of Planet Nine .
Appearing in the podcast are Mike Brown and the @ @ @ @ @ Zeeve Rogoszinski , co-author of one of the mission proposals .

Planet Nine is a hypothetical world in the far reaches of our solar system. Proposed in 2016 by Caltech astronomers Mike Brown and Konstantin Batygin, its existence would explain the unusual orbits of certain Kuiper belt objects (KBOs). But are we completely sure that Planet Nine in fact a planet?
A paper in September 2019 suggested the gravitational effects could instead be explained by the presence of a primordial black hole smaller than your fist. To get to the bottom of this mystery, there have been recent proposals to send fleets of tiny probes to the general region of this mysterious object.
In the July episode of Physics World Stories Andrew Glester gets the latest on the mystery of Planet Nine. Appearing in the podcast are Mike Brown and the University of Maryland’s Zeeve Rogoszinski, co-author of one of the mission proposals.


physicsworld--2020-07-17--X-rays unearth novel nanofeatures in bone - Physics World

A new X-ray technique has revealed hitherto unknown structures in human bone .
The technique , which uses a synchrotron beam to map the 3D orientation of nanocrystals and nanostructures within a material , advances our understanding of bone structure and how it relates to bone mechanics and bone disease .
According to its developers , the method could also shed light on other natural and synthetic structures in which crystal orientation plays a role in determining the material ’ s properties .
Bone is an impressive natural material .
It is both stiff , able to endure load without @ @ @ @ @ @ @ that it doesn ’ t break easily when bent or placed under load .
Stiffness and toughness are rarely found together in a single material , and indeed bone gets its unusual properties from two main constituents : protein-based collagen fibrils , reinforced by nanocrystals of a calcium phosphate mineral called hydroxylapatite .
These building blocks appear in various twisted patterns , and incorporate thin layers known as lamella that stack together like plywood .
However , the precise way they fit together has proved difficult to understand because their organization is complex @ @ @ @ @ @ @ Aarhus University in Denmark , the European Synchrotron ( ESRF ) in France , Chalmers University in Sweden and the Paul Scherrer Institute in Switzerland have now used X-ray scattering data to show that the small-scale structure of bone is not uniform , as previously assumed , but contains deviations in the orientation of the hydroxylapatite nanocrystals with respect to the bone ’ s nanostructure .
“ To the best of our knowledge , this is the first time that that the ‘ twisted plywood ’ pattern of human lamellar bone has been @ @ @ @ @ @ @ , ” says Marianne Liebi , a materials physicist at Chalmers and the study ’ s co-first author .
The researchers focused on a type of human bone known as trabecular bone , which is porous and found at the ends of long bones like the femur .
The pores in the bone are connected by thin rods and plates of bone tissue .
In their experiments , members of the team scanned a 40x40x40 micron cross-section of trabecular bone across a beam of synchrotron radiation while rotating the sample around its x @ @ @ @ @ @ @ X-ray scattering and wide-angle X-ray scattering , they were able to probe the bone ’ s nanoscale structures and the atomic structure of its biomineral crystal lattice at the same time .
To extract information on the bone ’ s 3D structure from their x-y scan , they used a technique called tensor tomography to analyse the intensity distribution of the scattered radiation in reciprocal space ( an imaginary space in which planes of atoms are represented by reciprocal points and all lengths are the inverse of their length in real space ) @ @ @ @ @ @ @ crystals in the material are not randomly oriented , the intensity of the X-ray scattering signals will be large for some orientations and small for others , explains co-team leader Henrik Birkedal , who is in the Department of Chemistry and iNANO at Aarhus .
“ This can be likened to the presence of landmasses on a globe , ” he says .
“ By mapping the variation of the scattering signals with sample orientation ( corresponding to making a topographic map in the globe analogy ) , we can determine how the @ @ @ @ @ @ @ ” The scattered intensity “ projection ” of the x-y scan revealed a clear lamellar structure of oriented material , interlaced with disordered regions .
According to Tilman Grunewald , the study ’ s other first author and a former ESRF scientist , “ it ’ s a bit too early ” to explain why the orientation of the hydroxylapatite nanocrystals is sometimes disordered , but the data nevertheless provides a focus for later research .
“ Essentially , our approach provides a new way of looking into the underlying structure of bone @ @ @ @ @ @ @ , the study ’ s co-leader and the scientist in charge of the ESRF ’ s ID13 beamline where the measurements were made , says that this new approach was made possible by “ drastic progress ” that is currently being made in X-ray synchrotrons .
“ We are expecting that the current upgrades of synchrotron sources will increase our power immensely in the next years , ” he adds .
The team now plan to use their method to analyse bone material from patients with diseases such as osteoporosis and other disorders @ @ @ @ @ @ @ , which can impair the bone ’ s mechanical properties .
They also hope to study types of bone microstructure other than the one analysed in this work .
“ Finally , we wish to understand the origin of the localized differences in orientation between nanostructure and crystals that we have observed , ” Birkedal tells Physics World .
“ This will likely require improving the resolution of our technique by using smaller X-ray beams.
” Full details of the technique are reported in Science Advances .

The different lamellae that make up the bone samples studied and their nanostructural orientation. (Courtesy: C Charnay)
A new X-ray technique has revealed hitherto unknown structures in human bone. The technique, which uses a synchrotron beam to map the 3D orientation of nanocrystals and nanostructures within a material, advances our understanding of bone structure and how it relates to bone mechanics and bone disease. According to its developers, the method could also shed light on other natural and synthetic structures in which crystal orientation plays a role in determining the material’s properties.
Bone is an impressive natural material. It is both stiff, able to endure load without deforming much, and tough, meaning that it doesn’t break easily when bent or placed under load. Stiffness and toughness are rarely found together in a single material, and indeed bone gets its unusual properties from two main constituents: protein-based collagen fibrils, reinforced by nanocrystals of a calcium phosphate mineral called hydroxylapatite. These building blocks appear in various twisted patterns, and incorporate thin layers known as lamella that stack together like plywood. However, the precise way they fit together has proved difficult to understand because their organization is complex at every length scale.
Researchers from Aarhus University in Denmark, the European Synchrotron (ESRF) in France, Chalmers University in Sweden and the Paul Scherrer Institute in Switzerland have now used X-ray scattering data to show that the small-scale structure of bone is not uniform, as previously assumed, but contains deviations in the orientation of the hydroxylapatite nanocrystals with respect to the bone’s nanostructure. “To the best of our knowledge, this is the first time that that the ‘twisted plywood’ pattern of human lamellar bone has been mapped in 3D at such high resolution,” says Marianne Liebi, a materials physicist at Chalmers and the study’s co-first author.
Tensor tomography
The researchers focused on a type of human bone known as trabecular bone, which is porous and found at the ends of long bones like the femur. The pores in the bone are connected by thin rods and plates of bone tissue.
In their experiments, members of the team scanned a 40x40x40 micron cross-section of trabecular bone across a beam of synchrotron radiation while rotating the sample around its x and y axes. By combining small-angle X-ray scattering and wide-angle X-ray scattering, they were able to probe the bone’s nanoscale structures and the atomic structure of its biomineral crystal lattice at the same time.
To extract information on the bone’s 3D structure from their x-y scan, they used a technique called tensor tomography to analyse the intensity distribution of the scattered radiation in reciprocal space (an imaginary space in which planes of atoms are represented by reciprocal points and all lengths are the inverse of their length in real space). If, for example, the crystals in the material are not randomly oriented, the intensity of the X-ray scattering signals will be large for some orientations and small for others, explains co-team leader Henrik Birkedal, who is in the Department of Chemistry and iNANO at Aarhus. “This can be likened to the presence of landmasses on a globe,” he says. “By mapping the variation of the scattering signals with sample orientation (corresponding to making a topographic map in the globe analogy), we can determine how the crystals or nanostructures are oriented in 3D.”
The scattered intensity “projection” of the x-y scan revealed a clear lamellar structure of oriented material, interlaced with disordered regions. According to Tilman Grunewald, the study’s other first author and a former ESRF scientist, “it’s a bit too early” to explain why the orientation of the hydroxylapatite nanocrystals is sometimes disordered, but the data nevertheless provides a focus for later research. “Essentially, our approach provides a new way of looking into the underlying structure of bone,” he says.
Synchrotron advances
Manfred Burghammer, the study’s co-leader and the scientist in charge of the ESRF’s ID13 beamline where the measurements were made, says that this new approach was made possible by “drastic progress” that is currently being made in X-ray synchrotrons. “We are expecting that the current upgrades of synchrotron sources will increase our power immensely in the next years,” he adds.
The team now plan to use their method to analyse bone material from patients with diseases such as osteoporosis and other disorders associated with age-related changes in bone structure, which can impair the bone’s mechanical properties. They also hope to study types of bone microstructure other than the one analysed in this work.
“Finally, we wish to understand the origin of the localized differences in orientation between nanostructure and crystals that we have observed,” Birkedal tells Physics World. “This will likely require improving the resolution of our technique by using smaller X-ray beams.”
Full details of the technique are reported in Science Advances.


physicsworld--2020-07-17--The virtual conference: thoughts from a first time ‘attendee’ - Physics World

This time last year I had just returned from the AAPM Annual Meeting in San Antonio , Texas , full of enthusiasm for the great talks I ’ d heard , old friends I ’ d caught up with , and all the new medical physics I ’ d learned .
I was also somewhat exhausted by the scorching temperatures in Texas and the long-haul flight home .
In 2020 , however , things are inevitably very different .
This year ’ s American Association for Physicists in Medicine ( AAPM ) Annual Meeting , held jointly with the Canadian @ @ @ @ @ @ @ , was meant to take place this week in Vancouver .
But due to the coronavirus pandemic , the organizers decided to turn the entire event virtual .
Despite missing out on a trip to Canada , I nevertheless “ attended ” this year ’ s meeting .
As well as hearing about some of the latest scientific developments , I was also keen to find out how a virtual conference could actually work .
The 2020 Joint AAPM|COMP Virtual Meeting incorporated the presentations that would have been given in Vancouver into five @ @ @ @ @ @ @ recorded their scientific presentations in advance , and these were then played during the scheduled session over a live Zoom call .
The presenters were also present at their respective sessions , to answer any questions from the audience after their recordings finished .
The first talk that I listened to had a few teething troubles , with some erroneous ghostly chat playing out over the recorded presentation .
But overall , and considering the immense technical task involved , all ran pretty smoothly on the technology side .
One major advantage of @ @ @ @ @ @ @ s no tie to any particular time zone .
After their scheduled slots , all of the scientific sessions are available to watch on-demand for six weeks after the meeting .
Indeed , being in Central European Summer Time , some six hours ahead of the conference ’ s Eastern Time-scheduled agenda , I watched all of the talks on catch-up the next day .
While this felt a little disconnected from the live event , it was great to be able to choose exactly which sessions I wanted to hear , and @ @ @ @ @ @ @ those disappointing timetable clashes that are inevitable at this type of large event .
Alongside , this virtual format opens up meeting attendance to many attendees who , for geographical , financial or other constraints , may not otherwise been able to attend .
Looking at the map of delegates that the organizers had created revealed that this truly was a global event .
And also perhaps more of a family-friendly event than in previous years .
Judging by the photos that I saw on Twitter , of delegates watching the conference talks @ @ @ @ @ @ @ flatmates and cats ( lots of cats ) , the ability to take part whenever , from wherever , is certainly a big bonus to many .
As one attendee Tweeted : “ I miss seeing colleagues in person , but as a new parent I definitely appreciate the benefits of a virtual # AAPMCOMP2020 !
” Of course , online attendance does come with issues of its own .
“ Overall , I ’ ve found it harder to focus during the virtual meeting relative to an in-person meeting , ” Catherine @ @ @ @ @ @ @ University of Wisconsin-Madison , told me .
“ Someone on Twitter mentioned that the amount of screen time you ’ re exposed to during a virtual conference makes it a challenge , while another person said that what makes a virtual conference tiring is sitting in the same place for long periods .
I definitely agree with both comments.
” Another obvious downside to the meeting going virtual is the lack of social contact .
Whether reconnecting with old friends and colleagues , or random meetings with strangers who may turn into new @ @ @ @ @ @ @ without the evening social events , the crowded coffee breaks , and the opportunity to simply bump into people wandering around the show , such interactions are beyond reach in this new regime .
The organizers definitely tried to address these shortfalls , for example by including “ social hour discussions ” in the agenda , running various Twitter-based competitions and introducing an app-based fitness challenge to replace the traditional 5K race that ’ s run each year .
A personal favourite of mine was the “ Medical Physics Family Storytime ” held @ @ @ @ @ @ @ “ fellow medical physicists share STEM-centric books for children of all ages ” .
Overall , as a delegate , I experienced both benefits and downsides to the virtual conference .
As a journalist , there are pros and cons too .
While it ’ s great to be able to pause a recorded presentation to take notes , it ’ s also impossible to catch a speaker after their talk to ask a quick question or take an on-site photo to use in a future article .
While the conference has now @ @ @ @ @ @ @ that I ’ d like to listen to .
And with six weeks to catch up on the content , my main problem may be knowing when to stop .
• Hear more of my thoughts on the 2020 Joint AAPM|COMP Virtual Meeting in this week ’ s Physics World Weekly podcast .

Attending a virtual conference allows you to pick and choose what presentations to listen to and when, but lacks the face-to-face contact of an on-site event. (Courtesy: iStock/metamorworks)
This time last year I had just returned from the AAPM Annual Meeting in San Antonio, Texas, full of enthusiasm for the great talks I’d heard, old friends I’d caught up with, and all the new medical physics I’d learned. I was also somewhat exhausted by the scorching temperatures in Texas and the long-haul flight home. In 2020, however, things are inevitably very different.
This year’s American Association for Physicists in Medicine (AAPM) Annual Meeting, held jointly with the Canadian Organization of Medical Physicists (COMP), was meant to take place this week in Vancouver. But due to the coronavirus pandemic, the organizers decided to turn the entire event virtual. Despite missing out on a trip to Canada, I nevertheless “attended” this year’s meeting. As well as hearing about some of the latest scientific developments, I was also keen to find out how a virtual conference could actually work.
The 2020 Joint AAPM|COMP Virtual Meeting incorporated the presentations that would have been given in Vancouver into five days of online sessions. Speakers had recorded their scientific presentations in advance, and these were then played during the scheduled session over a live Zoom call. The presenters were also present at their respective sessions, to answer any questions from the audience after their recordings finished. The first talk that I listened to had a few teething troubles, with some erroneous ghostly chat playing out over the recorded presentation. But overall, and considering the immense technical task involved, all ran pretty smoothly on the technology side.
One major advantage of a virtual conference is that there’s no tie to any particular time zone. After their scheduled slots, all of the scientific sessions are available to watch on-demand for six weeks after the meeting. Indeed, being in Central European Summer Time, some six hours ahead of the conference’s Eastern Time-scheduled agenda, I watched all of the talks on catch-up the next day. While this felt a little disconnected from the live event, it was great to be able to choose exactly which sessions I wanted to hear, and when to listen – with none of those disappointing timetable clashes that are inevitable at this type of large event.
Alongside, this virtual format opens up meeting attendance to many attendees who, for geographical, financial or other constraints, may not otherwise been able to attend. Looking at the map of delegates that the organizers had created revealed that this truly was a global event. And also perhaps more of a family-friendly event than in previous years. Judging by the photos that I saw on Twitter, of delegates watching the conference talks accompanied by their children, babies, flatmates and cats (lots of cats), the ability to take part whenever, from wherever, is certainly a big bonus to many. As one attendee Tweeted: “I miss seeing colleagues in person, but as a new parent I definitely appreciate the benefits of a virtual #AAPMCOMP2020!”
Of course, online attendance does come with issues of its own. “Overall, I’ve found it harder to focus during the virtual meeting relative to an in-person meeting,” Catherine Steffel, a PhD student at the University of Wisconsin-Madison, told me. “Someone on Twitter mentioned that the amount of screen time you’re exposed to during a virtual conference makes it a challenge, while another person said that what makes a virtual conference tiring is sitting in the same place for long periods. I definitely agree with both comments.”
Another obvious downside to the meeting going virtual is the lack of social contact. Whether reconnecting with old friends and colleagues, or random meetings with strangers who may turn into new collaborators or contacts for future research – without the evening social events, the crowded coffee breaks, and the opportunity to simply bump into people wandering around the show, such interactions are beyond reach in this new regime.
The organizers definitely tried to address these shortfalls, for example by including “social hour discussions” in the agenda, running various Twitter-based competitions and introducing an app-based fitness challenge to replace the traditional 5K race that’s run each year. A personal favourite of mine was the “Medical Physics Family Storytime” held on the first evening, in which “fellow medical physicists share STEM-centric books for children of all ages”.
Overall, as a delegate, I experienced both benefits and downsides to the virtual conference. As a journalist, there are pros and cons too. While it’s great to be able to pause a recorded presentation to take notes, it’s also impossible to catch a speaker after their talk to ask a quick question or take an on-site photo to use in a future article.
While the conference has now finished, there are still many presentations that I’d like to listen to. And with six weeks to catch up on the content, my main problem may be knowing when to stop.
Hear more of my thoughts on the 2020 Joint AAPM|COMP Virtual Meeting in this week’s Physics World Weekly podcast.