BACKGROUND AND PURPOSE: This study analyses the dosimetric and dose averaged 
Linear Energy transfer (LETd) correlation in paediatric craniopharyngioma (CP) 
patients with and without radiation-induced cerebral vasculopathies (RICVs) 
treated with pencil beam scanning (PBS) proton therapy (PT).
MATERIAL AND METHODS: We reviewed a series of 16 CP patients treated with PT to 
a median dose of 54 Gy(RBE). Two (12.5%) index patients presented RICVs 14 and 
24 months (median, 19) after PT. Organs at risks (OARs) as bilateral internal 
carotid arteries (ICAs) and circle of Willis were contoured based on CTs and 
MRIs pre- and post-PT. Dosimetry was reviewed and LETd distributions were 
calculated; LETd metric for PTVs and OARs were analysed. For a sub-cohort, 
dosimetric and LETd values robustness due to range uncertainties were computed.
RESULTS: For the two index patients, no correlation was observed between RICVs 
and OARs doses. However for those patients mean(maximum) LETd values in the 
affected OARs were up to 4.0 ± 0.4 (7.8 ± 0.1)keV/μm; those LETd values were 
significantly higher (p = 0.02) than the mean(maximum) LETd values for the rest 
of the cohort (mean: 3.1 ± 0.3, maximum: 4.8 ± 1.0 keV/μm). This was due to 
asymmetric field arrangement, thus resulting in marked asymmetric LETd 
distributions. For such arrangement, maximum LETd values variations in vascular 
structures due to range uncertainties were up to 1.2 keV/μm, whilst for the 
symmetric one they were up to 0.7 keV/μm.
CONCLUSIONS: For children with and without RICVs, quantitative analysis showed a 
significant correlation with LETd average/maximum values in vascular structures, 
whilst no correlation was found on dosimetric parameters.