Premium
Patient specific optimization of the relation between CT‐Hounsfield units and proton stopping power with proton radiography
Author(s) -
Schneider Uwe,
Pemler Peter,
Besserer Jürgen,
Pedroni Eros,
Lomax Antony,
KaserHotz Barbara
Publication year - 2005
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1833041
Subject(s) - hounsfield scale , calibration , calibration curve , stopping power , proton , nuclear medicine , proton therapy , dosimetry , radiography , materials science , mathematics , computed tomography , medicine , physics , optics , statistics , radiology , nuclear physics , detection limit , detector
The purpose of this work is to show the feasibility of using in vivo proton radiography of a radiotherapy patient for the patient individual optimization of the calibration from CT‐Hounsfield units to relative proton stopping power. Water equivalent tissue (WET) calibrated proton radiographs of a dog patient treated for a nasal tumor were used as baseline in comparison with integrated proton stopping power through the calibrated CT of the dog. In an optimization procedure starting with a stoichiometric calibration curve, the calibration was modified randomly. The result of this iteration is an optimized calibration curve which was used to recalculate the dose distribution of the patient. One result of this experiment was that the mean value of the deviations between WET calculations based on the stoichiometric calibration curve and the measurements was shifted systematically away from zero. The calibration produced by the optimization procedure reduced this shift to around0.4 mm . Another result was that the precision of the calibration, reflected as the standard deviation of the normally distributed deviations between WET calculation and measurement, could be reduced from 7.9 to6.7 mmwith the optimized calibration. The dose distributions based on the two calibration curves showed major deviations at the distal end of the target volume.