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Technical Note: Relative proton stopping power estimation from virtual monoenergetic images reconstructed from dual‐layer computed tomography
Author(s) -
Landry Guillaume,
Dörringer Fabian,
SiMohamed Salim,
Douek Philippe,
Abascal Juan F. P. J.,
Peyrin Françoise,
Almeida Isabel P.,
Verhaegen Frank,
Rinaldi Ilaria,
Parodi Katia,
Rit Simon
Publication year - 2019
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 - 10.1002/mp.13404
Subject(s) - digital enhanced cordless telecommunications , mean squared error , scanner , imaging phantom , stopping power , nuclear medicine , hounsfield scale , proton therapy , cone beam computed tomography , approximation error , mathematics , tomography , detector , computed tomography , physics , optics , algorithm , beam (structure) , medicine , computer science , statistics , radiology , telecommunications , wireless
Purpose The objective of this technical note was to investigate the accuracy of proton stopping power relative to water ( RSP ) estimation using a novel dual‐layer, dual‐energy computed tomography ( DL ‐ DECT ) scanner for potential use in proton therapy planning. DL ‐ DECT allows dual‐energy reconstruction from scans acquired at a single x‐ray tube voltage V by using two‐layered detectors. Methods Sets of calibration and evaluation inserts were scanned at a DL ‐ DECT scanner in a custom phantom with variable diameter D (0 to 150 mm) at V of 120 and 140 kV . Inserts were additionally scanned at a synchrotron computed tomography facility to obtain comparative linear attenuation coefficients for energies from 50 to 100 keV, and reference RSP was obtained using a carbon ion beam and variable water column. DL ‐ DECT monoenergetic (mono‐E) reconstructions were employed to obtain RSP by adapting the Yang–Saito–Landry ( YSL ) method. The method was compared to reference RSP via the root mean square error ( RMSE ) over insert mean values obtained from volumetric regions of interest. The accuracy of intermediate quantities such as the relative electron density ( RED ), effective atomic number ( EAN ), and the mono‐E was additionally evaluated. Results The lung inserts showed higher errors for all quantities and we report RMSE excluding them. RMSE for μ from DL ‐ DECT mono‐E was below 1.9%. For the evaluation inserts at D = 150 mm and V = 140 kV , RED RMSE was 1.0%, while for EAN it was 2.9%. RSP RMSE was below 0.8% for all D and V, which did not strongly affect the results. Conclusions In this investigation of RSP accuracy from DL ‐ DECT , we have shown that RMSE below 1% can be achieved. It was possible to adapt the YSL method for DL ‐ DECT and intermediate quantities RED and EAN had comparable accuracy to previous publications.