TY - JOUR
T1 - Dual-energy computed tomography proton-dose calculation with scripting and modified hounsfield units
AU - Kassaee, Anthony
AU - Cheng, Chingyun
AU - Yin, Lingshu
AU - Zou, Wei
AU - Li, Taoran
AU - Lin, Alexander
AU - Swisher-McClure, Samuel
AU - Lukens, John N.
AU - Lustig, Robert A.
AU - O'Reilly, Shannon
AU - Dong, Lei
AU - Hytonen, Roni
AU - Teo, Boon Keng Kevin
N1 - Funding Information:
Conflicts of Interest: Lei Dong, PhD, is an Associate Editor of the International Journal of Particle Therapy. This work was partially funded by Varian Medical Systems. The authors have no additional conflicts of interest to disclose. Acknowledgment: Space for work and resources were provided by the University of Pennsylvania. Ethical approval: All patient data were collected under University of Pennsylvania institutional review board–approved protocol.
Publisher Copyright:
© Copyright 2021 The Author(s).
PY - 2021/6/1
Y1 - 2021/6/1
N2 - Purpose: To describe an implementation of dual-energy computed tomography (DECT) for calculation of proton stopping-power ratios (SPRs) in a commercial treatmentplanning system. The process for validation and the workflow for safe deployment of DECT is described, using single-energy computed tomography (SECT) as a safety check for DECT dose calculation. Materials and Methods: The DECT images were acquired at 80 kVp and 140 kVp and were processed with computed tomography scanner software to derive the electron density and effective atomic number images. Reference SPRs of tissue-equivalent plugs from Gammex (Middleton, Wisconsin) and CIRS (Computerized Imaging Reference Systems, Norfolk, Virginia) electron density phantoms were used for validation and comparison of SECT versus DECT calculated through the Eclipse treatment planning system (Varian Medical Systems, Palo Alto, California) application programming interface scripting tool. An in-house software was also used to create DECT SPR computed tomography images for comparison with the script output. In the workflow, using the Eclipse system application programming interface script, clinical plans were optimized with the SECT image set and then forward-calculated with the DECT SPR for the final dose distribution. In a second workflow, the plans were optimized using DECT SPR with reduced range-uncertainty margins. Results: For the Gammex phantom, the root mean square error in SPR was 1.08% for DECT versus 2.29% for SECT for 10 tissue-surrogates, excluding the lung. For the CIRS Phantom, the corresponding results were 0.74% and 2.27%. When evaluating the head and neck plan, DECT optimization with 2% range-uncertainty margins achieved a small reduction in organ-at-risk doses compared with that of SECT plans with 3.5% rangeuncertainty margins. For the liver case, DECT was used to identify and correct the lipiodol SPR in the SECT plan. Conclusion: It is feasible to use DECT for proton-dose calculation in a commercial treatment planning system in a safe manner. The range margins can be reduced to 2% in some sites, including the head and neck.
AB - Purpose: To describe an implementation of dual-energy computed tomography (DECT) for calculation of proton stopping-power ratios (SPRs) in a commercial treatmentplanning system. The process for validation and the workflow for safe deployment of DECT is described, using single-energy computed tomography (SECT) as a safety check for DECT dose calculation. Materials and Methods: The DECT images were acquired at 80 kVp and 140 kVp and were processed with computed tomography scanner software to derive the electron density and effective atomic number images. Reference SPRs of tissue-equivalent plugs from Gammex (Middleton, Wisconsin) and CIRS (Computerized Imaging Reference Systems, Norfolk, Virginia) electron density phantoms were used for validation and comparison of SECT versus DECT calculated through the Eclipse treatment planning system (Varian Medical Systems, Palo Alto, California) application programming interface scripting tool. An in-house software was also used to create DECT SPR computed tomography images for comparison with the script output. In the workflow, using the Eclipse system application programming interface script, clinical plans were optimized with the SECT image set and then forward-calculated with the DECT SPR for the final dose distribution. In a second workflow, the plans were optimized using DECT SPR with reduced range-uncertainty margins. Results: For the Gammex phantom, the root mean square error in SPR was 1.08% for DECT versus 2.29% for SECT for 10 tissue-surrogates, excluding the lung. For the CIRS Phantom, the corresponding results were 0.74% and 2.27%. When evaluating the head and neck plan, DECT optimization with 2% range-uncertainty margins achieved a small reduction in organ-at-risk doses compared with that of SECT plans with 3.5% rangeuncertainty margins. For the liver case, DECT was used to identify and correct the lipiodol SPR in the SECT plan. Conclusion: It is feasible to use DECT for proton-dose calculation in a commercial treatment planning system in a safe manner. The range margins can be reduced to 2% in some sites, including the head and neck.
KW - Dual-energy CT
KW - Proton therapy
KW - Stopping-power ratios
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U2 - 10.14338/IJPT-20-00075.1
DO - 10.14338/IJPT-20-00075.1
M3 - Article
AN - SCOPUS:85115779193
SN - 2331-5180
VL - 8
SP - 62
EP - 72
JO - International Journal of Particle Therapy
JF - International Journal of Particle Therapy
IS - 1
ER -