TY - JOUR
T1 - Synthetic CT for single-fraction neoadjuvant partial breast irradiation on an MRI-linac
AU - Groot Koerkamp, Maureen L
AU - de Hond, Yvonne J M
AU - Maspero, Matteo
AU - Kontaxis, Charis
AU - Mandija, Stefano
AU - Vasmel, Jeanine E
AU - Charaghvandi, Ramona K
AU - Philippens, Marielle E P
AU - van Asselen, Bram
AU - van den Bongard, H J G Desirée
AU - Hackett, Sara S
AU - Houweling, Antonetta Christina
N1 - Publisher Copyright:
© 2021 Institute of Physics and Engineering in Medicine.
Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
Publisher Copyright:
© 2021 Institute of Physics and Engineering in Medicine.
PY - 2021/4/21
Y1 - 2021/4/21
N2 - A synthetic computed tomography (sCT) is required for daily plan optimization on an MRI-linac. Yet, only limited information is available on the accuracy of dose calculations on sCT for breast radiotherapy. This work aimed to 1) evaluate dosimetric accuracy of treatment plans for single-fraction neoadjuvant partial breast irradiation (PBI) on a 1.5T MRI-linac calculated on a) bulk-density sCT mimicking the current MRI-linac workflow and b) deep learning-generated sCT, and 2) investigate the number of bulk-density levels required. For ten breast cancer patients we created three bulk-density sCTs of increasing complexity from the planning-CT, using bulk-density for: 1) body, lungs, and GTV (sCTBD1); 2) volumes for sCTBD1plus chest wall and ipsilateral breast (sCTBD2); 3) volumes for sCTBD2plus ribs (sCTBD3); and a deep learning-generated sCT (sCTDL) from a 1.5T MRI in supine position. Single-fraction neoadjuvant PBI treatment plans for a 1.5T MRI-linac were optimized on each sCT and recalculated on the planning-CT. Image evaluation was performed by assessing mean absolute error (MAE) and mean error (ME) in Hounsfield Units (HU) between the sCTs and the planning-CT. Dosimetric evaluation was performed by assessing dose differences, gamma pass rates, and dose-volume histogram (DVH) differences. The following results were obtained (median across patients for sCTBD1/sCTBD2/sCTBD3/sCTDLrespectively): MAE inside the body contour was 106/104/104/75 HU and ME was 8/9/6/28 HU, mean dose difference in the PTVGTV was 0.15/0.00/0.00/-0.07 Gy, median gamma pass rate (2%/2mm, 10% dose threshold) was 98.9/98.9/98.7/99.4%, and differences in DVH parameters were well below 2% for all structures except for the skin in the sCTDL. Accurate dose calculations for single-fraction neoadjuvant PBI on an MRI-linac could be performed on both bulk-density and deep learning sCT, facilitating further implementation of MRI-guided radiotherapy for breast cancer. Balancing simplicity and accuracy, sCTBD2 showed the optimal number of bulk-density levels for a bulk-density approach.
AB - A synthetic computed tomography (sCT) is required for daily plan optimization on an MRI-linac. Yet, only limited information is available on the accuracy of dose calculations on sCT for breast radiotherapy. This work aimed to 1) evaluate dosimetric accuracy of treatment plans for single-fraction neoadjuvant partial breast irradiation (PBI) on a 1.5T MRI-linac calculated on a) bulk-density sCT mimicking the current MRI-linac workflow and b) deep learning-generated sCT, and 2) investigate the number of bulk-density levels required. For ten breast cancer patients we created three bulk-density sCTs of increasing complexity from the planning-CT, using bulk-density for: 1) body, lungs, and GTV (sCTBD1); 2) volumes for sCTBD1plus chest wall and ipsilateral breast (sCTBD2); 3) volumes for sCTBD2plus ribs (sCTBD3); and a deep learning-generated sCT (sCTDL) from a 1.5T MRI in supine position. Single-fraction neoadjuvant PBI treatment plans for a 1.5T MRI-linac were optimized on each sCT and recalculated on the planning-CT. Image evaluation was performed by assessing mean absolute error (MAE) and mean error (ME) in Hounsfield Units (HU) between the sCTs and the planning-CT. Dosimetric evaluation was performed by assessing dose differences, gamma pass rates, and dose-volume histogram (DVH) differences. The following results were obtained (median across patients for sCTBD1/sCTBD2/sCTBD3/sCTDLrespectively): MAE inside the body contour was 106/104/104/75 HU and ME was 8/9/6/28 HU, mean dose difference in the PTVGTV was 0.15/0.00/0.00/-0.07 Gy, median gamma pass rate (2%/2mm, 10% dose threshold) was 98.9/98.9/98.7/99.4%, and differences in DVH parameters were well below 2% for all structures except for the skin in the sCTDL. Accurate dose calculations for single-fraction neoadjuvant PBI on an MRI-linac could be performed on both bulk-density and deep learning sCT, facilitating further implementation of MRI-guided radiotherapy for breast cancer. Balancing simplicity and accuracy, sCTBD2 showed the optimal number of bulk-density levels for a bulk-density approach.
KW - convolutional networks
KW - MRI-linac
KW - MRI-only radiotherapy
KW - partial breast irradiation
KW - pseudo-CT
UR - http://www.scopus.com/inward/record.url?scp=85105092819&partnerID=8YFLogxK
U2 - 10.1088/1361-6560/abf1ba
DO - 10.1088/1361-6560/abf1ba
M3 - Article
C2 - 33761491
SN - 0031-9155
VL - 66
JO - Physics in medicine and biology
JF - Physics in medicine and biology
IS - 8
M1 - 085010
ER -