TY - JOUR
T1 - MRI geometric distortion
T2 - Impact on tangential whole-breast IMRT
AU - Walker, Amy
AU - Metcalfe, Peter
AU - Liney, Gary
AU - Batumalai, Vikneswary
AU - Dundas, Kylie
AU - Glide-Hurst, Carri
AU - Delaney, Geoff P.
AU - Boxer, Miriam
AU - Yap, Mei Ling
AU - Dowling, Jason
AU - Rivest-Henault, David
AU - Pogson, Elise
AU - Holloway, Lois
N1 - Funding Information:
The authors would like to thank Robba Rai and Ewa Juresic for their knowledge and assistance with the scanning of the phantom on the 3T; Haijie Jin's work on the breast planning script; Shekar Chandra for software help for image visualization; Dean Cutajar for setup assistance for computer systems and software; and the department of radiation oncology, Henry Ford Health System, for scanning and supplying phantom data for this study. The authors would like to acknowledge funding assistance from Cancer Australia and The National Breast Cancer Foundation project grant number 1033237, Liverpool and Macarthur Cancer Therapy Centres trust fund scholarship (AW), 1 R01 CA204189-01A1 (CGH) and the NSW Cancer Institute Leaders Program (PM).
Publisher Copyright:
© Creative Commons Attribution 3.0 Unported License.
PY - 2016
Y1 - 2016
N2 - The purpose of this study was to determine the impact of magnetic resonance imaging (MRI) geometric distortions when using MRI for target delineation and planning for whole-breast, intensity-modulated radiotherapy (IMRT). Residual system distortions and combined systematic and patient-induced distortions are considered. This retrospective study investigated 18 patients who underwent whole-breast external beam radiotherapy, where both CT and MRIs were acquired for treatment planning. Distortion phantoms were imaged on two MRI systems, dedicated to radiotherapy planning (a wide, closed-bore 3T and an open-bore 1T). Patient scans were acquired on the 3T system. To simulate MRI-based planning, distortion maps representing residual system distortions were generated via deformable registration between phantom CT and MRIs. Patient CT images and structures were altered to match the residual system distortion measured by the phantoms on each scanner. The patient CTs were also registered to the corresponding patient MRI scans, to assess patient and residual system effects. Tangential IMRT plans were generated and optimized on each resulting CT dataset, then propagated to the original patient CT space. The resulting dose distributions were then evaluated with respect to the standard clinically acceptable DVH and visual assessment criteria. Maximum residual systematic distortion was measured to be 7.9 mm (95% < 4.7 mm) and 11.9 mm (95% < 4.6 mm) for the 3T and 1T scanners, respectively, which did not result in clinically unacceptable plans. Eight of the plans accounting for patient and systematic distortions were deemed clinically unacceptable when assessed on the original CT. For these plans, the mean difference in PTV V95 (volume receiving 95% prescription dose) was 0.13 ± 2.51% and -0.73 ± 1.93% for right- and left-sided patients, respectively. Residual system distortions alone had minimal impact on the dosimetry for the two scanners investigated. The combination of MRI systematic and patient-related distortions can result in unacceptable dosimetry for whole-breast IMRT, a potential issue when considering MRI-only radiotherapy treatment planning.
AB - The purpose of this study was to determine the impact of magnetic resonance imaging (MRI) geometric distortions when using MRI for target delineation and planning for whole-breast, intensity-modulated radiotherapy (IMRT). Residual system distortions and combined systematic and patient-induced distortions are considered. This retrospective study investigated 18 patients who underwent whole-breast external beam radiotherapy, where both CT and MRIs were acquired for treatment planning. Distortion phantoms were imaged on two MRI systems, dedicated to radiotherapy planning (a wide, closed-bore 3T and an open-bore 1T). Patient scans were acquired on the 3T system. To simulate MRI-based planning, distortion maps representing residual system distortions were generated via deformable registration between phantom CT and MRIs. Patient CT images and structures were altered to match the residual system distortion measured by the phantoms on each scanner. The patient CTs were also registered to the corresponding patient MRI scans, to assess patient and residual system effects. Tangential IMRT plans were generated and optimized on each resulting CT dataset, then propagated to the original patient CT space. The resulting dose distributions were then evaluated with respect to the standard clinically acceptable DVH and visual assessment criteria. Maximum residual systematic distortion was measured to be 7.9 mm (95% < 4.7 mm) and 11.9 mm (95% < 4.6 mm) for the 3T and 1T scanners, respectively, which did not result in clinically unacceptable plans. Eight of the plans accounting for patient and systematic distortions were deemed clinically unacceptable when assessed on the original CT. For these plans, the mean difference in PTV V95 (volume receiving 95% prescription dose) was 0.13 ± 2.51% and -0.73 ± 1.93% for right- and left-sided patients, respectively. Residual system distortions alone had minimal impact on the dosimetry for the two scanners investigated. The combination of MRI systematic and patient-related distortions can result in unacceptable dosimetry for whole-breast IMRT, a potential issue when considering MRI-only radiotherapy treatment planning.
KW - Breast IMRT
KW - Geometric distortion
KW - Magnetic resonance imaging
UR - http://www.scopus.com/inward/record.url?scp=84995688308&partnerID=8YFLogxK
U2 - 10.1120/jacmp.v17i5.6242
DO - 10.1120/jacmp.v17i5.6242
M3 - Article
C2 - 28297426
AN - SCOPUS:84995688308
SN - 1526-9914
VL - 17
SP - 7
EP - 19
JO - Journal of Applied Clinical Medical Physics
JF - Journal of Applied Clinical Medical Physics
IS - 5
ER -