TY - JOUR
T1 - Quantifying intrafractional gastric motion using auto-segmentation on MRI
T2 - Deformation and respiratory-induced displacement compared
AU - Driever, Theo
AU - Hulshof, Maarten C. C. M.
AU - Bel, Arjan
AU - Sonke, Jan-Jakob
AU - van der Horst, Astrid
N1 - Funding Information: The authors like to thank Dr. Ray Sheombarsing for execution of the auto‐segmentation machine learning. This work was in part funded by the Dutch Cancer Society (KWF Kankerbestrijding; Grant No. KWF 10882). Publisher Copyright: © 2022 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, LLC on behalf of The American Association of Physicists in Medicine.
PY - 2023/4
Y1 - 2023/4
N2 - Background and purpose: For accurate pre-operative gastric radiotherapy, intrafractional changes must be taken into account. The aim of this study is to quantify local gastric deformations and compare these deformations with respiratory-induced displacement. Materials and methods: Coronal 2D MRI scans (15–16 min; 120 repetitions of 25–27 interleaved slices) were obtained for 18 healthy volunteers. A deep-learning network was used to auto-segment the stomach. To separate out respiratory-induced displacements, auto-segmentations were rigidly shifted in superior-inferior (SI) direction to align the centre of mass (CoM) within every slice. From these shifted auto-segmentations, 3D iso-probability surfaces (isosurfaces) were established: a reference surface for POcc = 0.50 and 50 other isosurfaces (from POcc = 0.01 to 0.99), with POcc indicating the probability of occupation by the stomach. For each point on the reference surface, distances to all isosurfaces were determined and a cumulative Gaussian was fitted to this probability-distance dataset to obtain a standard deviation (SDdeform) expressing local deformation. For each volunteer, we determined median and 98th percentile of SDdeform over the reference surface and compared these with the respiratory-induced displacement SDresp, that is, the SD of all CoM shifts (paired Wilcoxon signed-rank, α = 0.05). Results: Larger deformations were mostly seen in the antrum and pyloric region. Median SDdeform (range, 2.0–2.9 mm) was smaller than SDresp (2.7–8.8 mm) for each volunteer (p < 0.00001); 98th percentile of SDdeform (3.2–7.3 mm) did not significantly differ from SDresp (p = 0.13). Conclusion: Locally, gastric deformations can be large. Overall, however, these deformations are limited compared to respiratory-induced displacement. Therefore, unless respiratory motion is considerably reduced, the need to separately include these deformation uncertainties in the treatment margins may be limited.
AB - Background and purpose: For accurate pre-operative gastric radiotherapy, intrafractional changes must be taken into account. The aim of this study is to quantify local gastric deformations and compare these deformations with respiratory-induced displacement. Materials and methods: Coronal 2D MRI scans (15–16 min; 120 repetitions of 25–27 interleaved slices) were obtained for 18 healthy volunteers. A deep-learning network was used to auto-segment the stomach. To separate out respiratory-induced displacements, auto-segmentations were rigidly shifted in superior-inferior (SI) direction to align the centre of mass (CoM) within every slice. From these shifted auto-segmentations, 3D iso-probability surfaces (isosurfaces) were established: a reference surface for POcc = 0.50 and 50 other isosurfaces (from POcc = 0.01 to 0.99), with POcc indicating the probability of occupation by the stomach. For each point on the reference surface, distances to all isosurfaces were determined and a cumulative Gaussian was fitted to this probability-distance dataset to obtain a standard deviation (SDdeform) expressing local deformation. For each volunteer, we determined median and 98th percentile of SDdeform over the reference surface and compared these with the respiratory-induced displacement SDresp, that is, the SD of all CoM shifts (paired Wilcoxon signed-rank, α = 0.05). Results: Larger deformations were mostly seen in the antrum and pyloric region. Median SDdeform (range, 2.0–2.9 mm) was smaller than SDresp (2.7–8.8 mm) for each volunteer (p < 0.00001); 98th percentile of SDdeform (3.2–7.3 mm) did not significantly differ from SDresp (p = 0.13). Conclusion: Locally, gastric deformations can be large. Overall, however, these deformations are limited compared to respiratory-induced displacement. Therefore, unless respiratory motion is considerably reduced, the need to separately include these deformation uncertainties in the treatment margins may be limited.
KW - deformation
KW - gastric cancer
KW - intrafractional motion
KW - radiotherapy
UR - http://www.scopus.com/inward/record.url?scp=85145038658&partnerID=8YFLogxK
U2 - https://doi.org/10.1002/acm2.13864
DO - https://doi.org/10.1002/acm2.13864
M3 - Article
C2 - 36565168
SN - 1526-9914
VL - 24
JO - Journal of applied clinical medical physics / American College of Medical Physics
JF - Journal of applied clinical medical physics / American College of Medical Physics
IS - 4
M1 - e13864
ER -