Abstract
Delivery of breath-hold MR-guided SABR is time-consuming, and the use of real-time tumor-tracking in a sagittal plane may fail to detect out-of-plane displacements of organs-at-risk. Analysis of daily MR-scans performed pre- and post-SABR revealed frequent decreases in stomach volumes, and in the planned stomach doses.
Highlights
Material and methodsA pooled meta-analysis and systematic review of the outcomes of stereotactic ablative radiotherapy (SABR) for adrenal metastases revealed good 1-year local control rates, and low rates of toxicity [1]
The current study evaluates changes in the stomach volume and position arising after the initial on-table planning MRscans, and we studied the dosimetric impact of such changes
Changes in on-table stomach anatomy were studied on 3D-MR scans acquired in 70 pre-and post-treatment datasets derived from twenty patients, and pre-treatment scans were compared to post-treatment breath-hold scans
Summary
A pooled meta-analysis and systematic review of the outcomes of stereotactic ablative radiotherapy (SABR) for adrenal metastases revealed good 1-year local control rates, and low rates of toxicity [1]. After rigid registration of the GTV from the baseline MR-scan on the pre-treatment planning MR scan, OAR contours are propagated to this MR-of-the-day using deformable image registration. After SABR delivery, a repeat 3D MR scan was acquired, except for patients undergoing their final fraction This retrospective offline analysis was approved by the institutional ethics committee. Changes in on-table stomach anatomy were studied on 3D-MR scans acquired in 70 pre-and post-treatment datasets derived from twenty patients, and pre-treatment scans were compared to post-treatment breath-hold scans. Changes in stomach anatomy were evaluated in all available scans by matching post-treatment MR-scans manually to pretreatment MR-scan on the GTV, including both translations and rotations on the three planes. MR-scans that were derived from patients who exhibited reproducible breath-holds were studied for dosimetric changes, in order to minimize bias arising from variations in breath-hold positions on pre- and post-treatment MR-scans. A p-value threshold of 0.05 was used to indicate statistical significance
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