Program Information
Non-Contiguous MVCT Scanning for CSI Patient Set-Up Registration
G Baran1*, M Dominello2 , H Beydoun2, J Burmeister1 , (1) Karmanos Cancer Institute, Detroit, MI (2) Wayne State University School of Medicine, Detroit, MI
Presentations
MO-L-GePD-J(A)-6 (Monday, July 31, 2017) 1:15 PM - 1:45 PM Room: Joint Imaging-Therapy ePoster Lounge - A
Purpose: Using 6mm slice thickness, full length registration scans take 5-12 minutes depending on PTV length. CSI patients are often pediatric and unable to remain still for long periods of time. We retrospectively demonstrate the feasibility of using minimal slice number, non-contiguous, MVCT data sets to accurately register patients for cranio-spinal irradiation (CSI) and compare this method to a full PTV scan.
Methods: MVCT scans for 10 patients previously treated with CSI on Tomotherapy (Accuray, Sunnyvale, CA) were used for retrospective registration via bony anatomy match with the planning CT at three anatomical levels: base of skull, thoracic spine, and lumbar spine, using 10 slices with 6mm slice thickness for each level. Patients were immobilized with a head and shoulder mask and mid to lower body vac-lock cradle. Clinically, near-full PTV length MVCT scans ranging from 78-144cm had been acquired and used for pre-treatment image guidance. The three anatomical level registrations and their average are compared amongst each other and the clinical baseline (near-full PTV scan) to evaluate the potential use of non-contiguous MVCT imaging for set-up verification.
Results: Non-contiguous MVCT protocol at three anatomical levels using 10 slices each reduced imaging time to 3-5 minutes. Registrations at the level of the lumbar spine showed the greatest variation with respect to clinical baseline with 50% of required translational shifts >3mm, compared to 7% and 10% for base of skull and thoracic spine, respectively. The average 3D displacement vector between baseline and the average result for the entire 3 level registration (2.09 ± 1.11mm) is comparable to the uncertainty involved in repeated registrations using the full PTV method (2.17 ± 1.16mm).
Conclusion: The use of a three-level, non-contiguous MVCT data set provides CSI registration comparable to full-PTV MVCT registration.
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