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Evaluation of Patient Setup Using Catalyst Surface Mapping Technique

D Cao

D Cao*, X Xie, V Mehta, D Shepard, Swedish Cancer Institute, Seattle, WA

SU-E-J-52 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: In this study, we evaluated the accuracy and clinical effectiveness of a novel surface mapping system utilizing deformable image registration. Comparisons were made between the shifts determined using conebeam CT (CBCT) and those calculated using the surface mapping tool, the C-RAD Catalyst.

Materials and Methods: For the CBCT and surface mapping comparisons, a turkey was used as a patient surrogate. A reference CT scan was first taken when the turkey was frozen (non-deformable). Initial setups were made using the Catalyst system for each of two locations (spine and left breast). A CBCT scan was performed immediately after each Catalyst setup. The three dimensional shifts and rotations along three axes were recorded for comparison purposes. Setups were made using both the frozen (non-deformable) and unfrozen (deformable) turkey.

Results: When the turkey was frozen, surface mapping and CBCT setups agreed within 2mm. A 2-degree rotation along longitudinal axis detected by the Catalyst system was confirmed with CBCT based alignment. For tests performed after the turkey was defrosted, differences of up to 10mm were observed in the vertical positioning when comparing setups performed using surface mapping and CBCT. The left breast site setup using Catalyst agreed closely with the CBCT data even when significant body deformation was introduced. The rotations obtained from Catalyst and CBCT data agreed within 2 degrees for both treatment sites with body deformation.

Conclusions: As a surface mapping technology, the C-RAD Catalyst system can provide accurate and efficient patient setup when there is no significant body deformation. Caution must be exercised, however, in using this tool in cases where significant deformation may occur particularly when the isocenter is significantly displaced from the detected patient surface.

Funding Support, Disclosures, and Conflict of Interest: Research was partially funded by Elekta

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