Author: Ahmed A. Eldib, Teh Lin, Chang Ming Charlie Ma 👨🔬
Affiliation: Fox Chase Cancer Center 🌍
Purpose: Surface imaging has been used clinically more regularly. The accuracy of several commercial products has been studied. AAPM TG302 also has proposed the system quality assurance and commissioning programs. However, there is no study reporting the differences observed clinically between the different systems. This study is to report on the detection differences between VisionRT AlignRT(Vision RT,London,UK) and Varian Identify(Varian Medical Systems,Palo Alto,CA) and to propose the advantages on each system with respect to monitoring different treatment sites.
Methods: A mannequin from neck to pelvis was scanned in CT with 3 different isocenters delineated, Neck, Breast and Pelvis areas. Surface contours are imported to both AlignRT and Identify with the same isocenters. Fixed displacements have been introduced to the systems, i.e.,+/- 1cm,+/-2cm and combined on 3 translational directions. The real-time patient displacements from both systems are compared. We also investigated the shape of the region of interests on both systems. 5 patients treatment sessions from each system are compared with respect of the CBCT localization.
Results: In general, AlignRT underestimated the phantom displacements up to 14%. The largest discrepancy happened in the neck area while Identify shows a better prediction to an up to 7% underestimation. At breast area, 2 systems show comparable underestimation; however, AlignRT allows users to draw an individual side of breast, Identify requires the users draw larger area including contralateral breast with sternum. At Pelvis area, AlignRT shows up to 7.5% underestimation especially when all 3 directions have 2cm displacements while Identify reports up to 6% underestimation. For patient treatments, pelvis patients show ~1.5mm agreement between CBCT and both systems. For breast treatments, both systems reflect the CBCT shifts within 1mm discrepancy.
Conclusion: Both systems show reliability at patient treatment sessions. AlignRT reports underestimated surface displacements but has better choices of ROI lineation than Identify.