The Ohio State University James Cancer Hospital Columbus, Ohio
R. S. Handschuh, D. J. DiCostanzo, M. Ramani, N. Gupta, and A. Cetnar; The Ohio State University, Columbus, OH
Purpose/Objective(s): High-performance imaging (HPI) cone beam computed tomography (CBCT) on a c-arm linear accelerator (linac), now a clinical imaging option, is designed to improve image quality through advanced reconstruction algorithms (iCBCT), a larger imaging panel, and faster gantry speed (9 deg/s). This study evaluates clinical workflow changes resulting from implementing HPI. Materials/
Methods: Treatment plans were created on anthropomorphic phantoms for four anatomical sites (brain, thorax, pelvis, and spine). Users were asked to acquire and match images from HPI-CBCT (iCBCT reconstruction, 9 deg/s) and standard CBCT (FDK reconstruction, 6 deg/s), randomizing the order of acquisition method and disease site per user. Users matched images based on the institution’s typical clinical workflow (auto-matching followed by manual adjustments) for each disease site. An additional acquisition was completed for each treatment plan with auto-matching only. Time was recorded for acquisition, match, and total session. Registration shift results were compared between HPI and standard CBCT for clinical and auto-matching scenarios in brain, thorax, and pelvis workflows. To evaluate the increased gantry speed on treatment delivery, six treatment plans were identically delivered with automation on different linac control console versions and session times were recorded. Results: Compared to standard CBCT, HPI decreased the average scan times for 200O and 360O acquisitions by 10.7± 0.4s and 19.8 ±1.2s, respectively. Reconstruction times increased by 22.9 ±2.0s for 200 O and 39.0±1.9s for 360 O acquisitions when comparing iCBCT reconstruction to FDK. Clinical workflow average match time difference between HPI and standard CBCT are -3.7±10.5s, 6.6±22.4s, -2.4±39.9s, and 1.2±16.4s for brain, thorax, pelvis, and spine, respectively across five users. The average maximum shift differences for clinical matching between HPI and standard CBCT are reported in Table 1.Auto matching resulted in maximum vertical, longitudinal, lateral, and couch rotational shift differences of 0.02 cm, -0.03 cm, 0.06 cm, 0.2 degrees. Average time savings using automation of 3D and static gantry IMRT plans with fast gantry speed is 8.7±3.3 seconds. Conclusion: HPI on a linac results in similar match times and positioning results as standard CBCT. While reconstruction time increases with iCBCT when compared to FDK backprojection methods, HPI acquisition is consistently faster. HPI acquisition speed coupled with FDK reconstruction could result in an efficiency gain without a reduction in image quality required for accurate patient setup. Faster gantry speed capability during automated treatments results in faster treatment delivery for 3D and IMRT plans.
