Combifix or Vacloc Bags, Which One Is Better for Prostate Patient Setup and Immobilization?

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Compared to traditional used VacLoc bags, Combifix is a new patient setup and immobilization device for pelvic region treatment. It has adjustable kneefix and feetfix cushions. This study is to evaluate and compare these two device performance by analyzing patient pre-treatment setup and post-treatment radiographs from prostate patients treated with proton. Total 22 prostate patients were selected for the study, with 11 using Combifix and 11 using VacLoc bags for patient immobilization and setup. Pre-treatment setup radiographs and post-treatment radiographs were obtained to evaluate the setup residual errors and prostate intrafraction motion errors for both cohorts of patients. The systematic and random components of the residual errors and intrafraction motion errors were calculated and compared. Therapists were interviewed about their experiences using Combifix. For Combifix patients, the setup residual systematic errors are 0.02, 0.03 and 0.02cm in lateral (LR), longitudinal (SI) and Vertical (AP) directions, respectively. The residual random errors are 0.05, 0.07 and 0.07cm in LR, SI and AP directions, respectively. For VacLoc patients, the setup residual systematic errors are 0.0, 0.01 and 0.01cm in LR, SI and AP directions, respectively. The residual random errors are 0.02, 0.04 and 0.04cm in LR, SI and AP directions, respectively. The intrafraction motion errors are slightly larger than residual errors. For Combifix patients, the setup residual systematic errors are 0.04, 0.07 and 0.05cm in LR, SI and AP directions, respectively. The residual random errors are 0.08, 0.15 and 0.15cm in LR, SI and AP directions, respectively. For VacLoc patients, the setup residual systematic errors are 0.02, 0.05 and 0.05cm in LR, SI and AP directions, respectively. The residual random errors are 0.05, 0.12 and 0.11cm in LR, SI and AP directions, respectively. Therapists observed that there were less rotation errors but slightly more pitching errors at the beginning of patient setup. But after 1 or 2 corrections, the residual errors are very similar between the two immobilization devices. However, if multiple consecutive patients treated with Combifix device, it improves clinical flow. The error analyses of the patient initial setup and intrafraction motion showed that similar characteristics between the two patient immobilization devices. Nevertheless, improved clinical flow can be achieved by treating consecutive patients with Combifix devices.