Real time online matching in high dose per fraction treatments: Do radiation therapists perform as well as physicians?

PURPOSE: For high dose per fraction treatments such as stereotactic body radiotherapy (SBRT) in our department we require a physician to perform the pre-treatment on board imaging (OBI) match. The purpose of this study was to determine if patient matching positioning performed by radiation therapists (RTTs) is as accurate as physician matching.

METHODS: Sixteen RTTs and five physicians participated in this study. Data were collected from 113 patients totaling 324 measurements. 60 patients were treated for bone lesions, 53 for soft tissue lesions such as lung and liver. Matching was performed using kV-kV imaging for bones, and cone beam CT (CBCT) for soft tissue. All treatments were delivered on Varian linear accelerators (Palo Alto, CA). The initial match was performed by the RTTs and the shifts noted. The match was then reset, and the physician performed an independent match blinded to the RTT match. Physician shifts were applied for treatment. We used the Wilcoxon rank sum test to determine statistical significance between RTT and physician shifts.

RESULTS: The differences in patient shifts between physicians and RTTs were calculated in three translational and one rotational axis. The average vector shift was 0.88±0.57 cm vs. 0.91±0.57 cm for RTTs vs. physicians respectively. Neither the average vector nor the individual axis shifts were statistically significantly different (p>0.2). There was no significant difference when testing for bony or soft lesion matches separately.

CONCLUSIONS: RTT OBI matching is as accurate as physician matching for both bone and soft tissue lesions. Based on these results, RTTs are as qualified as physicians to perform a pre-treatment match. Thus, it may be feasible for the RTTs to perform the match, and the physician to review it off-line after treatment, without being present at the machine during treatment. Our results show that this approach does not compromise patient safety.