Radiation therapist led treatment of lung stereotactic ablative body radiation therapy patients in the absence of the radiation oncologist – An image matching consistency comparison study

Introduction: The aim of this study was to evaluate the consistency of day 1 cone-beam computed tomography (CBCT) image registration in lung stereotactic ablative body radiation therapy (SABR) among radiation oncologists (RO), radiation therapists (RTT) and paired RTTs, negating the need for RO to attend day 1 lung SABR treatment. Methods: Day 1 pre-treatment CBCT data sets were restored for ten lung SABR patients for offline image registration. All participants (2 ROs, 27 RTTs and 5 RTT pairs) performed image matches on three different days. The deviations between each offline match and day 1 reference data were analysed to assess the consistency of image registration among the three study groups. Other variables such as patient respiratory motion management method, RTT SABR experience, and time spent on image registration were evaluated. Results: All three study groups showed excellent consistency in CBCT matching results when compared to reference data. Average differences in all translational and rotational directions for each group were ΔTx 0.02 cm, ΔTy 0.04 cm, ΔTz 0.02 cm, ΔRx 0.43°, ΔRy 0.43°, ΔRz 0.47° for RT, ΔTx 0.02 cm, ΔTy 0.04 cm, ΔTz 0.04 cm, ΔRx 0.54°, ΔRy 0.66°, ΔRz 0.48° for RO and ΔTx 0.02 cm, ΔTy 0.06 cm, ΔTz 0.04 cm, ΔRx 0.39°, ΔRy 0.47°, ΔRz 0.49° for RTT pair. All deviations were within the study tolerance. Conclusions: Following appropriate education and training, lung SABR credentialed RTTs demonstrated the ability to perform high quality and consistent day1 pre-treatment CBCT matching potentially negating the need for routine approval from ROs.