Workflow evaluation of surface-guided initial patient set-up in radiotherapy.

Background and purpose: The desire to avoid tattooing radiotherapy patients lead us to implement surface-guided initial patient set-up (SGRT). To validate SGRT we investigated setup precision, user attitude, and impact on radiotherapy technician (RTT) workflow. Materials and methods: During a six-month period, initial setup was investigated on six linear accelerators (Truebeam, Varian), each equipped with a thermo-optical surface camera (ExacTrac Dynamic, Brainlab). Precision was assessed by comparing couch shifts based on x-ray imaging acquired after initial setup and number of x-ray imaging procedures for each fraction to data from the prior year, using a tattoo-based setup. The data was split into subgroups (thoracic, abdominal/pelvic, palliative and miscellaneous (gastrointestinal, head and neck, cranial and extremities)). User attitude and impact on RTT workflow was assessed qualitatively by questionnaire. RTTs were asked to rate how SGRT compared to tattoo-based setup and record the need for manual adjustments of the patient (e.g. pushing, lifting or pulling). Questionnaires were repeated 1.5 years after implementation. Results: We included 460 patients setup with SGRT, and 468 patients with tattoo-based methods. Median couch shifts and repeated imaging were comparable overall (0.6 cm and 9 % respectively for both setup methods), SGRT performed better for the thoracic and miscellaneous sites subgroups. RTTs preferred SGRT to laser and tattoo initial setup for >90 % of fractions. Manual adjustments were reduced with SGRT (15 % of fractions) compared to tattoo-based (60 % of fractions). Conclusions: SGRT achieved the same or better precision as tattoo-based initial setup while providing a better workflow and reduced physical adjustments performed by the RTTs by 75 %.