Impact of use of optical surface imaging on initial patient setup for stereotactic body radiotherapy treatments

Abstract

PurposeTo evaluate the effectiveness of surface image guidance (SG) for pre‐imaging setup of stereotactic body radiotherapy (SBRT) patients, and to investigate the impact of SG reference surface selection on this process.Methods and materials284 SBRT fractions (SG‐SBRT = 113, non‐SG‐SBRT = 171) were retrospectively evaluated. Differences between initial (pre‐imaging) and treatment couch positions were extracted from the record‐and‐verify system and compared for the two groups. Rotational setup discrepancies were also computed. The utility of orthogonal kVs in reducing CBCT shifts in the SG‐SBRT/non‐SG‐SBRT groups was also calculated. Additionally, the number of CBCTs acquired for setup was recorded and the average for each cohort was compared. These data served to evaluate the effectiveness of surface imaging in pre‐imaging patient positioning and its potential impact on the necessity of including orthogonal kVs for setup. Since reference surface selection can affect SG setup, daily surface reproducibility was estimated by comparing camera‐acquired surface references (VRT surface) at each fraction to the external surface of the planning CT (DICOM surface) and to the VRT surface from the previous fraction.ResultsThe reduction in all initial‐to‐treatment translation/rotation differences when using SG‐SBRT was statistically significant (Rank‐Sum test, α = 0.05). Orthogonal kV imaging kept CBCT shifts below reimaging thresholds in 19%/51% of fractions for SG‐SBRT/non‐SG‐SBRT cohorts. Differences in average number of CBCTs acquired were not statistically significant. The reference surface study found no statistically significant differences between the use of DICOM or VRT surfaces.ConclusionsSG‐SBRT improved pre‐imaging treatment setup compared to in‐room laser localization alone. It decreased the necessity of orthogonal kV imaging prior to CBCT but did not affect the average number of CBCTs acquired for setup. The selection of reference surface did not have a significant impact on initial patient positioning.

Recent advances in Surface Guided Radiation Therapy

“…Almost one third of all clinical SGRT users have implemented respiratory gating for SBRT treatments or conventional lung or abdominal RT, for patient positioning and/or motion management [ 32 ]. SGRT can improve pre-imaging treatment setup, decrease the necessity of orthogonal kV imaging prior to CBCT [ 73 ] and is promising in detecting deviations between pre- and post-treatment setup in SBRT [ 74 ]. Four-dimensional computed tomography (4DCT) acquisition and treatment delivery under surface guidance showed excellent temporal accuracy and consistency to the Varian RPM system in motion-tracking studies [ 75 – 77 ] and has the potential to improve respiratory motion management [ 78 ].…”

Feasibility of Optical Surface-Guidance for Position Verification and Monitoring of Stereotactic Body Radiotherapy in Deep-Inspiration Breath-Hold

“…Earlier data on SGRT and SBRT in free-breathing suggests that the pre-imaging treatment set-up for SBRT can be improved by SGRT compared to in-room laser localization of skin tattoos or skin marks ( 23 ). Moreover, SGRT reliably detects intrafractional shifts during treatment delivery when deviations extend 2 mm, as confirmed by CBCT ( 24 ).…”

A review of surface guidance in extracranial stereotactic body radiotherapy (SBRT/SABR) for set-up and intra-fraction motion management

“…SG reduced the pre-treatment shifts and the requirement for orthogonal kVs for bone alignment. 284 fractions were examined retrospectively, 113 SG-SBRT and 171 Non-SG-SBRT for comparison [6] .…”

“…Leong et al treated thoracic, abdominal and bony metastases. Of the 113 SG-SBRT patients treated, 50 employed Active Breathing Control for breathing management and were treated on inspiration [6] . The remainder were treated free breathing.…”

“…A number of commercial systems are available [1] , [2] , [3] , [4] . The additional benefit is that the system can also be used to monitor the patient throughout treatment for intra-fraction motion [5] , [6] , [7] , [8] .…”