A Retrospective Evaluation of Setup Errors Associated with Respiratory Motion Management Techniques in Stereotactic Body Radiation Therapy for Hepatic Malignancies.

Objective: This study aimed to evaluate setup errors associated with three respiratory motion management techniques in stereotactic body radiation therapy (SBRT) for individuals with hepatic malignancies. Methods: A retrospective analysis was conducted on data from 55 individuals with hepatic malignancies who underwent SBRT. Respiratory motion was managed using the Active Breathing Coordinator (ABC) in 11 cases, the BodyFIX system in 6 cases, and a thermoplastic body film combined with an airbag in 38 cases. Cone-beam computed tomography (CBCT) was conducted prior to each treatment session and registered with the reference computed tomography (CT) images acquired during the treatment planning phase to quantify setup errors in three dimensions: left-right (LR), superior-inferior (SI), and anterior-posterior (AP). Results: In the LR direction, the BodyFIX group had a 1.07 mm lower setup error than the ABC group, and the airbag group showed a 2.13 mm reduction compared to ABC and 1.06 mm compared to BodyFIX. In the SI direction, BodyFIX showed a 4.66 mm reduction and the airbag group a 5.45 mm reduction versus ABC. In the AP direction, reductions were 1.99 mm for BodyFIX and 2.86 mm for the airbag group compared to ABC. All differences were statistically significant. The airbag group also had relatively small planning target volume (PTV) margins. Conclusion: The airbag-based respiratory motion management technique demonstrated superior positioning accuracy, improved reproducibility, and the potential for PTV margin reduction in SBRT for hepatic malignancies. Further investigations are needed to verify the superiority of this approach in different populations and settings.