Author: Nina Burbure, Tawfik G. Giaddui, Shidong Li, Curtis Miyamoto, Jeremy Price, Bin Wang 👨🔬
Affiliation: FCCC at Temple University Hospital 🌍
Purpose: Frameless gamma knife (GK) treatments use a thermoplastic mask coupled with high-definition motion management system that utilizes an infrared camera, and a reflective marker placed on the patient’s nose. The treatment will gate/pause if the motion exceeds a user-set threshold and will stop if the patients do not return to a position in tolerance within a set time. Our objectives were to perform a retrospective analysis of frameless single fraction GK radiosurgery treatments, to identify possible correlations between treatment gating/pauses and patient specific parameters.
Methods: Forty-four treatments were retrospectively analyzed. The disease sites were brain metastases (n=41), vestibular schwannoma (n=2), and meningioma (n=1). The number of times the treatment was gated/paused was recorded and Pearson correlation coefficient was used to identify possible correlation with patient age, treatment time, number of lesions, number of shots, rotational and translational shifts of CBCT.
Results: The median: age was 66 years (36-87); dose was 20 Gy (9-24); number of lesions was 1 (1- 8); volume of lesions was 0.78 (0.005- 86.4) cc; volume coverage was 99.4% (93.2-100); prescription iso dose line was 57% (40 -98), planned treatment time was 44.05 min (16.3- 182.4) ; number of shots was 13 (1-92) and number of treatment gate/paus was 4 (0-62). The number of times treatment was stopped/resumed in each case was 0 (n=18), 1 (n=9), between 2-6 (n = 16) and 14 (n=1). A correlation was found between treatment gating and treatment planned time (r=0.6, P<0.001) and number of shots (r= 0.5, p= 0.0005). No correlation with other parameters was found.
Conclusion: Treatment time and number of shots showed some correlation with treatment gate/pause. Other factors like the patient’s medical condition may have an influence and needs to be investigated. This data may inform decisions to utilize a frame or frameless approach for GK treatments.