Room: Exhibit Hall | Forum 1
Purpose: This work investigated the variation of scattered radiation with gantry angle for a torso phantom and a head phantom for a C-Arm fluoroscopic system.
Methods: EGSnrc Monte-Carlo (MC) software was used to calculate the scatter distribution around the fluoroscopy machine for a super-ellipse (SE) torso and a cylindrical head phantom. The SE phantom was shaped to an average torso with 30 cm width and body-mass index of 20 while the cylindrical head phantom had a diameter of 19 cm and length of 24 cm. Scatter distributions were calculated as a function of LAO gantry angle to determine the dose in vertical planes on the tube side and detector side of the table. All MC simulations used 10^10 photons incident on the phantom. A library of 3D scatter dose-rate distributions is being developed.
Results: For angles other than 0 degrees, tube-side scattering is substantially higher than detector-side. For the SE phantom on the tube side at 30 cm from the beam centerline: the scattered dose rate is 5 times greater at 90 degrees than at 0 degrees at eye level; at knee height, the scattered dose rate is 1.5 times greater at 90 degrees than at 0 degrees. On the detector side: at eye level, the scattered dose rate is about 2 times higher at 0 degrees than at gantry angles 30 degrees and higher; the dose rate decreases with increasing angle also for waist and knee height. For the head phantom, the magnitude of scatter is lower but similar trends for scatter variation with angle are observed.
Conclusion: The scattered-radiation dose to interventional staff changes considerably with gantry angle and the change varies by height above the floor. Knowledge of the scatter distribution and the effect of gantry angle will help staff manage their dose during fluoroscopically-guided procedures.