Developing a database of 3D scattered radiation distributions for a C-arm fluoroscope as a function of exposure parameters and phantom

The purpose of this work is to develop a database of 3D scattered radiation dose-rate distributions to estimate the staff dose by location around a C-Arm fluoroscopic system in an interventional procedure room. The primary x-ray beam of a Toshiba Infinix fluoroscopy machine was modeled using EGSnrc Monte Carlo code and the scattered radiation distributions were calculated using 5 x 10⁹ photons per simulation. These 3D distributions were determined over the volume of the room as a function of various parameters such as the beam kVp and beam filter, the size and shape of the field, the angulation of the Carm, and the phantom size and shape. Two phantom shapes were used in this study: cylindrical and superellipses. The results show that shape of the phantom will affect the dose-rate distribution at distances less than 100 cm, with a higher intensity for the super-ellipse. The scatter intensity per entrance air kerma is seen to be approximately proportional to field area and to increase with increasing kVp. The scatter changes proportionally with increases in primary entrance air kerma for factors such as pulse rate, mA and pulse width. This database will allow estimation of the scatter distribution in the procedure room and, when displayed to the staff during a procedure, may facilitate a reduction of occupational dose.