Analytical Geometry Description, Clinical Node Distribution, and Geometric Performance of ZAP-X and Its Comparison With Gamma Knife

In radiotherapy, it is increasingly common to find specialized devices in different treatment techniques. The ZAP-X is a radiosurgery system which features a sophisticated and complex geometric design that allows to deliver a high dose of precisely targeted radiation while minimizing the radiation effect on the surrounding normal brain tissue. Its combination of yoked gimbals allows a maximum theoretical geometric efficiency of [Formula: see text] steradian solid angle coverage, which means that it is possible to cover 71% of the surface around the patient's head, making the ZAP-X the commercially available radiosurgery system with the largest beam coverage. While irradiation is possible from any angle in the Treatment Delivery System (TDS), collision-free space is limited in the Treatment Planning System (TPS), so the geometric performance that the ZAP-X can achieve in clinical practice is different and smaller than the theoretical geometric efficiency of the system. However, it has greater geometric efficiency (71%) and higher clinical geometric performance (39%) than the Gamma Knife system (31%). A general analytical geometric description of the gyroscopic system is provided, analyzing the movement and the different combinations of positions of its gantries to finally calculate its geometric efficiency, both from a theoretical and clinical point of view, and compare it with the Gamma Knife system.