What are the differences between gamma- and x-ray knife? Pg. 460
As stated previously, there are no significant clinical differences between gamma knife and x-ray knife treatments. However, the gamma knife can only be used for small lesions because of its field size limitation (maximum diameter 18mm), although several isocenters can be placed within the same target to expand or shape dose distribution. For treating multiple isocenters or targets, the gamma knife is more practical than the x-ray knife because of its simplicity of setup. For the same reasons, the gamma knife can produce a more conformal dose distribution than that possible with the x-ray knife unless the latter is equipped with special field-shaping collimators such as the dynamic MLC. On the other hand, the x-ray knife is far more economical because it is linac based. Besides, the linac can be used for all kinds of radiation therapy techniques including SRS, SRT, intensity modulated radiation therapy, and conventional radiation therapy.