Applications of Gamma Knife Radiosurgery for Experimental Investigations in Small Animal Models

Abstract

The Gamma Knife (GK) was not originally designed for experimentations in small animals. In fact, there are no compatible custom accessories or stereotactic frames on the market for the spatial positioning of small animals in the GK. In addition, the GK is intensively used for patient treatments, and consequently the access for research with small animals is limited. On the other hand, devices specially designed for the irradiation of small animals are available on the market. For examples, small animal irradiators can be purchasable from Best Theratronics (Theratronics, 2011), Rad Source Technologies (Rad Source Technologies, 2011), Precision X-Ray Inc. (Precision X-Ray, 2011) and Xstrahl-Gulmay Medical Inc. (Xstrahl, 2011). Compared to the GK, these small animal irradiators have the following advantages: lower cost, smaller size, some are shielded and thus don’t require a special shielded room, some can be combined with an imaging device that allows to image the animal and immediately irradiate the region of interest and, if needed, repeat imaging. Then, since irradiators designed for small animal already exist, why use a GK for animal experimentations? The answer should include technical as well as conceptual aspects. The most important benefit of using the GK for small animals is related to the difference between conventional external radiotherapy and GK radiosurgery (GKRS). Radiation deposition with a GK is produced by multiple concentric beams that allow high dose deposition in a very small volume. These converging beams of ionizing radiation in a precise volume allow a rapid fall-off of dose near the edges which limit adverse effects on the surrounding adjacent tissue.