For example, within chemotherapy, multiple agents are combined into a single cocktail to treat cancer. Combining multiple agents increases efficiency because different agents target different phases of the cell cycle [ref]. Similarly, Mukai et. al showed that the combination of radiofrequency ablation (RFA) and radiation therapy shows promise for large lung cancers [5]. He describes a synergy in which one procedure compliments the second by improving efficiency. Radiation therapy is relatively ineffective during certain phases of the cell cycle. The synergy of RFA and radiation therapy is likely due to cells which are radiosensitized by thermal therapy. Cells remain radiosensitized for up to 24 hours, therefore the efficiency of radiation therapy is increased during that window. This effect is summarized by Dewhirst et al in his review of the effects of thermal therapy [6]. The increased effectiveness of combining multiple modes of treatment is frequently time-dependent, as described for RFA and radiation therapy. Tight coupling of multiple modes or treatment are necessary for effective treatment …show more content…
It uses physical markers, or fiducials, which are surgically embedded in and around a tumor to locate it within the body. With the assistance of the fiducials, high doses of radiation can be delivered to the tumor with submillimeter accuracy. In recent years, real time imaging of the fiducials allows SBRT to account for a tumor’s movement caused by breathing. Typical markers are small gold cylinders roughly 0.8 x 5mm. They are placed in a tumor and around its periphery to allow imaging to generate a 4D map of the tumor in the body during respiration. Fiducial markers are limited by two factors: low visibility and movement after placement. First, poor placement may result in low visibility due to poor alignment or markers which overlap on images. Overlapping markers limit the ability to generate a 3D image. Second, the markers frequently shift or settle after their initial placement. While the initial placement of the markers may be ideal for imaging, movement of the markers may results in reduced visibility. SBRT has proven to be an effective form of treatment and has been greatly improved by visible markers to track the tumors location. Performing SBRT with an highly visible marker, closely following RFA, will take advantage of the radiosensitivity of the tissue and increase the effectiveness of the