TU‐F‐BRF‐09: Feasibility Study of Spatial and Temporal Fractionation Using a Table‐Top Image‐Guided MRT System

Purpose: Microbeam radiation therapy is a promising experimental radiotherapy method for cancer treatment. Synchrotron studies have shown that MRT can preferentially ablate tumors while mostly preserving the surrounding normal tissues. Our purpose is to develop a compact microbeam irradiator that can be accessible for laboratory research on MRT's therapeutic mechanism, with the ultimate goal of translating this technique for clinical applications. Utilizing a carbon nanotube field emission X‐ray source array, our lab has developed a first of its kind table‐top microbeam irradiator. The purpose of this study is to investigate the possibility of increasing the total dose to the tumor region using spatial and temporal fractionation. Methods: MRI and CT scans were acquired and registered to locate both the target region and the landmark in the treatment coordinate space. A crossbeam treatment configuration was planned to achieve the desired dosage and tumor coverage. One array of 300 μm‐thick microbeams was delivered to the target on the first day. Another array, perpendicular to the first one, was delivered the next day targeting the same region. The feasibility of this image‐guided MRT procedure was evaluated using a phantom. Gafchromic EBT2 film was employed to characterize the targeting accuracy and the delivered tumor dose. Results: The preliminary phantom study showed that a cross‐pattern of microbeam arrays was successfully delivered with sub‐millimeter targeting accuracy. The delivered dose in the target region was doubled. The fraction of tumor volume that received the peak dose was increased. Conclusion: Temporal fractionation of crosspatterned microbeams can be delivered to the same target region. The feasibility of this procedure was investigated with a phantom study. Once implemented, this procedure has the potential of increasing the tumor control effect of MRT and of achieving better normal tissue recovery.