Enable preclinical, high-precision image-guided radiotherapy research with a stand-alone small animal IGRT system

Many preclinical studies involving novel particle radiotherapy techniques have been conducted without precise image guidance due to the lack of an image-guided small animal radiotherapy research platform for them, such as ultra-high dose rate radiation (UHDR), mini-beam, and grid therapy. This limitation restricts the complexity of research questions that can be effectively addressed.

We developed a workflow to utilize 3D imaging on a Small Animal Radiation Research Platform (SARRP) for precise targeting of internal regions in small animals with a separated treatment beam.

Our approach mimics the workflow of patient treatment to decouple the imaging process from the radiation system. The SARRP cone-beam CT system was used to image and center the target. Alignment markers were then added to the top surface of the animal platform using the SARRP's well-calibrated laser system, which was consequently transferred and aligned to a collimator in a clinical treatment room. Validation of the method was performed using BB targets within both a mouse phantom and a euthanized rat. The distance between the center of the radiation field and the BB was measured to determine the setup error for the entire procedure. The use of a collimator reduces the impact of setup uncertainty in the treatment room.

Our approach achieved a setup accuracy of approximately 0.5 mm, ensuring the target was consistently positioned at the center of the collimated radiation field center after transferring from the SARRP system. This is comparable to the isocentricity of the SARRP itself (∼±0.5 mm).

By decoupling the imaging and radiation systems while maintaining sub-millimeter setup accuracy, this workflow introduces flexibility for conducting high-precision, image-guided preclinical studies across different radiation modalities and techniques, for example, protons, electrons, neutrons, UHDR (FLASH), Small-Field-RT, etc. The workflow uses simple equipment and can be easily implemented by other centers.