Improving CBCT for Liver IG-SBRT Using Gadoxetate Disodium

This is a feasibility study requiring only three patients to serve as a proof of concept that gadoxetate disodium (a liver specific contrast agent) can be used to improve images taken just before liver SBRT treatments. The hypothesis of this research is that if gadoxetate disodium improves image quality at the time of treatment, then it can be used for image guided radiotherapy (IGRT). Image guidance is the procedure where the 3D CT image that is used to plan a radiotherapy treatment, is aligned to a 3D image taken just before treatment. The better the alignment, the more accurate the treatment, which is crucial for high dose treatments such as SBRT. This research is important for two main reasons. First, it is much less invasive than the standard of care which involves surgically implanting markers in the liver that can move over time. The benefit to harm ratio for surgery, compared to an injection, is much more dramatic. Furthermore, not all patients are surgical candidates, and therefore in those cases radiation oncologists must prescribed a larger area to treat to ensure that none of the cancerous region is missed. The drawback to this method is the irradiation of more normal tissue than necessary, which although deemed to have a greater benefit than harm, is not ideal. Secondly, this research has strong implications in the field of radiation oncology to move towards patient oriented radiotherapy treatments. If successful, radiation treatment to the liver could be performed in less treatments because of the confidence given to radiation oncologists of the cancer location; knowing exactly the healthy liver regions to avoid.