Prototype ultrasound transducer / system for intraoperative image-guided brachytherapy: proof-of-concept in a breast cancer patient

Intraoperative radiation therapy (IORT) involves the application of high dose radiation (HDR) to adjacent tissue following surgical resection of a tumor. Recently, it was shown that X-ray CT provides clinically useful image guidance to better verify the presence of air voids, or adjacency to skin or bone, that determine optimal, and safe, dosing. As a lower cost, safer and real-time alternative, we assembled a prototype ultrasound device to provide real-time intraoperative image guidance, viewed from within the minimally invasive HDR applicator, as a substitute for X-ray CT. Sequences of offset 2D image planes were interpolated to a 3D grid image data set. Imaging resolution was spatially variant (approximately 0.5 mm axial, 2 mm azimuth). We successfully conducted a single human patient study, involving a breast cancer resection, in an intraoperative setting. Despite a number of practical challenges relating to the dimensions and materials of the components employed, the prototype device worked satisfactorily. Air voids were readily evident in the reconstructed images. In addition to breast cancer, the method has applicability in other cancers involving tumor resection - e.g. prostate cancer.