SU‐E‐T‐253: Treatment Planning and Dose Delivery of Photon Radiation Therapy of Cardiac Arrhythmias for Isolated Perfused Porcine Hearts

Purpose: To develop treatment plans and delivery techniques for ex situ isolated perfused (Langendorff) porcine hearts in order to explore the feasibility of using photon radiation to create cardiac lesions as a treatment for cardiac arrhythmias. Methods: Six domestic swines were used for the creation of Langendorff preparation, of which three received radiation and three served as a control group. For the study group, treatment planning was performed on their CT images. Two stainless‐steel clips in the CS ostium and in the pulmonary artery and the beaker were contoured and assigned to the proper CT numbers. Treatment couch attenuation and clip scattering were also taken into account. The AV node was contoured and was positioned at the isocenter of the accelerator. MLC were used to provide conformal shaping of the photon beam and a 1 cm margin was added around the AV node to accommodate cardiac motion. 3D conformal planning technique was chosen. Two orthogonal KV images were acquired before the radiation delivery for accurate positioning of the heart. Results: 200 Gy was successfully delivered to the AV node of the heart in the service mode of the machine. The field size was about 3 × 3 cm^2. The dose distribution was not uniform in the target due to the one or three fixed beam arrangement. The averaged delivery time was about 40 minutes with an averaged dose rate of 600 MU/min. Complete heart block was observed during treatment and notable cellular damages were presented in the histological specimen. Conclusion: Simple and efficient treatment plan and delivery technique are required to deliver high dose to the ex situ isolated hearts in a short time window. Flattening‐Filter‐Free mode of the Linac will dramatically decrease the delivery time and therefore allow the development of more complicated treatment plans, for example, the IMRT. Dr. DL Packer in the past 12 months has provided consulting services for Abiomed, Biosense Webster, Inc., Boston Scientific, CardioFocus, CardioInsight, Excerpta Medica, FoxP2 Medica LLC, InfoBionic, Inc., Johnson & Johnson Healthcare Systems, Johnson & Johnson, MediaSphere Medical, LLC, Medtronic CryoCath, OrthoMcNeill, Sanofi‐aventis, Siemens, St. Jude Medical, and Siemens AG. Dr. Packer received no personal compensation for these consulting activities. [PLEASE NOTE: any web or printed program must include this statement of noncompensation] Dr. DL Packer receives research funding from the Biosense Webster, Boston Scientif