Development of a Cardiac and Respiratory Phantom (CARP) for use in Radiosurgery Dosimetry

Abstract

Cardiac Radiosurgery is one of the newest modalities for management of ventricular tachyarrhythmia (VT). It precisely targets radiation to the heart using a high-dose single fraction treatment to scar or destroy cardiac tissue that is allowing irregular electrical signals. Patients often have ICDs with leads that have metal components close to the targets for treatment within the heart. These ICD leads are easily distinguished in kilovolt imaging avoiding any need for additional invasive surgery to implant fiducial markers within the patient. Although respiratory motion management techniques are well established in the radiotherapy setting, there are currently no commercially available systems that evaluate the effects of cardiac motion on respiratory tracking. The cardiac and respiratory phantom (CARP) is designed to mimic cardiac-coupled respiratory motion for use in determining the ability of a medical linear accelerator to track an ICD lead as a motion surrogate. The phantom displaces a platform, which can house ICD leads and dosimeters, in the cranio-caudal and medial-lateral directions. The cardiac and respiratory rates and displacements are user controlled through a computer which is coupled to the phantom by an Arduino. The CARP can achieve up to 150 breaths and 250 cardiac beats per minute to within a 1% error, for standard displacements. The total cardiac and respiratory travel ranges achieved are 3.5 and 4cm, respectively. The CARP can successfully be used as a quality assurance tool in the setting of tracked radiosurgery for cardiac targets.