Use of the Metal Deletion Technique for Radiotherapy Planning in Patients with Cardiac Implantable Devices.

BACKGROUND: The number of cancer patients with cardiac implantable electronic devices receiving radiotherapy is increasing. Irradiation of such patients can cause malfunctions in pacemakers and implantable cardioverter-defibrillators. In this respect, it is necessary to make a proper irradiation plan for such cancer patients to minimize the dose received by both cardiac devices and pacing leads. However, planning computed tomography (CT) scans have metal artifacts that degrade the image quality and make it difficult to create a qualitative radiation plan. In fact, there is a problem of correct contouring not only of critical organs and planning target volume, but also of cardiac devices and pacing leads during the planning of CT scan operations. PATIENTS AND METHODS: To analyze this issue, we tested the Metal Deletion Technique (MDT) on nine cancer patients with different tumor localizations near cardiac implantable electronic devices and device types who were treated at the Masaryk Memorial Cancer Institute. We conducted a radiotherapy planning in Eclipse Treatment Planning System, version 11.0 (Varian, Palo Alto, Canada) (employing three-dimensional conformal radiation therapy, intensity-modulated radiation therapy, volumetric-modulated arc therapy and stereotactic body radiation therapy irradiation techniques). We analyzed the influence of MDT on plan parameters and compared CT scans without and with application of the MDT method. RESULTS: The results confirm the need to use the MDT method for reduction the likelihood of malfunctions in devices. The greatest error in determining the dose received by implantable devices and pacing leads is more than 3% of the total dose. It can significantly change the patients treatment plan. CONCLUSION: The data obtained in this experiment are crucial for physicists when selecting radiation techniques and suitable methods for planning the irradiation of patients with implantable electronic devices. Key words radiation therapy - cardiac devices - Metal Deletion Technique - artifacts - quality improvement.