Purpose: To assess the radiation treatment of a patient with two deep brain stimulator (DBS) systems without causing a malfunction of the DBS devices either during the patient's course of radiation treatment or over a 9-month follow-up period.
Methods: Patient was to be treated on an Accuray Tomotherapy Hi-Art treatment machine for 35 fractions to a total dose of 70Gy. After imaging was performed to correctly position the patient for treatment, screened nanoDots were placed on the surface of the patient's head/shoulder mask at the superior edges of the DBS devices with 0.5cm of bolus on top of each nanoDot. The nanoDots were placed this way to avoid extensive discomfort to the patient. The bolus was placed to mimic the depth of the DBS. One treatment fraction was delivered to the patient with the nanoDots in place. The nanoDots were then sent to Landauer's Special Service Dosimetry (LSSF) for processing.
Results: Based on the patient's treatment plan, the maximum accumulated predicted radiation dose to the patient's right and left DBSs would be 8.9Gy and 6.25Gy respectively. With the treatment beam being 6MV, neutrons were not a concern. The LSSD report indicated, from the one treatment fraction, a radiation dose of 29.6cGy and 38.5cGy to the right and left DBSs, respectively. This result would indicate a total radiation dose over the planned 35 treatment fractions of 10.37Gy and 13.45Gy to the right and left DBS, respectively. Unfortunately, the patient decided to discontinue treatments after 10 fractions had been delivered, resulting in total radiation doses of 2.96Gy and 3.85Gy to the right and left DBSs, respectively. Patient has not reported any malfunction of either DBS since treatment.
Conclusion: The Medtronic DBS can receive radiation doses up to 3.85Gy without causing a device failure, either during or after a patient's radiation treatment course.
Dose, Optical Dosimetry, Radiation Risk