Modification of Total Body Irradiation to Reduce Risk of Damage to Spinal Cord Stimulator
Abstract
Purpose
It is well established that radiation can damage electronic medical devices; however, there is little guidance for managing spinal cord stimulators (SCS) in the radiation oncology setting. Total body irradiation therapy (TBI) presents especial risk to electronic medical devices, like SCS, because it is typically neutron-producing, involves high MU, and the device will be in the primary field. Here we present a case in which volumetric modulated arc therapy (VMAT) total body irradiation (TBI) was used in place of traditional TBI to reduce risk of SCS damage while meeting all clinical goals.
Methods
A 59 year-old patient presented for TBI treatment of acute myeloid leukemia. To reduce risk of damaging the patient’s Nevro Senza SCS system with the pulse generator (IPG) implanted in the left flank, two goals were established: avoid neutron production, and reduce dose to the IPG as low as reasonably achievable. The patient received 4 Gy of 6 MV VMAT TBI in two fractions with dose shaping to avoid the IPG.
Results
The SCS IPG received a maximum dose of 1.88 Gy, as measured by thermoluminescent detectors. The measured dose was greater than the planned maximum dose of 0.91 Gy due to unexpected IPG movement (maximum displacement was 2.2 cm inferior to planned geometry) from soft tissue displacement during patient setup. Upon follow-up, no device malfunction was observed.
Conclusion
Through modification of the original treatment plan, dose to the SCS IPG was reduced to less than half of the prescription dose and neutrons were avoided altogether. Modification of this plan reduced risk of SCS damage, maintained clinical goals, and was delivered without placing undue burden on the clinical schedule. Future treatments of patients with SCS should avoid neutron production and reduce dose around the device using an avoidance margin of at least 2 cm.