Abstract Archives of the RSNA, 2011
SSK11-08
Magnetic Resonance Imaging-induced Heating of Deep Brain Stimulation Implants: An Empirical-specific Absorption Rate Evaluation
Scientific Formal (Paper) Presentations
Presented on November 30, 2011
Presented as part of SSK11: Neuroradiology (Neuroradiology Movement Disorders)
Goldie R Boone MS, Presenter: Nothing to Disclose
Geoffrey D. Clarke PhD, Abstract Co-Author: Nothing to Disclose
The purpose of this research study was to evaluate the induced heating of brain tissues located near the electrodes of a bilaterally implanted deep brain stimulation (DBS) device and to determine the applicability of regulatory limits.
The magnetic resonance imaging system induced heating was measured using custom designed and fabricated phantom testing apparatus. The testing apparatus consisted of specialized phantoms, designed for the placement of an implantable pulse generator (IPG) and associated leads and electrodes and a fiber optic thermometry (FOT) system in tissue-equivalent materials (saline and gelled-saline). The FOT system acquired real-time temperature measurements of the induced heating at the surface of the right distal and proximal and the left distal and proximal metallic DBS electrodes via the FOT probes. The rate of change in temperature over a 6 minute averaging period for each probe location was used to evaluate and calculate the 1) spatially localized temperature increase, 2) spatially localized specific absorption rate (SAR), and 3) the average head SAR in the phantom.
The anatomical MPRAGE and functional EP2D-BOLD pulse sequences scanned on two identical Siemens’ Magnetom TIM Trio 3T scanners were below the IEC’s spatially localized temperature limit of 1 °C, spatially localized SAR limit of 10 W•kg-1, and average head SAR of 3.2 W•kg-1 (saline only), however, they are all substantially above the Medtronic recommended average head SAR limit of 0.1 W•kg-1. The EP2D pcASL and TSE T2 pulse sequences were above the IEC’s spatially localized temperature limit and spatially localized SAR limit. In addition, the EP2D pcASL and TSE T2 pulse sequences are estimated to have average head SARs above the IEC limit and the Medtronic limit.
The functional imaging pulse sequences generated temperature rises that more than doubled the recommended spatially localized temperature limit and produced SAR values that nearly doubled the spatially localized SAR limit. The observations in this research study support the use of anatomical and functional MRI and TMS of patients with a bilateral DBS device implant provided that modifications are made to the 3T pulse sequences
This research provides a method by which clinicians can verify the safety and efficacy of the pulse sequences used in the anatomical and functional imaging of patients with neurostimulation devices.
Boone, G,
Clarke, G,
Magnetic Resonance Imaging-induced Heating of Deep Brain Stimulation Implants: An Empirical-specific Absorption Rate Evaluation. Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL.
http://archive.rsna.org/2011/11013859.html