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Kirsch, J.

Publications and source records attributed to Kirsch, J..

2 recordsLinked to original sources
bioRxiv2018

Reconfigurable MRI coil technology can substantially reduce RF heating at the tips of bilateral deep brain stimulation implants

Patients with deep brain stimulation (DBS) implants can significantly benefit from magnetic resonance imaging (MRI) examination, however, access to MRI is restricted in this patients because of safety concerns due to RF heating of the leads. Recently we introduced a patient-adjustable reconfigurable MRI coil system to reduce the SAR at the tip of deep brain stimulation implants during MRI at 1.5T. A simulation study with realistic models of single (unilateral) DBS leads demonstrated a substantial reduction in the local SAR up to 500-fold could be achieved using the coil system compared to quadrature birdcage coils. Many patients however, have bilateral DBS implants and the question arises whether the rotating coil system can be used in for them. This work reports the results of phantom experiments measuring the temperature rise at the tips of bilateral DBS implants with realistic trajectories extracted from postoperative CT images of 10 patients (20 leads in total). A total of 200 measurements were performed to record temperature rise at the tips of the leads during 2 minutes of scanning with the coil rotated to cover all accessible rotation angles. In all patients, we were able to find an optimum coil rotation angle and reduced the heating of both left and right leads to a level below the heating produced by the body coil. An average heat reduction of 65% was achieved for bilateral leads. Reconfigurable coil technology introduces a promising approach for imaging of patients with DBS implants.

biophysics↗
bioRxiv2018

Reducing RF-Induced Heating Near Implanted Leads Through High-Dielectric Capacitive Bleeding of Current (CBLOC)

Patients with implanted medical devices such as deep brain stimulation or spinal cord stimulation are often unable to receive magnetic resonance imaging (MRI). This is because once the device is within the radiofrequency (RF) field of the MRI scanner, electrically conductive leads act as antenna, amplifying the RF energy deposition in the tissue and causing possible excessive tissue heating. Here we propose a novel concept in lead design in which 40cm lead wires are coated with a ~1.2mm layer of high dielectric constant material (155 <{varepsilon} r < 250) embedded in a weakly conductive insulation ({sigma} = 20 S/m). The technique called High-Dielectric Capacitive Bleeding of Current, or CBLOC, works by forming a distributed capacitance along the lengths of the lead, efficiently dissipating RF energy before it reaches the exposed tip. Measurements during RF exposure at 64 MHz and 123 MHz demonstrated that CBLOC leads generated 20-fold less heating at 1.5 T, and 40-fold less heating at 3 T compared to control leads. Numerical simulations of RF exposure at 297 MHz (7T) predicted a 15-fold reduction in specific absorption rate (SAR) of RF energy around the tip of CBLOC leads compared to control leads.

biophysics↗