Subhendra Nath Sarkar PhD, RT, Abstract Co-Author: Nothing to Disclose

David Brian Hackney MD, Abstract Co-Author: Nothing to Disclose

Stephen Flaherty MBA, ARRT, Presenter: Nothing to Disclose

Jeremy Stormann BS, ARRT, Abstract Co-Author: Nothing to Disclose

Rafeeque A. Bhadelia MD, Abstract Co-Author: Nothing to Disclose

Jean Pearson BS, ARRT, Abstract Co-Author: Nothing to Disclose

Feng Dong MS, RT, Abstract Co-Author: Nothing to Disclose

Jason Mangosing ARRT, Abstract Co-Author: Nothing to Disclose

Benjamin Jenkins BA, ARRT, Abstract Co-Author: Nothing to Disclose

Efstathios Papavassiliou MD, Abstract Co-Author: Nothing to Disclose

To assess the safety, diagnostic quality and the challenges of a comprehensive brain MR examination developed with a very low RF power (< 0.1 W/kg) for patients with implanted deep brain stimulators (DBS) for evaluating implantation accuracy or neurologic complications.

We modified clinical brain MR sequences at 1.5T (3D T1 MPRAGE, DWI and FSE based 2D T2 and FLAIR) with substantially reduced RF flip angle, and increased RF pulse widths and echo spacings to achieve one order of magnitude lower RF power (SAR) verified by negligible local heating in denatured egg phantoms. 20 Parkinson's patients (potential DBS recipients), adequately restrained to minimize head motion, were imaged at whole head avg. SAR < 3 W/kg. The low SAR sequences at a SAR < 0.1 W/kg were applied on 10 consented, post-implantation patients with deactivated DBS and were compared with high SAR images pre-implantation and with 5 age-matched non-DBS patients with routine brain MR. The images were reviewed with approval from an institutional IRB. SNR, CNR and image blur for several deep brain and cortical structures were evaluated.  

Deep brain and selected GM/WM structures seemed to have acceptable quality (evaluated from SNR, CNR and image blur) in spite of the significantly lower SAR. The tissue SNR and CNR from low-SAR MR were approximately 20-30% less compared to 5 age-matched non-DBS patients presumably due to advanced RF coils and normal RF power used in the later group. Regardless of SAR, 25% of the patients due to excessive tremors had noticeable, although acceptable, MR image blur unchanged at low SAR. The pre-surgical T1 and T2w images at high SAR were useful to guide DBS implantation while post-surgical low-SAR images helped assess DBS lead position accuracy and neurologic complications such as infection, hemorrhage or infarction. None of the DBS recipients reported any neurologic deficit arising from the MR procedure.

Simple RF pulse modifications and careful patient handling can produce acceptable quality T1, T2, FLAIR and Diffusion weighted MR images at very low RF power and seem to offer a comprehensive brain MR examination satisfying highly restrictive RF safety criteria for patients with DBS.  

The demonstrated set of MR sequences with simple RF pulse modifications offer a comprehensive brain MRI pathway for DBS or similar implant patients satisfying highly restrictive RF power constraints.

Sarkar, S, Hackney, D, Flaherty, S, Stormann, J, Bhadelia, R, Pearson, J, Dong, F, Mangosing, J, Jenkins, B, Papavassiliou, E, Comprehensive Brain MRI of Patients with Deep Brain Stimulators at Very Low Radio Frequency Power.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11012455.html