The overall goal of this work is to create an MRI imaging environment that eliminates the possibility of RF burns for recipients of cardiac pacemaker, deep brain stimulator, and other neuro-stimulator devices. Today, about 3 million Americans have implanted pacemakers that typically contraindicate any form of head, chest, or muskulo-skeletal MRI scan. Recent clinical safety studies for imaging device recipients at 1.5T have been performed without incident and no related fatalities for pacemakers have occurred since the 1980s. Guidelines for deep brain stimulator recipients typically require head transmit coils and only at 1.5T but at least two MR induced brain injuries have occurred at 1.0T. The general failure to identify adverse outcomes does not prove safety because these results cannot be extrapolated to other field strengths;guidelines are tied to scanner power which is reported inconsistently, and MRI systems lack robust methods of predicting and avoiding potential heating conditions based on physically existing preconditions. Improved engineering of the MR scanner itself can solve this problem. This will require an integration of electromagnetic safety sensors that can independently detect or search for dangerous resonances, MRI RF field mapping methods that can detect lead wire currents responsible for heating but at sensitivities well below physical heating thresholds, and distributed transmit array systems that deposit RF power only where needed. If the physical conditions for heating can be detected and imaged, regardless of field strength, patient orientation, or device, an RF excitation system can be designed to prevent heating.
The aims of this research are to: 1) Develop an RF safety prescreen system to detect dangerous interactions before the MRI scan. Integrated external sensor systems will be developed for 1.5T, and extended to 3T. These systems will detect potential resonant device interactions that may produce RF heating and can be used before the patient even enters the MRI scan room. 2) Develop an MRI safety pre-scan to detect and quantify dangerous interactions with a low power MRI scan. MRI pulse sequences will detect and quantify induced RF currents on conductive structures, and use these measurements to grade risk, and predict potential heating for other sequences. 3) Develop safer MRI systems for the future using advanced RF transmission methods. Transmit array excitation systems and optimized pulse sequences will minimize electromagnetic coupling and RF heating near implanted devices. This will be tested in an in vivo animal model at 3T to show that RF currents on an implanted lead can be nulled while providing a sufficiently uniform RF field for imaging. .Ultimately, this work will lead to a clinically testable system. Achieving these goals will substantially increase access to MRI for a broad class of patients with cardiac or neuro-stimulator implants who are currently denied access out of fear of RF heating danger.

Public Health Relevance

Technology to enhance RF safety in MRI scanners- is important to public health because it will enable the 3 million Americans with cardiac pacemakers or deep brain stimulator implants to safely undergo MRI exams without fear of unintended local RF burns. Underutilization of MRI scanners with these patients can be avoided, and the risk of adverse events or unsafe settings can be substantially eliminated.

Agency
National Institute of Health (NIH)
Institute
National Institute of Biomedical Imaging and Bioengineering (NIBIB)
Type
Research Project (R01)
Project #
5R01EB008108-05
Application #
8255450
Study Section
Biomedical Imaging Technology Study Section (BMIT)
Program Officer
Liu, Guoying
Project Start
2007-09-01
Project End
2015-01-31
Budget Start
2012-02-01
Budget End
2013-01-31
Support Year
5
Fiscal Year
2012
Total Cost
$472,048
Indirect Cost
$170,037
Name
Stanford University
Department
Engineering (All Types)
Type
Schools of Engineering
DUNS #
009214214
City
Stanford
State
CA
Country
United States
Zip Code
94305
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Ellenor, Christopher W; Stang, Pascal P; Etezadi-Amoli, Maryam et al. (2015) Offline impedance measurements for detection and mitigation of dangerous implant interactions: an RF safety prescreen. Magn Reson Med 73:1328-39
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Etezadi-Amoli, Maryam; Stang, Pascal; Kerr, Adam et al. (2015) Controlling radiofrequency-induced currents in guidewires using parallel transmit. Magn Reson Med 74:1790-802
Jordanova, Kalina V; Nishimura, Dwight G; Kerr, Adam B (2014) B1 estimation using adiabatic refocusing: BEAR. Magn Reson Med 72:1302-10

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