ISMRM 23rd Annual Meeting & Exhibition • 30 May - 05 June 2015 • Toronto, Ontario, Canada

Scientific Session • Implantable Medical Devices & Modelling

Tuesday 2 June 2015

Room 714 A/B

10:00 - 12:00


T.B.A., T.B.A.

10:00 0299.   Subject Specific Body Model Creation using MR Fingerprinting
Leeor Alon1,2, Martijn Cloos1,2, Assaf Tal3, Daniel K. Sodickson1,2, and Christopher M. Collins1,2
1Center for Advanced Imaging Innovation and Research (CAI2R), New York University School of Medicine, New York, NY, United States, 2Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, United States, 3Weizmann Institute, Rehovot, Israel

RF safety is frequently assessed using computer electromagnetic simulations performed on a limited number of body models. Up to now creation of multi-tissue body models has been highly complex and required considerable manual intervention and time for proper segmentation of tissues. In this work, we present a method for the automatic creation of segmented body part models using MR fingerprinting. Segmentation is performed by relying on the different spin dynamics exhibited by tissues as captured by MR fingerprinting.

10:12 0300.   
Analysis of DNA Double-Strand Breaks in human Peripheral Blood Mononuclear Cells after exposure to 7T MRI
Mahsa Fatahi1, Annika Reddig2, Bjoern Friebe3, Dirk Reinhold2, and Oliver Speck1
1Department of Biomedical Magnetic Resonance, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany, 2Institute of Molecular and Clinical Immunology, Otto-von-Guericke-University Magdeburg, Germany, 3Department of Radiology and Nuclear Medicine, Otto-von-Guericke-University Magdeburg, Germany

Although ultra-high field magnetic resonance imaging (UHF MR) has been applied for 10 years with a very good safety record, the scientific basis for safe use in broader clinical applications is weak. In this in vitro study, we addressed the question of the potential genetic damage, particularly induction of DNA double-strand breaks. We assessed the impact of 7T MRI scans on induction of DSBs on human Peripheral blood mononuclear cells (PBMC). Our results showed no significant increase in DSBs level, in all individuals, immediately, 1 h and 20 h after 7T MRI exposure, compared to the unexposed group.

10:24 0301.   Simplified computational models of medical devices for accurate RF heating simulations with significantly reduced computational cost
Alan Ross Leewood1, Beth J Hess1, Matthew Huser1, Sharath Gopal1, Gonzalo G. Mendoza2, Maria Ida Iacono2, Wolfgang Kainz2, Sunder S Rajan2, and Leonardo M Angelone2
1MED Institute, Inc., West Lafayette, IN, United States, 2Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, MD, United States

Many medical implants are geometrically complex and often feature very small structures. This research presents an analysis of RF-induced heating based on two examples of computational geometric simplified models. Computational simulations were performed to at 128 MHz with two different devices (an 80-mm Nitinol self-expanding stent and an 80-mm stainless steel orthopedic screw) in the ASTM phantom. For each device, a full geometric fidelity and a defeatured model were generated. The defeatured models allowed for significant reduction in computational cost (up to 75%) while showing small (less than 10%) difference of predicted RF-induced heating compared to the full featured model.

10:36 0302.   What is the SAR for Routine Clinical MRI Exams at 1.5T?
Deborah Anne Langman1, Subashini Srinivasan1,2, and Daniel B Ennis1,2
1Radiological Sciences, UCLA, Los Angeles, CA, United States, 2Bioengineering, UCLA, Los Angeles, CA, United States

Understanding the time course of RF deposition during typical clinical exams may yield useful information for defining testing guidelines and device performance criteria for implanted devices. Our objective was to retrospectively characterize and evaluate scanner reported SAR, B1-RMS, and sequence timing for patients undergoing routine cardiovascular or neurological MRI exams. Our analysis of clinical cardiac exams shows that the cumulative duration with SAR exposure >3.5 W/kg was 5-minutes of a 51-minute exam. Our analysis of clinical neurological exams shows that the cumulative duration with SAR exposure >2 W/kg was 10-minutes of a 30-minute exam.

10:48 0303.   Ensuring Safety and Functionality of Electroglottography Measurements During Lung MRI
Ali Caglar Ozen1, Louisa Traser2,3, Tetiana Dadakova1, Michael Burdumy1, Matthias Echternach2, and Michael Bock1
1Department of Radiology, Medical Physics, University Medical Center, Freiburg, Germany, 2Institute of Musicians Medicine, University Medical Center, Freiburg, Germany, 3Department of Otolaryngology, University Medical Center Freiburg, Germany

Monitoring of glottal behavior during dynamic MRI studies is desired for better understanding of the physiologic process of singing. To this aim an EGG device was modified to enable simultaneous EGG measurements during MR image acquisitions. After successfully applying the safety measurements according to the standards, simultaneous EGG recording with either dynamic 3D FLASH or 2D trueFISP image acquisitions in a 34y-old singer was performed during different phonatory tasks.

11:00 0304.   
From Real-Time SAR Assessment to Temperature Distributions in Coronary Stents at 7T
Lukas Winter1, Eva Oberacker1, Celal Özerdem1, Yiyi Ji1, Florian von Knobelsdorff-Brenkenhoff1,2, Gerd Weidemann3, Bernd Ittermann3, Frank Seifert3, and Thoralf Niendorf1,2
1Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrück Center for Molecular Medicine, Berlin, Germany, 2Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité and the Max-Delbrueck Center for Molecular Medicine, Berlin, Germany, 3Physikalisch Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany

En route to broader clinical UHF-CMR studies it is essential to gain a better insight into the interaction of coronary stents with radiofrequency fields. Previous explorations into the assessment of SAR and temperature levels are valuable but constrained to the very specific experimental setup used. Recognizing the need for a universal SAR estimation of passive conducting implants, this work links SAR derived from a real-time SAR estimation to actual temperature behavior. To meet this goal, numerical thermal simulations, E-field measurements and RF heating experiments are performed in coronary stents.

11:12 0305.   Comprehensive analysis of temperature rise generated by a titanium rod inside 1.5T MRI RF whole body coil
Mikhail Kozlov1,2 and Gregor Schaefers1
1MR:comp GmbH, Gelsenkirchen, North Rhine Westphalia, Germany, 2MPI, Leipzig, Saxony, Germany

We investigated temperature rise generated by a reference titanium rod inside 1.5T whole body coil and 3D EM and temperature simulation simplification consequences. The induced temperature rise normalized to incident tangential electric field was found to be dependent on distance to the phantom wall. In all simulation temperature rise of rod tip and especially inside rod hole was found noticeable less than maximum temperature rise in ASTM liquid. Influence of fiber glass temperature probe on power deposition and temperature rise in vicinity of the probe should be taken into account when uncertainty budget is considered.

11:24 0306.   A Quadraure RF Coil with Reduced Heating of DBS Implants - permission withheld
Hai Lu1 and Shumin Wang1
1Auburn University, Auburn, AL, United States

DBS implant heating inside MRI scanner is a major safety concern for scanning implant patients. In order to prevent catastrophic ablations of surrounding tissues, current approaches include using head-only transceiver coils with much reduced SAR limits or redesigned lead wires with RF chocks. Such procedures prevent many clinical useful protocols that are based on the spin-echo sequence from being applied, and exclude patients with different types of implant leads from being scanned. The aim of this study is to develop a new RF transmitter based on the transverse electromagnetic mode of parallel-plate waveguide.

11:36 0307.   A System for Attenuating and Monitoring Acoustic Noise during Infant MRI Studies
Michael Valente1,2, Lei Zhou3, Longchuan Li1,2, Sarah Shultz1,2, and Xiaoping Hu3
1Pediatrics, Emory University, Atlanta, GA, United States, 2Marcus Autism Center, Children's Healthcare of Atlanta, Atlanta, GA, United States, 3Biomedical Engineering, Emory University, Atlanta, GA, United States

We developed a noise attenuation system for infant MRI studies that consists of an acoustic hood inserted into the MRI bore and a pair of headphones with embedded microphones for real-time monitoring of in-ear noise levels. This system is capable of attenuating overall noise levels below 70dB during structural, diffusion and functional scans and can quickly detect elevated noise exposure caused by improper headphone placement. This system meets NICU standards for newborn noise exposure and will greatly improve the success rate of imaging naturally sleeping infants.

11:48 0308.   An Assessment of Radio Frequency Induced Heating of a Vascular Stent during Magnetic Resonance Imaging of a Pig
David C. Gross1,2 and Orlando P. Simonetti3,4
1Biomedical Engineering, The Ohio State University, Columbus, OH, United States, 2Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, United States, 3Internal Medicine, Division of Cardiovascular Medicine, The Ohio State University, Columbus, OH, United States,4Radiology, The Ohio State University, Columbus, OH, United States