ELECTRONIC POSTER - ismrm

heart between 20 and 40°C. As a result of applying several MR imaging sequences on 12 pig hearts with implanted temporary
pacemaker leads in a whole body MRI (1.5 T), no substantial heating was observed.
14:30 3891. Impact of Imaging Landmark on RF-Induced Heating of Cardiac Pacemakers and
Other Medical Devices in MRI
Peter Nordbeck 1,2 , Oliver Ritter 1 , Ingo Weiss 3 , Daniel Gensler 2 , Marcus Warmuth 2 ,
Volker Herold 2 , Peter M. Jakob 2 , Mark E. Ladd 4 , Harald H. Quick 5 , Wolfgang R. Bauer 1
1 Internal Medicine I, University of Würzburg, Würzburg, Germany; 2 Experimental Physics V, University of
Würzburg, Würzburg, Germany; 3 Biotronik GmbH & Co. KG, Berlin, Germany; 4 Diagnostic and Interventional
Radiology, University of Duisburg-Essen, Essen, Germany; 5 Medical Physics, University Erlangen-Nürnberg,
Erlangen, Germany
The purpose of this study was to further assess the impact of the imaging landmark on the risk for unintended MRI-induced implant
heating by measuring the RF-induced electric fields in a body phantom under several imaging conditions at 1.5 T in 3 different
scanners. The results show that global RF coupling is highest with the torso centered along the superior-inferior direction of the
transmit coil. The induced E-fields inside the body shift when changing body positioning. Potential hazards can be reduced by
adequate selection of MR imaging landmark in patients with implanted medical devices.
15:00 3892. Thermal and Electrical Characterization of PAA and HEC Gel Used in MRI
Testing of Active and Passive Medical Implants
Holly Moschiano 1 , Warren Dabney 1 , Robert S. Johnson 1 , Lana Placek 1
1 Greatbatch Medical, Clarence, NY, United States
Polyacrylic acid (PAA) gel has been used historically as the phantom material in MRI testing of passive and active medical implants.
However, PAA exhibits undesirable variability in bulk electrical and thermal properties due to the presence of crystallites.
Hydroxyethyl Cellulose (HEC) gel has been referenced in the most recent version of ASTM F 2182-02a as an acceptable substitute for
PAA gel. HEC gel has similar electrical, thermal, and materials properties as PAA gel. Variations in electrical conductivity and
specific heat capacity can greatly affect the amount of temperature rise seen in a test phantom in an MRI environment.
Wednesday 13:30-15:30 Computer 49
13:30 3893. Insulation, Lead-Length, and Sample-Size Affect the MRI-Safety of Implanted
Leads
Ananda Kumar 1 , Perry Karmarkar 1 , William A. Edelstein 1 , Paul A. Bottomley 1
1 Suite B307, 1101 E 33rd Street, SurgiVision Inc, Baltimore, MD, United States
Concerns about RF heating of implanted devices precludes MRI for many patients who could otherwise benefit. Implanted leads are
insulated and vary in length, depending on function and patient size. We investigated experimentally and theoretically the local
specific absorption rate (SAR) and heating of leads as a function of sample size, lead length, and insulation thickness in gel phantoms
exposed to 4W/kg at 1.5T. Heating and SAR are maximum at the bare electrode, increasing with lead insulation thickness and sample
size. SAR is highly nonuniform so sensor sampling volume is critical for matching local theoretical SAR with measured temperature
changes.
14:00 3894. Effect of Linear Phase Electric Field Variation on Implant Lead Heating
Yigitcan Eryaman 1 , Volkan Acikel 1 , Esra Abaci Turk 1 , Nikolay Vladimirovic Viskusenko 1 ,
Ergin Atalar 1
1 UMRAM,National Magnetic Resonance Research Center,Department of Electrical Engineering, Bilkent
Univesity, Ankara, Turkey
In this work it is shown that a helical lead experiences a linear phase electric field variation in a typical quadrature birdcage coil. It is
demonstrated that the effect of linear phase excitation maximizes heating at one tip and minimizes the heating at the other one.
14:30 3895. Changing Boundary Conditions: Effects on Catheter Heating
Samuel O. Oduneye 1 , Sudip Ghate 2 , Kevan JT Anderson 1 , Graham A. Wright 1
1 Medical Biophysics, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada;
2 Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada
During an MRI examination induced radio frequency (RF) currents on electric conductors, such as electrode lines within catheters,
may cause heating in surrounding regions .The objective of this study was to investigate the effects of RF induced heating as a result
of changing boundary conditions at the point of connection of a catheter to the MR-guided clinical system. In our setup, the
termination represents a sudden change of impedance, an additional reflection point, where heating occurs; both simulation and
experimental results show that this point alters significantly the current along the wire, the overall reflection coefficient and heating
properties.