Assessment of MRI Induced Heating of Cardiac Pacing Leads: Relevance to Target Patient Populations Presenter: Daniel G. Hullihen Jr. Director of Business Development RSNA 2006 November 28, 2006

2 Tissue proximal to implanted lead electrodes can experience significant heating during magnetic resonance imaging (MRI) Lead heating depends on many factors MR technologists reposition patients in bore Patients, and MR scanner bores, come in different sizes

3 Patient shoulder width varies and is 36 cm for 5 th percentile adult females Patients can be positioned off center in the bore to optimally image region of interest Pacing system and lead path can vary significantly from patient to patient

4 Three different bipolar pacing lead designs Four different lateral MRI bore positions Determination of MRI induced heating – Full range of clinically relevant positions

5 Left installation Right installation

6 Test Samples Used: Standard bipolar active fixation pacing lead (Commercially Available) Prototype bipolar active fixation pacing lead with resonant circuit in distal tip (Resonant Circuit) Prototype bipolar active fixation pacing lead without resonant circuit in distal tip (Control)

7 Luxtron® model 3100 fluoroptic thermometry system with SSM model optical probes Gelled-saline solution: 5.8 g PAA, 0.8 g NaCl per liter of de-ionized water in head / torso phantom vessel (ASTM F a) GE 1.5 Tesla MR system, body coil, FSE- XL, whole body average SAR: W/kg

8 Lead developed for testing with readily available components Resonant Circuit Components

9 Leads placed in four (4) lateral positions 1.Initial Position: Centerline in bore 2.Second Position: 9.5cm ( ~40%) off centerline in bore 3.Third Position: 17cm ( ~71%) off centerline in bore 4.Fourth Position: On Edge, 24cm off centerline in bore; extreme case

10 Initial Position: Centerline in bore

11 Second Position: 9.5cm ( ~40%) off centerline in bore

12 Third Position: 17cm ( ~71%) off centerline in bore

13 Forth Position: On Edge, 24cm off centerline in bore

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15 In all positions the lead with the resonant circuit in the distal tip had temperature increases of less than 0.75ºC.

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17 Shifting a patient laterally in the MR scanner bore significantly affects heating of tissue at the distal tip of pacing leads. Incorporating a resonant circuit into the distal tip of the lead makes the lead less prone to tissue heating with respect to a patient’s lateral position in the scanner’s bore.