assessment of mri induced heating of cardiac pacing leads: relevance to target patient populations...
TRANSCRIPT
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 •
The FocusThe Focus
• 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 •
Clinical SignificanceClinical Significance
• Patient shoulder width varies and is 36 cm for 5th 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 •
Experimental InvestigationExperimental Investigation
• Three different bipolar pacing lead designs
• Four different lateral MRI bore positions
• Determination of MRI induced heating
– Full range of clinically relevant positions
5 •
Lead Position ExamplesLead Position Examples
Left installation
Right installation
6 •
Materials and MethodsMaterials and Methods
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 •
MaterialsMaterials
• 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 F2182-02a)
• GE 1.5 Tesla MR system, body coil, FSE-XL, whole body average SAR: 2.0181 W/kg
8 •
Materials and MethodsMaterials and Methods
• Lead developed for testing with readily available components
Resonant Circuit Components
9 •
PositioningPositioning
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 •
MethodsMethods
Initial Position: Centerline in bore
11 •
MethodsMethods
Second Position: 9.5cm ( ~40%) off centerline in bore
12 •
MethodsMethods
Third Position: 17cm ( ~71%) off centerline in bore
13 •
MethodsMethods
Forth Position: On Edge, 24cm off centerline in bore
16 •
Lead Heating vs. Lateral Lead Heating vs. Lateral PositionPosition
Mean of Maximum Lead Temperature Rise v. Bore Position
21.0
22.0
23.0
24.0
25.0
Centerline ~40% ~71% EdgePhantom Position in Bore
Max. T
em
p (C
)
Resonance Ckt Mean Control Mean
Commercial Lead Mean
17 •
ConclusionsConclusions
• 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.