MR Safety Evaluation of Orthopedic Devices: Why It's Important and How to Select Test Device Configuration

Transcription

1 Safety Evaluation of Orthopedic Devices: Why It's Important and How to Select Test Device Configuration ORS Annual Meeting March 5, 2016 Beth Hess, PhD 1

2 MED Institute has more than 30 years of experience with medical device testing, data analysis, and global regulatory submissions Located in West Lafayette, Indiana Founded in 1983 Engineering Services R&D Simulation Testing Regulatory Consulting Clinical Study Management ISO Accredited Laboratory ISO and ISO Certified (BSI) We serve on several medical device standard committees 2

3 I scanners use strong magnetic fields and radio waves to make images Superconducting magnet Aligns hydrogen nuclei in your body 1.5T or 3T Radiofrequency coils Operate at 64 MHz (1.5T scanner) or 128 MHz (3T scanner) Transmit and receive RF energy Hydrogen nuclei absorb and release RF energy 3

4 I is an increasingly prevalent imaging modality Benefits Excellent tissue contrast No evidence of long-term negative effects Risks from metallic objects Thorough screening for loose metal Implants? 4

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6 ASTM F2503 provides standard practice for marking devices for safety in the environment An Safe device is Nonmagnetic Contains no metal Does not conduct electricity Poses no known hazards in all environments An Conditional device may be used safely only within an environment that matches its conditions of safe use Any device with an unknown I safety status should be assumed to be Unsafe 6

7 Conditions of safe use for passive medical devices should consider four hazards in the environment 1. Magnetically induced displacement force ASTM F Magnetically induced torque ASTM F Radiofrequency (RF) induced heating ASTM F Image artifacts ASTM F2119 7

8 Conditions of safe use for passive medical devices should consider four hazards in the environment 1. Magnetically induced displacement force ASTM F2052 Consider for all metallic devices Depends on Static magnetic field Spatial gradient of the static magnetic field Device magnetic saturation The approach Test in a 3T scanner ying_objects/chair_4.html Test location where the spatial gradient is known Test article having the maximum sum of each comprised alloy s mass multiplied by its magnetic susceptibility 8

9 Conditions of safe use for passive medical devices should consider four hazards in the environment 2. Magnetically induced torque ASTM F2213 Consider for all metallic devices Depends on Static magnetic field Device dimensions and geometry Device magnetic saturation The approach Test in a 3T scanner Longest device Test article having the maximum sum of each comprised alloy s mass multiplied by its magnetic susceptibility 9

10 Conditions of safe use for passive medical devices should consider four hazards in the environment 3. Radiofrequency (RF) induced heating ASTM F2182 Consider for all electrically conductive devices Depends on Electrical and thermal properties of the device Electrical and thermal properties of the surrounding tissue Energy of the RF pulses Device geometry and configuration Location of the device relative to the RF coil Location of the patient relative to the RF coil The approach Use numerical simulation to identify worst case configuration 10

11 RF induced heating of passive implants evaluated using a gel phantom in accordance with ASTM F

12 Use numerical simulation to identify worst case configuration for ASTM F2182 test Tests are expensive FEA helps determine 1.5T or 3T scanner Implant size and configuration Where to measure temperature 12 1/8 Titanium rod Temperature rise following 450 s of RF application ( C) Length (m) 1.5T 3T 12

13 RF induced heating of a generic hip implant for 1.5 T 13

14 Conditions of safe use for passive medical devices should consider four hazards in the environment 4. Image artifacts ASTM F2119 Consider for all metallic devices Depends on Static magnetic field Alignment of the device pulse sequence parameters The approach Test in a 3T scanner Test article having the maximum sum of each comprised alloy s mass multiplied by its magnetic susceptibility 14

15 Demonstrating conditions for use for passive implants will allow more patients access to I scans 1. Magnetically induced displacement force ASTM F Magnetically induced torque ASTM F Radiofrequency (RF) induced heating ASTM F Image artifacts ASTM F

16 Thank you Beth Hess