Safety in the MRI Suite: Considerations for Medical Devices and - - PowerPoint PPT Presentation

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Safety in the MRI Suite: Considerations for Medical Devices and - - PowerPoint PPT Presentation

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Safety in the MRI Suite: Considerations for Medical Devices and Equipment Josh White, Ph.D. The scope of services performed during this investigation may not Exponent adequately address the needs of other users of this report, and any reuse

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The scope of services performed during this investigation may not adequately address the needs

  • f other users of this report,

and any reuse of this report or its findings, conclusions, or recommendations is at the sole risk of the user.

Safety in the MRI Suite: Considerations for Medical Devices and Equipment

Josh White, Ph.D. Exponent Biomedical Engineering

February 27, 2019

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Importance of MRI Safety

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The Guardian FDA MAUDE Database

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SLIDE 3

Vascular Surgery Orthopaedics Peripheral Vascular Neurosurgery/Spine Electrophysiology Gynecology Cardiovascular Neurovascular Urology Ophthalmology General Surgery Diabetes

Biomedical Engineering

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SLIDE 4

Vascular Surgery Orthopaedics Peripheral Vascular Neurosurgery/Spine Electrophysiology Gynecology Cardiovascular Neurovascular Urology Ophthalmology General Surgery Diabetes

Biomedical Engineering

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SLIDE 5

The Interface of MRI with Medical Devices

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EMRF | TRTF

Increasing Use of MRI Systems Increasing Number of Patients with Medical Devices

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SLIDE 6

MRI Compatibility Testing

Define Risks Evaluate Device MRI Labeling

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SLIDE 7

MRI Compatibility Testing

Define Risks Evaluate Device MRI Labeling

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Device-Specific Cryogens Contrast Agents General Application

  • f MRI
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SLIDE 8

MRI Basics

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SLIDE 9

MRI Basics

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Ma Magne net: Create strong static magnetic

  • field. Align hydrogen atoms.

Direct ection o

  • f

ma magnet etic f c fiel eld

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SLIDE 10

MRI Basics

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Ma Magne net: Create strong static magnetic

  • field. Align hydrogen atoms.

Ra Radiofreq equen ency cy (RF (RF) ) Coil: Apply electromagnetic wave in pulses that transfers energy to certain hydrogen atoms.

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SLIDE 11

MRI Basics

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Ma Magne net: Create strong static magnetic

  • field. Align hydrogen atoms.

Ra Radiofreq equen ency cy (RF (RF) ) Coil: Apply electromagnetic wave in pulses that transfers energy to certain hydrogen atoms. Gradi dient C Coil: : Modify the main magnetic field to allow spatial encoding in the x-, y-, and z-directions. y x z

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SLIDE 12

Types of Medical Devices and Equipment

Passive Devices Active Devices

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SLIDE 13

Types of Medical Devices and Equipment

Passive Devices

  • No power source.
  • Therapy provided by design of medical

device, passive release of drug from a drug-eluting stent, etc.

Active Devices

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Twin Palm Orthopedics Corin MedicalExpo ADAM

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SLIDE 14

Types of Medical Devices and Equipment

Passive Devices

  • No power source.
  • Therapy provided by design of medical

device, passive release of drug from a drug-eluting stent, etc.

Active Devices

  • Power source.
  • Often deliver therapy due to

programmed output from the power source.

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Twin Palm Orthopedics Corin MedicalExpo ADAM MDDI CHOC

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SLIDE 15

Device-Related MRI Risks

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SLIDE 16

Device-Related MRI Risks

Potential Hazard Cause from MRI Scanner Heat RF Field Gradient Field Vibration Gradient Field Force Static Field Torque Static Field Unintended Stimulation RF Field Gradient Field Device Malfunction Static Field RF Field Gradient Field Combined Fields Image Artifact Combined Fields

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Thermal Mechanical Electrical Functional

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SLIDE 17

Device-Related MRI Risks

Potential Hazard Cause from MRI Scanner Heat RF Field Gradient Field Vibration Gradient Field Force Static Field Torque Static Field Unintended Stimulation RF Field Gradient Field Device Malfunction Static Field RF Field Gradient Field Combined Fields Image Artifact Combined Fields

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Thermal Mechanical Electrical Functional

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SLIDE 18

Device-Related MRI Risks

Potential Hazard Cause from MRI Scanner Heat RF Field Gradient Field Vibration Gradient Field Force Static Field Torque Static Field Unintended Stimulation RF Field Gradient Field Device Malfunction Static Field RF Field Gradient Field Combined Fields Image Artifact Combined Fields

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Thermal Mechanical Electrical Functional

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SLIDE 19

Device-Related MRI Risks

Potential Hazard Cause from MRI Scanner Heat RF Field Gradient Field Vibration Gradient Field Force Static Field Torque Static Field Unintended Stimulation RF Field Gradient Field Device Malfunction Static Field RF Field Gradient Field Combined Fields Image Artifact Combined Fields

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Thermal Mechanical Electrical Functional

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SLIDE 20

Device-Related MRI Risks

Potential Hazard Cause from MRI Scanner Heat RF Field Gradient Field Vibration Gradient Field Force Static Field Torque Static Field Unintended Stimulation RF Field Gradient Field Device Malfunction Static Field RF Field Gradient Field Combined Fields Image Artifact Combined Fields

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Thermal Mechanical Electrical Functional

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SLIDE 21

Device-Related MRI Risks

Potential Hazard Cause from MRI Scanner Heat RF Field Gradient Field Vibration Gradient Field Force Static Field Torque Static Field Unintended Stimulation RF Field Gradient Field Device Malfunction Static Field RF Field Gradient Field Combined Fields Image Artifact Combined Fields

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Thermal Mechanical Electrical Functional

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SLIDE 22

MRI Compatibility Testing

Define Risks Evaluate Device MRI Labeling

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SLIDE 23

MRI Compatibility Testing

Define Risks Evaluate Device MRI Labeling

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SLIDE 24

Device-Related MRI Risks

Potential Hazard Cause from MRI Scanner International Test Standard Heat RF Field ISO 10974:8 ASTM F2182 Gradient Field ISO 10974:9 Vibration Gradient Field ISO 10974:10 Force Static Field ISO 10974:11 (ASTM F2052) Torque Static Field ISO 10974:12 (ASTM F2213) Unintended Stimulation RF Field ISO 10974:13 Gradient Field ISO 10974:15 Device Malfunction Static Field ISO 10974:14 RF Field ISO 10974:15 Gradient Field ISO 10974:16 Combined Fields ISO 10974:17 Image Artifact Combined Fields ASTM F2119

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SLIDE 25

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Testing in Accordance with Existing Standards Works

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SLIDE 26

Passive and Active Medical Devices

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Indiamart

ADAM

Integer

MDDI

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SLIDE 27

Challenges with Traditional Testing

Passive Devices

  • Determination of Worst Case

Configurations for Multi-Configuration Devices.

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Active Devices

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SLIDE 28

Challenges with Traditional Testing

Passive Devices

  • Determination of Worst Case

Configurations for Multi-Configuration Devices.

Active Devices

  • More complex devices.
  • Determination of worst case

configurations.

  • Measurement of transfer function.
  • Validated simulation environment.
  • Utilization of human body modeling.

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SLIDE 29

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Testing in Accordance with Existing Standards Has Limitations

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SLIDE 30

Gaps in Standards

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Gaps in Standards

Passive Devices

  • ASTM F2182
  • ASTM F2119
  • ASTM F2052
  • ASTM F2213

Active Devices

  • ISO 10974
  • ASTM F2182
  • ASTM F2119
  • ASTM F2052
  • ASTM F2213

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SLIDE 32

Gaps in Standards

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SLIDE 33

Gaps in Standards

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AST STM F F2182 2182 AST STM F F2119 2119 AST STM F F2052 2052 AST STM F F2213 2213 ISO SO 10974 10974 AST STM F F2182 2182 AST STM F F2119 2119 AST STM F F2052 2052 AST STM F F2213 2213

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SLIDE 34

Gaps in Standards

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AST STM F F2182 2182 AST STM F F2119 2119 AST STM F F2052 2052 AST STM F F2213 2213 ISO SO 10974 10974 AST STM F F2182 2182 AST STM F F2119 2119 AST STM F F2052 2052 AST STM F F2213 2213

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SLIDE 35

Breast Tissue Marker

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LEICA

  • Potential Hazards
  • Displacement
  • Torque
  • RF Heating
  • Artifact
  • Tests
  • Defined by standards
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SLIDE 36

Breast Tissue Marker

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Schematic of displacement test setup.

Conclusion from testing: marker fails test for displacement.

Magnified view of the displacement test setup.

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SLIDE 37

Breast Tissue Marker

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Weight ght Win Wind Weight ght Schematic of displacement test setup. Magnet etic c Fo Forc rce Example of a windsock.

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SLIDE 38

Ventilator

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  • Potential Hazards
  • Displacement
  • Malfunction
  • Tests
  • No exact standards exist to guide

testing.

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SLIDE 39

Ventilator

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MRI Scanner Differ eren ent ma magnet etic f c fiel eld strengths hs

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SLIDE 40

Ventilator

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Differ eren ent t tes est loc locations MRI Scanner Differ eren ent ma magnet etic f c fiel eld strengths hs

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SLIDE 41

Peripheral stent

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  • Potential Hazards
  • Displacement
  • Torque
  • RF Heating
  • Artifact
  • Tests
  • Defined by standards
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SLIDE 42

Peripheral stent

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Schematic of the electric fields in a phantom used for testing, as well as an example of a simulated ANSYS human body model with its corresponding electric field distribution.

Limitations: Limited test setup, positioning, long metallic devices

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SLIDE 43

Peripheral stent

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Schematic of a human body model in a simulated RF coil, as well as the corresponding electric fields in the human body during the MRI.

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Peripheral stent

5 10 15 20 3 6 9 12 15

Temperature (°C) Time (min)

RF-Induced Temperature Rise

Benchtop Simulated Flow Conditions

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Hypothetical temperature rise measured from a stent during MRI testing, as well as when computational modeling is performed to incorporate fluid flow. A temperature distribution around the stent is also shown.

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SLIDE 45

Peripheral stent

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Benchtop Testing Human Body Modeling Computational Fluid Dynamics

Define Risks Evaluate Device MRI Labeling

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SLIDE 46

Neurovascular Embolization Coil

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  • Potential Hazards
  • Displacement
  • Torque
  • RF Heating
  • Artifact
  • Tests
  • Defined by standards

Cook Medical Vessel Aneurysm Coil

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SLIDE 47

Neurovascular Embolization Coil

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Image artifact of a gold/copper IUD when imaged with a spin- echo sequence. Image artifact a stainless steel IUD when imaged with a gradient echo sequence.

Bussman et al. 2018

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SLIDE 48

Neurovascular Embolization Coil

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Traditional Testing with Sequence #1 Coil Diameter Artifact

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Neurovascular Embolization Coil

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Clinical scan with Sequence #2 Vessel Unknown

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Neurovascular Embolization Coil

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Vessel Unknown Clinical scan with Sequence #2 Interpretation: Artifact Interpretation: Blockage Traditional Testing with Sequence #1

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Neurovascular Embolization Coil

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Vessel Unknown Clinical scan with Sequence #2 Modified Testing with Sequence #2 Interpretation: Artifact

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SLIDE 52

MRI Compatibility Testing

Define Risks Evaluate Device MRI Labeling

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Ty Types es o

  • f Label

eling MR Safe MR Conditional MR Unsafe

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MR Conditional Labeling

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  • Examples of restrictions included in conditional labeling include the

following:

  • Scanner strength.
  • Maximum allowable spatial static magnetic field gradient.
  • Scanning modes.
  • Types of scanners.
  • Limitations to patient positioning inside the scanner.
  • Allowable scan duration.
  • Maximum allowable gradient slew rate.
  • Amount of image artifact.
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SLIDE 54

Revisiting the Ventilator and Embolization Coil

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  • Example: Ventilator should be maintained outside the 5 gauss line

surrounding the MRI scanner line at all times. Ventilator should be tethered to the wall during scanning.

  • Example: Ventilator should always be operated in Mode 1 during MRI
  • scanning. Operation in Mode 2 during MRI scanning may result in

incorrect delivery of therapy.

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SLIDE 55

Revisiting the Ventilator and Embolization Coil

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  • Example: Ventilator should be maintained outside the 5 gauss line

surrounding the MRI scanner line at all times. Ventilator should be tethered to the wall during scanning.

  • Example: Ventilator should always be operated in Mode 1 during MRI
  • scanning. Operation in Mode 2 during MRI scanning may result in

incorrect delivery of therapy.

  • Example: Non-clinical testing demonstrated that the image artifact

caused by Neurovascular embolization coil extends approximately 4 cm from the coil. When evaluated in a saccular aneurysm model with a magnetic resonance angiography scan sequence, the artifact extends approximately 1.2 cm from the coil.

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SLIDE 56

Considerations for MRI Compatibility Testing

Define Risks Evaluate Device MRI Labeling

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  • Clinically relevant analyses
  • 7 Tesla and other ultra high field

scanners

  • New scanner designs and scan

sequences

Cons

  • nsidera

rations for for fu future re MR MRI t testing ng

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SLIDE 57

Questions?

jwhite@exponent.com

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