RE: Docket No. FDA-2019-D-2837: Testing and Labeling ...€¦ · AdvaMed Comments on FDA Draft...

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October 30, 2019

Division of Dockets Management (HFA-305)

Food and Drug Administration

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RE: Docket No. FDA-2019-D-2837: Testing and Labeling Medical Devices for

Safety in the Magnetic Resonance Environment Draft Guidance for Industry

and Food and Drug Administration Staff; Availability

Dear Sir or Madam:

The Advanced Medical Technology Association (“AdvaMed”) is pleased to provide

comments on the Food and Drug Administration’s (FDA’s or “Agency”) draft guidance

entitled “Testing and Labeling Medical Devices for Safety in the Magnetic Resonance

Environment.”

The Advanced Medical Technology Association (AdvaMed) is the world’s largest trade

association representing medical device and diagnostics manufacturers. AdvaMed's

member companies produce the innovations that are transforming health care through

earlier disease detection, less invasive procedures and more effective treatments.

AdvaMed has more than 400 member companies, ranging from the largest to the smallest

medical technology innovators and manufacturers. AdvaMed advocates for a legal,

regulatory and economic environment that advances global health care by assuring

worldwide patient access to the benefits of medical technology. The Association

promotes policies that foster the highest ethical standards, rapid product approvals,

appropriate reimbursement, and access to international markets.

AdvaMed has both general and specific comments in table format below.

General Comments

AdvaMed commends the Agency on its efforts to aid harmonization and globalization by

referencing the listed international standards. Due to the large number of devices that are

affected by the guidance, it would be helpful to have more example devices added to the

scope section such as infusion pumps, oxygen tanks, pacemakers and tissue markers to

clarify for sponsors whether the guidance applies to their device(s). The guidance also

covers a broad range of devices and medical equipment. It would be helpful to organize

the guidance into separate, clearly defined sections that are applicable to different types

of devices such as implantable devices, wearable devices, partially implantable devices,

or adjacent equipment, such as oxygen tanks. The current organization may lead to some

confusion as it reaches too broadly and covers both devices and adjacent equipment.

http://www.advamed.org/

Division of Dockets Management (HFA-305) Docket No. FDA-2019-D-2837

October 30, 2019

of 27

October 30, 2019 Page 2 of 27 Docket No. FDA-2019-D-2837

Specific Comments

AdvaMed’s specific comments are included below in table format.

In closing, thank you for the opportunity to provide our input and comments on the draft

guidance, “Testing and Labeling Medical Devices for Safety in the Magnetic Resonance

Environment.” Please don’t hesitate to contact me if you have any questions.

Sincerely,

/s/

Tara Federici

Vice President

Technology and Regulatory Affairs

AdvaMed Comments on FDA Draft Guidance on Testing and Labeling Devices for Safety in the Magnetic Resonance Environment

October 30, 2019 of 27 Docket No. FDA-2019-D-2837

Edit #

ID # Change Reason

1.

ToC

Restructure Table of Contents and organization of guidance to remove H. Extent of Image Artifact from Section V. Addressing Hazards for Medical Devices in the MR Environment.

Revise language discussing Image Artifact within this guidance document so as not to present this as a type of hazard. Presentation of information related to Image Artifact should not imply that this represents a hazard to the patient.

Image artifact is not considered a harmful interaction impacting patient safety. Image artifact is also not considered to be an issue with respect to medical device function or performance. As stated in ASTM F2503, the affected image quality or image artifacts are not considered to be a harmful interaction between the medical device and MR environment: “3.1.1 harmful interaction—unintended direct or indirect interaction of items with MR equipment, especially with the static magnetic field, the gradient fields and the RF fields of the MR equipment, that can pose hazards to patients or other persons.”

2.

44

III. Terminology Add: Partially implanted medical device

This type of device is commonly referred to in the guidance document but not included in the Terminology section. Adding this item to Terminology would be helpful.



Edit #

ID # Change Reason

3.

49

Revise to make clear that the definition of “active medical device” is specific to medical devices that have no fully or partially implanted components.

This clarification would help to clearly distinguish the definition of “active medical device” from the definition of “active implantable medical device.” Clarity and distinction is necessary in order to have a clear understanding as to which portions of this guidance are applicable to which types of devices (implanted vs. non-implanted/partially implanted).

4.

69

We recommend providing a more concrete definition on the difference between MR conditional and MR Safe.

The MR conditional definition is quite broad allowing for a large grey area as to what can be considered MR conditional versus MR Safe. We feel this needs to be better specified either through the MR conditional definition or in the MR safe definition. For example: if a device is MR Safe in all known MR imaging modes and pulse sequences, except for a single experimental sequence not commonly used, would the device be considered MR Safe except for XYZ parameters, or MR Conditional with a warning against exposure to XYZ parameters? Please provide additional clarification to delineate between how a device may be labeled MR Safe vs MR Conditional.



Edit #

ID # Change Reason

5.

71

Add clarification or a footnote stating that “switched gradient magnetic field” does not need to be included on MR Conditional labeling for passive devices with a scientific or experimental justification.

The switched gradient magnetic fields are currently not addressed in labeling for most passive devices. Please provide guidance as to whether it can be omitted if there are no restrictions on switched gradients for safe scanning. This statement is in conflict with line 650 stating that specific parameters can be omitted.

6.

89

Add the following:

This guidance references specific sections, protocols, and approaches from FDA recognized Standards current as of the release of this document. Should a newer version of the Standard be published and recognized by the FDA, the new approaches and protocols will represent the most current testing to be followed as recommended by the agency.

We recommend that the standards section add a clause discussing how FDA’s recognition of newer standard versions will be handled by this guidance. This information is needed to ensure continuity as new standards are released and recognized by the Agency.

7.

145

Revise: “for which the medical device may be exposed” To: “for which the medical device is labeled for intended use”

To clarify that the assessment is only required for the device’s intended and labeled use.



Edit #

ID # Change Reason

8.

149 - 150

Revise statement to include “may”: The characteristics of the static magnetic field, gradient magnetic fields and radiofrequency coils may vary significantly and thus can lead to different risk profiles.”

It is not always true that the characteristics of these fields vary significantly with different magnetic field strength. For example, gradient magnetic fields do not vary significantly between 1.5T and 3T magnetic fields.

9.

164

Revise: “Both the static magnetic field and the spatial field gradient of the static magnetic field induce ….” To: “The spatial gradient of the static field induce….” Add a new sentence explaining the gradient of the static magnetic field gives rise to translation force, while misalignment of magnetic material in static field results in torque.

The first proposed change is intended to simplify the sentence. The second edit is for clarification purposes.



Edit #

ID # Change Reason

10.

185 - 186

Add the following: A magnetically induced deflection force of less than or equal to the gravitational force on the medical device is often used as a conservative acceptance criterion. For certain implant grade metals such as titanium, cobalt chrome and stainless steels, a rationale may be sufficient in showing that the induced forces are expected to be significantly lower than 1G.

An option for a rationale should be provided as testing is not always necessary, especially when implant grade materials are being utilized.

11. 196

Add a clarifying sentence that misalignment of magnetic material in static field results in torque.

Per our recommended sentence on line 164, please clarify that misalignment of magnetic material in static field results in torque.

12.

204 - 205

Add the following: “…the longest medical device or the device with the largest proportion of magnetic material to total mass, generally serves as a worst-case for assessing magnetically induced torque.”

To be consistent with the language on lines 174-176 of the draft guidance.

13.

220

Remove materials and physical properties as example characteristics.

Material composition or physical properties of the RF coil are not characteristics that are required to be incorporated into RF transmit coil simulations. ISO/TS 10974, Annex J identifies shape, size, type, and shield as relevant characteristics for RF transmit coil simulations.



Edit #

ID # Change Reason

14.

221

Revise: “RF transmit mode” To: “RF excitation”

Use of the term “mode” can be confusing for end users. In ASTM F2503, the latest agreement was to use the term “RF excitation.”

15.

221

Revise: “circularly polarized, multi-channel-2 (MC-2)” To: “circularly polarized (CP), multichannel-2 (MC-2)”

Suggest revision to align with terminology format per latest agreement in ASTM F2503.

16.

227 - 228

Remove reference to “a clinically relevant worst-case heating scenario” as part of RF safety evaluation consideration.

The assessment of RF safety should be based on risk assessment similar to assessment of other MR environment hazards and not be dependent on a worst-case scenario. This statement should be revised to make clear that these assessments should be consistent with ISO/TS 10974 and be based on risk assessment and not focusing only on a worst-case scenario. In addition, the draft standard PC 76, uses a risk-based assessment to determine a percentile for the heating comparison, rather than a worst-case approach.

17. 249

Revise to clarify specific magnetic field strengths. When stating “3.0T or less,” it is not clear if this is referring only to 3T and 1.5T or inclusive of other field strengths.



Edit #

ID # Change Reason

18.

248

Revise to include the terms “insulated” and “uninsulated”: “…2 cm in all directions and at least 3 cm from another uninsulated or any distance from another insulated metallic medical device does not need to be tested with respect to RF induced heating…”

The distance calculation to avoid any RF coupling with neighboring devices should clarify this is referring to uninsulated metallic devices.

19.

266

Remove the following: “for the temperature/time dose”

Temperature/time dose is currently not the only acceptance criteria measurement for RF induced heating accepted by a regulatory agency. For example, for cardiac rhythm management devices (a type of active implantable medical device), rise in pacing capture threshold (PCT) is used as an acceptance criterion for RF induced heating. The use of PCT rise as an acceptance criterion is consistent with AAMI PC76 (draft). Therefore, we recommend removal of the reference to temperature/time dose in order to make the guidance document less limiting in terms of acceptance criteria measurements. Alternatively, one could include additional language in the guidance document regarding rise in pacing capture threshold (PCT) as an option for acceptance criteria measurement.



Edit #

ID # Change Reason

20.

266 - 268

Acceptance criteria for the temperature/time dose should be established based on the location of the medical device in or on the body using scientific rationale or existing literature. No rationale is needed for a temperature increase of less than or equal to 2° C at the labeled SAR condition.

Temperature increase depends on how much (specific absorption rate) SAR is applied. Therefore, SAR must be defined.

21.

270

Heating induced by switched magnetic field gradients, (dB/dt) Comment - please clarify that this applies to AIMD only.

Clarification of section

22.

272

Add and strike the following: Exposure to switched magnetic fields (gradient pulses) can induce eddy currents on conductive surfaces of metallic implants, and internal conductive components of AIMDs and in conductive loops of leads and wires placed inside the bore of the MR system.

In the context of the AIMD, eddy currents induced in leads is not a heating hazard and does not lead to an electrical malfunction and/or extrinsic potential unintended stim hazard. In addition, internal conductive components of AIMDs are a source of heating.

23.

280 - 281

Strike the following: There are no standard test methods for the assessment of gradient induced heating for passive medical devices. The methods in ISO/TS 10974 may be adopted to be used more broadly.”

Since ISO /TS 10974 applies to active implantable medical devices (AIMDs), we should not expand the scope of test method to passive implants without scientific data. It is not necessary to quantify heating induced by switched magnetic field gradient with a passive implant.



Edit #

ID # Change Reason

24.

290 - 293

Strike the following: “The 510(k) Summary or the Summary of Safety and Effectiveness Decision (SSED) should include the acceptance criteria upon which the allowable heating was determined. For example: A local temperature rise of <insert temperature> is not expected to produce thermal injury adjacent to the device.”

The requirement and supporting rationale to place this information in the 510(k) Summary or SSED is not provided within this guidance document. The purpose for including this information in the 510(k) Summary or SSED is not clear. Inclusion of such a statement may be confusing, misleading, or subject to misinterpretation when taken out of context if included in these public-facing documents. Additionally, acceptance criteria identification in 510(k) Summaries or SSEDs are not required for other types of testing.

25.

294

Add the following: Gradient Induced Vibration (AIMD Only)

Clarify the section only applies for AIMD.

26.

295

Revise:

The MR system’s pulsed gradient magnetic fields may induce …

To:

The MR system’s static Bo and pulsed gradient magnetic fields induced …

Correct description of the underlying MR scanner EM fields giving rise to vibration.



Edit #

ID # Change Reason

27.

299 - 301

Add and strike the following:

“… gradient induced vibration is generally not expected to pose a tissue damage hazard for tissue damage passive and AIMDs implanted subcutaneously or sub-pectoral. Less common AIMDs that can impart vibration to tissues with higher susceptibility such as nerves or brain may require tissue damage assessment.”

The assertion is incorrect.

Medical device malfunction due to vibration cyclical fatigue can cause mechanical damage, broken wires, etc.

This is inconsistent with FDA’s request to have ISO 10974 re-introduce the vibration-induced tissue damage clause which requires assessment due to concern that AIMD vibration of more sensitive tissues such as nerves may cause damage e.g., cochlear nerve, optic nerve, vagal nerve, etc.

28.

303

Revise to make acceptance criteria statement be specific to malfunction device damage or relocate to Section G. Medical Device Malfunction

Although location of the medical device should be considered during evaluation of gradient induced vibration, the evaluation should address the potential for device malfunction by establishing acceptance criteria that evaluates device malfunction specific to functions of the device. The guidance should make clear that evaluating potential for device malfunction due to gradient induced vibration should be specific to evaluating impact to device functionality.

29.

305 - 306

Add the following: Gradient Induced Extrinsic Electrical Potential (Unintended Stimulation from AIMD)

Clarify the section only applies for AIMD.



Edit #

ID # Change Reason

30. 307 - 309 and

312

and

328

Consider expanding applicability to devices containing electrodes and not specifically only devices with elongated leads with electrodes. Suggest rephrasing to reflect language on this topic in ISO/TS 10974

The possibility to induce electrical potential at electrodes can occur in devices other than those that have elongated leads that contain electrodes. It is not clear whether the guidance is indicating that this hazard is specific only to medical devices that contain leads or if applicability includes devices that contain electrodes, such as leadless pacemaker.

31.

320 - 321

Add the following: Rectification of RF pulses from MR Exams (Unintended Stimulation from AIMD)

Clarify the section only applies for AIMD, edits suggested

32. 333 Change reference to Section G.

Section G describes medical device malfunction not Section H.

33.

345

Define “electrically active medical device” within this guidance document or use consistent terminology throughout the guidance.

It is not clear whether “electrically active medical device” is the same as an “active medical device.” An active medical device is defined as a medical device relying on a source of electrical energy for its functioning. “Electrically active medical device” should be defined if the meaning is different than “active medical device” in order to make clear the distinction between these two device types.



Edit #

ID # Change Reason

34.

348 - 350

Revise statement to improve clarity as to what is meant by “this can be viewed as part of addressing the electromagnetic compatibility (EMC)/ immunity to electromagnetic interference (EMI) of active medical devices in the MR environment”

Otherwise, we suggest removing this statement.

More clarity is needed as to what is meant by “viewed as part.” Does this mean EMC/EMI testing inherently covers MRI safety testing? Or does completing MRI safety testing as recommended in this guidance document then fulfill part of EMC/EMI testing requirements?

As currently written, this statement is confusing and is not helpful to understanding regulatory expectations.

35.

363

Revise:

“typical MRI protocols”

To:

“MRI sequences”

ISO/IS 10974 will no longer focus on use of “typical MRI protocols” and will instead focus on sequences with high gradient and RF exposures



Edit #

ID # Change Reason

36.

364 - 366

Revise as follows: These methods rely on testing a functioning medical device (verified by checking before the test) and monitoring the medical device where practical, during exposure (scan) if applicable and immediately afterward for indications of malfunction.

To align with ISO-TS 10974 Section 17.4.4 which indicates 30 minutes for Combined Fields testing and to document the timeframe for testing of individual field testing, add “where practical” and strike “immediately.” This will help avoid confusion. The term “immediately” is also ambiguous and potentially burdensome. In addition, the qualifier “where practical” is appropriate given that not all devices can be monitored during a scan.

Add the clause “if applicable” with respect to need for monitoring medical device during MRI scan exposure. It is not always necessary to monitor device function during exposure to MRI scanning, such as devices that will have therapeutic functionality turned off during scan.

37.

379

Add definition of “passive medical devices” to terminology section.

The term “passive medical devices” is not clearly defined in this guidance document. This term should be defined in order to provide clarity on how passive medical devices are distinguished from active medical devices.

38.

384

Revise as follows:

“…switched gradient magnetic fields (dB/dt), and/or RF fields heating…”

Within the context of this system, it would be more appropriate to refer to demonstrating no adverse effect from RF field rather than heating. Identification of RF field is also more consistent with the rest of the sentence which identifies other types of energy fields present in MRI environment and not the potential hazard.



Edit #

ID # Change Reason

39.

390 - 396

Recommend the guidance make clearer for which types of devices the recommendations in this paragraph are applicable. Suggest revision to make clear that this is applicable to non-implanted devices.

In addition, consider relocating this paragraph elsewhere in this guidance document.

The preceding paragraphs within this section mention considerations for active implantable medical devices, non-implanted active medical devices, and passive medical devices and therefore, clear distinctions between what test considerations are applicable for each of these device types and active medical device is recommended.

In addition, it is not clear that a paragraph regarding evaluating MRI scanner operation is applicable to this section discussing evaluating MR environment impact on medical device function. Section G, “Medical Device Malfunction” refers to effects on the candidate medical device, whereas effects on imaging are associated with the MR system and can be moved to section H.

Additional clarity on applicability of this paragraph to the device types in scope of this guidance would be helpful, such as explaining whether these considerations are applicable to devices that are present outside of the MRI bore.



Edit #

ID # Change Reason

40.

390 - 396

Revise as follows: “In addition, you should assess and demonstrate that the active medical device does not affect the operation of the MR system and the MRI image quality. Additional information regarding image artifact is addressed in the next section. While no standardized test methods currently exist, a qualitative assessment of image quality and a measurement of signal to noise ratio (SNR) using standardized test methods (such as NEMA MS 1) with and without the medical device present may be useful”

In general, devices can affect the image so the statement is incorrect. In addition, RF interference from the AIMD would be a new requirement not currently referenced in the ISO-TS 10974 standard and the test method and acceptance criteria are not defined and could lead to confusion. More specifically, metallic implants are expected to affect image quality, so the text should not assert that one must demonstrate that the medical device should not affect MRI image quality. The recommendation to assess and demonstrate that the medical device does not affect MR system operation will present an undue burden to AIMD manufacturers. No instances of AIMDs affecting MR scanner operation have been documented. AIMD RF communication is often disabled when programmed to an MRI scanning mode, or if communication is present, it is typically well outside of the frequency band of MRI RF operation. The variety of MR scanner technology and scan sequences across MR scanner vendors is extensive, so a comprehensive assessment of this theoretical hazard would be a very burdensome task. Clear test methods and acceptance criteria, along with better alignment with the MR scanner vendor & AIMD manufacturers (e.g,. TS 10974 joint working group) is needed before this demonstration should be recommended for all AIMD manufacturers.



Edit #

ID # Change Reason

41.

396

We recommend adding an additional section after section G, Medical Device Malfunction that addresses alarms for non-implanted medical equipment. The additional section should address Effective Alarm Notification as referenced in IEC 60601-1-8 - General requirements, tests and guidance for alarm systems in medical electrical equipment and medical electrical systems.

This information is needed because MRI chambers can limit visibility to medical device interfaces and the audio signals that are associated with the alarm signals. Instructions are needed to direct the end user on how to address and proceed when an alarm signal is present.

42.

401 - 402

Revise as follows:

“This hazard should be addressed for all medical devices intended to enter the MR environment by including a statement in the MR Conditional labeling to inform health care providers about the potential for medical device-induced image artifacts.”

The statement in the guidance document does not provide sufficient clarity as to what it means to “address artifacts” in labeling in a way that would provide clear information to the end user.

43.

410

Revise:

“largest proportion”

To:

“largest amount”

A medical device that has the largest proportion of magnetic material with respect to its mass will result in smaller image artifacts when compared to a larger device with more magnetic material (but a smaller proportion with respect to its mass).



Edit #

ID # Change Reason

44.

414 - 416

Please clarify what is meant by “manufacturing labeling” in the context of this section.

What is the implied testing to meet this requirement? Specific use of a medical device within the MRI is important as to what this/these test(s) looks like. For example, certain MR configurations are determined by product workflows. Are those workflows and configurations able to be accounted for in this test set-up e.g., room RF noise as detected by the use of a whole body transmit-receive RF coil vs. receive-only head coil?

45.

422

Provide clarification on what type of “standard of care” procedures are being referred to in the context of this sentence.

Clarification is needed in order to understand what types of procedures will require additional information regarding image artifact. It is not clear if by “standard of care” procedures, this is dependent or independent of the indicated use population of the medical device under evaluation. It is also not clear if the “standard of care” is referring to standard practice for implantation of the medical device under evaluation.

46.

440

Remove “absolute worst-case” and revise statement to recommend determining acceptance criteria based on risk analysis.

The assessment of RF safety should be based on risk assessment, similar to assessment of other MR environment hazards and not be dependent upon a worst-case scenario.

47.

471 - 472

MRI Safe:

Question/Comment: If you have a non-conductive device with a small (<2mm) non-ferromagnetic material such as a platinum radiopaque marker, can this be labeled MR Safe by radio-opacity logic?

Provide clarification on the limits of this section, defining the minimum and maximum range to be classified as MR Safe.



Edit #

ID # Change Reason

48.

497 - 498

Replace: “The included information should also address the artifacts that the presence of the medical device may induce in acquired images.” With “The labeling should also include a statement to inform users about the potential for medical device induced image artifacts.” In addition, we suggest including an example statement to be included in labeling, such as: “The presence of the <device> may produce an image artifact. Some manipulation of scan parameters may be required to compensate for the artifact.”

The statement in the draft guidance document does not provide sufficient clarity as to what it means to “address artifacts” in labeling in a way that would provide clear information to the end user.



Edit #

ID # Change Reason

49.

512

We recommend that the guidance clarify when a medical device card is or is not needed for a medical device.

The guidance states that a patient medical device card identifying the MR safety status is needed for each medical device that the patient has with them in the MR environment. It is not clear if this card is also needed for hospital-owned equipment that the hospital will be bringing into the MR environment. Please clarify if there is a difference in medical device card requirements between patient-used equipment vs. hospital-used equipment (e.g., patient-owned insulin pump vs. hospital-used infusion pump). This information is needed because it makes sense that the hospital would need the medical cards for the devices the patient is bringing with them but not necessarily needed for equipment the hospital uses, since the hospital should already be aware of the equipment’s MR safety status based on purchasing requirements and review of the device labeling.

50.

535 - 586

We recommend more example symbols be provided and that the guidance include symbols that are internationally recognized.

In addition, add symbols for MR Conditional in Section C.

The MR Safe example symbols show a green square, but typical international standards use a triangle. Please update and add examples of internationally recognized symbols for both MR Safe and Unsafe example labeling. This information is needed in order to harmonize with international labeling standards.

The guidance omits the symbol for MR conditional in Section C.

Please also clarify if black/white labeling is acceptable.

51.

586

We recommend providing a more concrete definition on the difference between MR conditional and MR Safe.

The difference between MR safe and MR conditional is not well-defined. Please clarify if devices can only be labeled as MR Safe if they meet 100% of the standard test requirements or if the device can still be MR safe with some limitations.



Edit #

ID # Change Reason

52.

601 - 607

Make allowances for type of information to include in patient medical device card due to size limitations in a typical size used for patient medical device cards. Consider revising recommendation to allow use of symbols and simplified text to convey safety information and to allow links to company websites for further details.

Typically, patient medical device cards are sized to be similar to that of a credit card in order to facilitate ease of carrying the card in a person’s wallet or purse. While having safety information is important, the presentation of information in a clear manner may be limited due to physical size restrictions of a patient medical device card. It will be difficult to accommodate lengthy statements due to space restrictions and it will not be helpful to the end user (if, for example, the font size is too small to accommodate recommended text and it is hard to read). Additionally, being able to link to company websites for additional information would be helpful.

53.

612

It may be of benefit to provide an example of the minimum required information for a patient medical card for passive implants with relatively few conditions.

The example provided in line 601 “A statement such as: ‘This person <…” seems to be too restrictive, while also not applicable to all passive devices. Specifically, language such as “may result in severe patient injury or death” or “device malfunction” may not be applicable. Similarly, the recommended language of “severe patient injury” and/or “patient death” does not align with the example given in Appendix 2, line 716, which more broadly states “Failure to follow these conditions may result in injury to the patient.”



Edit #

ID # Change Reason

54.

631

Revise as follows: MR Conditional Medical Devices intended to enter the MR system bore The MR Conditional labeling for a medical device intended to enter the MR system bore 617 should include: 3. Permitted radiofrequency (RF) field exposure b. 3T RF excitation (e.g., Circularly Polarized (CP), Multichannel-2 (MC-2))

RF excitation options only applies to 3T (not 1.5T). RF excitation mode is not commonly provided on 1.5T scanners by the MR System manufacturers, nor is it selectable by the MRI operator at this time. Therefore, the inclusion of this criteria may impose an impractical requirement for the end user. Clarify that this labeling item applies to 3T only. A labeling item should not be required for 1.5 T given the CP option – labeling should not contain obvious or unnecessary information.

55.

627 - 635

Recommend qualifiers be added where applicable to clarify when the information is needed or not. For example, more background could be added as to when SAR vs B1+rms might be used (B1+rms is unlikely to be used for 1.5T if most scanners don’t display the parameter). We suggest pointing to ASTM or other technical specifications if additional clarification is provided in those documents.

Not having qualifiers as to when these labeling requirements are applicable could lead to confusion with both the FDA reviewer and manufacturer, and ultimately confusion by the clinician which could lead to unsafe recommendations for the patient. It is useful to have more information pertaining to “when needed” if additional information is available.

56.

635

Add the following: d. Maximum permitted B1+rms value [ T] (optional)

As MRI scanners prior to ~2010 were not required to display a value of B1+RMS, it is recommended that reporting of this value be an optional addition to reporting of SAR values in bullet point ‘c.’. Note: both are measures of RF exposure limits and SAR is a historical standard measure reported/measured.



Edit #

ID # Change Reason

57.

636

Add the following: Permitted time-varying gradient field exposure (may be applicable to AIMDs only)

As stated in Section C. “Heating”, subsection “Heating induced by switched magnetic field gradients…”, it is desirable to reiterate in the recommended labeling requirements that gradient induced medical device heating may not be applicable to passive devices. This aligns with the draft guidance language in line 279, stating that “no standard test methods for assessment of gradient induced heating for passive medical devices” exist and that the existing test methods for AIMDs “may be adopted” more broadly, based on applicability to undefined passive devices.

58.

638

Strike the following: “b. maximum spatial encoding gradient amplitude [mT/m] per axis”

Maximum spatial encoding gradient amplitude is not a metric of interest in MRI time-varying gradient hazard testing of implantable devices. The gradient test levels are informed by Annex A of ISO/TS 10974. The defined levels are scaled based on gradient slew rate only, so providing gradient slew rate in labeling is sufficient for permitted time-varying gradient field exposure labeling. Additionally, spatial encoding gradient amplitude is not a controllable parameter on MR scanner consoles and specifying a limit may lead to confusion for MR technicians, potentially resulting in the delay/cancellation of needed imaging.

59.

639

We recommend removing wait time labeling information from #5. It is unclear how to test for wait period. There is no guidance in the ASTM standards related to wait time. Multiple questions arise, such as, what percent decrees from peak temperature would be required?

Subjective, ambiguous. Clarify or remove.



Edit #

ID # Change Reason

60.

682

We recommend clarifying when it is and is not acceptable to use the recommended labeling for “Safety in MRI Not Evaluated.”

The wording of the guidance seems to indicate that the “Safety in MRI Not Evaluated” recommended labeling is only intended for devices that have historically not provided any information about MRI safety. However, if a new device is composed of materials known to be completely magnetically inert then is the “Safety in MRI Not Evaluated” labeling still applicable? Based on the first paragraph it appears as though a device manufacturer can justify why no MR safety testing was needed and apply the recommended labeling. If this is the case, please explicitly state that this rational can also apply to new devices and not just devices with a history of not providing MR safety data.

61.

691

Replace “migration” with “unwanted movement” and remove “image artifact” Thus, revise from “It has not been tested for heating, migration, or image artifact in the MR environment” to “It has not been tested for heating or unwanted movement in the MR environment.”

Unwanted movement is more consistent with hazard descriptions for MR induced Force and Torque. Image artifact is not considered a harmful interaction impacting the ability to safely scan a patient.

62.

695

We recommend adding examples of devices where “Safety in MRI Not Evaluated” labeling might also be applicable (i.e., resorbable polymer mesh).

This section provides examples of devices that are not appropriate for “Safety in MRI Not Evaluated” labeling. It is important to also provide acceptable example devices so that manufacturers can know what types of devices might be eligible for this labeling.



Edit #

ID # Change Reason

63.

711

Revise Appendix 1 title to specify this example is for submission content. Revise to – “Appendix 1. Example of Test Result Summary Included in Regulatory Submission”

It would be helpful to make clear the purpose for this type of test result summary table is to facilitate review of a regulatory submission.

64.

716

For the “Limits on Scan Duration” section, please provide guidance on how to label devices that were tested under the current common practice of 15-minute scan durations.

Most historical RF heating tests for passive devices have been conducted for 15-minute scan durations.

65.

716

Revise as follows: 4 2 W/kg whole body average SAR for (60 15) minutes of continuous RF (a sequence or back to back series/scan without breaks) followed by a wait time of (10) minutes if this limit is reached.

Better example as it aligns with ASTM F2182-11a.



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ID # Change Reason

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Appendix 2 MR Conditional Label Examples – Table 3 Consider clarifying that RF Excitation is only applicable for higher magnet strengths by splitting into separate rows for 1.5T vs. 3T or separate tables for 1.5T and 3T MR Conditional labeling. One could also consider adding a footnote explanation such as the following: “If the labeled field strength includes scanners that can operate in MC-2, then RF Excitation is a necessary parameter. All 1.5T scanners only operate in Circularly Polarized (CP) RF Excitation for the integrated whole body transmit coil, therefore it is recommended to omit this parameter.”

Evaluate user need and usability of MR Conditional labeling calling out RF Excitation of “Circularly Polarized (CP)” for 1.5T scanners. Per the Joint Working Group on ISO 10974 discussion, our understanding is that all 1.5T scanners operate as CP; however, this information is not currently displayed on the user interface for 1.5T scanners. Thus 1.5T labeling specifying the RF Excitation could result in user inconvenience and the potential of denying safe scans. Alternatively, if there is a desire to include RF Excitation in MR Conditional implant labeling across all magnet strengths, then users need a way to determine their scanner’s RF Excitation capability/setting.

RE: Docket No. FDA-2019-D-2837: Testing and Labeling ...€¦ · AdvaMed Comments on FDA Draft...

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