Cook Medical adheres to the system of MRI compatibility terms developed in 2005 by the American Society for Testing and Materials (ASTM). This adoption came about in an effort to clarify the terminology and, more important, because misuse of old terminology could result in serious accidents for patients and other individuals. This new system references the MR environment where testing took place, which includes the location inside the static magnetic field and its magnitude, spatial gradients, time-varying magnetic fields, radio frequency (RF) magnetic field pulses and specific absorption rates (SAR).

Taking these conditions into consideration, three new categories were developed: MR Safe, MR Conditional, and MR Unsafe. In this system, "safe" and "unsafe" are the two extremes. "Conditional" is in the middle and characterizes the behavior of a medical device under specific conditions in the MRI environment as determined by testing. In addition to the new terms, the ASTM International document introduced corresponding icons consistent with international standards for colors and shapes of safety signs. The icons are intended for use on items that may be brought into or near the MRI environment as well as in product labeling. The new terminology and icon structure is intended to help clarify matters related to biomedical implants and devices to ensure the safe use of MRI technology.

	MR Safe—An item that poses no known hazards in all MRI environments. MR Safe items include nonconducting, nonmetallic, nonmagnetic items such as plastic, silicone and glass. An item may be determined to be MR Safe on the basis of scientific rationale rather than test data.
	MR Conditional—An item that has been demonstrated to pose no known hazards in a specified MRI environment with specified conditions of use. Field conditions should be enumerated on the product, its packaging or in the enclosed literature. Additional conditions, including specific configurations of the item (e.g., the routing of leads used for a neurostimulation system) may be required.
	MR Unsafe—An item that is known to pose hazards in all MRI environments. MR Unsafe items include magnetic items such as a pair of ferromagnetic scissors.

Read Zenith Endovascular Graft Frequently Asked Questions

Zenith Flex AAA Endovascular Graft MRI Safety and Compatibility Download

MRI Safety and Compatibility
Non-clinical testing has demonstrated that the Zenith AAA Endovascular Graft is MR Conditional. It can be scanned safely under the following conditions:

1.5 Tesla Systems:

• Static magnetic field of 1.5 Tesla
• Spatial gradient field of 450 Gauss/cm
• Maximum whole body averaged specific absorption rate (SAR) of 2 W/kg for 15 minutes of scanning

In non-clinical testing, the Zenith AAA Endovascular Graft produced a temperature rise of less than or equal to 1.4 °C at a maximum whole body averaged specific absorption rate (SAR) of 2.8 W/kg, as assessed by calorimetry for 15 minutes of MR scanning in a 1.5 Tesla Magnetom, Siemens Medical Magnetom, Numaris/4 Software, Version Syngo MR 2002B DHHS MR Scanner. The maximum whole body averaged specific absorption rate (SAR) was 2.8 W/kg, which corresponds to a calorimetry measured value of 1.5 W/kg.

3.0 Tesla Systems:

• Static magnetic field of 3.0 Tesla
• Spatial gradient field of 720 Gauss/cm
• Maximum whole body averaged specific absorption rate (SAR) of 2 W/kg for 15 minutes of scanning

In non-clinical testing, the Zenith AAA Endovascular Graft produced a temperature rise of less than or equal to 1.9 °C at a maximum whole body averaged specific absorption rate (SAR) of 3.0 W/kg, as assessed by calorimetry for 15 minutes of MR scanning in a 3.0 Tesla Excite, GE Electric Healthcare, G3.0-052B Software, MR Scanner. The maximum whole body averaged specific absorption rate (SAR) was 3.0 W/kg, which corresponds to a calorimetry measured value of 2.8 W/kg.

The image artifact extends throughout the anatomical region containing the device, obscuring the view of immediately adjacent anatomical structures within approximately 20 cm of the device, as well as the entire device and its lumen, when scanned in nonclinical testing using the sequence: Fast spin echo, in a 3.0 Tesla, Excite, GE Electric Healthcare, with G3.0-052B software, MR system with body radiofrequency coil.

For all scanners, the image artifact dissipates as the distance from the device to the area of interest increases. MR scans of the head and neck and lower extremities may be obtained without image artifact. Image artifact may be present in scans of the abdominal region and upper extremities, depending on distance from the device to the area of interest.

Clinical information is available for seventeen patients who received MRI scans after stent-graft implantation. There have been no reported adverse events or device problems in any of these patients as a result of having received an MRI. Additionally, there have been well over 50,000 Zenith AAA Endovascular Grafts implanted worldwide, in which there have been no reported adverse events or device problems as a result of MRI.

Cook Recommends that the patient register the MR conditions disclosed in this IFU with the MedicAlert Foundation. The MedicAlert Foundation can be contacted in the following manners:

Zenith TX2 MRI Compatibility Download

Non-clinical testing has demonstrated that the Zenith TX2 TAA Endovascular Graft is MR Conditional. It can be scanned safely under the following conditions:

1.5 Tesla Systems:

• Static magnetic field of 1.5 Tesla
• Spatial gradient field of 450 Gauss/cm
• Maximum whole-body-averaged specific absorption rate (SAR) of 2 W/kg for 15 minutes of scanning

In non-clinical testing, the Zenith TX2 TAA Endovascular Graft produced a temperature rise of less than 1.4°C at a maximum whole-body-averaged specific absorption rate (SAR) of 2.8 W/kg for 15 minutes of MR scanning in a 1.5 Tesla Magnetom, Siemens Medical Magnetom MR scanner. The maximum whole-body-averaged specific absorption rate (SAR) was 2.8 W/kg, which corresponds to a calorimetry measured value of 1.5 W/kg.

3.0 Tesla Systems:

• Static magnetic field of 3.0 Tesla
• Spatial gradient field of 720 Gauss/cm
• Maximum whole-body-averaged specific absorption rate (SAR) of 2 W/kg for 15 minutes of scanning

In non-clinical testing, the Zenith TX2 TAA Endovascular Graft produced a temperature rise of less than 1.9°C at a maximum whole-body-averaged specific absorption rate (SAR) at 3.0 W/kg for 15 minutes of MR scanning in a 3.0 Tesla, Excite, GE Electric Healthcare MR scanner. The maximum whole-body-averaged specific absorption rate (SAR) was 3.0 W/kg, which corresponds to a calorimetry measured value of 2.8 W/kg.

The image artifact extends throughout the anatomical region containing the device, obscuring the view of immediately adjacent anatomical structures within approximately 20 cm of the device, as well as the entire device and its lumen, when scanned in non-clinical testing using the sequence: Fast spin echo in a 3.0 Tesla, Excite, GE Electric Healthcare, with G3.0-052B software, MR system with body radiofrequency coil.

For all scanners, the image artifact dissipates as the distance from the device to the area of interest increases. MR scans of the lower extremities may be obtained without image artifact. Image artifact may be present in scans of the abdominal, upper extremity, and head and neck region, depending on distance from the device to the area of interest.

Clinical information is available on six patients who received MRI scans during the course of the clinical trial. There have been no reported adverse events or device problems in any of these patients as a result of having received an MRI. Additionally, there have been approximately 3,000 patients implanted with Zenith TAA Endovascular Grafts worldwide, in which there have been no reported adverse events or device problems as a result of MRI.

Cook recommends that the patient register the MR conditions disclosed in this IFU with the MedicAlert Foundation. The MedicAlert Foundation can be contacted in the following manners:

The following is a list of frequently asked questions and answers regarding Cook Medical's MRI statement for Zenith® endovascular grafts.

1. Which Zenith devices are covered in this statement?
All U.S. commercially available Zenith grafts are covered by the new Zenith MR Conditional statement, including:

• Zenith AAA Endovascular Grafts (main body and iliac legs)
• Zenith Flex® AAA Endovascular Grafts (main body, iliac legs and main body extensions)
• Zenith AAA Endovascular Graft Ancillary Components (main body extensions, iliac leg extensions, converters, occluders and iliac plugs)
• Zenith Renu® AAA Ancillary Grafts (main body extension and converter configurations). Refer to question #15.
• Zenith TX2® TAA Endovascular Grafts (proximal components, proximal-tapered components, distal components, proximal extensions and distal extensions)

2. Is the new Zenith MR Conditional statement retroactive and applicable to all Zenith products?
All current and previous versions of commercially available U.S. Zenith grafts are covered by the new Zenith MR Conditional statement. See question #1 for a complete list of Zenith products.

3. Is there a limit to how many components can be scanned (e.g., multiple ESBE, ESLE, etc.)?
No limit to the number of components that can be scanned has been established.

4. The patient's current Zenith patient ID card says the patient should not be scanned. Do we follow the card or follow the website information?
The information shown on the website reflects updated testing of Zenith devices and replaces the information that was current at the time the patient's device and device ID card were produced.

5. On the patient ID card is the statement, “Because of potential risks, the MRI facility should allow for prompt intervention, if necessary.” Does Cook advise free-standing MRI centers not scan this patient, as they are not prepared for prompt intervention?
As long as the center is following the MR Conditional parameters and the equipment has been validated, the Zenith grafts may be safely scanned. If scanning parameters exceed the specified conditions found to be safe for this device, or the MRI scanner is known to be out of calibration, prompt intervention should be available.

6. Is the Zenith graft MRI Safe?
The Zenith grafts are considered safe to scan in the MR environment when the specified conditions of use/scanning are not exceeded. Per FDA standards, the Zenith grafts are considered MR Conditional. MR Conditional means the grafts have been demonstrated to pose no known hazards in a specified MR environment with specified conditions of use. The specified MR environment and specified conditions of use for the Zenith grafts are listed in the new Zenith MR Conditional statement.

7. What changed in the Zenith graft to make it MR Conditional?
Nothing has changed with the Zenith graft. Additional MR testing and analyses were performed that confirm the grafts fall within the FDA guidelines of MR Conditional.

8. Under what conditions were the grafts tested?
The test conditions associated with MR testing are stated in the Instructions for Use. These Instructions for Use can be found on the Cook Medical website at www.cookmedical.com.

9. What is the specific absorption rate (SAR) and how is it measured?
SAR is a measure of the absorption of radio frequency energy deposited in biological tissue. SAR is typically measured in watts per kilogram (W/kg).

10. What if the patient is in the scanner over 15 minutes?
The maximum whole body averaged SAR is reported as a function of watts per kilogram over a continuous 15 minute period of scanning. Having the patient in the nonactive MR scanner does not contribute to the SAR. Testing for induced heating and reporting of the maximum whole body averaged specific SAR are reported for 15 minutes of continuous scanning; however, the continuous scanning time in the clinical setting is unlikely to exceed 15 minutes. Radio-frequency-induced heating during MR imaging has been evaluated with nonclinical testing for Zenith products for a total of 15 minutes of continuous scanning. The maximum temperature rise detected was a clinically safe temperature of 1.9°C. Longer scan times have not been established; however, scanning may be stopped and restarted for an additional 15 minutes.

11. Do the stainless steel stents of the Zenith devices produce unsafe levels of force during MR imaging?
The forces imparted by the Zenith stents have been established to be safe with nonclinical testing and clinical data.

12. What does the spatial gradient field of 720 gauss/cm mean? How do we figure that out?
The spatial gradient field is defined as the rate of change in the magnetic field as a function of position. This typically occurs just outside the bore of the MR system. The spatial gradient can exert a translational force on a device. This maximum spatial gradient is typically reported by the manufacturer of the MR system.

13. What is the maximum whole body averaged SAR reported by the MR system?
This number is reported by the manufacturer of the MR system and is defined as the total RF power deposition in the patient divided by the mass.

14. What is the maximum whole body averaged SAR measured by calorimetry?
This is the measured SAR of the gelled saline phantom used in nonclinical testing.

15. Is it safe to scan a patient with a Zenith Renu AAA Ancillary Graft used in conjunction with a preexisting graft?
If the preexisting graft is MR Unsafe, the MRI should not be performed. If the preexisting graft is MR Safe or MR Conditional, the MRI can be performed under the conditions stated in the Zenith MRI Compatibility statement and by the manufacturer of the preexisting graft, with the following exception. The feasibility of scanning the Zenith Renu AAA Ancillary Graft inside a preexisting graft that contains metallic stents on the inner diameter of the graft for a significant length (> 50 mm) has not been established and may pose a risk of RF heating.