POLICY NO.: A106
APPROVED DATE: 06/07/04
EFFECTIVE DATE: 07/01/04
REVIEWED DATE:
MRI
DEPARTMENT OF RADIOLOGY
SUBJECT: MRI of Patients with Vagal Nerve Stimulators
( VNS )
I.
Policy
Vagal nerve stimulators are being used to reduce the frequency of seizures in adults and adolescents over age
12. VNS consists of electrical signals that are applied to the vagus nerve in the neck for transmission to the
brain. Because of the components of the device, caution must be used in the performance of MRI. Known risks
include heat induced in the Bipolar lead and activation of the device and stimulation. Testing has been
performed on a 1.5 Tesla General Electric Signa Imager only, using a phantom. Based on the results of these
tests documented in the Reference Manual for Magnetic Resonance Safety, 2003 ed.Pg.201-204, the following
guidelines will be followed in the performance of MRI in patients with Vagal Nerve Stimulators:
1.
2.
3.
4.
5.
The VNS must be turned off by the patient’s MD or nurse prior to arriving to the
MRI suite. If an outside physician implanted the VNS, the patient must go to his/her
office, have the VNS turned off by the appropriate person, and provide MRI written
documentation that the device was turned off, by whom, and the date and time. If the
patient’s VNS was implanted by a VCUHS physician, they must provide us with the
name of the physician or nurse who turned off the device so we can verify with that
person that the device has been turned off. The patient must return to the appropriate
person after the MRI exam to have the VNS turned back on.
Only a transmit and receive type RF head coil is to be used for MRI imaging. Do not
use a whole body RF coil. The head coil should not extend over the patient’s neck or
upper chest.
Use only a 2.0 Tesla scanner or less.
Standard Absorption Rate (SAR) should be < 1.3 W/kg for an average adult patient.
The patient must be able to communicate to the technologist or nurse if they feel any
discomfort.
II. Purpose
To establish the safety guidelines to be used in scanning patients with Vagal Nerve Stimulators
III. Responsibility
MRI Technologists
Radiologists
Referring MDs and their nurses