Vascular access ports, infusion pumps, and catheters are implants and devices commonly used to provide long-term vascular administration of chemotherapeutic agents, antibiotics, analgesics and other medications (also, see information pertaining to other similar devices including Ambulatory Infusion Pumps, Insulin Pumps, the IsoMed Implantable Constant-Flow Infusion Pump, Prometra Programmable Pumps, the SynchroMed, SynchroMED EL, and SynchroMed II Drug Infusion Systems).

Vascular access ports are usually implanted in a subcutaneous pocket over the upper chest wall with the catheters inserted in the jugular, subclavian, or cephalic vein. Vascular access ports have a variety of similar features (e.g., a reservoir, central septum, and catheter) and may be constructed from different materials including stainless steel, titanium, silicone, and plastic. Because of the widespread use of vascular access ports and associated catheters and the high probability that patients with these devices may require MR procedures, it has been important to characterize the MRI issues for these implants.

Three of the implantable vascular access ports and catheters evaluated for safety with MR procedures showed measurable magnetic field interactions during exposure to the MR systems (typically 1.5-Tesla) used for testing, but the interactions were minor relative to the in vivo applications of these implants. Therefore, an MR procedure is acceptable at 1.5-Tesla or less in a patient that has one of the vascular access ports or catheters shown in The List.

With respect to MR imaging and artifacts, in general, vascular access ports that produce the least amount of artifact are made entirely from nonmetallic materials. The ones that produce the largest artifacts are composed of metal(s) or have metal in an unusual shape (e.g., the OmegaPort Access Devices).

Even vascular access ports made entirely from nonmetallic materials are “seen” on the MR images because they contain silicone. The septum portion vascular access ports is typically made from silicone. Using MR imaging, the Larmor precessional frequency of fat is close to that of silicone (i.e. 100-Hz at 1.5-T). Therefore, silicone used in the construction of a vascular access port may be observed on MR images with varying degrees of signal intensity depending on the pulse sequence that is used.

If a radiologist did not know that this type of vascular access port was present in a patient, the MR signal produced by the silicone component of the device could be considered an abnormality, or at the very least, present a confusing image. For example, this may cause a diagnostic problem in a patient evaluated for a rupture of a silicone breast implant, because silicone from the vascular access port may be misinterpreted as an “extracapsular silicone implant rupture.”

MRI at 3-Tesla and Vascular Access Ports and Catheters. For the vascular access ports and catheters assessed for magnetic field interactions at 3-Tesla, these items did not exhibit substantial magnetic field interactions and, therefore, will not move or dislodge in this MR environment. Because of the design aspects typically used for vascular access ports, MRI-related heating is rarely an issue. However, for certain catheters, MRI-related heating can be substantial and pose possible problems for patients referred for MRI examinations, as reported recently by Owen, et al. (2014).

For the accessories, some (e.g., Huber needle) showed measurable magnetic field interactions (see The List). However, during the intended uses of these accessories, it is unlikely that they will present a problem in 3-Tesla or less MR environments considering that the simple application of adhesive tape or other appropriate means of retention effectively counterbalances the magnetic qualities of these devices (Unpublished Observations, F.G. Shellock).

REFERENCES

Owens S, et al. Evaluation of epidural and peripheral nerve catheter heating during magnetic resonance imaging. Reg Anesth Pain Med 2014;39:534-9.

Shellock FG. Biomedical implants and devices: Assessment of magnetic field interactions with a 3.0-Tesla MR system. J Magn Reson Imag 2002;16:721-732.

Shellock FG, Nogueira M, Morisoli S. MR imaging and vascular access ports: Ex vivo evaluation of ferromagnetism, heating, and artifacts at 1.5-T. J Magn Reson Imag 1995;4:481-484.

Shellock FG, Shellock VJ. Vascular access ports and catheters tested for ferromagnetism, heating, and artifacts associated with MR imaging. Magnetic Resonance Imaging 1996;14:443-447.

Titterington B, Shellock FG. Evaluation of MRI issues for an access port with a radiofrequency identification (RFID) tag. Magnetic Resonance Imaging 2013;31:1439-44.