Pediatric cardiovascular interventional devices: effect on CMR images at 1.5 and 3 Tesla

Abstract

BackgroundTo predict the type and extent of CMR artifacts caused by commonly used pediatric trans-catheter devices at 1.5 T and 3 T as an aid to clinical planning and patient screening.MethodsEleven commonly used interventional, catheter-based devices including stents, septal occluders, vascular plugs and embolization coils made from either stainless steel or nitinol were evaluated ex-vivo at both 1.5T and 3T. Pulse sequences and protocols commonly used for cardiovascular magnetic resonance (CMR) were evaluated, including 3D high-resolution MR angiography (MRA), time-resolved MRA, 2D balanced-SSFP cine and 2D phase-contrast gradient echo imaging (GRE). We defined the signal void amplification factor (F) as the ratio of signal void dimension to true device dimension. F1 and F2 were measured in the long axis and short axes respectively of the device. We defined F3 as the maximum extent of the off-resonance dark band artifact on SSFP measured in the B0direction. The effects of field strength, sequence type, orientation, flip angle and phase encode direction were tested. Clinical CMR images in 3 patients with various indwelling devices were reviewed for correlation with the in-vitro findings.ResultsF1 and F2 were higher (p<0.05) at 3T than at 1.5T for all sequences except 3D-MRA. Stainless steel devices produced greater off-resonance artifact on SSFP compared to nitinol devices (p<0.05). Artifacts were most severe with the stainless steel Flipper detachable embolization coil (Cook Medical, Bloomington, IN), with F1 and F2 10 times greater than with stainless steel stents. The orientation of stents changed the size of off-resonance artifacts by up to two fold. Sequence type did influence the size of signal void or off-resonance artifact (p<0.05). Varying the flip angle and phase encode direction did not affect image artifact.ConclusionStainless steel embolization coils render large zones of anatomy uninterpretable, consistent with predictions based on ex-vivo testing. Most other commonly used devices produce only mild artifact ex-vivo and are compatible with diagnostic quality in-vivo studies. Knowledge of ex-vivo device behavior can help predict the technical success or failure of CMR scans and may preempt the performance of costly, futile studies.

Effects of heart valve prostheses on phase contrast flow measurements in Cardiovascular Magnetic Resonance – a phantom study

“…It has already been described that elements from stainless steel cause stronger artefacts than Nitinol-based products [19, 28]. Our in vitro results are supported by single case examples, but have to be evaluated in a larger cohort.…”

“…The influence on the magnetic field depends on the material. The induced local magnetic field distortions have different impact on flow measurements [19, 28]. …”

Optimized protocols for cardiac magnetic resonance imaging in patients with thoracic metallic implants

“…Preliminary work has acknowledged this issue in the imaging of patients with congenital heart disease [16,17]. For example, sternal wires frequently obscure the border of an anterior aorta or neo-aorta, portions of a Fontan are obscured by septal occluders placed in the fenestration, and branch pulmonary arteries are obscured by bare metal stents.…”

Pediatric Body MR Angiography: Principles, Techniques, and Current Status in Body Imaging

“…Contraindications to MRI in general include cardiac pacemakers, cochlear implants, nontitanium aneurysm clips, implantable cardiac defibrillators, neurostimulators, and electronically programmed drug infusion pumps, among others. Contrastenhanced MRA images are generally of diagnostic quality when obtained at 1.5 T for pediatric patients who have had implanted devices, including stents not made of stainless steel [21]. However, the evaluation of the stented segment of the vessels may not be optimal all the time because of artifacts.…”