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.
Highlights
To predict the type and extent of cardiovascular magnetic resonance (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
Serial follow up imaging is often performed with cardiovascular magnetic resonance (CMR)
Pulse sequence type Imaging was performed with sequences routinely employed for cardiovascular imaging at our institution, including: 2D balanced-Steady State Free Precession (SSFP) for cardiac cine imaging and 2D-flow encoded Gradient Echo for phase-contrast flow measurements, high-resolution, spoiled 3D Gradient Echo (GRE) for contrast enhanced magnetic resonance angiography (MRA) and spoiled 3D gradient echo imaging (GRE) with view-sharing for timeresolved contrast enhanced MRA (TWIST)
Summary
To 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. Trans-catheter procedures in children with congenital heart disease have become a mainstay of therapy for many lesions. These procedures involve the placement of stents, vascular occluders, embolization devices and many other implantable devices. Serial follow up imaging is often performed with cardiovascular magnetic resonance (CMR). CMR is well suited to patients with congenital heart disease because of the quality of modern imaging, the lack of ionizing radiation, freedom from contrast nephrotoxicity and the likelihood of multiple follow up studies. CMR and magnetic resonance angiography (MRA) have become the gold standard for imaging many subgroups of congenital heart disease patients, e.g. assessing right ventricular and pulmonary vascular status in treated Tetralogy of Fallot (ToF) patients. Whereas imaging at 3T has potential advantages over 1.5T due to enhanced signal to noise ratio (SNR) [1,2], metal artifacts are potentially more problematic at 3T than at 1.5T [3]
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