Ultra-short echo time magnetic resonance imaging for detection of pulmonary arteriovenous malformation recanalization after coil embolization: a case report and a phantom study

Assessment of pulmonary arteriovenous malformation with ultra-short echo time magnetic resonance imaging

PURPOSE

The purpose of this study was to evaluate the diagnostic performance of ultra-short echo time magnetic resonance imaging (UTE MRI) in the assessment of pulmonary arteriovenous malformation (PAVM).

METHODS

Eighteen consecutive patients (mean [± standard deviation] age, 48.6 ± 16.8 years) with 46 untreated PAVMs who underwent and thin-section computed tomography (CT) and UTE MRI with a 1.5-Tesla and 3-Tesla unit were retrospectively assessed. Two radiologists evaluated the diagnostic capabilities of UTE MRI for the detection and classification of PAVMs with reference to CT. Sensitivity, specificity, and kappa statistics were calculated with reference to CT. We also compared the differences in PAVM measurements between CT and MRI.

RESULTS

The sensitivity and specificity of UTE-MRI for the detection of PAVMs were 89.1% and 100%, respectively, for reader 1 and 87.0% and 100%, respectively, for reader 2. In the classification of PAVMs, inter-modality agreement in reader 1 and 2 were both substantial (κ = 0.78 and 0.69, respectively). The measurements of the PAVM feeding artery and sac on CT and MRI were strongly correlated in both readers 1 and 2 (R² = 0.981 and 0.983, respectively). Both readers 1 and 2 slightly underestimated the diameter of the PAVM feeding artery and sac on UTE MRI (p < 0.001).

CONCLUSION

This study indicates that UTE MRI is a feasible and promising modality for noninvasive assessment of PAVMs.

Ultra-short echo time magnetic resonance angiography using a modified signal targeting with alternative radio frequency spin labeling technique for detecting recanalized pulmonary arteriovenous malformation after coil embolization

Pulmonary arteriovenous malformation (PAVM) is a rare vascular anomaly, for which transcatheter embolization with metallic coils is the standard of care. Although detecting recanalization after embolotherapy is crucial, direct visualization of residual flow with computed tomography or magnetic resonance (MR) imaging is generally difficult due to metal artifacts. We present a case of recanalized PAVM after coil embolization detected by ultra-short echo time MR angiography using a modified signal targeting with an alternative radio frequency spin labeling technique.

Noncontrast MR angiography: An update

Both computed tomography (CT) angiography (CTA) and contrast-enhanced MR angiography (CEMRA) have proven to be useful and accurate cross-sectional imaging modalities over a wide range of vascular territories and vascular disorders. A key advantage of MRA is that, unlike CTA, it can be performed without the administration of a contrast agent. In this review article we consider the motivations for using noncontrast MRA, potential contrast mechanisms, imaging techniques, advantages, and drawbacks with respect to CTA and CEMRA, and the level of evidence for using the various MRA techniques. In addition, we explore new developments that promise to expand the reliability and range of clinical applications for noncontrast MRA, along with functional MRA capabilities not available with CTA or CEMRA. Level of Evidence: 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;49:355-373.

[Comparison of Influence of Susceptibility Artifact due to Metallic Embolic Material in MRA Image]

PURPOSE

To identify the influence of susceptibility artifact caused by commonly used trans-catheter embolic devices for vascular lesions in the body on the images of various magnetic resonance angiography (MRA) techniques as an aid to patient screening after endovascular embolization.

MATERIALS AND METHODS

We constructed vascular phantoms in which three embolic materials; platinum coil, Inconel coil, and vascular plug, were placed. Each phantom was imaged with three types of MRA techniques as follows: ultra-short echo time magnetic resonance imaging (UTE), three-dimensional fast advanced spin echo (3D-FASE), time-resolved contrast MRA with key hole technique (Key hole). For each embolic material, four reviewers compared the visual capabilities of the vessel lumen and surrounding area of each MRA technique by using a four-point visual scoring system. The quantitative values of susceptibility artifacts generated from each embolic material were compared between each MRA technique.

RESULTS

For all MRA techniques, the platinum coil showed the highest visual score (median=four-point) among all the embolic materials (p<0.05). In the platinum coil, the MR signal in the coil was clearly depicted in UTE. For all MRA technique, the quantitative values of the susceptibility artifacts were the lowest in platinum coil among all the embolic materials (p<0.05).

CONCLUSION

UTE is less susceptible to susceptibility artifact of embolic materials.