Diagnostic Performance of a Lower‐dose Contrast‐Enhanced 4D Dynamic MR Angiography of the Lower Extremities at 3 T Using Multisegmental Time‐Resolved Maximum Intensity Projections

Abstract

Background For peripheral artery disease (PAD), MR angiography (MRA) is a well‐established diagnostic modality providing morphologic and dynamic information comparable to digital subtraction angiography (DSA). However, relatively large amounts of contrast agents are necessary to achieve this. Purpose To evaluate the diagnostic accuracy of time‐resolved 4D MR‐angiography with interleaved stochastic trajectories (TWIST‐MRA) by using maximum intensity projections (MIPs) of dynamic images acquired with reduced doses of contrast agent. Study Type Retrospective. Population Forty adult PAD patients yielding 1088 artery segments. Field Strength/Sequence A 3.0 T, time‐resolved 4D MR‐angiography with TWIST‐MRA and MIP of dynamic images. Assessment DSA was available in 14 patients (256 artery segments) and used as reference standard. Three‐segmental MIP reconstructions of TWIST‐images after administration of 3 mL of gadolinium‐based contrast agent (Gadoteridol/Prohance®, 0.5 M) per anatomical level (pelvis, thighs, and lower legs) yielded 256 artery segments for correlation between MRA and DSA. Three independent observers rated image quality (scale: 1 [nondiagnostic] to 4 [excellent]) and the degree of venous overlay (scale: 0 [none] to 2 [significant]) for all segments. Diagnostic accuracy for the detection of >50% stenosis and artery occlusion was calculated for all observers. Statistical Tests Binary classification test (sensitivity, specificity, positive/negative predictive values, diagnostic accuracy). Intraclass correlation coefficients (ICCs), logistic regression analysis with comparison of areas under the receiver‐operating‐characteristics (ROC) curves (AUCs) with the DeLong method. Bland–Altman‐comparison. Results High diagnostic performance was achieved for the detection of >50% stenosis (sensitivity 92.9% [84.3–99.9% (95%‐CI)] and specificity 98.5% [95.7–99.8% (95%‐CI)]) and artery occlusion (sensitivity 93.1% [77.2–99.2% (95%‐CI)] and specificity 99.1% [96.9–99.9% (95%‐CI)]). Inter‐reader agreement was excellent with ICC values ranging from 0.95 to 1.0 for >50% artery stenosis and occlusion. Image quality was good to excellent for both readers (3.41 ± 0.72, 3.33 ± 0.65, and 3.38 ± 0.61 [mean ± SD]) with good correlation between observer ratings (ICC 0.71–0.81). No significant venous overlay was observed (0.06 ± 0.24, 0.23 ± 0.43 and 0.11 ± 0.45 [mean ± SD]). Data Conclusion MIPs of dynamic TWIST‐MRA offer a promising diagnostic alternative necessitating only reduced amounts (50%) of gadolinium‐based contrast agents for the entire runoff vasculature. Evidence Level 3 Technical Efficacy Stage 2

Effect of Contrast Agent Dose Reduction on Vascular Enhancement and Image Quality in Thoracoabdominal Dynamic 3-Dimensional Magnetic Resonance Angiography

“…These findings are in contrast to previous studies, which reported a high image quality for a dose of 0.03 mmolGd/kg 6,7 or even lower fixed-volume GBCA doses 8,11 . There are 2 factors that may explain this: first, these studies were performed at 3 T, and second, these studies only evaluated arterial vessels.…”

Editorial for “Diagnostic Performance of a Lower‐Dose Contrast Enhanced 4D Dynamic MR Angiography of the Lower Extremities at 3 T Using Multi‐Segmental Time Resolved Maximum Intensity Projections”

“…Magnetic resonance imaging (MRI) angiography (MRA) appears as an appealing alternative, either as an MRI with multi‐station contrast enhancement (CE) or as time resolution (TR) MRA. Indeed, MRA has high diagnostic accuracy and has been recently proposed as the imaging modality of choice 1–6 …”

“…Interobserver agreement was excellent with intraclass correlation coefficient values ranging from 0.95 to 1.0 for >50% stenosis and occlusion. Image quality was good to excellent for both readers (3.41 and 3.38), with good correlation between observer ratings (Intraclass correlation coefficient [ICC] 0.71–0.81) 6 …”

“…Image quality was good to excellent for both readers (3.41 and 3.38), with good correlation between observer ratings (Intraclass correlation coefficient [ICC] 0.71-0.81). 6 Among the limitations of the study, few details on ancillary medical therapy were provided. Moreover, the addition of positive and negative likelihood ratios, diagnostic odds ratios, and Youden index for the diagnostic evaluation would allow the readers to evaluate the performance of the model in a more precise and prevalence-independent fashion.…”

“…Indeed, MRA has high diagnostic accuracy and has been recently proposed as the imaging modality of choice. [1][2][3][4][5][6] In this issue of the journal, the authors used DSA to evaluate the diagnostic accuracy of time-resolved 4D MRA with interleaved stochastic trajectories (TWIST-MRA) by using maximum intensity projections (MIPs) of dynamic images acquired with reduced doses of contrast agent. Analyzing 14 patients with a total of 256 artery segments, a high diagnostic performance was achieved for detecting >50% stenosis with a sensitivity and specificity of 92.9% and 98.5%, respectively, and detecting artery occlusion with a sensitivity and specificity of 93.1% and 99.1%, respectively.…”