Black-Blood Magnetization Prepared 2 Rapid Acquisition Gradient Echoes: A Fast and Three-Dimensional MR Black-Blood T1 Mapping Technique for Quantitative Assessment of Atherosclerosis and Venous Thrombosis

Abstract

Background: Blood flow signals may be a confounder in quantifying T₁ values of plaque or thrombus and how to realize black-blood T₁ mapping remains a challenge task.

Purpose: To develop a fast and three-dimensional black-blood T₁ mapping technique for quantitative assessment of atherosclerosis and venous thrombosis.

Study type: Sequence development and optimization via phantoms and volunteers as well as pilot prospective.

Phantom and subjects: Numerical simulations, a standard phantom, 8 healthy volunteers (mean age, 22 ± 1 years; 5 males), and 19 patients (mean age, 57 ± 14 years; 13 males) with atherosclerosis or venous thrombosis.

Field strength/sequence: 3T/inversion recovery spin-echo sequence (IR-SE), magnetization prepared 2 rapid acquisition gradient echoes (MP2RAGE), and black-blood prepared MP2RAGE (BB-MP2RAGE).

Assessment: The black-blood preparation (i.e., delay alternating with nutation for tailored excitation, DANTE) was incorporated into MP2RAGE for black-blood T₁ mapping. The BB-MP2RAGE was optimized numerically based on the Bloch equation, and then the phantom study was performed to verify the accuracy of T₁ mapping by BB-MP2RAGE against IR-SE and MP2RAGE. Preliminary clinical validation was prospectively performed to assess the flow suppression effect and its potential application in plaque and thrombosis identification.

Statistical tests: Pearson correlation test, Bland-Altman analysis, paired t-test, and intraclass correlation coefficient. A P value <0.05 indicates a statistically significant difference.

Results: Phantom experiments showed comparable accuracy of T₁ maps by BB-MP2RAGE with IR-SE and MP2RAGE (all r² > 0.99); Compared to MP2RAGE, BB-MP2RAGE effectively nulled the blood flow signals, and had a significant improvement in contrast-to-noise ratio between static tissue and blood (250.5 ± 66.6 vs. 91.9 ± 35.9). BB-MP2RAGE can quantify plaque or thrombus T₁ relaxation time with blood flow signal suppression.

Data conclusion: Accurate T₁ mapping with sufficient blood flow suppression was achieved by BB-MP2RAGE. BB-MP2RAGE has the potential to quantitatively characterize atherosclerosis and venous thrombosis.

Level of evidence: 1 TECHNICAL EFFICACY: Stage 1.

Keywords: T1 mapping; atherosclerosis; black‐blood imaging; venous thrombosis.