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

BackgroundBlood 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.PurposeTo develop a fast and three‐dimensional black‐blood T1 mapping technique for quantitative assessment of atherosclerosis and venous thrombosis.Study TypeSequence development and optimization via phantoms and volunteers as well as pilot prospective.Phantom and SubjectsNumerical 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/Sequence3T/inversion recovery spin‐echo sequence (IR‐SE), magnetization prepared 2 rapid acquisition gradient echoes (MP2RAGE), and black‐blood prepared MP2RAGE (BB‐MP2RAGE).AssessmentThe 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 TestsPearson correlation test, Bland–Altman analysis, paired t‐test, and intraclass correlation coefficient. A P value <0.05 indicates a statistically significant difference.ResultsPhantom 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 ConclusionAccurate 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 Evidence1Technical EfficacyStage 1