Simultaneous T1, T2, and T2* Mapping of Carotid Plaque: The SIMPLE* Technique.

Background Quantitative T1, T2, and T2* measurements of carotid atherosclerotic plaque are important in evaluating plaque vulnerability and monitoring its progression. Purpose To develop a sequence to simultaneously quantify T1, T2, and T2* of carotid plaque. Materials and Methods The simultaneous T1, T2, and T2* mapping of carotid plaque (SIMPLE*) sequence is composed of three modules with different T2 preparation pulses, inversion-recovery pulses, and acquisition schemas. Single-echo data were used for T1 and T2 quantification, while the multiecho (ME) data were used for T2* quantification. The quantitative accuracy of SIMPLE* was tested in a phantom study by comparing its measurements with those of reference standard sequences. In vivo feasibility of the technique was prospectively evaluated between November 2020 and February 2022 in healthy volunteers and participants with carotid atherosclerotic plaque. The Pearson or Spearman correlation test, Student t test, and Wilcoxon rank-sum test were used. Results T1, T2, and T2* estimated with SIMPLE* strongly correlated with inversion-recovery spin-echo (SE) (correlation coefficient [r] = 0.99), ME-SE (r = 0.99), and ME gradient-echo (r = 0.99) sequences in the phantom study. In five healthy volunteers (mean age, 25 years ± 3 [SD]; three women), measurements were similar between SIMPLE* and modified Look-Locker inversion recovery, or MOLLI (1151 msec ± 71 vs 1098 msec ± 64; P = .14), ME turbo SE (31 msec ± 1 vs 31 msec ± 1; P = .32), and ME turbo field echo (24 msec ± 2 vs 25 msec ± 2; P = .19). In 18 participants with carotid plaque (mean age, 65 years ± 9; 16 men), quantitative T1, T2, and T2* of plaque components were consistent with their signal characteristics on multicontrast images. Conclusion A quantitative technique for simultaneous T1, T2, and T2* mapping of carotid plaque with 100-mm3 coverage and 0.8-mm3 resolution was developed using the proposed SIMPLE* sequence and demonstrated high accuracy and in vivo feasibility. © RSNA, 2023 Supplemental material is available for this article.

A Novel Subtraction Method to Reduce Metal Artifacts of Cerebral Aneurysm Embolism Coils.

OBJECTIVE: To investigate a novel subtraction method (S-MAR), combing metal artifact reduction (MAR), virtual monochromatic imaging (VMI), and subtraction CT angiography (CTA) to remove the metal artifacts of coils after endovascular embolotherapy of intracranial aneurysms. METHOD: In this retrospective study, 29 patients with 38 coils after endovascular embolotherapy of intracranial aneurysms who underwent cerebral CTA using a dual-layer detector spectral CT were included. Conventional CT images (CI), virtual non-enhanced (VNC) images and VMI ranging from 40 to 120 KeV in steps of 10 were reconstructed. These images were then postprocessed to CIMAR, VMIMAR and VNCMAR with MAR software (O-MAR; Philips Healthcare, Cleveland, OH, USA). The novel subtraction method (S-MAR) was derived from subtraction imaging between VNCMAR and the optimal VMIMAR. Contrast-to-noise (CNR) and Noise(Background) of CI, CIMAR, VMI, and VMIMAR were calculated quantitatively. Two Independent radiologists qualitatively assessed artifacts in all images using coil artifact score (CA score), a 5-point Likert scale. Besides, all coils were divided into two groups (group 1: diameter < 5.0 mm, group 2: diameter ≥ 5.0 mm). Differences between two groups were statistically analyzed. RESULTS: The optimal KeV was 40 KeV. Strong correlations between diameter of coils and the CA score of CI were found (rs = 0.652, P < 0.05). CNR, Noise and CA score were significantly improved by CIMAR and VMIMAR compared with CI (P < 0.05). The S­MAR showed significantly better performance compared with CI, CIMAR, VMI, and VMIMAR in reducing metal coil artifacts according to the CA score (P < 0.05), especially in group 2. CONCLUSION: The novel S­MAR proved to be a promising method to reduce coil metal artifacts and elevate the vessel visualization adjacent to coils. It could develop to be widely used in cerebral CTA after coiled aneurysms.

Hemodynamic analysis of the recipient parasylvian cortical arteries for predicting postoperative hyperperfusion during STA-MCA bypass in adult patients with moyamoya disease.

OBJECTIVE: Superficial temporal artery-middle cerebral artery (STA-MCA) bypass is a common approach for treating moyamoya disease (MMD); however, the selection of recipient vessels is still controversial, and its relationship with postoperative cerebral hyperperfusion (CHP) has not been revealed. The aim of the study was to investigate the relationship between the hemodynamic sources of the recipient parasylvian cortical arteries (PSCAs) and the occurrence of postoperative CHP. METHODS: The authors retrospectively analyzed the clinical data from 68 adult patients (75 hemispheres) with MMD who underwent STA-MCA bypass. Based on their hemodynamic sources from the MCA and non-MCAs, the PSCAs were classified as M-PSCAs and non-M-PSCAs, and their distributional characteristics were studied. Moreover, the patients' demographics, incidence of postoperative CHP, and post- and preoperative relative cerebral blood flow values were examined. RESULTS: The digital subtraction angiography analysis demonstrated that 40% (30/75) of the recipient PSCAs had no hemodynamic relationship with the MCA. The post- and preoperative relative cerebral blood flow values of the M-PSCA group were significantly higher than those of the non-M-PSCA group (p < 0.001). Multivariate analysis revealed that the hemodynamic source of PSCAs from the MCA was significantly associated with the development of focal (p = 0.003) and symptomatic (p = 0.021) CHP. Twelve (85.7%) of the 14 patients with symptomatic CHP and all 4 (100%) patients with postoperative hemorrhage were from the M-PSCA group. CONCLUSIONS: This study revealed that direct anastomoses of PSCAs with anterograde hemodynamic sources from the MCA had a high risk of postoperative CHP during STA-MCA bypass in adult patients with MMD.