Strategically acquired gradient echo (STAGE)-derived MR angiography might be a superior alternative method to time-of-flight MR angiography in visualization of leptomeningeal collaterals

Impaired T1 mapping and Tmax during the first 7 days after ischemic stroke. A retrospective observational study

OBJECTIVE

To measure the relative T1 (rT1) value in different hypo-perfused regions after ischemic stroke using T1 mapping derived by Strategically Acquired Gradient Echo (STAGE) and assess its relationship with onset time and severity of ischemia.

MATERIALS AND METHODS

Sixty-three patients with acute anterior circulation ischemic stroke from 2017 to 2022 who underwent STAGE, diffusion weighted imaging (DWI) and dynamic susceptibility contrast perfusion weighted imaging (DSC-PWI) within 7 days were retrospectively enrolled. The areas with reduced diffusion and hypo-perfusion were segmented based on apparent diffusion coefficient (ADC) value < 0.62 × 10-3mm2/s and time-to-maximum (Tmax) thresholds (4, 6, 8, and 10 seconds). We measured the T1 value in the diffusion reduced and every 2 s Tmax strata regions and calculated rT1 (T1ipsi/T1contra) to explore the relationship between rT1 value, Tmax, and onset time.

RESULTS

rT1 value was increased in diffusion reduced (1.42) and hypo-perfused regions (1.02, 1.06, 1.12, 1.27, Tmax 4-6 s, 6-8 s, 8-10 s, > 10 s, respectively; all different from 1, P < 0.001). rT1 value was positively correlated with Tmax (rs = 0.61, P < 0.001) and onset time in area with reduced diffusion (rs = 0.39, P = 0.014).

CONCLUSIONS

Increased rT1 value in different hypo-perfused brain regions using T1 mapping derived by STAGE may reflect the edema; it was associated with the severity of Tmax and showed a weak correlation with the onset time in diffusion reduced areas.

The incomplete circle of Willis is associated with vulnerable intracranial plaque features and acute ischemic stroke

BACKGROUND

The circle of Willis (CoW) plays a significant role in intracranial atherosclerosis (ICAS). This study investigated the relationship between different types of CoW, atherosclerosis plaque features, and acute ischemic stroke (AIS).

METHODS

We investigated 97 participants with AIS or transient ischemic attacks (TIA) underwent pre- and post-contrast 3T vessel wall cardiovascular magnetic resonance within 7 days of the onset of symptoms. The culprit plaque characteristics (including enhancement grade, enhancement ratio, high signal in T1, irregularity of plaque surface, and normalized wall index), and vessel remodeling (including arterial remodeling ratio and positive remodeling) for lesions were evaluated. The anatomic structures of the anterior and the posterior sections of the CoW (A-CoW and P-CoW) were also evaluated. The plaque features were compared among them. The plaque features were also compared between AIS and TIA patients. Finally, univariate and multivariate regression analysis was performed to evaluate the independent risk factors for AIS.

RESULT

Patients with incomplete A-CoW showed a higher plaque enhancement ratio (P = 0.002), enhancement grade (P = 0.01), and normalized wall index (NWI) (P = 0.018) compared with the patients with complete A-CoW. A higher proportion of patients with incomplete symptomatic P-CoW demonstrated more culprit plaques with high T1 signals (HT1S) compared with those with complete P-CoW (P = 0.013). Incomplete A-CoW was associated with a higher enhancement grade of the culprit plaques [odds ratio (OR):3.84; 95% CI: 1.36-10.88, P = 0.011], after adjusting for clinical risk factors such as age, sex, smoking, hypertension, hyperlipemia, and diabetes mellitus. Incomplete symptomatic P-CoW was associated with a higher probability of HT1S (OR:3.88; 95% CI: 1.12-13.47, P = 0.033), after adjusting for clinical risk factors such as age, sex, smoking, hypertension, hyperlipemia, and diabetes mellitus. Furthermore, an irregularity of the plaque surface (OR: 6.24; 95% CI: 2.25-17.37, P < 0.001), and incomplete symptomatic P-CoW (OR: 8.03, 95% CI: 2.43-26.55, P = 0.001) were independently associated with AIS.

CONCLUSIONS

This study demonstrated that incomplete A-CoW was associated with enhancement grade of the culprit plaque, and incomplete symptomatic side P-CoW was associated with the presence of HT1S of culprit plaque. Furthermore, an irregularity of plaque surface and incomplete symptomatic side P-CoW were associated with AIS.

CAU-Net: A Deep Learning Method for Deep Gray Matter Nuclei Segmentation

The abnormal iron deposition of the deep gray matter nuclei is related to many neurological diseases. With the quantitative susceptibility mapping (QSM) technique, it is possible to quantitatively measure the brain iron content in vivo. To assess the magnetic susceptibility of the deep gray matter nuclei in the QSM, it is mandatory to segment the nuclei of interest first, and many automatic methods have been proposed in the literature. This study proposed a contrast attention U-Net for nuclei segmentation and evaluated its performance on two datasets acquired using different sequences with different parameters from different MRI devices. Experimental results revealed that our proposed method was superior on both datasets over other commonly adopted network structures. The impacts of training and inference strategies were also discussed, which showed that adopting test time augmentation during the inference stage can impose an obvious improvement. At the training stage, our results indicated that sufficient data augmentation, deep supervision, and nonuniform patch sampling contributed significantly to improving the segmentation accuracy, which indicated that appropriate choices of training and inference strategies were at least as important as designing more advanced network structures.