High-resolution compressed sensing time-of-flight MR angiography outperforms CT angiography for evaluating patients with Moyamoya disease after surgical revascularization

A 3-Minute Ultrafast MRI and MRA Protocol for Screening of Acute Ischemic Stroke

OBJECTIVE

To evaluate the diagnostic performance of a 3-min ultrafast brain MRI and MRA protocol for screening of acute ischemic stroke.

METHODS

This study involved 67 adult patients who underwent ultrafast and reference MRI and MRA scans from September 2023 to June 2024 for stroke evaluation. Two readers independently assessed the ultrafast and reference MRI and MRA images in a masked and randomized manner for acute and chronic infarct and hemorrhage as well as large-vessel occlusion and severe stenosis. A 3-point Likert scale was used to evaluate diagnostic quality of the ultrafast sequences and Cohen's κ was used to assess interrater agreement.

RESULTS

The ultrafast MRI and MRA protocol showed high diagnostic quality, with 98% of sequences rated as diagnostic. Raters showed perfect agreement in identifying acute infarcts, aneurysms, and vascular occlusions using both ultrafast and reference protocols and near-perfect agreement (>95%) for detecting acute hemorrhage and severe stenosis. For chronic conditions such as chronic infarction and chronic hemorrhage, there was substantial agreement with κ values ranging from 0.73 to 0.76.

DISCUSSION

The screening ultrafast MRI and MRA protocol can effectively identify acute ischemic stroke and intracranial large-vessel occlusion with high diagnostic accuracy while significantly reducing acquisition time, making it suitable for initial stroke triage. Evaluation for chronic pathologies on the ultrafast protocol is inferior compared with standard MRI and MRA imaging.

Multi-parameter MRI-Based Machine Learning Model to Evaluate the Efficacy of STA-MCA Bypass Surgery for Moyamoya Disease: A Pilot Study

Superficial temporal artery-middle cerebral artery (STA-MCA) bypass surgery represents the primary treatment for Moyamoya disease (MMD), with its efficacy contingent upon collateral vessel development. This study aimed to develop and validate a machine learning (ML) model for the non-invasive assessment of STA-MCA bypass surgery efficacy in MMD. This study enrolled 118 MMD patients undergoing STA-MCA bypass surgery. Clinical features were screened to construct a clinical model. MRI features were extracted from the middle cerebral artery supply area using 3D Slicer and employed to build five ML models using logistic regression algorithm. The combined model was developed by integrating the radiomics score (Rad-score) with the clinical features. Model performance validation was conducted using ROC curves. Platelet count (PLT) was identified as a significant clinical feature for constructing the clinical model. A total of 3404 features (851 × 4) were extracted, and 15 optimal features were selected from each MRI sequence as predictive factors. Multivariable logistic regression identified PLT and Rad-score as independent parameters used for constructing the combined model. In the testing set, the AUC of the T1WI ML model [0.84 (95% CI, 0.70-0.97)] was higher than that of the clinical model [0.66 (95% CI, 0.46-0.86)] and the combined model [0.80 (95% CI, 0.66-0.95)]. The T1WI ML model can be used to assess the postoperative efficacy of STA-MCA bypass surgery for MMD.

Superior Visualization of Neovascularization with Silent Magnetic Resonance Angiography Compared to Time-of-Flight Magnetic Resonance Angiography After Bypass Surgery in Moyamoya Disease

OBJECTIVE

The evaluation of postsurgical neoangiogenesis in patients with moyamoya disease (MMD) is crucial for appropriate patient management. This study aimed to assess the visualization of neovascularization after bypass surgery using noncontrast-enhanced silent magnetic resonance angiography (MRA) with ultrashort echo time and arterial spin labeling.

METHODS

After bypass surgery, 13 patients with MMD were followed up for >6 months between September 2019 and November 2022. They underwent silent MRA in the same session as time-of-flight magnetic resonance angiography (TOF-MRA) and digital subtraction angiography (DSA). Two observers independently rated the visualization of neovascularization in both types of MRA from 1 (not visible) to 4 (nearly equal to DSA), with reference to DSA images as the standard.

RESULTS

The mean scores were significantly higher for silent MRA compared with TOF-MRA (3.81 ± 0.48 and 1.92 ± 0.70, respectively) (P < 0.01). The intermodality agreements were 0.83 and 0.71 for silent MRA and TOF-MRA, respectively. TOF-MRA depicted the donor artery and recipient cortical artery after direct bypass surgery, although fine neovascularization developed after indirect bypass surgery was poorly visualized. Silent MRA could reveal the developed bypass flow signal and perfused middle cerebral artery territory, which was almost equal to the DSA images.

CONCLUSIONS

Silent MRA achieves better visualization of postsurgical revascularization in patients with MMD than TOF-MRA. Moreover, it may have the potential to provide visualization of the developed bypass flow equivalent to DSA.

Clinical use of color Doppler ultrasonography to predict and evaluate the collateral development of two common revascularizations in patients with moyamoya disease

Objective

To explore the value of color Doppler ultrasonography (CDU) to predict preoperatively and evaluate postoperatively the collateral development of two common revascularizations in patients with moyamoya disease (MMD).

Methods

We prospectively enrolled 49 patients with MMD who underwent unilateral superficial temporal artery (STA) -middle cerebral artery (MCA) anastomosis or encephalo-duro-arterio-synangiosis (EDAS). The parameters of the extracranial arteries, including STA, internal carotid artery (ICA), external carotid artery (ECA), and vertebral artery (VA), were performed before and at 3–6 months after surgery. DSA results were used to assess surgical collateral development.

Results

To predict good collateral development before STA-MCA anastomosis, the preoperative D > 1.75 mm in the STA had the highest area under the Receiver Operating Characteristic curve (AUC). To predict good collateral development before EDAS, the preoperative EDV > 12.00 cm/s in the STA had the highest AUC. To evaluate the good collateral development after STA-MCA anastomosis, the postoperative EDV > 16.50 cm/s in the STA had the highest AUC. To evaluate the good collateral development after EDAS, an increase of D of 0.15 mm in the STA had the highest AUC. Logistic regression analysis showed that the preoperative RI and EDV in the STA were highly correlated with collateral development. Besides, the preoperative RI was an independent risk factor for collateral development.

Conclusion

CDU could predict preoperatively and evaluate postoperatively the collateral development of STA-MCA anastomosis and EDAS surgery postoperatively by detecting ultrasound parameters of the STA.

Radiation Dose Reduction Opportunities in Vascular Imaging

Computed tomography angiography (CTA) has been the gold standard imaging modality for vascular imaging due to a variety of factors, including the widespread availability of computed tomography (CT) scanners, the ease and speed of image acquisition, and the high sensitivity of CTA for vascular pathology. However, the radiation dose experienced by the patient during imaging has long been a concern of this image acquisition method. Advancements in CT image acquisition techniques in combination with advancements in non-ionizing radiation imaging techniques including magnetic resonance angiography (MRA) and contrast-enhanced ultrasound (CEUS) present growing opportunities to reduce total radiation dose to patients. This review provides an overview of advancements in imaging technology and acquisition techniques that are helping to minimize radiation dose associated with vascular imaging.