Visualization of lenticulostriate arteries at 3T: Optimization of slice-selective off-resonance sinc pulse-prepared TOF-MRA and its comparison with flow-sensitive black-blood MRA

Fast imaging of lenticulostriate arteries by high-resolution black-blood T1-weighted imaging with variable flip angles and acceleration by compressed sensitivity encoding

OBJECTIVE

We investigated the feasibility of using compressed sensitivity encoding (CS-SENSE) to accelerate high-resolution black-blood T1-weighted imaging with variable flip angles (T1WI-VFA) for efficient visualization and characterization of lenticulostriate arteries (LSAs) on a 3.0 T MR scanner.

MATERIALS AND METHODS

Twenty-five healthy volunteers and 18 patients with the cerebrovascular disease were prospectively enrolled. Healthy volunteers underwent T1WI-VFA sequences with different acceleration factors (AFs), including conventional sensitivity encoding (SENSE) AF = 3 and CS-SENSE AF = 3, 4, 5, and 6 (SENSE3, CS3, CS4, CS5, CS6, respectively) at 3 Tesla MRI scanner. Objective evaluation (contrast ratio and number, length, and branches of LSAs) and subjective evaluation (overall image quality and LSA visualization scores) were used to assess image quality and LSA visualization. Comparisons were performed among the 5 sequences to select the best AF. All patients underwent both T1WI-VFA with the optimal AF and digital subtraction angiography (DSA) examination, and the number of LSAs observed by T1WI-VFA was compared with that by DSA.

RESULTS

Pair-wise comparisons among CS3, CS4, and SENSE3 revealed no significant differences in both objective measurements and subjective evaluation (all P > 0.05). In patients, there was no significant difference in LSA counts on the same side between T1WI-VFA with CS4 and DSA (3, 3-4 and 3, 3-3, P = 0.243).

CONCLUSIONS

CS3 provided better LSA visualization but a longer scan duration compared to CS4. And, CS4 strikes a good balance between LSA visualization and acquisition time, which is recommended for routine clinical use.

High-resolution magnetic resonance vessel wall imaging provides new insights into Moyamoya disease

Moyamoya disease (MMD) is a rare condition that affects the blood vessels of the central nervous system. This cerebrovascular disease is characterized by progressive narrowing and blockage of the internal carotid, middle cerebral, and anterior cerebral arteries, which results in the formation of a compensatory fragile vascular network. Currently, digital subtraction angiography (DSA) is considered the gold standard in diagnosing MMD. However, this diagnostic technique is invasive and may not be suitable for all patients. Hence, non-invasive imaging methods such as computed tomography angiography (CTA) and magnetic resonance angiography (MRA) are often used. However, these methods may have less reliable diagnostic results. Therefore, High-Resolution Magnetic Resonance Vessel Wall Imaging (HR-VWI) has emerged as the most accurate method for observing and analyzing arterial wall structure. It enhances the resolution of arterial walls and enables quantitative and qualitative analysis of plaque, facilitating the identification of atherosclerotic lesions, vascular entrapment, myofibrillar dysplasia, moyamoya vasculopathy, and other related conditions. Consequently, HR-VWI provides a new and more reliable evaluation criterion for diagnosing vascular lesions in patients with Moyamoya disease.

Visualization of the lenticulostriate arteries, long insular arteries, and long medullary arteries on intra-arterial computed tomography angiography with ultrahigh resolution in patients with glioma

PURPOSE

The anatomical association between the lesion and the perforating arteries supplying the pyramidal tract in insulo-opercular glioma resection should be evaluated. This study reported a novel method combining the intra-arterial administration of contrast medium and ultrahigh-resolution computed tomography angiography (UHR-IA-CTA) for visualizing the lenticulostriate arteries (LSAs), long insular arteries (LIAs), and long medullary arteries (LMAs) that supply the pyramidal tract in two patients with insulo-opercular glioma.

METHODS

This method was performed by introducing a catheter to the cervical segment of the internal carotid artery. The infusion rate was set at 3 mL/s for 3 s, and the delay time from injection to scanning was determined based on the time-to-peak on angiography. On 2- and 20-mm-thick UHR-IA-CTA slab images and fusion with magnetic resonance images, the anatomical associations between the perforating arteries and the tumor and pyramidal tract were evaluated.

RESULTS

This novel method clearly showed the relationship between the perforators that supply the pyramidal tract and tumor. It showed that LIAs and LMAs were far from the lesion but that the proximal LSAs were involved in both cases. Based on these results, subtotal resection was achieved without complications caused by injury of perforators.

CONCLUSION

UHR-IA-CTA can be used to visualize the LSAs, LIAs, and LMAs clearly and provide useful preoperative information for insulo-opercular glioma resection.

Visualizing Cerebral Small Vessel Degeneration During Aging and Diseases Using Magnetic Resonance Imaging

Cerebral small vessel disease is a major contributor to brain disorders in older adults. It is associated with a much higher risk of stroke and dementia. Due to a lack of clinical and fluid biomarkers, diagnosing and grading small vessel disease are highly dependent on magnetic resonance imaging. In the past, researchers mostly used brain parenchymal imaging markers to represent small vessel damage, but the relationships between these surrogate markers and small vessel pathologies are complex. Recent progress in high-resolution magnetic resonance imaging methods, including time-of-flight MR angiography, phase-contrast MR angiography, black blood vessel wall imaging, susceptibility-weighted imaging, and contrast-enhanced methods, allow for direct visualization of cerebral small vessel structures. They could be powerful tools for understanding aging-related small vessel degeneration and improving disease diagnosis and treatment. This article will review progress in these imaging techniques and their application in aging and disease studies. Some challenges and future directions are also discussed. EVIDENCE LEVEL: 4. TECHNICAL EFFICACY: 3.

Peliminary exploration on the differential diagnosis between meningioma and schwannoma using contrast-enhanced T1WI flow-sensitive black-blood sequence

Introduction

Contrast-enhanced T₁WI flow-sensitive black-blood (CE-T1WI FSBB) is a newly developed sequence which had not been widely used for differential diagnosis of brain tumors.

Methods

To quantify the pre-operative imaging features of intratumoral microbleeds and intratumoral vessels using CE-T₁WI FSBB scan and study the differences in biological behavior of meningiomas and schwannomas underlying the imaging features. Seventy-three cases of meningiomas and 24 cases of schwannomas confirmed by postoperative pathology were included. Two neuroradiologists independently counted intratumoral vessels and intratumoral microbleeds based on CE-T₁WI FSBB images. The vessel density index (VDI) and microbleed density index (MDI) were the number of intratumoral vessels and the number of intratumoral microbleeds divided by the tumor volume, respectively. The consistency test of intratumoral vessel count and intratumoral microbleed count based on CE-T₁WI FSBB were summarized using 2-way random intraclass correlation coefficients (ICC). Mann-Whitney U-test and chi-square test were used to determine significant differences between meningiomas and schwannomas, and fibrous meningiomas and epithelial meningiomas. P<0.05 was considered statistically significant.

Results

The ICC of intratumoral vessels count and intratumoral microbleeds count were 0.89 and 0.99, respectively. There were significant differences in the number of intratumoral microbleeds (P<0.01) and MDI values (P<0.01) between meningiomas and schwannomas. There were no differences in the number of intratumoral vessels (P=0.64), VDI (P=0.17), or tumor volume (P=0.33). There were also differences in the number of intratumoral microbleeds (P<0.01), the MDI value (P<0.01), and the sex of patients (P<0.05) between fibrous meningiomas and epithelial meningiomas.

Discussion

CE-T₁WI FSBB can be a new technique for differentiating schwannomas from meningiomas, and even different types of meningiomas. Schwannomas have a higher incidence of intratumoral hemorrhage, more intratumoral microbleeds, and higher MDI values than meningiomas, which provides a new basis for preoperative differential diagnosis and treatment decisions.

Preoperative Assessment of Blood Vessels and Intratumoral Microbleeds in Brain Tumors Based on a 3D Contrast-Enhanced T1 -Weighted Flow-Sensitive Black-Blood Sequence

BACKGROUND

Three-dimensional (3D) contrast-enhanced T₁ -weighted flow-sensitive black-blood (CE-T₁ WI FSBB) is a newly developed black blood sequence by adding motion probing gradient pulses to gradient echo (GRE) sequences, which has important value for the preoperative assessment of tumor brain blood supply vessels and intratumoral microbleeds.

PURPOSE

To compare 3D CE-T₁ WI FSBB and 3D contrast-enhanced fast spin echo (FSE) sequence for T₁ WI for preoperative assessment of blood vessels and microbleeds in brain tumors and to investigate the correlation between visible vessels and microbleeds.

STUDY TYPE

Prospective.

SUBJECTS

One hundred and seventy-five patients with brain tumors, 65 were male, 110 were female. Including histologically confirmed 73 meningiomas, 23 schwannomas, 20 gliomas, 7 hemangioblastomas, 5 metastases, 2 lymphomas, 2 hemangiopericytomas, 2 germ cell tumors, 1 craniopharyngioma, and 1 cholesteatoma.

FIELD STRENGTH/SEQUENCE

A 3-T, CE-T₁ WI FSBB, GRE; 3-T, CE-T₁ WI, FSE.

ASSESSMENT

Three neuroradiologists counted the number of intratumoral vessels on CE-T₁ WI and CE-T₁ WI FSBB images separately, and they counted the number of intratumoral microbleeds on CE-T₁ WI FSBB images. Brain tumors were classified into grade I, grade II, and grade IV according to the World Health Organization (WHO) grading. Differences in the ability of CE-T₁ WI FSBB and CE-T₁ WI to display intratumoral vessels were compared. The mean counts of three observers were used to study the correlation between vessels and microbleeds.

STATISTICAL TESTS

Two-way random intraclass correlation coeficient (ICC) was used for inter-reader agreement regarding intratumoral vessel and microbleed counts, and the linear regression analysis (with F-test) was used to study the correlation between intratumoral vessels and microbleeds based on CE-T₁ WI FSBB (α = 0.05).

RESULTS

Inter-reader agreements for intratumoral vessel count on CE-T₁ WI (ICC = 0.93) and CE-T₁ WI FSBB (ICC = 0.92), and the agreement for intratumoral microbleed count on CE-T₁ WI FSBB (ICC = 0.99) were excellent. There were statistically significant differences in intratumoral vessel counts between CE-T₁ WI and CE-T₁ WI FSBB using Mann-Whitney U -test: image readers could identify more intratumoral vessels on CE-T₁ WI FSBB images, particularly for meningiomas, schwannomas, gliomas, and WHO grade I tumors. The number of intratumoral vessels had a significant positive effect on the number of intratumoral microbleeds (microbleeds = 5.024 + 1.665 × vessels; F = 11.51).

DATA CONCLUSION

More intratumoral vessels could potentially be identified using a 3D CE-T₁ WI FSBB sequence compared to a CE-T₁ WI sequence, and the number of intratumoral vessels showed a positive linear relationship with the number of intratumoral microbleeds, which might suggest that brain tumors with rich blood supply were more prone to intratumoral microbleeds.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 3.

Variations in the branching patterns of the anterior choroidal artery: an angiographic study with special reference to temporal lobe epilepsy surgery

BACKGROUND

The preservation of the anterior choroidal artery (AChA) is essential for avoiding neurological sequelae after mesial temporal lobe epilepsy (mTLE) surgery. The purpose of this study is to reveal the anatomical variation in which the perforating branches arise from the plexal segment of the AChA by using a modern neuroimaging modality.

METHODS

This study analyzed 3D rotational angiography (3DRA) images from 56 subjects. The AChA and perforating branches were visualized using slab MIP. We analyzed branching patterns, courses of the perforating arteries arising from the plexal segment of the AChA, and the anastomosis of the AChA with other cerebral arteries.

RESULTS

The slab MIP applied to 3DRA visualized one or more perforating branches from the AChA in 92.9% of cases. The presence of perforating branches arising from the AChA plexal segment was 17.3%. Most of the branching points of plexal perforators were likely located in the operative field during hippocampal resection. The course of the AChA plexal perforators included the posterior limb of the internal capsule. Anastomosis with other cerebral arteries was visualized in 25% of the AChA with plexal perforators.

CONCLUSIONS

3DRA slab MIP was useful for visualizing the perforating branches of the AChA. Our results showed the possibility that surgical manipulation of the choroid plexus may cause infarction in the AChA territory. We suggest that the existence of the AChA plexal perforators should be recognized to further enhance the safety of hippocampal resection for mTLE.

Neuroimaging at 7 Tesla: a pictorial narrative review

Neuroimaging using the 7-Tesla (7T) human magnetic resonance (MR) system is rapidly gaining popularity after being approved for clinical use in the European Union and the USA. This trend is the same for functional MR imaging (MRI). The primary advantages of 7T over lower magnetic fields are its higher signal-to-noise and contrast-to-noise ratios, which provide high-resolution acquisitions and better contrast, making it easier to detect lesions and structural changes in brain disorders. Another advantage is the capability to measure a greater number of neurochemicals by virtue of the increased spectral resolution. Many structural and functional studies using 7T have been conducted to visualize details in the white matter and layers of the cortex and hippocampus, the subnucleus or regions of the putamen, the globus pallidus, thalamus and substantia nigra, and in small structures, such as the subthalamic nucleus, habenula, perforating arteries, and the perivascular space, that are difficult to observe at lower magnetic field strengths. The target disorders for 7T neuroimaging range from tumoral diseases to vascular, neurodegenerative, and psychiatric disorders, including Alzheimer's disease, Parkinson's disease, multiple sclerosis, epilepsy, major depressive disorder, and schizophrenia. MR spectroscopy has also been used for research because of its increased chemical shift that separates overlapping peaks and resolves neurochemicals more effectively at 7T than a lower magnetic field. This paper presents a narrative review of these topics and an illustrative presentation of images obtained at 7T. We expect 7T neuroimaging to provide a new imaging biomarker of various brain disorders.

Visualization of lenticulostriate artery by intracranial dark-blood vessel wall imaging and its relationships with lacunar infarction in basal ganglia: a retrospective study

OBJECTIVES

There is close relationship between lenticulostriate arteries (LSAs) and lacunar infarctions (LIs) of the basal ganglia. The study aims to visualize the LSAs using high-resolution vessel wall imaging (VWI) on 3T system and explore the correlation between LSAs and LIs.

METHODS

Fifty-six patients with LIs in basal ganglia, and 44 age-matched control patients were enrolled and analyzed retrospectively. The raw VWI images were reformatted into coronal slices in minimum intensity projection for further observation of LSAs. The risk factors of LIs in basal ganglia were analyzed by univariate and multivariate logistic regression. The correlation and linear regression analysis between the LSAs and LIs, ipsilateral MCA-M1 plaques were investigated.

RESULTS

The total number (p < 0.01) and length (p < 0.01) of LSAs were statistically different between basal ganglias with and without LIs. The total number of LSAs and ipsilateral MCA-M1 plaques were independently related to LIs in basal ganglias. The mean length of LSAs were negatively correlated with number (r = - 0.33, p = 0.002) and volume (r = - 0.37, p = 0.001) of LIs. Age, drinking history, and mean length of LSAs were associated with LI occurrence in basal ganglia, and mean length of LSAs was correlated with larger volume of LIs.

CONCLUSIONS

Number of LSA reduction and ipsilateral MCA-M1 plaques were associated with the presence of LIs in basal ganglias. Age increasing, drinking history, and shorter LSAs were correlated with the increasing of LIs.

KEY POINTS

• Patients with LIs tend to have shorter LSAs. • The characteristics of LSAs and ipsilateral MCA-M1 plaques are associated with LIs in basal ganglias. • Age, drinking history, and mean length of LSAs are correlated with LI features in basal ganglias.

Validation of choroidal anastomosis on high-resolution magnetic resonance imaging as an imaging biomarker in hemorrhagic moyamoya disease

OBJECTIVES

This study aimed to investigate the association between dilation and proliferation and anastomosis of perforating arteries, and intracranial hemorrhage in moyamoya disease (MMD) patients, using high-resolution magnetic resonance imaging (HRMRI).

METHODS

Adult patients with MMD at advanced stages were prospectively enrolled and underwent HRMRI exams. Dilation and proliferation of the lenticulostriate artery (LSA), medullary artery, and anterior or posterior choroidal arteries (AChA or PChA) were assessed. Abnormal anastomoses were identified between (1) the LSA and the medullary or insular arteries; (2) the thalamo-geniculate, thalamo-tuberal, or thalamo-perforating arteries and the medullary or insular arteries; and (3) the AChA or PChA and the medullary or insular arteries. The association between these variables and hemorrhagic events was calculated using univariate and multivariate analyses.

RESULTS

Fifty patients (14 men; mean age, 35.4 ± 9.7 years) were finally analyzed, including 17 hemorrhagic patients and 33 non-hemorrhagic patients. The inter-rater agreement for the qualitative evaluation of perforating arteries was good. Dilation and proliferation of the AChA or PChA (88.2% versus 54.5%, p = 0.027), and choroidal anastomosis (64.7% versus 18.2%, p = 0.002) were more frequently observed in patients with hemorrhage. Multivariate logistic regression showed that choroidal anastomosis remained significantly associated with hemorrhage (odds ratio = 5.95, 95% confidence interval = 1.21-29.25, p = 0.028).

CONCLUSIONS

Choroidal anastomosis is independently associated with hemorrhagic events in adult patients with MMD at advanced stages. HRMRI can provide detailed information on both the anatomies and abnormal collaterals in MMD, which facilitates risk estimates of bleeding in MMD.

KEY POINTS

• High-resolution magnetic resonance imaging allows for the evaluation of perforating arteries in patients with moyamoya disease. • Choroidal anastomosis is associated with hemorrhagic events in patients with moyamoya disease. • High-resolution magnetic resonance imaging might facilitate further grading and classification of moyamoya vessels.

Asymmetric lenticulostriate arteries in patients with moyamoya disease presenting with movement disorder: three new cases

OBJECTIVE

Unilateral movement disorder associated with moyamoya disease is a rare finding and the mechanism remains to be fully elucidated. Theories postulated include contralateral cerebral ischemic or hemorrhagic lesions, and/or hypoperfusion. However, few studies have reported such patients without contralateral lesions nor hypoperfusion. This study aimed to explore the potential mechanism of those who had neither contralateral cerebral lesions nor hypoperfusion.

METHODS

Neuroradiological features of lenticulostriate arteries in three cases with unilateral movement disorder associated with moyamoya disease who had neither contralateral lesions nor hypoperfusion were mainly analyzed.

RESULTS

Angiography and 3 T black-blood T1-weighted intracranial vessel wall imaging both demonstrated a significant asymmetry between bilateral lenticulostriate arteries qualitatively and quantitatively on admission. After one-year follow-up, two patients' vessel wall imaging indicated that the asymmetry diminished, and the symptoms spontaneously resolved.

CONCLUSION

This report demonstrated that patients with moyamoya disease with unilateral movement disorder who had neither contralateral lesions nor hypoperfusion may be related to the asymmetry between bilateral lenticulostriate arteries through basal ganglia.

Visualization of Lenticulostriate Arteries on CT Angiography Using Ultra-High-Resolution CT Compared with Conventional-Detector CT

BACKGROUND AND PURPOSE

The newly developed ultra-high-resolution CT is equipped with a 0.25-mm detector, which has one-half the conventional section thickness, one-half the in-plane detector element width, and one-half the reconstructed pixel width compared with conventional-detector CT. Thus, the ultra-high-resolution CT scanner should provide better image quality for microvasculature than the conventional-detector CT scanners. This study aimed to determine whether ultra-high-resolution CT produces superior-quality images of the lenticulostriate arteries compared with conventional-detector CT.

MATERIALS AND METHODS

From February 2017 to June 2017, thirteen patients with aneurysms (4 men, 9 women; mean age, 61.2 years) who underwent head CTA with both ultra-high-resolution CT and conventional-detector CT were enrolled. Two board-certified radiologists determined the number of all lenticulostriate arteries on the CTA coronal images of the MCA M1 segment reconstructed from 512 matrixes on conventional-detector CT and 1024 matrixes on ultra-high-resolution CT.

RESULTS

There were statistically more lenticulostriate arteries identified on ultra-high-resolution CT (average, 2.85 ± 0.83; 95% CI, 2.509-3.183) than on conventional-detector CT (average, 2.17 ± 0.76; 95% CI, 1.866-2.480) (P = .009) in 16 of the total 26 MCA M1 segments.

CONCLUSIONS

Improvements in lenticulostriate artery visualization were the result of the combined package of the ultra-high-resolution CT scanner plus the ultra-high-resolution scanning protocol, which includes higher radiation doses with lower than the national diagnostic reference levels and stronger adaptive iterative dose-reduction processing. This package for ultra-high-resolution CT is a simple, noninvasive, and easily accessible method to evaluate microvasculature such as the lenticulostriate arteries.

Assessment of the Hemodynamics of Autogenous Arteriovenous Fistulas With 4D Phase Contrast-Based Flow Quantification MRI in Dialysis Patients

BACKGROUND

Regular monitoring of autogenous arteriovenous fistulas (AVFs) for hemodialysis patients has importance. Hence, 4D flow MRI may be an alternative for assessing the hemodynamics of AVFs.

PURPOSE

To compare the hemodynamics of AVFs using Doppler ultrasound (DUS) and 4D-MRI in renal dialysis patients.

STUDY TYPE

Case-control study from October 2017 to April 2018.

POPULATION

Fifty patients (age [range] = 59.52 [39-71] years) with AVFs were included.

FIELD STRENGTH/SEQUENCE

Black-blood MRI and 4D flow MRI at 3.0T and AVF ultrasonography were also performed.

ASSESSMENT

The hemodynamics acquired from 4D flow MRI and ultrasonography by two radiologists were compared. The AVF anatomy was described through an examination of the black-blood MRI.

STATISTICAL TESTS

The consistency of AVF anatomy and hemodynamics and the consistency of the hemodynamics of AVFs from 4D flow MRI and ultrasound were analyzed by paired t-tests. The morphological parameters of AVFs acquired from black-blood MRI were used for a Pearson correlation analysis with the hemodynamic parameters obtained from 4D flow MRI data.

RESULTS

The consistency of the morphological and hemodynamic parameters measured from MRI by the two radiologists was good (all P < 0.01). The velocities and flow volumes from the 4D flow MRI and vascular ultrasound of AVFs were in moderate agreement (all P < 0.05, r = 0.292-0.569), except for the peak flow velocity at the anastomosis (P = 0.366, r = -0.078). The flow volume and WSS near the anastomotic site were closely related to the morphology of the AVFs (all P < 0.05). The hemodynamics of the complications group were significantly different from those of patients without any complications (normal patients group) (all P < 0.01).

DATA CONCLUSION

Compared with ultrasonography, 4D flow MRI is a promising technique to noninvasively estimate the AVF hemodynamics of renal dialysis patients.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:1272-1280.

The Visualization Methods of Occluded Dural Sinus for Safe Transvenous Embolization of Dural AVFs

BACKGROUND

Transvenous embolization (TVE) via occluded sinus is one option for the treatment of dural arteriovenous fistulas. Understanding of the anatomical characteristics of the occluded sinus is difficult. It is often hard to reach the shunt point because of some risk of vessel perforation.

METHODS

We assessed usefulness of T1 Volumetric Isotropic TSE Acquisition (VISTA) Black Blood (BB) and 3D-T1 Fast Field Echo (FFE) for the evaluation and visualization of an occluded sinus. Evaluation of T1 VISTA BB and 3D-T1 FFE was performed preoperatively. TVE was performed via the occluded sinus while referring to the visualized reconstruction image.

RESULTS

Fourteen cases of TVE were performed between 2009 and 2015. The entire occluded sinus, including both thrombus and blood flow, was seen as the high-intensity region on 3D FFE T1 gadlinium (Gd). On the other hand, thrombus was seen as the iso- or high-intensity region and blood flow as the low-intensity region on T1 VISTA BB. The maximum intensity projection reconstruction image of 3D FFE T1Gd could visualize the whole occluded sinus and was useful for microcatheter maneuver. Total shunt obliteration was achieved in 13 cases (92.8%) except for one.

CONCLUSIONS

Magnetic resonance imaging evaluation of the occluded sinus using both T1 VISTA BB and 3D FFE T1Gd gives us valuable information of the occluded sinus regarding the development and the course of the occluded sinus, the length of the thrombotic occlusion, and leads to safer catheter maneuvers in TVE.

Whole-brain magnetic resonance imaging of plaque burden and lenticulostriate arteries in patients with different types of stroke

Background

Large-vessel atherosclerotic disease is an important pathogenesis of deep-perforator infarction (DPI). However, altered vessel walls of intracranial large arteries and distribution of small arteries in DPI are unclear because of the limited resolution of current imaging techniques. In this study the intracranial plaque burden and lenticulostriate artery (LSA) distribution in patients with recent DPI and non-DPI using whole-brain vessel-wall imaging (WB-VWI) were investigated.

Methods

A total of 44 patients with recent DPI (23 patients) or non-DPI (21 patients) due to intracranial atherosclerotic disease were prospectively enrolled. WB-VWI was performed in all the patients using a three-dimensional T1-weighted vessel-wall magnetic resonance technique. Hemispheres with DPI and non-DPI were considered as the DPI group and non-DPI group, respectively. Hemispheres without a history of stroke were the control group. The intracranial plaque burden was compared between the DPI and non-DPI groups. The number and length of visualized LSA branches among DPI, non-DPI, and control groups were also evaluated.

Results

A total of 77 hemispheres were analyzed (23 in the DPI group, 21 in the non-DPI group, and 33 in the control group). Plaque burden was lower (p = 0.047) in the DPI group (82.0 ± 45.9 mm³) compared with the non-DPI group (130.9 ± 90.3 mm³). There was a significant reduction (p = 0.002) in length of visualized LSA branches in the DPI group (74.1 ± 21.7 mm) compared with the control group (104.6 ± 33.3 mm).

Conclusions

WB-VWI enables the combination of vessel-wall and LSA imaging in one image setting, which can provide information about plaque burden and LSA distribution.

Visualization of the lenticulostriate arteries at 3T using black-blood T1-weighted intracranial vessel wall imaging: comparison with 7T TOF-MRA

OBJECTIVES

The objective of this study was to explore the feasibility of using intracranial T1-weighted vessel wall imaging (VWI) to visualize the lenticulostriate arteries (LSAs) at 3T.

MATERIAL AND METHODS

Thirteen healthy volunteers were examined with VWI at 3T and TOF-MRA at 7T during the same day. On the vascular skeletons obtained by manual tracing, the number of stems and branches of LSAs were counted. On the most prominent branch in every hemisphere, the contrast-to-noise ratio (CNR), the full length and the local length (5-15 mm above MCAs) were measured and compared between the two methods. Nine stroke patients with intracranial artery stenosis were also recruited into the study. The branches of LSAs were compared between the symptomatic and asymptomatic side.

RESULTS

The extracted vascular trees were in good agreement between 7T TOF-MRA and 3T VWI. The two acquisitions showed similar numbers of the LSA stems. The number of branches revealed by 3T VWI was slightly lower than 7T TOF. The full lengths were slightly lower by VWI at 3T (p = 0.011, ICC = 0.917). The measured local lengths (5-15 mm from MCAs) showed high coherence between VWI and TOF-MRA (p = 0.098, ICC = 0.970). In stroke patients, 12 plaques were identified on MCA segments, and nine plaques were located on the symptomatic side. The average numbers of LSA visualized by 3T VWI were 4.3±1.3 on the symptomatic side and 5.0±1.1 on the asymptomatic side.

CONCLUSION

3T VWI is capable of depicting LSAs, particularly the stems and the proximal segments, with comparable image quality to that of 7T TOF-MRA.

KEY POINTS

• T1-weighted intracranial VWI at 3T allows for black-blood MR angiography of lenticulostriate artery. • 3T intracranial VWI depicts the stems and proximal segments of the lenticulostriate arteries comparable to 7T TOF-MRA. • It is feasible to assess both large vessel wall lesions and lenticulostriate vasculopathy in one scan.

Quantitative assessment of symptomatic intracranial atherosclerosis and lenticulostriate arteries in recent stroke patients using whole-brain high-resolution cardiovascular magnetic resonance imaging

BACKGROUND

It has been shown that intracranial atherosclerotic stenosis (ICAS) has heterogeneous features in terms of plaque instability and vascular remodeling. Therefore, quantitative information on the changes of intracranial atherosclerosis and lenticulostriate arteries (LSAs) may potentially improve understanding of the pathophysiological mechanisms underlying stroke and may guide the treatment and work-up strategies. Our present study aimed to use a novel whole-brain high-resolution cardiovascular magnetic resonance imaging (WB-HRCMR) to assess both ICAS plaques and LSAs in recent stroke patients.

METHODS

Twenty-nine symptomatic and 23 asymptomatic ICAS patients were enrolled in this study from Jan 2015 through Sep 2017 and all patients underwent WB-HRCMR. Intracranial atherosclerotic plaque burden, plaque enhancement volume, plaque enhancement index, as well as the number and length of LSAs were evaluated in two groups. Enhancement index was calculated as follows: ([Signal intensity (SI)plaque/SInormal wall on post-contrast imaging] - [SIplaque/SInormal wall on matched pre-contrast imaging])/(SIplaque / SInormal wall on matched pre-contrast imaging). Logistic regression analysis was used to investigate the independent high risk plaque and LSAs features associated with stroke.

RESULTS

Symptomatic ICAS patients exhibited larger enhancement plaque volume (20.70 ± 3.07 mm3 vs. 6.71 ± 1.87 mm3 P = 0.001) and higher enhancement index (0.44 ± 0.08 vs. 0.09 ± 0.06 P = 0.001) compared with the asymptomatic ICAS. The average length of LSAs in symptomatic ICAS (20.95 ± 0.87 mm) was shorter than in asymptomatic ICAS (24.04 ± 0.95 mm) (P = 0.02). Regression analysis showed that the enhancement index (100.43, 95% CI - 4.02-2510.96; P = 0.005) and the average length of LSAs (0.80, 95% CI - 0.65-0.99; P = 0.036) were independent factors for predicting of stroke.

CONCLUSION

WB-HRCMR enabled the comprehensive quantitative evaluation of intracranial atherosclerotic lesions and perforating arteries. Symptomatic ICAS had distinct plaque characteristics and shorter LSA length compared with asymptomatic ICAS.

Magnetic resonance angiography with compressed sensing: An evaluation of moyamoya disease

Compressed sensing (CS) reconstructions of under-sampled measurements generate missing data based on assumptions of image sparsity. Non-contrast time-of-flight MR angiography (TOF-MRA) is a good candidate for CS based acceleration, as MRA images feature bright trees of sparse vessels over a well-suppressed anatomical background signal. A short scan time derived from CS is beneficial for patients of moyamoya disease (MMD) because of the frequency of MR scans. The purpose of this study was to investigate the reliability of TOF-MRA with CS in the evaluation of MMD. Twenty-two patients were examined using TOF-MRA with CS (CS-TOF) and parallel imaging (PI-TOF). The acceleration factors were 3 (CS3) and 5 (CS5) for CS-TOF, and 3 (PI3) for PI-TOF. Two neuroradiologists evaluated the MMD grading according to stenosis/occlusion scores using the modified Houkin’s system, and the visibility of moyamoya vessels (MMVs) using a 3-point scale. Concordance was calculated with Cohen’s κ. The numbers of MMVs in the basal ganglia were compared using Bland-Altman analysis and Wilcoxon’s signed-rank tests. MRA scan times were 4:07, 3:53, and 2:42 for PI3, CS3, and CS5, respectively. CS-reconstruction completed within 10 minutes. MMD grading and MMV visibility scales showed excellent correlation (κ > .966). Although the number of MMVs was significantly higher in CS3 than in PI3 (p < .0001) and CS5 (p < .0001), Bland-Altman analysis showed a good agreement between PI3, CS3, and CS5. Compressed sensing can accelerate TOF-MRA with improved visualization of small collaterals in equivalent time (CS3) or equivalent results in a shorter scan time (CS5).

Z-Spectrum analysis provides proton environment data (ZAPPED): a new two-pool technique for human gray and white matter

A new technique - Z-spectrum Analysis Provides Proton Environment Data (ZAPPED) - was used to map cross-relaxing free and restricted protons in nine healthy subjects plus two brain tumor patients at 3T. First, MT data were acquired over a wide symmetric range of frequency offsets, and then a trio of quantitative biomarkers, i.e., the apparent spin-spin relaxation times (T2,f, T2,r) in both free and restricted proton pools as well as the restricted pool fraction Fr, were mapped by fitting the measured Z-spectra to a simple two-Lorentzian compartment model on a voxel-by-voxel basis. The mean restricted exchangeable proton fraction, Fr, was found to be 0.17 in gray matter (GM) and 0.28 in white matter (WM) in healthy subjects. Corresponding mean values for apparent spin-spin relaxation times were 785 µs (T2,f) and 17.7 µs (T2,r) in GM, 672 µs (T2,f) and 23.4 µs (T2,r) in WM. The percentages of Ff and Fr in GM are similar for all ages, whereas Fr shows a tendency to decrease with age in WM among healthy subjects. The patient ZAPPED images show higher contrast between tumor and normal tissues than traditional T2-weighted and T1-weighted images. The ZAPPED method provides a simple phenomenological approach to estimating fractions and apparent T2 values of free and restricted MT-active protons, and it may offer clinical useful information.