Neurovascular Imaging Research

Neurovascular disease is one of the major causes of morbidity and mortality worldwide and is the number one cause of adult disability. Medical imaging, including magnetic resonance, computed tomography and positron emission tomography, is increasingly important in the management of numerous neurovascular diseases. Continued innovations in imaging technologies are needed to improve prevention, diagnosis, treatment and therapeutic monitoring. The neurovascular imaging research program is committed to the development of novel imaging techniques and promotion of their clinical applications in various neurovascular conditions and disorders. Our long-term mission is to develop innovative, accurate and reliable imaging solutions to provide precise neurovascular disease management.

• Zhaoyang Fan, PhD
• Qi Yang, MD, PhD

Current research in the neurovascular imaging research program focuses on:

• Carotid artery vessel wall imaging
• Carotid atherosclerotic plaque characterization
  
• Intracranial artery vessel wall imaging
  
• Imaging characterization of ischemic stroke patients
  
• Cerebral venous sinus thrombosis imaging
  
• Quantitative image analysis for atherosclerotic plaques
  

Multicontrast Atherosclerosis Characterization for Carotid Atherosclerotic Plaques

Carotid atherosclerotic disease (CAD) is a degenerative disease of the arterial wall caused by the buildup of fatty substances and cholesterol deposits. Disrupted atherosclerotic plaques can lead to transient ischemic attack and cerebral thromboembolic stroke, the leading cause of mortality and morbidity worldwide.

Current management guidelines for CAD are primarily based on the degree of luminal stenosis as determined by medical imaging, with high-grade (greater than 70 percent) stenosis as an indication for surgery or interventional procedures. However, the degree of stenosis may not be an accurate indicator of the severity of disease.

Characterization of so-called vulnerable plaque features, such as the presence of a large lipid-rich necrotic core with an overlying thin/ruptured fibrous cap, intraplaque hemorrhage and calcification can help better identify high-risk lesions. In this regard, magnetic resonance imaging (MRI) has shown unique strengths over other commonly used diagnostic imaging modalities that merely provide information on luminal stenosis.

The multicontrast atherosclerosis characterization (MATCH) technique employs a 3-D spoiled segmented fast low-angle shot readout to acquire data with three different contrast weightings following a nonselective inversion pulse and various inversion-recovery times. This is the first 3-D MRI technique that acquires spatially coregistered multicontrast image sets in a single scan for adequate characterization of carotid plaques (Figure 1).

Whole-Brain Vessel Wall Imaging Using Inversion-Recovery Prepared 3-D Variable-Flip-Angle Turbo Spin-Echo

Cerebrovascular disease, a major cause of morbidity and mortality worldwide, can arise from diverse intracranial vessel wall pathologies such as atherosclerosis, dissection and vasculitis. Methods traditionally used for the diagnosis of the disease are based on lumenography imaging, limited to the detection of luminal abnormalities, thus inadequate for differentiating various wall pathologies.

Recently, there is a growing interest in high-resolution black-blood (BB) MRI, given its capacity to directly assess the intracranial vessel wall and to potentially unravel etiology. Recently, we proposed an inversion-recovery prepared sampling perfection with application-optimized contrast using different flip angle evolutions (IR-SPACE), as a 3-D BB MRI approach to provide remarkable suppression of cerebrospinal fluid signals, enhanced T1 contrast weighting and, most importantly, whole-brain spatial coverage (Figure 2).

Magnetic Resonance Black-Blood Thrombus Imaging

Cerebral venous thrombosis (CVT), including thrombosis of cerebral veins and major dural sinuses, is a relatively uncommon form of stroke that usually affects young individuals. During the past decades, improved diagnosis and treatment have improved the outcome of CVT.

However, there is often a diagnostic delay in patients with CVT, because the confirmation of the diagnosis always relies on the combination of different imaging modalities, such as computed tomography, magnetic resonance (MR), MR venography and conventional X-ray angiography. These methods assess CVT indirectly by imaging venous flow perturbation caused by thrombus. However, given the variation in venous anatomy, it is sometimes difficult to exclude CVT with existing noninvasive imaging studies.

Based on 3-D variable-flip-angle turbo spin-echo, we developed a black-blood MR technique, called black-blood thrombus imaging (BTI), which allows the thrombus to be well isolated from the surrounding tissues. Thus, early detection of CVT is feasible with a high diagnostic accuracy (Figure 3).

The neurovascular imaging research program, led by Zhaoyang Fan, PhD, has active collaboration with internal Cedars-Sinai and external research investigators and clinicians. Key collaborators include:

Internal Collaborators

• Michael Alexander, MD
• Bruce Gewertz, MD
  
• Nestor Gonzalez, MD
  
• Debiao Li, PhD
  
• Daniel Luthringer, MD
  
• Patrick Lyden, MD
  
• Menahem Marcel Maya, MD
  
• Frank Moser, MD
  
• Wouter Schievink, MD
  
• Konrad Schlick, MD
  
• Prediman K. Shah, MD
  
• Shlee Song, MD
  
• Janet Wei, MD
  

External Collaborators

• Jiangang Duan, MD, Xuanwu Hospital, Beijing, China
• Xiuhai Guo, MD, Xuanwu Hospital, Beijing, China
• Xunming Ji, MD, Xuanwu Hospital, Beijing, China
• Weijian Jiang, MD, China PLA General Hospital, Beijing
• Eline Kooi, PhD, Maastricht University, the Netherlands
• Fengyuan Man, MD, China PLA General Hospital, Beijing
• Jiayu Sun, MD, West China Hospital of Sichuan University, Chengdu, China
• Wei Yu, MD, Anzhen Hospital, Beijing, China