High-resolution magnetic resonance imaging for detection of carotid plaques

Diagnostics Accuracy of Magnetic Resonance Imaging in Detection of Atherosclerotic Plaque Characteristics in Carotid Arteries Compared to Histology: A Systematic Review

Carotid plaque composition represents one of the main risk factors of future ischemic stroke. MRI provides excellent soft tissue contrast that can distinguish plaque characteristics. Our objective was to analyze the diagnostic accuracy of MRI imaging in the detection of carotid plaque characteristics compared to histology in patients with symptomatic and asymptomatic carotid atherosclerosis through a systematic review. After prospective registration in PROSPERO (ID CRD42022329690), Medline Ovid, Embase.com, Cochrane Library, and Web of Science Core were searched without any search limitation up to May 27, 2022 to identify eligible articles. Of the 8168 studies, 53 (37 × 1.5 T MRI, 17 × 3 T MRI) evaluated MRI accuracy in the detection of 13 specific carotid plaque characteristics in 169 comparisons. MRI demonstrated high diagnostic accuracy for detection of calcification (3 T MRI: mean sensitivity 92%/mean specificity 90%; 1.5 T MRI: mean sensitivity 81%/mean specificity 91%), fibrous cap (1.5 T: 89%/87%), unstable plaque (1.5 T: 89%/87%), intraplaque hemorrhage (1.5 T: 86%/88%), and lipid-rich necrotic core (1.5 T: 89%/79%). MRI also proved to have a high level of tissue discrimination for the carotid plaque characteristics investigated, allowing potentially for a better risk assessment and follow-up of patients who may benefit from more aggressive treatments. These results emphasize the role of MRI as the first-line imaging modality for comprehensive assessment of carotid plaque morphology, particularly for unstable plaque. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 2.

Diagnostic Performance of Contrast-Enhanced Ultrasound and High-Resolution Magnetic Resonance Imaging for Carotid Atherosclerotic Plaques: A Systematic Review and Meta-Analysis

OBJECTIVES

The aim of this meta-analysis was to evaluate the diagnostic value of contrast-enhanced ultrasound (CEUS) and high-resolution magnetic resonance imaging (HR-MRI) in patients with carotid vulnerable plaques.

METHODS

A systematic review was conducted in PubMed, Embase, Cochrane Library, and Web of Science using the search terms carotid artery, atherosclerotic plaque, CEUS, contrast-enhanced ultrasound, HR-MRI, and high-resolution magnetic resonance. Studies published since the establishment of the library until December 2021 were retrieved. The statistical analyses were performed with Meta-DiSc version 1.4. Beyond that, the potential sources of heterogeneity for CEUS and HR-MRI were explored.

RESULTS

Nine articles were included in this study. For CEUS, the pooled sensitivity and specificity for detecting carotid vulnerable plaques 91% (95% confidence interval [CI]: 84%, 95%) and 67% (95% CI: 54%, 79%), respectively. For HR-MRI, the pooled sensitivity and specificity were 78% (95% CI: 72%, 83%) and 65% (95% CI, 56%, 73%), respectively. The area under the summary receiver operating characteristic curve for CEUS and HR-MRI were 0.9218 and 0.8129, respectively. However, the difference in diagnostic accuracy between CEUS and HR-MRI diagnostic accuracy was not statistically significant.

CONCLUSIONS

The study shows that the sensitivity of CEUS was higher than that of HR-MRI, and the specificity was similar to HR-MRI. CEUS and HR-MRI provide a similar diagnostic yield in detecting a vulnerable plaque. Thus, CEUS may be a useful tool for the diagnosis of carotid vulnerable plaques.

Custom, spray coated receive coils for magnetic resonance imaging

We have developed a process for fabricating patient specific Magnetic Resonance Imaging (MRI) Radio-frequency (RF) receive coil arrays using additive manufacturing. Our process involves spray deposition of silver nanoparticle inks and dielectric materials onto 3D printed substrates to form high-quality resonant circuits. In this paper, we describe the material selection and characterization, process optimization, and design and testing of a prototype 4-channel neck array for carotid imaging. We show that sprayed polystyrene can form a low loss dielectric layer in a parallel plate capacitor. We also demonstrate that by using sprayed silver nanoparticle ink as conductive traces, our devices are still dominated by sample noise, rather than material losses. These results are critical for maintaining high Signal-to-Noise-Ratio (SNR) in clinical settings. Finally, our prototype patient specific coil array exhibits higher SNR (5 × in the periphery, 1.4 × in the center) than a commercially available array designed to fit the majority of subjects when tested on our custom neck phantom. 3D printed substrates ensure an optimum fit to complex body parts, improve diagnostic image quality, and enable reproducible placement on subjects.

Preprocedural Carotid Plaque Echolucency as a Predictor of In-Stent Intimal Restenosis after Carotid Artery Stenting

OBJECTIVES

In-stent intimal restenosis (ISR) caused by neointimal hyperplasia can develop <24 months after carotid artery stenting (CAS). The utility of plaque imaging by carotid ultrasonography (US) or magnetic resonance imaging (MRI) has been investigated for the prediction of ipsilateral stroke. We aimed to investigate whether these imaging techniques are useful for detecting carotid plaques prone to ISR.

MATERIALS AND METHODS

We examined 133 patients (mean age of 72.1 ± 8.4 years old) that received CAS at a single hospital from 2014 to 2018. A pre-CAS carotid plaque evaluation was performed by carotid angiography, duplex carotid US, and black-blood carotid artery MRI (BB-MRI). The mean stenosis rate was 71.0 ± 12.3% by the North American Symptomatic Carotid Endarterectomy Trial (NASCET) methods. Follow-up carotid angiography was performed 6 months after CAS in all patients according to a predefined protocol. ISR was defined as in-stent intimal hyperplasia more than 50% stenosed based on the NASCET criteria. The selection of the stent type was at the discretion of the treating physician. Predictors of ISR were determined by multivariate logistic regression analysis.

RESULTS

Follow-up angiography demonstrated ISR in 33 patients (24.8%). In 44 patients, more than two stents were deployed. Univariate logistic regression analyses demonstrated echolucent lesion, floating plaque, complete occlusive or pseudo-occlusive lesion, and closed-cell stent use as significantly associated with ISR (>50%). Multivariate logistic regression analysis demonstrated that echolucent lesion (OR 4.667, 95% CI 1.849-11.779) and closed-cell stent use (OR .378, 95% CI .148-.968) were significantly associated with ISR.

CONCLUSIONS

Preprocedural plaque characterization by carotid US appeared to be useful to predict ISR 6 months after CAS.

Diagnostic performance of MRI for detecting intraplaque hemorrhage in the carotid arteries: a meta-analysis

OBJECTIVES

To investigate the diagnostic performance of MRI in diagnosing carotid atherosclerotic intraplaque hemorrhage (IPH) and to provide a clinical guide for MRI application.

METHODS

We searched MEDLINE, Embase, and Cochrane library from the earliest available date of indexing through November 30, 2017. All investigators screened and selected studies comparing the use of MRI with histology. The accuracy to diagnose pathological IPH was expressed by sensitivity, specificity, negative likelihood ratios (LRs), positive LRs, and the area under summary receiver-operating characteristic (SROC) curve. We calculated the post-test probability to assess the clinical utility of MRI.

RESULTS

We analyzed 696 patients from 20 articles. The sensitivity and specificity were 87% (95% CI, 81-91%) and 92% (95% CI, 87-95%), respectively. The positive and negative LRs were 10.27 (95% CI, 6.76-15.59) and 0.15 (95% CI, 0.10-0.21), respectively. The area under SROC curve was 0.95 (95% CI, 0.93-0.97). MRI was accurate in confirming or in ruling out disease over a wide range of pre-test probabilities of IPH: MRI could increase the post-test probability to > 80% in patients with a pre-test probability > 27% and could decrease the post-test probability to < 20% in patients with a pre-test probability < 64%.

CONCLUSION

Non-invasive MRI has excellent specificity and good sensitivity for diagnosing IPH. MRI is a tool for confirming or ruling out carotid atherosclerotic IPH.

KEY POINTS

• Non-invasive MRI has excellent performance for diagnosing IPH, which is a component of vulnerable plaque. • The high accuracy of MRI for IPH helps clinicians analyze the prognosis of clinical events and plan personalized treatment.

A Protocol-Based Decision for Choosing a Proper Surgical Treatment Option for Carotid Artery Stenosis

OBJECTIVE

There are two established surgical treatment options for carotid artery stenosis. Carotid endarterectomy (CEA) has been accepted as a gold standard for surgical treatment while carotid artery stenting (CAS) has recently become an alternative option. Each treatment option has advantages and disadvantages for the treatment outcomes. We propose a protocol for selection of a proper surgical treatment option for carotid artery stenosis.

MATERIALS AND METHODS

A total of 192 published articles on management of carotid artery stenosis were reviewed. Preoperatively considerable factors which had been repeatedly noted in those articles for the risk/benefits of CEA or CAS were selected. According to those factors, a protocol with four categories was established.

RESULTS

CEA or CAS is indicated when the patient has a symptomatic stenosis ≥ 50%, or when the patient has an asymptomatic stenosis ≥ 80%. Each treatment option has absolute indications and favorable indications. Each absolute indication is scored with three points, and each favorable indication, one point. Based on the highest scores, a proper treatment option (CEA or CAS) is selected.

CONCLUSION

We have been treating patients according to this protocol and evaluating the outcomes of our protocol-based decision because this protocol might be helpful in assessment of risk/benefit for selection of a proper surgical treatment option in patients with carotid artery stenosis.

Clinical value of black-blood high-resolution magnetic resonance imaging for intracranial atherosclerotic plaques

The present study evaluated the value of black-blood high-resolution magnetic resonance imaging (HRMRI) for the visualization of intracranial atherosclerosis (ICAS) plaques. A total of 110 patients with cerebral artery or vertebrobasilar stenosis, vessel occlusion or a significantly weakened signal in black-blood magnetic resonance angiography (MRA; three-dimensional time-of-flight) were examined. Black-blood MRA was used to observe whether plaques were present in the abnormal vascular walls. Among the 110 patients with cerebral infarction, 16 cases presented with no significant abnormality of the lumen and walls, while plaques were observed in 94 cases. The plaques were categorized according to their signal characteristics, which resulted in the identification of four cases of type I and II plaques, 15 cases of type III, 26 cases of type IV and V, 23 cases of type VI, 11 cases of type VII, 14 cases of type VIII and one case of a mixed plaque. In summary, 3.0 T black-blood HRMRI was demonstrated to objectively exhibit characteristics of various types of ICAS plaques. Therefore, this imaging technique may be applied as a key method for the clinical non-invasive determination of ICAS plaques.

Pathophysiology of flow impairment during carotid artery stenting with an embolus protection filter

OBJECTIVE

Carotid artery stenting (CAS) is a well-accepted treatment for atherosclerotic stenosis of carotid arteries. Since the occurrence of distal embolization with CAS is still a major concern embolus protection devices (EPD) are usually employed during the procedure. We examined two types of embolus protection filters (Angioguard XP (AG); Filterwire EZ (FW)) and evaluated the function. Thus, the filter was examined postoperatively and the cause of intraoperative flow impairment was evaluated.

MATERIALS AND METHODS

CAS was performed for 54 patients with carotid artery stenosis (55 lesions: 25 AG; 27 FW; 3 others). After completing CAS the filter membrane was stained with hematoxylin-eosin (HE) solution and removed from the filter strut. Once mounted on a glass slide the filter was evaluated under a microscope. The area occupied with debris was measured and the relationship to intraoperative flow impairment was evaluated. Furthermore, the relationship between perioperative ischemic complications and intraoperative flow impairment was statistically analyzed.

RESULTS

Microscopic observation of the slide revealed the pore density of the FW was 1.5 times higher than that of the AG and the filter area of the FW was 2.5 times wider than than the AG. HE staining facilitated characterization of the debris composition. The area occupied with debris was significantly more in the AG (0.241 ± 0.13 cm(2)) than in the FW (0.129 ± 0.093 cm(2)). Thus, fibrin was significantly more precipitated in the AG. Flow impairment occurred in 6 AG cases (24.0 %) and 4 FW cases (14.8 %). It was induced by filter obstruction in the AG and by vasospasms in the FW. Three cases treated with AG (12.0 %) were complicated with cerebral infarction and all of them were related to flow impairment. One FW case (3.7 %) was complicated with cerebral infarction in presence of preserved flow throughout the intervention.

CONCLUSION

Filter function is different according to each design. The cause of flow impairment was attributable to filter obstruction in the AG group and to vasospasms in the FW group. Filter obstruction tends to result in cerebral infarction.

Magnetic resonance imaging features of vulnerable plaques in an atherosclerotic rabbit model

BACKGROUND

Noninvasive detection of vulnerable plaque has a significant implication for prevention and treatment of atherosclerotic diseases. The aim of this study is to investigate the difference between vulnerable plaques and stable plaques in magnetic resonance (MR) images.

METHODS

Atherosclerosis was induced in twenty male New Zealand white rabbits by high cholesterol diet and balloon injury of the abdominal aorta. After baseline (pre-triggering) MR imaging (MRI) scan, the rabbits underwent pharmaceutical triggering with Russell's viper venom and histamine to induce atherothrombosis, followed by another MRI scan 48 hours later (post-triggering). Rabbits were euthanized to obtain pathological and histological data. The results of MRI were compared with those of pathology and histology.

RESULTS

MRI showed that abdominal aorta of the rabbits had pathological change of atherosclerosis in different degrees. Seventy-five plaques were analysed, among which 14 had vulnerable thrombi and 61 stable. Thrombosis was identified in 7 of 11 rabbits by post-triggering MRI, the sensitivity and K value of MR in detection of vulnerable plaque was 71% and 0.803 (P < 0.05). MRI data significantly correlated with the histopathological data in fibrous cap thickness (r = 0.749) plaque area (r = 0.853), lipid core area (r = 0.900). Compared with stable plaques, vulnerable plaques had a significantly thinner fibrous cap ((0.58 ± 0.27) mm vs. (0.95 ± 0.22) mm), larger lipid core area ((7.56 ± 2.78) mm(2) vs. (3.29 ± 1.75) mm(2)), and a higher ratio of lipid core area/plaque area ((55 ± 16)% vs. (27 ± 17)%), but plaque area was comparable in two groups on MRI. The ratio of lipid core area/plaque area was a strong predictor of vulnerable plaques.

CONCLUSION

MRI could distinguish vulnerable plaques from stable plaques in a rabbit model of atherothrombosis and may thus be useful as a noninvasive modality for detection of vulnerable plaques in humans.

Assessment of Carotid Plaque Stability Based on the Dynamic Enhancement Pattern in Plaque Components With Multidetector CT Angiography

Background and Purpose—

Recent studies have investigated plaque morphology to determine patients who are at high risk of carotid atherosclerosis. In this study, we investigated whether a difference in dynamic enhancement pattern in plaque components could be useful to assess plaque stability with multidetector CT angiography.

Methods—

Fifty-nine lesions with moderate to severe carotid atherosclerosis in 51 patients (33 symptomatic, 18 asymptomatic) were consecutively included. Early- and delayed-phase images were obtained in 3 equivalent axial slices with multidetector CT angiography. Hounsfield units (HU) in the early phase were subtracted from those in the delayed phase in plaques (ΔHU) and compared with clinical features, MRI-based plaque characteristics, and histological findings with 20 surgical specimens acquired from carotid endarterectomy.

Results—

The ΔHU was significantly higher in asymptomatic than that in symptomatic presentation ( P =0.02). With MRI, a higher ΔHU was negatively correlated with signal intensity on T1-weighted imaging ( r =−0.56, P <0.0001). Histology confirmed that ΔHU was positively correlated with fibrous tissue ( r =0.67, P =0.001) and negatively correlated with a lipid-rich necrotic core with hemorrhage ( r =−0.70, P <0.001). Moreover, less neovascularization and inflammation was found in plaques with a higher ΔHU.

Conclusions—

Delayed-phase images provide information regarding the dynamic change in contrast media from the early arterial phase. An increase in HU from the early phase on multidetector CT angiography indicates plaque stability with more fibrous tissue and a less lipid-rich necrotic core, intraplaque hemorrhage, and neovascularization.

Evaluation of multicontrast MRI including fat suppression and inversion recovery spin echo for identification of intra-plaque hemorrhage and lipid core in human carotid plaque using the mahalanobis distance measure

Intra-plaque hemorrhage (IPH) and lipid core, characteristics of rupture prone carotid plaques, are often visualized in vivo with MRI using T1 weighted gradient and spin echo, respectively. Increasing magnetic field strength may help to identify IPH and lipid core better. As a proof of concept, automatic segmentation of plaque components was performed with the Mahalanobis distance (MD) measure derived from image contrast from multicontrast MR images including inversion recovery spin echo and T1 weighted gradient echo with fat suppression. After MRI of nine formaldehyde-fixated autopsy specimens, the MDs and Euclidean Distances between plaque component intensities were calculated for each MR weighting. The distances from the carotid bifurcation and the size and shape of calcification spots were used as landmarks for coregistration of MRI and histology. MD between collagen/cell-rich area and IPH was largest with inversion recovery spin echo (4.2/9.3, respectively), between collagen/cell-rich area/foam cells and lipid core with T1 weighted gradient echo with fat suppression (26.9/38.2/4.6, respectively). The accuracy of detection of IPH, cell-rich area, and collagen increased when the MD classifier was used compared with the Euclidean Distance classifier. The enhanced conspicuity of lipid core and IPH in human carotid artery plaque, using ex vivo T1 weighted gradient echo with fat suppression and inversion recovery spin echo MRI and MD classifiers, demands further in vivo evaluation in patients.

Relationship between lectin-like oxidized low-density lipoprotein receptor 1 expression and preoperative echogenic findings of vulnerable carotid plaque

PURPOSE

Lectin-like oxidized low-density lipoprotein 1 (LOX1) is an important cell surface receptor for the progression of atherosclerosis. Our purpose is to clarify the relationships of LOX1 and atherosclerotic factors for the vulnerability of carotid plaque and preoperative echogenic findings.

METHODS

We examined LOX1 expression, matrix metalloproteinase (MMP)-2,9, and tissue inhibitor of MMP (TIMP)-2 by immunohistochemical analysis using carotid endarterectomy specimens obtained from 14 patients. Groups were divided into stable plaque group A and vulnerable plaque group B by preoperative echogenic findings of carotid plaques. Endothelial immunoreactivity was calculated, and the immunohistochemical findings were compared.

RESULTS

LOX1 was remarkably expressed, especially in smooth muscle cells in vulnerable plaque and colocalized in MMP-9 positive cells and apoptotic cells. All LOX1, MMP-2,9, and TIMP2 were remarkably expressed in the subendothelial layer in group B compared with group A. The endothelial LOX1 index was 63.75 +/- 4.92 in group A and 83.0 +/- 5.02 in group B (p = 0.02). The endothelial MMP-2 index was 24.38 +/- 5.50 in group A and 32.83 +/- 6.79 in group B (p = 0.01). The endothelial MMP-9 index was 46.13 +/- 6.31 in group A and 59.17 +/- 2.14 in group B (p = 0.002). The endothelial TIMP-2 index had no significant difference between two groups (p = 0.14).

CONCLUSION

LOX-1 may play an important role in the progression of vulnerable carotid plaque and might regulate vulnerable plaque formation in cooperation with MMPs and TIMP-2. Endothelial MMP-2 might suppress TIMP-2 activation in vulnerable plaques.

Clinical indications for high-field 1.5 T intraoperative magnetic resonance imaging and neuro-navigation for neurosurgical procedures. Review of initial 100 cases

Initial experiences are reviewed in an integrated operation theater equipped with an intraoperative high-field (1.5 T) magnetic resonance (MR) imager and neuro-navigation (BrainSUITE), to evaluate the indications and limitations. One hundred consecutive cases were treated, consisting of 38 gliomas, 49 other tumors, 11 cerebrovascular diseases, and 2 functional diseases. The feasibility and usefulness of the integrated theater were evaluated for individual diseases, focusing on whether intraoperative images (including diffusion tensor imaging) affected the surgical strategy. The extent of resection and outcomes in each histological category of brain tumors were examined. Intraoperative high-field MR imaging frequently affected or modified the surgical strategy in the glioma group (27/38 cases, 71.1%), but less in the other tumor group (13/49 cases, 26.5%). The surgical strategy was not modified in cerebrovascular or functional diseases, but the success of procedures and the absence of complications could be confirmed. In glioma surgery, subtotal or greater resection was achieved in 22 of the 31 patients (71%) excluding biopsies, and intraoperative images revealed tumor remnants resulting in the extension of resection in 21 of the 22 patients (95.4%), the highest rate of extension among all types of pathologies. The integrated neuro-navigation improved workflow. The best indication for intraoperative high-field MR imaging and integrated neuro-navigation is brain tumors, especially gliomas, and is supplementary in assuring quality in surgery for cerebrovascular or functional diseases. Immediate quality assurance is provided in several types of neurosurgical procedures.

Advanced imaging applications for endovascular procedures

Advanced imaging techniques, particularly in CT and MRI, have become state-of-the-art to support the performance of interventional neuroradiologic procedures. Multidetector CT scanners with submillimeter detectors and real-time workstations have allowed the use of a noninvasive study, CT angiography, as a first-line diagnostic study at many institutions to detect and evaluate the morphology of aneurysms. Follow-up for postsubarachnoid spasm now includes transcranial Doppler, CT angiography, and sometimes perfusion to guide therapy. While both intracranial and extracranial stenosis have long been well evaluated by MR and CT angiography, information about the intimal wall and plaque morphology is now possible. In the setting of acute ischemia, CT with perfusion or MR with diffusion and perfusion has increased the ability to separate territory at risk from infarcted tissue, and can help to guide more appropriate intervention. This article addresses current state-of the-art imaging applications as well as a few techniques on the horizon that show great promise in helping to characterize those lesions amenable to endovascular therapy.

The 150th anniversary of Nagasaki University School of Medicine: recovery from the atomic disaster and evolution of the department of neurosurgery

NAGASAKI IS LOCATED on the western edge of Japan, closer to the Asian continent. Because of this geographical proximity, Nagasaki became a gateway for the introduction of continental culture and civilization to Japan. After the port of Nagasaki was opened for trade with the Portuguese in 1571, Nagasaki had a central role in cultural exchange with the West and China until the latter half of the 19th century. As a result of the political situation, students came to Nagasaki from all over Japan to obtain information on Western science, especially in medicine, turning Nagasaki into a hub for modern academic studies. The first medical facility in Japan educating doctors in the Western style was founded in Nagasaki in 1857. Despite the tragedy of World War II, the medical school arose again. More than 10 000 physicians have completed their studies at the medical school since its founding. The Department of Neurosurgery at Nagasaki University had its origins within the Second Department of Surgery and became an independent department in 1973. The post of professor was assumed by Kazuo Mori and succeeded in 1991 by Shobu Shibata and in 2003 by Izumi Nagata, who holds the post at the time of this writing. Neurosurgery is dynamic and constantly changing at Nagasaki University with work in progress on technological, diagnostic, and surgical innovations that permit the treatment of highly complex cases. In 2007, the 150th anniversary of the founding of Nagasaki University School of Medicine was celebrated with a number of commemorative events.

Observation of the embolus protection filter for Carotid Artery Stenting

BACKGROUND

Carotid artery stenting in patients with high surgical risk is considered as an effective alternative to carotid endarterectomy. Because the occurrence of distal embolization with CAS is still a major concern, an embolus protection device is usually used during the procedure. We developed a technique for observation of embolus protection filter and evaluated the debris or thrombus microscopically, and the pathologic findings were compared with preoperative imaging studies.

METHODS

After completing CAS, the filter membrane was stained with HE solution and removed from filter strut. Mounting onto a glass slide, the filter was evaluated under a microscope. Plaque debris and appearance of filter membrane were evaluated, and the covered area was measured. The pathologic findings were compared with preoperative imaging studies.

RESULTS

Microscopic observation of the slide revealed atheromatous debris as well as thrombotic material to the filter membrane. Hematoxylin-eosin stain facilitates the characterization of the debris composition, namely, thrombotic debris, calcified debris, organized debris, fibrous debris, and lipid-rich debris. The subtypes of debris were consistent with preoperative imaging studies. Thus, in cases of intraprocedural flow impairment, more than 50% of the filter area was covered with debris or thrombotic material.

CONCLUSION

Carotid plaque debris captured during carotid stenting with protection filter can be visualized with HE stain on the glass side. This simple method allows us to better understand the plaque debris and appearance of embolus protection filter.

Intraoperative 3T MR imaging for spinal cord tumor resection: feasibility, timing, and image quality using a "twin" MR-operating room suite

We assessed feasibility, safety, and timing of an original intraoperative MR procedure in 3 cases of resection of spinal cord glioma by using a clinical 3T MR system connected to an adjacent operating room in a design being coined "twin" or "dual" MR-operating room suite.

Review: Stroke in type 2 diabetes

Stroke is the second most frequent cause of death worldwide and the most frequent cause of permanent disability. Patients with diabetes are at 1.5 to three times the risk of stroke compared with the general population. Cerebrovascular disease causes 20% of deaths in diabetic patients. Interestingly, there are some striking differences of stroke patterns between diabetic and non-diabetic subjects suffering a stroke. Even more important is the fact that diabetes dramatically increases the risk of stroke in younger subjects as well as women. These data highlight the need for detection and treatment of diabetes particularly in these patient groups. This review summarises several aspects of stroke in type 2 diabetes, focusing on differences from non-diabetic stroke.

Intracranial internal carotid artery stenosis with vulnerable plaques successfully treated by stenting under cerebral protection

Percutaneous transluminal angioplasty with stenting (PTA/stenting) for intracranial atherosclerotic stenoses is usually performed without any protection devices. We report a unique case of atherothrombotic stenosis with the vulnerable plaque in the cavernous portion of the internal carotid artery (ICA), which was successfully treated by PTA/stenting under cerebral protection with the flow reversal system. A 68-year-old woman presented repetitive transient ischemic attacks in the right ICA territory. Cerebral angiography revealed 80% stenosis in the cavernous portion of the right ICA. High-resolution magnetic resonance imaging (HR-MRI) demonstrated lipid-rich plaques at this lesion. PTA/stenting was performed with a proximal protection device under flow reversal. A filter device captured much amount of atherothrombotic debris with lipid-rich macrophages and leukocytes, which was consistent with HR-MRI findings. Some selected cases of intracranial atherothrombotic ICA stenoses may need endovascular treatment with cerebral protection system. HR-MRI is useful to evaluate plaque characteristics even in the cavernous portion of the ICA.

Middle cerebral artery plaque imaging using 3-Tesla high-resolution MRI

Diagnosis of deep subcortical infarcts based on atherosclerosis of the middle cerebral artery (MCA) is important because this type of infarct is usually more aggressive than typical lacunar infarcts. However, current imaging techniques are of limited utility in the diagnosis of MCA plaques. Here, we report the use of 3-Tesla (3T) high-resolution moderate T2-weighted imaging (HRT2WI) to detect MCA plaques in three patients with acute MCA perforator territory infarcts. MCA plaques were seen with HRT2WI in a patient with MCA stenosis, which was observed by magnetic resonance angiography (MRA). Of the two patients without MCA stenosis (also confirmed by MRA), one had thin MCA plaques and the other had normal walls based on HRT2WI. Progression of symptoms occurred in the patients with plaques. We conclude that 3T HRT2WI can identify plaque on MCA walls and has the potential to identify patients at risk for stroke progression or recurrence.

Potential of magnetic resonance plaque imaging using superparamagnetic particles of iron oxide for the detection of carotid plaque

Macrophages and by-products are important in plaque destabilization in atherosclerosis. Ultra-small superparamagnetic particles of iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging may be suitable for the detection of macrophages in atherosclerotic plaques. The present study investigated the potential of MR plaque imaging using SPIO in 10 patients scheduled for carotid endarterectomy before and 24-43 hours after administration of SPIO (fercarbotran, 0.016 ml/kg). Three-dimensional gradient recalled acquisition in the steady state (3D-GRASS) was used for detecting macrophages within plaques. Signal loss on the post-contrast 3D-GRASS images was found in 5 of 10 cases, and accumulation of SPIO particles in the vessel wall was confirmed in 4 of these 5 cases. Intracytoplasmic localization of SPIO particles within recruited macrophages was verified by double staining analysis. A correlation between MR plaque imaging using SPIO and localization of macrophages was demonstrated in 6 of 10 patients. This study indicates that MR plaque imaging using SPIO is a potential functional imaging tool to detect infiltration of macrophages in human atherosclerotic carotid plaque.

Characterization of carotid atherosclerosis and detection of soft plaque with use of black-blood MR imaging

BACKGROUND AND PURPOSE

In the treatment of carotid atherosclerosis, the rate of stenosis and characteristics of plaque should be assessed to diagnose vulnerable plaques that increase the risk for cerebral infarction. We performed carotid black-blood (BB) MR imaging to diagnose plaque components and assess plaque hardness based on MR signals.

MATERIALS AND METHODS

Three images of BB-MR imaging per plaque were obtained from 70 consecutive patients who underwent carotid endarterectomy (CEA) to generate T1- and T2-weighted images. To evaluate the relative signal intensity (rSI) of plaque components and the relationship between histologic findings and symptoms, we prepared sections at 2-mm intervals from 34 intact plaques. We then calculated the relative overall signal intensity (roSI) of 70 plaques to assess the relationship between MR signal intensity and plaque hardness and symptoms.

RESULTS

The characteristics of rSI values on T1- and T2-weighted images of fibrous cap (FC), fibrosis, calcification, myxomatous tissue, lipid core (LC) with intraplaque hemorrhage (IPH), and LC without IPH differed. Symptomatic plaques were associated with FC disruption (P < .001) and LC with IPH (P < .05). The roSI on T1-weighted images was significantly higher for soft than nonsoft plaques. When the roSI cutoff value was set at 1.25 (mean of the roSI), soft plaques were diagnosed with 79.4% sensitivity and 84.4% specificity. The roSI was also significantly higher for symptomatic than for asymptomatic plaques. Soft and nonsoft plaques as well as symptomatic and asymptomatic plaques did not significantly differ on T2-weighted images.

CONCLUSION

BB-MR imaging can diagnose plaque components and predict plaque hardness. This procedure provides useful information for planning therapeutic strategies of carotid atherosclerosis.

Detection of unstable carotid artery stenosis using MRI

BACKGROUND AND PURPOSE

Carotid artery stenosis can be classified by magnetic resonance imaging (MRI) as lesion types I-VIII according to a modified histological scheme based on American Heart Association (AHA) guidelines. Lesion types IV-V and VI are regarded as high-risk plaques.We aimed to evaluate the clinical relevance of this classification for identifying unstable plaques.

METHODS

Eighty-five patients (29 female) with severe carotid artery stenosis (diagnosed by Doppler and duplex ultrasonography) were imaged using a 1.5 T scanner with bilateral phased-array carotid coils. T1-, T2-, time-offlight (TOF) and proton-density (PD)-weighted studies were obtained. The carotid plaques were classified as lesion types III-VIII according to the MRI-modified AHA criteria.

RESULTS

Thirty-five patients presented with a recently symptomatic stenosis; 50 patients were asymptomatic. Lesion types IV-V (51.4 % vs. 22 %) and VI (20 % vs. 4%; P < 0.0001) were found significantly more often in symptomatic patients compared to those without a history of cerebral ischemia.

CONCLUSIONS

The distribution of lesion types differs significantly between symptomatic and asymptomatic carotid artery stenosis. High-risk lesion types IV-V and VI were overrepresented in recently symptomatic patients. MRI according to the modified AHA-criteria may be a suitable tool for detection of unstable carotid lesions.

Asymptomatic carotid artery plaques: use of magnetic resonance imaging to characterize vulnerable plaques in 6 cases

BACKGROUND

Echography is a convenient and noninvasive method of characterizing carotid artery plaques. However, recent reports suggest that multisequential MR imaging may yield better data regarding the instability of asymptomatic carotid artery plaques. Therefore, the goal of the present study was to show the useful information for asymptomatic carotid artery plaque.

METHODS

A total of 6 patients (5 men, 1 woman; age range, 62-76 years; mean age, 69.2 years) with carotid artery plaques, which were detected during medical check-up using carotid MR angiography and/or echography, underwent MR imaging. Two-dimensional TOF MR angiography, T1WI, and fat-suppressed, cardiac-gated, black-blood proton density image, and T2WI were obtained with a 1.5-T MR imager. All plaques underwent carotid endarterectomy and histological examination.

RESULTS

The MR imaging demonstrated high signals in at least one modality in 4 of 7 plaques. In the remaining 3 patients, MR imaging detected partial-high signals, which corresponded to histologically confirmed partial lipid core or hemorrhagic components in the fibrous tissues The TOF MR imaging showed 2 cases of thin fibrous caps, and MR imaging also showed a large mural thrombus in 1 patient.

CONCLUSIONS

Magnetic resonance imaging was useful in characterizing factors associated with plaque instability in patients with asymptomatic carotid artery plaques and may help guide therapeutic strategies for asymptomatic carotid artery plaques.