Effect of carotid artery flow changes on the stability of plaque and typing characteristics of cerebral infarction / 局解手术学杂志

objective To observe the influence of hemodynamic changes caused by extracranial carotid stenosis on the plaque stability, and analyze the relationship of cerebral infarction classification,criminal artery stenosis degree and plaque stability to offer evidence for evalu-ating nosogenesis,clinical diagnosis,treatment and prevention of cerebral infarction. Methods CDFI,CTA were performed in 168 patients with acute cerebral infarction,some moderate and severe and occlusive carotid artery which were demonstrated by CTA and CDFI were further checked by DSA during convalescence. Totally 168 acute cerebral infarction patients were divided into 5 groups based on the criminal artery stenosis degree. To evaluate the plaque stability and flow field changes with CDFI and CTA,OCSP clinical classification and brain image clas-sification were finished according to CTA. Patients were classified into 4 subtypes,namely cortical infarction,basal ganglion infarction,corona radiata infarction and posterior infarction,according to the lesion distributions. Observe the changes of flow field and stability of plaque,and compare the relationship between different degree of stenosis and the classification of lesion of infarction. Results Among the 168 criminal arteries,there was 17. 9% of normal,22. 6% of mild stenosis,30. 9% of moderate stenosis,14. 8% of severe stenosis,and 14. 3% of occlu-sion,and the moderate stenosis proportion was the highest. When the stenosis degree was over 50%,it may lead to the changes of flow field, speeding up of blood flow,forming of turbulent flow,and increasing of plaque instability in which lipid plaque and admixture plaque was the highest. PACI is the commonest in all moderate groups. Admixture plaque is usually seen in severe stenosis and occlusion, while fibrous plaque is usually seen in mild stenosis. Conclusion Moderate carotid stenosis may lead to the increase of plaque instability as a result of the changes of flow field,and it may prone to artery-artery embolization.

The Significance of Vascular MR Contrast Enhancement in Carotid Stenosis

PURPOSE: To determine the significance of vascular MR contrast enhancement in carotid stenosis. MATERIALS AND METHODS: Forty patients that had angiographically proved carotid stenosis were selected for the study. A blind interpretation of vascular enhancement on an enhanced T1 weighted image, the lesion pattern on a DWI (diffusion weighted image), a perfusion defect on a MR perfusion image, the degree of stenosis, and collateral flow on cerebral DSA (digital subtraction angiography) was made by two observers, retrospectively. DWI lesion patterns were classified as having no high signal intensity, small PAI (perforating artery infarcts), large PAI, pial infarcts, territorial infarcts, and border zone infarcts. We evaluated the statistical correlation between vascular enhancement and the degree of stenosis, collateral flow, the DWI lesion pattern and the presence of a perfusion defect, respectively. RESULTS: The degree of carotid stenosis and the frequency of vascular enhancement correlated statistically (p=0.000). The presence of retrograde collateral flow on cerebral DSA and the border zone infarcts pattern on DWI were related with the occurrence of vascular enhancement (p=0.002, p=0.004). In 23 patients that underwent a MR perfusion study, the presence of a perfusion defect was also related to the occurrence of vascular enhancement (p=0.002). CONCLUSION: Vascular MR contrast enhancement may indicate a cerebral hypoperfusion in carotid stenosis.

Results of Carotid Artery Stenting using Filter Wire in 24 Consecutive Symptomatic Patients with Severe Stenosis

PURPOSE: The aims of this study were to analyze the results of carotid artery stenting using distal protection with FilterWire, and evaluate the effectiveness of FilterWire for distal embolic protection. MATERIALS AND METHODS: Between June and December in 2004, elective carotid artery stenting using FilterWire was attempted in 25 lesions of 24 consecutive patients. All patients were symptomatic, with recurrent transient ischemic attacks (TIA) or a stroke. The cerebral ischemic lesions of embolic origin were evaluated before and after the procedure using magnetic resonance imaging, including diffusion-weighted images. Both pre- and post-procedural 99mcTc-ECD SPECT were performed to assess the cerebral blood flows. Any visible debris within the FilterWire was sent for histological/cytological analyses. RESULTS: Technical success was achieved all 25 cases. The mean pre-procedural stenosis was 89% (range 70-100%), and that immediately after stent placement was nearly 0%. With the exception of only one major stroke (1/25, 4%), no periprocedural complications were encountered. On the diffusion weighted images, new lesions were observed in four patients (4/25, 16%), but these were clinically silent. FilterWire-related transient spasm occurred in eight of the 25 procedures (32%). CONCLUSION: Carotid artery stenting, with FireWire distal protection, seems technically feasible, safe and effective in preventing procedural related embolic complications.

An Experimental Study on the Optimization of Parameter Values for Magnetic Resonance Angiography using a Phantom Model of Ulcerated Stenotic Internal Carotid Artery

PURPOSE: It has been suggested that an ulceration or hemorrhage within an atheroma on a stenotic carotid artery is a clinically important cause of transient ischemic attack(TIA). In previous studies, due to its inherent signal loss by static or turbulent flow, magnetic resonance angiography(MRA) proved to be an unreliable methed for the evaluation of subtle changes of ulceration. To improve the detectability of the ulceration within atheroma, avascular phantom was filled with gadolinium solution of various concentrations during various MR sequences. MATERIALS AND METHODS: Several vascular phantoms made of elastic silicon mimicking an ulcerated stenotic internal carotid artery(ICA) were constructed, and gadolinium solution of different concentrations (1:1000 and 1:200 of Gd-DTPA) and distilled water were introduced into the vascular phantoms using a computerized pulsatile pump. To evaluate maximum intensity projection(MIP), multiple planar reconstruction(MPR) and source images, axial and coronal images of MRA with 2D-TOF(time of flight) and 3D-TOF were reviewed. Each image of various sequences was compared with plain X-ray films of each phantom filled with barium. RESULTS: On all MR suquences, the images of the phantom of the normal carotid bifurcation were superior to the images of ulcerated and stenotic phantoms. MPR and MIP were the optimal image for detecting and defining ulceration and stenosis. Better quality images were obtained when a higher concentration of Gd-DTPA was used and when the 3D-TOF technique instead of the 2D-TOF technique was applied. CONCLUSION: This study reveals that a combination of higher concentration gadolinium with MPR and MIP on 3D-TOF technique could be optimal for the evaluation of ulceration and/or stenosis at the bifurcation of the carotid artery.

Hemodynamic Changes on Phantoms of the Internal Carotid Arterial Stenosis: MRA, DSA and CFD

PURPOSE: The most important factor discrediting the reliability of MRAs is the overestimation of the degree of stenosis in the internal carotid artery(ICA). The purpose of this study is to evaluate the second aryhemodynamics and the cause(s) for the overestimation of the degree of variable stenotic phantoms of the carotidartery using steady-state flow on MRAs. MATERIALS AND METHODS: Using scrylic materials, normal and variable stenotic phantoms of the bifurcated carotid artery were constructed (40% and 65%). Flow patterns were evaluated with axial and coronal imaging of MRAs (2D-TOF and 3D-TOF) and DSAs of phantoms constructed from an automated closed-type circulatory system filled with 10% glucose solution. These findings were then compared with those obtained from CFD. RESULTS: 3D-TOF axial MRA of asymmetrically 40 percent stenotic phantom revealed 40 percent stenosis identical to the stenotic region of phantoms with continued poststenotic signal loss, whereas 3D-TOFzsial MRA of symmetrically 65 percent stenotic phantom showed markedly decreased signal intensity at the poststenotic segment resembling occlusion. Source image of 2D-TOF coronal MRA showed redistribution (from theinternal to external carotid artery side) of the central axis of inflow depending upon the degree of stenosis ofthe ICA ; this redistribution can be a cause of the decreased signal at the poststenotic segment, due to a reduced volume of flow through the stenotic segment. The general hemodynamics of the variable stenotic phantoms on MRA were identical to the hemodynamics on DSA and CFD. CONCLUSION: Although dephasing from turbulent flow and character of maximum intensity projection (MIP) were suggested as the main cause of the decreased poststenotic signal, our study indicated that a hemodynamically redistributed central axis of inflow and reduced flow volume through stenotic channel is one of the basic factors of the decreased signal intensity ot the poststenotic segmenton MRA.