肾动脉狭窄患者血氧水平依赖磁共振成像研究

目的:运用血氧水平依赖磁共振成像(BOLD MRI)序列评估肾动脉狭窄患者肾脏氧合状态,分析患者肾脏R2*值与健康人R2*值及自身肾动脉狭窄程度之间的关系。方法:使用西门子3.0T磁共振机对28例肾动脉狭窄患者及16例健康志愿者的肾脏进行BOLD扫描,所得图像通过西门子工作站及MATLAB软件进行处理分析、手动勾画感兴趣区,得到R2*值,进行分析比较。结果:正常健康人肾髓质R2*值(29.61±2.26)高于皮质(18.23±1.77),肾脏上、中、下部R2*值差异无统计学意义。肾动脉狭窄患者肾皮质、髓质R2*值(21.14±4.90);(36.25±8.04)均较正常人有显著增高,其差异具有统计学意义(P<0.05),且髓质变化更为敏感。在患者组各亚组中,肾动脉重度狭窄患者肾髓质R2*值(44.20±6.01)较其他各亚组明显增高,差异具有统计学意义(P<0.05),而肾动脉重度狭窄患者肾皮质R2*值(24.06±5.94)仅显著高于无明显狭窄组(18.96±3.62)(P<0.05),与轻、中度狭窄患者(20.20±2.01);(19.14±1.86)并差异无统计学意义。分别对患者组皮质和髓质R2*值与所对应一侧肾脏肾小球滤过率进行相关性分析,未发现有显著的相关性。结论:BOLD MRI序列是一种有效的无创性评估肾脏氧合状态的检查方法,在肾动脉狭窄程度的判断上具有一定的意义和作用,而且是检测肾髓质缺血缺氧的敏感手段。     

Detection of coronary artery stenosis with whole-heart coronary magnetic resonance angiography.

OBJECTIVES: We sought to determine the diagnostic performance of whole-heart coronary magnetic resonance (MR) angiography for detecting significant coronary artery disease. BACKGROUND: The accuracy of whole-heart coronary MR angiography has not been determined in a large number of patients. METHODS: Three-dimensional coronary MR angiograms covering the entire heart were obtained during free breathing in 131 patients. Images were acquired during a patient-specific time window in the cardiac cycle with minimal motion of the coronary artery. Significant coronary artery disease was defined on X-ray coronary angiography as a diameter reduction of > or =50% in coronary arteries with a reference diameter of > or =2 mm. RESULTS: The acquisition of MR angiography was completed in 113 (86%) of 131 patients, with an imaging time averaged at 12.9 +/- 4.3 min. On a patient-based analysis, the sensitivity, specificity, positive and negative predictive value, and accuracy of MR angiography were 82% (95% confidence interval [CI] 69% to 91%), 90% (95% CI 79% to 96%), 88% (95% CI 74% to 95%), 86% (95% CI 75% to 93%), and 87% (95% CI 79% to 92%), respectively. These values in the individual segments were 78% (95% CI 68% to 85%), 96% (95% CI 95% to 97%), 69% (95% CI 60% to 77%), 98% (95% CI 96% to 98%), and 94% (95% CI 96% to 96%). CONCLUSIONS: Whole-heart coronary MR angiography allows for noninvasive detection of significant narrowing in coronary arterial segments with a diameter of > or =2 mm with moderate sensitivity and high specificity.     

Assessment of stable coronary artery disease by cardiovascular magnetic resonance imaging: Current and emerging techniques

Coronary artery disease(CAD) is a leading cause of death and disability worldwide. Cardiovascular magnetic resonance(CMR) is established in clinical practice guidelines with a growing evidence base supporting its use to aid the diagnosis and management of patients with suspected or established CAD. CMR is a multi-parametric imaging modality that yields high spatial resolution images that can be acquired in any plane for the assessment of global and regional cardiac function, myocardial perfusion and viability, tissue characterisation and coronary artery anatomy, all within a single study protocol and without exposure to ionising radiation. Advances in technology and acquisition techniques continue to progress the utility of CMR across a wide spectrum of cardiovascular disease, and the publication of large scale clinical trials continues to strengthen the role of CMR in daily cardiology practice. This article aims to review current practice and explore the future directions of multi-parametric CMR imaging in the investigation of stable CAD.     

Localization of a misplaced coronary artery stent by magnetic resonance imaging

Coronary artery stents have been developed to overcome arterial abrupt closure and restenosis following balloon angioplasty. Complications of stent insertion include loss of the device from its delivery system into the peripheral circulation. Certain types of stents are almost radiolucent, making localization of the lost devices difficult. Nonferromagnetic metallic biomedical implants induce alteration of the local magnetic field and this leads to loss of signal from the surrounding tissues. We have used this property to localize a misplaced coronary artery stent in a 53-year-old man who underwent unsuccessful stent insertion. A 0.5 Tesla magnetic resonance scanner was used to acquire gradient-echo and spin-echo images. An in vitro experiment was first carried out on a stent similar to that used in our patient to establish that it was nonferromagnetic and to determine the optimum imaging technique. Gradient-echo images with a relatively long echo time (22 ms) gave the largest area of signal loss around the stent, and this sequence was used for localization of the stent found in the patient's left profunda femoris artery. This was subsequently confirmed by digital radiography. We have demonstrated the convenience and practicality of using magnetic resonance imaging for the localization of a misplaced coronary artery stent in a patient. The technique is safe, noninvasive, and uses no ionizing radiation.     

Evaluation of mitral stenosis by cine magnetic resonance imaging.

To evaluate the ability of cine magnetic resonance imaging (cine MRI) in the assessment of mitral stenosis (MS), we studied 20 patients (14 women and 6 men, mean age 60.6 +/- 8.5 years) with rheumatic mitral valve stenosis by using an 0.5 T magnet. Cine MRI showed several signs of MS. Mitral leaflet thickening, reduced diastolic opening, and abnormal valve motion toward the left ventricular outflow tract were all common features. MS was also characterized by an abnormal diastolic transmitral signal from blood. Both left atrial and left ventricular dimensions were similar to those obtained at two-dimensional echocardiography (2-DE) (r = 0.89 and r = 0.86, respectively; p less than 0.001). A significant relationship was also found between the maximum mitral leaflet separation measured by cine MRI in diastole and the mitral valve area as calculated using the pressure half-time method and continuous wave Doppler (r = 0.81; p less than 0.001). These data indicate the improved ability of MRI to detect and assess MS and also suggest that this technique may contribute to the noninvasive assessment of MS.     

Myocardial perfusion magnetic resonance imaging for diagnosing coronary arterial stenosis

It has been reported that myocardial perfusion MRI is a useful method for evaluating the severity of myocardial ischemia. We evaluated whether the severity of coronary arterial stenosis could be assessed by the signal-intensity time curve (SITC) obtained by myocardial perfusion MRI. The subjects consisted of 10 patients who showed no abnormalities on coronary angiographies (CAG) (A group), 12 with single-vessel disease of 75-90% stenosis on CAG (B group), and 15 with single-vessel disease of 90% or more stenosis (C group). After infusion of dipyridamole for 4 minutes, gadolinium-diethylenetriamine pentaacetic acid was administered intravenously, followed by serial acquisition of T1-weighted left ventricular short-axis MR images. These images were evaluated after dividing them into the following 3 myocardial segments: anterior wall, lateral wall, and inferior wall. Mean values of the slope of SITC ( 1.4 +/- 0.2 vs 1.1 +/- 0.2. P < 0.01), and increases to the peak corrected SI (deltaSI) (47.5 +/- 1.9 % vs 33.7 +/- 2.4%, P < 0.01) in normal myocardial segments were significantly greater than in ischemic segments in the C group, while there was no significant distinction between normal and ischemic segments in the B group. The mean values of time to the peak SI were not significantly different between normal and ischemic regions in the B and C groups. The results suggest that myocardial segments exhibiting 30% decreases in both the slope and deltaSI of SITC can be diagnosed as having 90% or more severe coronary stenosis. The present study shows that visual and SITC evaluations of myocardial perfusion MR images may be useful for clinically evaluating the severity of coronary stenosis.     

Quantitative evaluation of coronary stenosis by coronary magnetic resonance angiography

Coronary magnetic resonance angiography (coronary MRA) can detect, noninvasively, a high proportion of severe stenotic lesions found on coronary angiograms. However, quantitative evaluation of coronary artery stenosis by coronary MRA has been performed only in a small number of patients. This study was designed to determine whether coronary MRA can assess the degree of stenosis using the two-dimensional segmented turbo-FLASH method (2D method). We studied 108 patients with technically adequate coronary MRA images. The blood flow signal intensity on coronary MRA was classified as markedly decreased, moderately decreased, or normal. The severity of coronary artery stenosis was determined by the caliper method, and coronary stenosis was rated using a seven-point scale (0%, 25%, 50%, 75%, 90%, 99%, and 100%) in accordance with the American Heart Association classification system. Patients were classified into three groups: normal coronary artery (0%–25% stenosis), moderate stenosis (50%–75% stenosis), and severe stenosis (90%–100% stenosis). The degree of stenosis on coronary angiography and the decrease in coronary MRA signal intensity were compared. The right coronary artery was evaluated in 64 patients and the left coronary artery in 73 patients. When a marked or moderate decrease in coronary MRA blood flow signal intensity was defined as indicating stenosis, the sensitivity and specificity of coronary MRA for detecting angiographically severe stenosis were 85% and 80%, respectively. A moderate decrease in coronary MRA blood flow signal intensity detected angiographically moderate stenoses with a sensitivity of 38% and a specificity of 83%. Coronary MRA can detect a high proportion of severe stenoses but only a low proportion of moderate stenoses. Technical improvements are required before coronary MRA can be used clinically. Received: June 23, 2000 / Accepted: December 16, 2000     

Assessment of myocardial perfusion for detection of coronary artery stenoses by steady-state, free-precession magnetic resonance first-pass imaging

Objective

To evaluate the diagnostic impact of magnetic resonance imaging (MRI) first‐pass perfusion using steady‐state, free‐precession (SSFP) sequences with parallel imaging (SENSE) for detection of coronary stenoses.

Design

Prospective observational study.

Setting

University hospital, cardiac MRI and catheterisation laboratories.

Patients and methods

228 patients were examined with coronary angiography and MRI (1.5 T Intera CV). A three‐slice, short‐axis SSFP perfusion scan with a saturation prepulse was performed during infusion of adenosine and at rest followed by myocardial scar (late enhancement) imaging. Gadolinium‐DTPA was given at 0.1 mmol/kg body weight. Perfusion images were visually assessed. Analysis for myocardial hypoperfusion was done according to patient group and according to vessel.

Results

Sensitivity, specificity and accuracy of MRI first‐pass perfusion for detection of a coronary artery stenosis (>50% luminal narrowing) in the total patient group were 93.0%, 85.7%, 91.2% and for a significant lesion (>70% luminal narrowing) 96.1%, 72.0%, 88.2%, respectively. Based on 536 coronary artery territories without myocardial scar, the sensitivity of MRI perfusion analysis for detection of a significant lesion was for the left anterior descending artery 91.4%, for the circumflex artery 81.6% and for the right coronary artery 65.1% (p<0.001).

Conclusions

MRI first‐pass perfusion analysis using an SSFP sequence with three myocardial slices was a highly accurate diagnostic method for detection of coronary artery stenoses. This MRI technique can be included in daily practice and has the potential to guide the indication for invasive coronary angiography.     

非粥样硬化性冠状动脉狭窄的影像学评价

冠状动脉粥样硬化是引起心肌缺血的最重要原因,经皮冠状动脉造影是评价冠状动脉解剖学狭窄的"金标准".但是,还有一些非粥样硬化的原因也会引起心肌缺血导致胸痛症状,并且有明确的缺血证据,像心电图ST段压低、心肌灌注缺损、心肌节段性运动异常、异常代谢产物等.     

Noninvasive detection of coronary artery stenosis using contrast-enhanced three-dimensional breath-hold magnetic resonance coronary angiography

OBJECTIVES: The purpose of this study was to evaluate a contrast-enhanced three-dimensional (3D) breath-hold magnetic resonance (MR) technique for detection of coronary artery stenoses. BACKGROUND: The accuracy of previously published MR coronary angiography protocols varies widely. Recently, coronary artery imaging using T1-shortening contrast agent has become possible, but so far there are no data concerning its clinical application. METHODS: Magnetic resonance coronary angiography was performed in 50 patients with suspected coronary artery disease. Magnetic resonance data acquisition using an ultrafast 3D gradient-echo sequence lasted over 32 heartbeats within one single breath-hold. Twenty milliliters of gadopentetate dimeglumine was injected at a flow rate of 1 ml/s for two successive studies covering the main coronary arteries in single-oblique planes. Stenosis assessment by MR was compared with significant (diameter stenosis > 50%) stenoses on X-ray angiography. Evaluation was limited to the proximal and mid-coronary artery segments. RESULTS: Two hundred sixty-eight of 350 artery segments (76.6%) could be evaluated. Left circumflex coronary artery was only evaluable in 50% of cases by MR. In the evaluable segments, 48 of 56 stenoses and 193 of 212 nonstenotic segments were correctly classified by MR. On a patient basis, MR correctly identified 34 of 36 patients with and 8 of 14 patients without significant coronary stenoses as demonstrated by X-ray angiography (sensitivity 94.4%, specificity 57.1%). CONCLUSIONS: Oblique projection contrast-enhanced MR coronary angiograms obtained within one single breath-hold permit identification of patients with coronary stenoses in the proximal and mid segments of the major coronary arteries with satisfactory accuracy.     

Prediction of necessity for coronary artery revascularization by adenosine contrast-enhanced magnetic resonance imaging

BACKGROUND: An in-depth assessment of coronary heart disease (CHD) risk factors in Koreans was conducted to develop effective risk reduction strategies for this population. METHOD: Based on 2001 Korea National Health and Examination Survey, a cross-sectional survey, this paper presents the prevalence of major CHD risk factors and estimates future risk by applying the Framingham model and CHD risk factor guidelines of the National Cholesterol Education Program Adult Treatment Panel III (NCEP) to 4639 Koreans aged 20 to 79 years. RESULT: Our findings indicate that CHD is a major health threat to Koreans. Among these factors, low high-density lipoprotein cholesterol (HDL-C) was seen in 35.1% of men and 17.8% of women; both had a low rate of controlled high blood pressure (men 13.7%, women 23.6%), and age-adjusted current smoking was especially high (61.6%) in men. The 10-year CHD risk averaged 11.1% in men and 5.5% in women based on Framingham model, and 7.4% and 1.4% based on NCEP guidelines. About 9.1% of men and 2.6% of women were "high-risk," (>20%) based on the Framingham model, and 4.7% and 0.7%, respectively, on the NCEP guideline. Diabetes was the most prevalent risk factor among high-risk individuals and total cholesterol in men and low HDL-C in women was fairly high regardless of prediction method. CONCLUSION: These findings suggest that current coronary heart health of Koreans is nearly comparable to that of western developed countries. Developing and implementing effective population-based intervention strategies focusing on diabetes is warranted to lower the CHD risk for Koreans.     

Noninvasive determination of coronary artery bypass graft patency by cine magnetic resonance imaging

Cine magnetic resonance imaging (MRI) is a gradient-recalled, retrospectively gated, fast-scan technique that depicts laminar flowing blood as bright signal and has been proposed as a useful method for determination of coronary artery bypass graft (CABG) patency. Therefore, we performed a blinded prospective study to assess the value of cine MRI determination of CABG patency in 20 patients with 45 CABG proximal anastomoses who were undergoing repeat angiography. Ten normal subjects served as controls to define normal intrathoracic vascular patterns. There were 21 left anterior descending (LAD) grafts, of which four were left internal mammary (LIMA), 12 left circumflex (Cx), and 12 right coronary (RCA) grafts. After localizing spin-echo coronal images were obtained, multiple axial multislice interleaved cine MRI acquisitions, each consisting of two to four 5-10-mm-thick slices at eight to 24 frames per cardiac cycle, were obtained from the superior main pulmonary artery to the inferior left ventricle. Each acquisition took 5-8 minutes with a subsequent 5-10 minutes of computer image reconstruction. Total study time per patient was 50-75 minutes. Known to cine MRI interpreters were the original surgical CABG insertions but not the angiographic findings. A graft was called patent if a bright graft flow signal, not corresponding to a normal vessel, was identified on multiple frames at multiple levels abutting the great vessels or epicardial surface of the heart. Angiographically, there were 33 patent grafts, of which 29 were identified as patent by cine MRI (sensitivity, 88%).(ABSTRACT TRUNCATED AT 250 WORDS)     

Planimetry of mitral valve stenosis by magnetic resonance imaging

OBJECTIVES: We sought to determine whether noninvasive planimetry of the mitral valve area (MVA) by magnetic resonance imaging (MRI) is feasible and reliable in patients with mitral stenosis (MS). BACKGROUND: Accurate assessment of MVA is particularly important for the management of patients with valvular stenosis. Current standard techniques for assessing the severity of MS include echocardiography (ECHO) and cardiac catheterization (CATH). METHODS: In 22 patients with suspected or known MS, planimetry of MVA was performed with a 1.5-T magnetic resonance scanner using a breath-hold balanced gradient echo sequence (true FISP). Data were compared with echocardiographically determined MVA (ECHO-MVA, n = 22), as well as with invasively calculated MVA by the Gorlin-formula at (CATH-MVA, n = 17). RESULTS: The correlation between MRI- and CATH-MVA was 0.89 (p < 0.0001), and the correlation between MRI- and ECHO-MVA was 0.81 (p < 0.0001). The MRI-MVA slightly overestimated CATH-MVA by 5.0% (1.60 +/- 0.45 cm(2) vs. 1.52 +/- 0.49 cm(2), p = NS) and ECHO-MVA by 8.1% (1.61 +/- 0.42 cm(2) vs. 1.48 +/- 0.42 cm(2), p < 0.05). On receiver-operating characteristic curve analysis, a value of MRI-MVA below 1.65 cm(2) indicated mitral stenosis (CATH-MVA < or =1.5 cm(2)), with a good sensitivity and specificity (89% and 75%, respectively). CONCLUSIONS: Magnetic resonance planimetry of the mitral valve orifice in mitral stenosis offers a reliable and safe method for noninvasive quantification of mitral stenosis. In the clinical management of patients with mitral stenosis, it has to be considered that planimetry by MRI slightly overestimates MVA, as compared with MVA calculated echocardiographically and at catheterization.     

Quantification of valvular aortic stenosis by magnetic resonance imaging

Background Assessing the aortic valvular orifice is important in judging the severity of aortic stenosis. Magnetic resonance imaging visualizes in-plane valvular motion. We studied the value of magnetic resonance planimetry of the aortic valve orifice. Methods We used breath-hold gradient echocardiographic sequences on a clinical magnetic resonance system (1.5 T) and studied 25 patients with symptomatic valvular aortic stenosis. We performed a planimetry of the valvular orifice in systolic images of the valvular plane. The results were compared with echocardiography (continuity equation) and cardiac catheterization (Gorlin formula). Results Magnetic resonance planimetry was feasible in all patients, and the image quality was invariably adequate. The magnetic resonance imaging results correlated well with the data calculated from catheterization and less robustly with the echocardiographic results. The 3 methods were similar in terms of leading to clinical decisions. Conclusions We suggest that magnetic resonance flow planimetry of the aortic valve orifice offers a simple, reliable, fast, and safe method to noninvasively quantify aortic stenosis. (Am Heart J 2002;144:329-34.)     

Usefulness of cardiac magnetic resonance imaging for coronary artery disease detection

Cardiac magnetic resonance imaging (cMRI) is a promising non-invasive technique to assess the presence of coronary artery disease (CAD), which is free of ionizing radiation and iodine contrast. cMRI can detect CAD by angiographic methods or indirectly by perfusion stress techniques. While coronary angiography by cMRI remains limited to research protocols, stress perfusion cMRI is currently being applied worldwide in the clinical setting. Studies have shown good correlation between adenosine-induced stress myocardial perfusion cMRI and single-photon-emission computed tomography or positron emission tomography to detect CAD. Quantitative methods to analyze cMRI perfusion data have been developed in an attempt to provide a more objective imaging interpretation. Standardization of such quantitative methods, with minimal operator dependency, would be useful for clinical and research applications. Myocardial perfusion reserve (MPR), calculated using Fermi deconvolution technique, has been compared with well established anatomical and physiological CAD detection techniques. MPR appears to be the most accurate quantitative index to detect anatomical and hemodynamically significant CAD. Beyond physiological assessment of CAD, cMRI provides information regarding regional and global left ventricular function and morphology, myocardial infarction size, transmurality and viability. Such comprehensive information would require the performance of multiple tests if other modalities were used. This article describes current applications of cMRI for evaluation of patients with CAD.