Accuracy of MRI evaluation of pulmonary blood supply in patients with complex pulmonary stenosis or atresia

Detailed imaging of pulmonary artery (PA) anatomy and significant aorto-pulmonary collaterals (APCs) is crucial for surgical planning and follow-up in patients with complex congenital heart disease (CHD) and pulmonary stenosis or atresia. Because examination by echocardiography is often technically limited and catheterization is invasive, this study evaluated the diagnostic accuracy of magnetic resonance imaging (MRI) as an alternate non-invasive tool. Thirteen patients (median age 28 years, range: 1–44 years) underwent both cardiac catheterization and MRI within a median of two months (range 0.1–8 months). Diagnoses included tetralogy of Fallot (TOF) with pulmonary atresia (n = 8), TOF with pulmonary stenosis (n = 2), single left ventricle with pulmonary stenosis (n = 2), and complex heterotaxy with pulmonary stenosis (n = 1). The MRI sequences used in this study were ECG-gated spin echo and gradient echo sequences acquired in multiple planes. Compared to catheterization, MRI had 100% sensitivity and specificity for the diagnosis of main PA (n = 6) and branch PA (n = 13) hypoplasia or stenosis, as well as discontinuous (n = 4) or absent (n = 10) branch PAs. There was complete agreement between catheterization and MRI identification of significant APCs (n = 18). Main PA atresia was noted by MRI in four patients but was not definitively seen by catheterization in any. MRI but not catheterization precisely defined the distance between discontinuous PAs and their relationship to other mediastinal structures. In conclusion, cardiac MRI is a reliable non-invasive imaging modality to define PA and APC anatomy in patients with complex pulmonary stenosis or atresia.     

A novel technique using biplane cine magnetic resonance imaging to evaluate left ventricular volume in children

The purpose of the study is to determine the feasibility of a novel simplified technique using cine magnetic resonance imaging (MRI) to assess left ventricular (LV) volume and ejection fraction (EF) validated by comparison with biplane LV angiography. Previous MRI studies to assess LV volumes have used multiple axial planes, which are compromised by partial volume effects and are time consuming to acquire and analyze. Accordingly, we developed a simplified imaging approach using biplane cine MRI and imaging planes aligned with the intrinsic cardiac axes of the LV. We studied 20 children (aged 4 months to 10 years) with various heart diseases. The accuracy of cine MRI was compared with that of LV angiography in all patients. LV volumes were calculated using Simpson's rule algorithm, for both MRI and LV angiography. LV volumes determined from MRI were slightly underestimated but correlated reasonably well with angiographic volumes (LVEDV: Y = 0.88X + 1.58, r = 0.99, LVESV: Y = 0.73X + 1.03, r = 0.98). Most importantly, even in patients who had abnormal ventricular curvature such as in tetralogy of Fallot, MRI determined LV volumes correlated well with angiographic values. The MR study was completed within 35 min in all patients. In conclusion, simplified biplane cine MRI, using the intrinsic LV axis planes, permits noninvasive assessment of LV volumes in views comparable to standard angiographic projections and appears practical for clinical use in childhood heart disease since the scan and analysis times are relatively short.     

Evaluation of pulmonary blood supply by nuclear magnetic resonance imaging in patients with pulmonary atresia

Nuclear magnetic resonance (NMR) imaging defines the blood pool without the need for contrast medium. Consequently, it may be useful for defining the pulmonary circulation in patients with pulmonary atresia, in whom opacification of these vessels can be problematic. Ten patients with pulmonary atresia were evaluated by gated NMR imaging. The morphology of the right ventricular outflow tract, the size and the course of the central pulmonary vessels and the source of the collateral supply to the lung were assessed. Central pulmonary arteries were identified and measured in 9 of the 10 patients. One patient had no detectable central pulmonary arteries. Angiography confirmed the NMR findings in all but two patients, in whom NMR scanning visualized a main pulmonary artery that was not seen on angiography. Collateral arteries arising from the aorta or the arch vessels, as well as intracardiac malformations and aortic arch anomalies, were identified in all 10 patients. In six patients with palliative surgery, NMR imaging correctly demonstrated all patent shunts. Nuclear magnetic resonance imaging appears to be an effective noninvasive technique for evaluating patients with pulmonary atresia. However, tomographic thickness and spatial resolution are still limiting factors for this technique in infants.     

重度颅内动脉狭窄活体高分辨磁共振成像初探

目的 观察症状性重度颅内动脉狭窄(SSIS)活体高分辨磁共振成像(HRMRI)的初探结果.方法 用3.0T MR扫描仪对5例SSIS患者进行HRMRI检查,盲法分析影像资料.结果 3例管壁呈典型的粥样硬化改变,呈偏心性增厚、大的脂质坏死核心、纤维帽破裂、不均匀强化.2例管壁为非粥样硬化可能性大,1例管腔内可见斜形隔膜与轻度增厚的管壁相连,增强后呈均匀强化;另1例管壁向心性明显增厚,增强后无强化.结论 SSIS的活体HRMRI成像是可行的,能够提供狭窄处的管壁信息,但仍需进一步研究其应用价值.     

应用心脏电影磁共振成像评估无明显心血管症状的2型糖尿病患者左心室功能

目的 利用心脏电影磁共振成像(MRI)评估无明显心血管症状的2型糖尿病患者左心室结构及功能变化.方法 入选2005年11月至2006年1月至天津医科大学总医院糖尿病门诊就诊的2型糖尿病患者85例(2型糖尿病组)及同期健康体检者43名(正常对照组),采用单因素两样本组内随机设计方法进行研究.行左心室短轴位电影MRI,计算并比较左心室整体功能指标(包括舒张末期容积指数、收缩末期容积指数、每搏输出量指数、心脏指数、射血分数、舒张末期质量指数和收缩末期质量指数)、局部功能(舒张末期厚度、收缩末期厚度、室壁增厚率和室壁运动)和血液动力学指标(高峰射血率、高峰射血时间、高峰充盈率和高峰充盈时间).计量资料行独立样本成组t检验,性别构成采用x2检验.采用Logistic逐步回归分析评估性别、年龄、身高、体重、体重指数、病程和空腹血糖对左心室功能影响的显著性.结果 2型糖尿病组收缩末期容积指数低于正常对照组[分别为(22±8)、(25±5)ml/m2,t=2.265,P＜0.05],射血分数高于正常对照组(分别为59%±9%、56%±6%,t=-2.457,P＜0.05),室壁增厚,高峰充盈率低于正常对照组[分别为(282±73)、(321±99)ml/s,t=2.508,P＜0.05].Logistic逐步回归分析显示,空腹血糖对左心室功能受损的影响近乎有统计学意义(x2=3.781,P=0.052).结论 心脏电影MRI是左心室功能测量的"金标准",能可靠评价无明显心血管症状的2型糖尿病患者左心室功能改变.无明显心血管症状的2型糖尿病患者舒张功能障碍早于收缩功能障碍,控制空腹血糖水平对避免发生左心室功能受损可能具有意义.     

Changes of pulmonary vein orifice size and location throughout the cardiac cycle: dynamic analysis using magnetic resonance cine imaging

INTRODUCTION: Anatomically guided left atrial ablation is used increasingly for treatment of atrial fibrillation (AF). Three-dimensional mapping systems used for pulmonary veins (PV) encircling ablation procedures anticipate a stable size and position of the PV orifice. The aim of the current study was therefore to analyze changes of PV orifice size and location throughout the cardiac cycle using cine magnetic resonance imaging (MRI). METHODS AND RESULTS: Twenty-five healthy volunteers were studied using a 1.5 Tesla MRI system. MR angiograms were acquired with a breath-hold three-dimensional fast-spoiled gradient-echo imaging (3D FSPGR) sequence in the coronal plane before and after gadolinium injection. Maximum intensity projections and multiplanar reformations were performed to reconstruct images of the PV. Bright blood cine imaging in the axial view was acquired by a steady-state free precession pulse sequence. Twenty bright blood images were obtained per cardiac cycle. The axial (anterior-posterior) PV orifice diameter was measured in all 20 images. For analysis of PV movement the location of the orifice posterior edge was plotted on scale paper. PV orifice size depends on the stage of the cardiac cycle with the largest diameter in late atrial diastole and a mean decrease of 32.5% during atrial systole. Location changes of the PV orifice are in the range of up to 7.2 mm and larger in the coronal (lateral-medial) than in the sagittal (anterior-posterior) direction. CONCLUSION: PV orifice size and location is not as stable as anticipated by three-dimensional mapping systems used for PV encircling left atrial ablation procedures. RF application close to the presumed orifice location should therefore be avoided to minimize the risk of PV stenosis.     

磁共振脑灌注成像对先天性血管狭窄脑组织血供评估与临床治疗相关性研究

目的探讨磁共振灌注加权成像(PWI)对先天性血管狭窄脑组织血供评估与临床治疗价值的研究。 方法选取2016年6月至2019年6月就诊牡丹江医学院附属红旗医院,除外其他病变通过DSA或CTA已确诊的先天性血管狭窄患者64例,选择感兴趣区通过后处理软件处理后得到局部脑血容量(rCBV)、局部脑血流量(rCBF)、相对平均通过时间(rMTT),达峰时间(rTTP)等相关参数的数值。比较存在临床症状患者与无临床症状患者灌注上差异及存在临床症状患者不同区域的灌注情况。 结果比较存在临床症状患者与无临床症状患者灌注rCBV、rCBF、rMTT及rTTP差异,rCBF数值减低、而rMTT和rTTP数值呈现出延长(P<0.05),而两组间rCBV值无统计学差异;先天性血管狭窄患者狭窄区供血rCBF及rCBV值的减低、rMTT及rTTP值出现延长,有统计学意义(P<0.05)。 结论磁共振脑灌注功能成像技术可以有效评估先天性脑血管狭窄脑组织血供情况,对临床脑血供情况评估及治疗方案的选择具有重要意义。     

室间隔完整型肺动脉闭锁及肺动脉瓣狭窄的手术治疗

目的探讨新生儿、婴儿室间隔完整型肺动脉闭锁及危重型肺动脉瓣狭窄的手术治疗。方法19例患儿,其中室间隔完整型肺动脉膜性闭锁10例,危重型肺动脉瓣狭窄9例。15例经胸正中切口体外循环心脏不停跳下完成手术,4例经左胸后外侧切口非体外循环下完成手术。除早期1例同期行动脉导管未闭（PDA）结扎及卵圆孔未闭缝合术外,其余18例均保留PDA、单纯切开肺动脉瓣。结果本组围术期死亡2例,院外死亡1例。其余16例术后当日肺动脉跨瓣压差为37—132mmHg,平均61mmHg;2周后为26～77mmHg,平均43mmHg,较术后早期明显降低（P〈0．05）。出院前不吸氧下测动脉血氧饱和度78％～92％,平均85％,较术前明显增高（P〈0．05）。随访PDA均闭合,右心室较术前明显增大,三尖瓣反流消失或明显减轻,房水平分流消失。结论对室间隔完整型肺动脉闭锁及危重型肺动脉瓣狭窄实施单纯肺动脉瓣切开术治疗安全有效。     

颅内大动脉狭窄患者Wingspan支架置入前后高分辨率核磁共振影像的变化

目的采用高分辨率MRI(HR-MRI)技术,评价Wingspan支架置入前后,颅内大动脉病变部位管壁和管腔影像的变化。方法回顾性连续纳入2013年12月至2014年12月,首都医科大学宣武医院神经介入诊断治疗科收治的症状性颅内动脉重度狭窄(狭窄率70%~99%)患者9例,病变位置包括大脑中动脉、基底动脉和椎动脉颅内段。采用头部三维HR-MRI成像技术,通过影像注册和匹配,分析和比较Wingspan支架释放前后,病变部位管壁强化面积变化;通过Pearson相关性分析以及Bland-Altman统计图,比较HR-MRI与DSA测量狭窄率的一致性。结果支架置入技术成功率为100%,无相关并发症。(1)Wingspan支架置入术后狭窄部位管壁钆剂强化较术前明显减弱,置入术后比术前强化面积下降了(87±16)%,差异有统计学意义(t=2.325,P=0.049)。(2)支架置入术前,HR-MRI和DSA测量的平均狭窄率分别为(82±6)%和(82±8)%,差异无统计学意义(t=0.051,P=0.961);术后HR-MRI和DSA的平均狭窄率分别为(16±12)%和(21±12)%,差异无统计学意义(t=1.345,P=0.216)。(3)支架置入术前与术后,HR-MRI和DSA测量狭窄率的Pearson相关系数分别为0.347(P=0.361)和0.545(P=0.129)。Bland-Altman统计图显示,大多数据点位于一致性界限内(x-±1.96 s)。结论 HR-MRI作为一种体内无创性成像手段,可用于评估颅内支架释放后病变部位管壁、管腔和原有斑块的变化,可用于评价颅内动脉管壁影像重建。     

Assessment of gastric motor function by cine magnetic resonance imaging

Background and Aim:  The aim of the present study was to evaluate gastric motor function by magnetic resonance imaging (MRI) and investigate whether this examination is a useful tool for therapeutic efficacy or postoperative gastric motor function.
Methods:  Twenty-five healthy volunteers and 10 gastric cancer patients with pylorus-preserving gastrectomy (PPG) underwent cine-MRI. Gastric volume was determined by 3D-volumetry. Gastric motility was quantified by calculating the gastric motility index (GMI).
Results:  The image acquisition and analysis were successfully carried out for all subjects. In healthy volunteers, mean frequency, amplitude, velocity of gastric peristaltic waves and GMI 30 min after the intake of jelly were 3/min, 8.8 mm, 2.2 mm/s and 19.6 mm²/s, respectively. Mean amplitude (8.8 vs 10.4 mm, P  = 0.027), velocity (2.2 vs 2.6 mm/s, P  < 0.001) of peristaltic waves, and GMI (19.6 vs 26.7 mm²/s, P  < 0.001) significantly increased at 30 min after giving mosapride citrate (MS). Mean gastric volume after MS administration was significantly decreased; 0 min (317.3 vs 272.9 mL, P  = 0.021), 45 min (263.4 vs 206.4 mL, P  = 0.004) and 60 min (228.7 vs 165 mL, P  = 0.001). PPG patients with postprandial symptoms were observed having antiperistalsis-like contraction waves and reflux of gastric contents from the pyloric region into the upper part of the stomach. Mean gastric volume in PPG patients with postprandial symptoms at 30 min after intake of jelly tended to be greater than in those without such symptoms.
Conclusions:  The present study demonstrates that cine-MRI is a sensitive and non-invasive imaging technique for simultaneously measuring gastric motility and emptying.     

成人先天性心脏病合并肺动脉高压患者的心脏磁共振评估

目的 探讨心脏磁共振（cardiac magnetic resonance,CMR）评价先天性心脏病合并肺动脉高压患者心室功能的临床价值.方法 对26例先天性心脏病合并肺动脉高压的患者行CMR检查,分别测量并计算右心室与左心室的短轴缩短率、舒张末期直径、舒张末期容积、收缩末期容积、每搏排血量、射血分数等心功能参数及主动脉、肺动脉直径,同时评价室间隔运动、心肌延时强化.采用配对样本t检验比较左、右心室功能参数,采用两个独立样本t检验比较室间隔运动正常组和异常组的右心功能情况,采用卡方检验比较室间隔运动异常与心肌延时强化的关联.结果 右心室舒张末期直径、舒张末期容积、收缩末期容积均显著高于左心室,差异有统计学意义（P＜0.05）;右心室短轴缩短率、射血分数均显著低于左心室,差异有统计学意义（P＜0.05）.26例患者中,14例室间隔运动异常,14例出现心肌延时强化.室间隔运动异常组心肌延时强化出现比例明显高于室间隔运动正常组,差异有统计学意义（P＜0.05）.同时,室间隔运动异常组的右心室舒张末期直径、舒张末期容积均显著高于正常组,差异有统计学意义（P＜0.05）;右心室短轴缩短率显著低于正常组,差异有统计学意义（P＜0.05）;射血分数低于正常组,但差异无统计学意义（P=0.08）.结论 合并肺动脉高压的成人先天性心脏病患者右心功能较左心功能差,室间隔运动异常患者的右心功能更差,室间隔运动异常患者出现心肌延时强化比例高.CMR能够提供先天性心脏病合并肺动脉高压患者的左、右心室功能及相关结构信息,对治疗和预后有重要价值.     

Contrast enhanced-cardiovascular magnetic resonance imaging in patients with pulmonary hypertension.

AIMS: To determine the presence and extent of delayed contrast enhancement (DCE) in patients with pulmonary hypertension (PHT) using contrast enhanced-cardiovascular magnetic resonance imaging (ce-CMR). METHODS AND RESULTS: Twenty-five patients with PHT underwent ce-CMR and right heart catheterization. Right ventricular (RV) and left ventricular (LV) volumes, ejection fraction, mass, and DCE mass were determined with ce-CMR. Mean pulmonary artery pressure (mean PAP) averaged 43 (12) mmHg and cardiac output 4.3 (1.2) L/min. DCE was demonstrated in 23 out of 25 patients. DCE was confined to the RV insertion points (RVIPs) in seven patients and extended into the interventricular septum (IVS) in the remaining 16 patients. In these 16 patients, septal contrast enhancement was associated with IVS bowing. The extent of contrast enhancement correlated positively with RV end-diastolic volume/body surface area, RV mass, mean PAP, and pulmonary vascular resistance and correlated inversely with RV ejection fraction. CONCLUSION: DCE was present within the RVIPs and IVS of most patients with PHT studied. Extent of DCE correlated with RV function and pulmonary haemodynamics. DCE was associated with IVS bowing and may provide a novel marker for occult septal abnormalities directly relating to the haemodynamic stress experienced by these patients.     

Changes of the left ventricle after myocardial infarction—estimation with cine magnetic resonance imaging during the first six months

Background: In recent years, the interest of cardiologists has focused increasingly on the morphologic and functional changes of the left ventricle after myocardial infarction (MI), due to their great prognostic significance for the patient. Hypothesis: The aim of this study was to evaluate changes in left ventricular morphology and function during the first 6 months following MI. Methods: In all, 61 patients (17 women, 44 men, age 36–83 years) were examined with cine magnetic resonance imaging (CMRI) 1,4, and 26 weeks after myocardial infarction. Thirty-two patients had anterior MI and 29 patients had posterior MI. According to enzyme-derived infarct weight, 15 patients had small infarcts (<20 g), 19 had intermediate-sized infarcts (20–40 g), and 27 patients had large infarcts (>40 g). CMRI was performed in the true short axis of the left ventricle. In each examination, left ventricular end-diastolic and end-systolic volume indices (LVEDVI, LVESVI), stroke volume index (LVSVI), ejection fraction (LVEF), and regional thickness, mass, and motility of the myocardial wall—diastolic thickness (IDdia), infarct mass (IM) and motility (MOT) of the infarct area and diastolic and systolic thickness (VDdia, VDsys), muscular mass (VM), and motility (VMOT)—were determined. In addition, patients were divided into subgroups according to New York Heart Association (NYHA) functional status at baseline. Results: In the total group, LVEDVI increased from 73·9 ± 23·5 ml/m² to 85·4 ± 28·1 ml/m² (p <0·001) and LVESVI from 40·5 ± 19·4 ml/m² to 51·2 ± 29·0 ml/m² (p <0·001). In the subgroups the development depended on infarct size and location. LVSVI and LVEF remained more or less constant except for large anterior infarctions. All changes of the myocardial wall depended on infarct size and location: In all patients IDdia decreased from 10·4 ± 1·6 mm to 8·9 ± 1·7 mm (p <0·001), IMOT from 2·0± 1·6 mm to 0·5 ±2·9 mm (p<0·001). IM increased from 41 ± 21 g to 45 ± 25 g (p <0·001). In the total group, VDdia increased from 11·9 ± 1·6 mm to 12·4 ± 1·8 mm (p <0·05), VDsys from 16·6 ± 2·5 mm to 17·2 ± 3·1 mm (p <0·05). In the subgroups changes varied: VDdia and VDsys decreased markedly in large anterior wall infarctions. VM increased in the total cohort from a mean of 246 ± 66 g to 276 ± 80 g (p <0·001). VMOT decreased from 7·1 ±2·4 mm to 6·3 ± 2·7 mm (p <0·05). Loss of motility was most pronounced in anterior infarctions. The volume–mass ratio, a measure of the success of compensation of volume increase by myocardial hypertrophy, decreased in small infarcts, remained unchanged in intermediate infarcts, and increased in large infarcts. There was a trend toward improvement of the NYHA functional status during the observation period. Conclusions: Changes of the left ventricular chamber during the first 6 months following MI are dependent on its size and location, with large anterior infarctions having the worst course. Myocardial wall remodeling is also dependent on infarct size and location, and the volume–mass ratio increases in the presence of large areas of necrosis, indicating the noncompensatory effect of myocardial hypertrophy. However, these changes have no clinical effect during the first half year after MI.     

The pulmonary circulation and its systemic arterial supply in pulmonary atresia

The pulmonary circulation and its systemic arterial supply in cases of pulmonary atresia were studied angiocardiographically. In 69% of the cases the pulmonary arteries were hypoplastic and supplied by a patent ductus arteriosus or a few large systemic arteries. A classification into four groups is suggested, and a developmental paradox represented by this classification is discussed.     

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.     

Absent pulmonary valve syndrome with associated anomalies of the pulmonary blood supply

We report four cases of so-called absent pulmonary valve syndrome associated with absence or anomalous origin of the left pulmonary artery. The fate of the patients with this condition appears to be affected mainly by the occurrence of pulmonary complications (three of our patients died of pulmonary causes, two of them after surgery). The proper timing of corrective surgery is still uncertain. Preoperative investigations should strive to obtain a clear-cut identification of the pulmonary arteries, particularly the left one or, in its absence, of the anomalous vascular supply to the lung. Right ventriculography, as employed by us, is insufficient. Pulmonary angiography, aortography and pulmonary vein "wedge" angiography may be needed.     

Likelihood ratios in the diagnosis of renal artery stenosis by magnetic resonance angiography compared with renal angiography

BACKGROUND: Renal angiography (RA) is considered to be the gold standard for the diagnosis of renal artery stenosis (RAS). However, it is invasive and potentially harmful; hence there is a need for an optimal noninvasive test. Magnetic resonance angiography (MRA) is currently accepted as the optimal noninvasive test by many. However, its major drawback is its inability to grade quantitatively the degree of stenosis. In this study, likelihood ratios (LR) were used to compare the diagnostic accuracy of MRA with that of RA. METHODS: To test the hypothesis that semiquantitatively graded MRA would correlate with RA, a retrospective analysis was performed to determine the LR of MRA to diagnose RAS compared with RA. It was believed that LR > or = 10.0 or < or =0.1 might generate conclusive changes from pretest to post-test probabilities. In this study a total of 94 renal arteries from 48 patients were analyzed for RAS by MRA and RA. Stenoses were graded by MRA as mild (<50%), moderate (50% to 75%), or severe (>75%); and by RA as <75% or > or =75% stenosis. RESULTS: The LR was 0.13 (95% CI = 0.09 to 0.19) for mild stenosis, 0.11 (95% CI = 0.08 to 0.15) for moderate stenosis, and 2.2 (95% CI = 1.9 to 3.1) for severe stenosis by MRA. CONCLUSIONS: Nonsevere stenosis can be sufficiently diagnosed by MRA and may not warrant RA. However, it may be insufficiently precise to establish severe RAS based on LR results. Therefore, for severe RAS by MRA, the decision to obtain RA can be made with the help of post-test probability, which is determined using pretest probability and LR.