肥厚型心肌病的磁共振影像诊断应用初探

目的 评价肥厚型心肌病的磁共振影像诊断价值。材料与方法 ２０例肥厚型心肌病患者,行磁共振ＴＳＥ多层面平扫和磁共振电影（ｃｉｎｅ－ＭＲＩ）检查,用ＡＲＧＵＳ专用心功能分析软件分析左室心肌质量、各节段心壁厚度及心肌增厚率等参数。结果 （１）肥厚型心肌病主要累及室间隔及左室前、侧壁,呈非对称分布,肥厚心肌与左室后下壁比率≥１．５。（２）肥厚心肌的心肌增厚率显著低于正常心肌（Ｐ〈０．０１）。（３）梗阻型左     

肥厚型心肌病的MRI诊断

目的：探讨磁共振成像(MRl)对肥厚型心肌病(HCM)的诊断价值，并与超声心动图的结果相对比；同时通过磁共振电影观察心脏功能的改变及心室壁厚度于心动周期内的变化情况。材料和方法：15例肥厚型心肌病患者，MRI扫描时应用心电门控，分别进行自旋回波(SE)序列和梯度回波(GE)序列(电影)检查观察心室壁和心内血流动力学的改变；同时进行超声心动图检查。结果：于舒张末期在左心室中部水平(短轴位)分别测得心室前壁、侧壁、后壁和室间隔的室壁厚度，在心脏长轴位测得心尖部的室壁厚度，并与二维超声结果相比较，并根据心脏电影MRI计算出室间隔和心室侧壁的室壁增厚率。结论：(1)肥厚型心肌病以心室壁的异常肥厚为特点，MRI表现既有左室壁对称性普遍肥厚；亦有非对称性局部心肌肥厚的各类亚型。根据血流动力学的改变MRI可区分梗阻型和非梗阻型。(2)对于心室(前)侧壁、心尖部和室间隔局限性增厚的HCM，MRI能准确定位和分段，对室壁厚度的测量较二维超声心动图亦更准确。(3)电影MRI可反映心动周期内心腔内的血流动力学改变；同时更清楚地显示出心肌于舒张期和收缩期不同时相的动态变化情况。     

Heterogeneity of myocardial wall motion and thickening in the left ventricle evaluated with quantitative gated SPECT

BACKGROUND: Global and regional ventricular function may be evaluated by using gated myocardial perfusion single photon emission computed tomography (SPECT). This study investigated two parameters of regional contraction of the left ventricle, segmental wall motion (WM) and wall thickening (WT), to determine their similarity and disparity in each myocardial segment in patients with normal myocardial perfusion. METHODS AND RESULTS: Thirty-five patients with normal myocardial perfusion and cardiac function (mean left ventricular ejection fraction, 62.6%+/-8.8%) were included in this study. A 1-day stress/rest protocol was used as a means of acquiring technetium 99m (Tc-99m) sestamibi gated SPECT protocol for each patient. A commercially available software package for quantitative gated SPECT (QGS) was used to generate cine loop three-dimensional surface display and SPECT images. The left ventricle was divided into 9 segments to score WM and WT (on a scale of 0 to 4, with 0 being normal and 4 being severely reduced) by 6 independent observers. The WM score was significantly higher than the WT score in the septum, whereas the WM score was lower than the WT score in the inferior segment. Similar WM and WT scores were observed in the remaining segments. CONCLUSIONS: Heterogeneous myocardial WM and WT were observed by using QGS software. These findings suggest that different criteria are required in each segment to evaluate segmental WM and WT by means of gated myocardial perfusion SPECT.     

A comparison of MRI and echocardiography in hypertrophic cardiomyopathy.

This study compares MRI and echocardiography as imaging modalities in hypertrophic cardiomyopathy, with particular reference to measurement of left ventricular wall thickness and mass. 10 subjects underwent echocardiography and MRI. Contiguous 10 mm short axis 35 degrees flip angle cine gradient recalled echo MR images were acquired from the apex to the base of the left ventricle at 1.5 tesla. Standard M-mode and cross-sectional echocardiographic views of the left ventricle were obtained. Excellent agreement between measurements occurred with MRI and M-mode echocardiographic assessment of the thickness of the anterior interventricular septum (95% limits of agreement -1.5 to +1.5 mm). Other comparisons of MRI vs M-mode echocardiographic measurements had the following limits of agreement: posterior free wall -3.3 to +2.9 mm; end-diastolic dimension -5 to +8 mm, left ventricular mass -291 to +55.5 g. Comparing MRI with cross-sectional echocardiographic measurements, the limits of agreement were: anterior interventricular septum -2.4 to +1.7 mm, posterior interventricular septum -2.4 to +2.9 mm, posterior free wall -3.4 to +2.5 mm, anterior free wall -2.4 to +1.7 mm, end-diastolic dimension -4.1 to +8 mm. MRI estimates of LVM in systole vs diastole showed good agreement with 95% limits of agreement of -20 to +17 g, with excellent interobserver variability in diastole (-9 to +5 g) and in systole (-7 to +12 g). In conclusion, MRI is superior to echocardiography for the quantification of ventricular mass in the abnormal left ventricle because it does not make invalid geometrical assumptions. Comparisons of wall thickness show greater discrepancy with increasing distance from the echocardiographic transducer. This study suggests that sequential echocardiography could rationalize the need for MRI in left ventricular hypertrophy. A change in anterior septal thickness of > or = 3 mm on echocardiography merits a further MRI study.     

肥厚型心肌病心功能异常的磁共振电影成像分析

目的 应用磁共振电影成像（ｃｉｎｅ－ＭＲＩ）方法探讨肥厚型心肌病的左心室功能的变化。方法 １２例肥厚型心肌病患者,行ＭＲ快速自旋回波（ＴＳＥ）多层面平扫和ｃｉｎｅ－ＭＲＩ检查,用ＡＲＧＵＳ专用心功能分析软件分析射血分数、心肌增厚率、心腔（左心室）容积及时间－容积变化曲线等参数。结果 （１）肥厚型心肌病主要累及左心室前、侧壁及室间隔,肥厚心肌的心肌增厚率显著低于正常心肌（ｔ＝１５．１,Ｐ〈０．０１）     

心肌淀粉样变性的MRI与超声心动图诊断价值

目的 探讨心肌淀粉样变性的MRI与超声心动图诊断价值.方法 回顾性分析11例经病理活检证实的心肌淀粉样变性患者的MR和超声心动图检查结果.结果 MRI和超声心动图示心肌淀粉样变性患者中,11例均存在不同程度的左心室、室间隔轻度增厚,5例房间隔轻度增厚,7例左心室心肌质量增加,7例左心房增大,6例左心室射血分数减低,10例舒张功能减低,多伴随心包积液、胸腔积液.8例MRI延迟增强显示特征性的弥漫性、广泛性心内膜下至透壁性延迟强化.6例超声心动图显示心肌回声增强,呈磨玻璃样改变,并可见散在颗粒样斑点状强回声.结论 超声心动图具有较好的初步诊断价值,延迟增强MRI能为心肌淀粉样变性诊断及鉴别诊断提供更为全面、丰富的信息.     

Simultaneous measurement of blood and myocardial velocity in the rat heart by phase contrast MRI using sparse q-space sampling

PURPOSE: To measure cardiac blood flow patterns and ventricular wall velocities through the cardiac cycle in anesthetized Wistar Kyoto (WKY) rats. MATERIALS AND METHODS: A gradient-echo cine pulse sequence incorporating pulsed field gradients (PFGs) provided phase contrast (PC) motion encoding. We achieved a range of velocity sensitivity that was sufficient to measure simultaneously the large flow velocities within the cardiac chambers and aortic outflow tract (up to 70 cm s(-1) during systole), and the comparatively small velocities of the cardiac wall (0-3 cm s(-1)). A scheme of sparsely sampling q-space combined with a probability-based method of velocity calculation permitted such measurements along three orthogonal axes, and yielded velocity vector maps in all four chambers of the heart and the aorta, in both longitudinal and transverse sections, for up to 12 time-points in the cardiac cycle. RESULTS: Left ventricular systole was associated with a symmetrical laminar flow pattern along the cardiac axis, with no appearance of turbulence. In contrast, blood showed a swirling motion within the right ventricle (RV) in the region of the pulmonary outflow tract. During left ventricular diastole a plume of blood entered the left ventricle (LV) from the left atrium. The ventricular flow patterns could also be correlated with measurements of left ventricular wall motion. The greatest velocities of the ventricular walls occurred in the transverse cardiac plane and were maximal during diastolic refilling. The cardiac wall motion in the longitudinal axis demonstrated a caudal-apical movement that may also contribute to diastolic refilling. CONCLUSION: The successful measurements of blood and myocardial velocity during normal myocardial function may be extended to quantify pathological cardiac changes in animal models of human cardiac disease.     

Quantification of cardiac function by conventional and cine magnetic resonance imaging

Magnetic resonance imaging (MRI) has been effective for depicting cardiac anatomy and is already established as a technique for the evaluation of some structural abnormalities of the heart and pericardium. With recent advances, MRI can now be used to quantitate cardiac function. Multiphasic ECG-gated spin-echo imaging has been used to quantitate right and left ventricular volumes and ejection fraction. left ventricular mass, and regional myocardial wall thickening. The new technique of cine MRI acquires frames during the cardiac cycle with a time resolution corresponding to 20 msec up to approximately 40 frames for an average cardiac cycle. This technique uses narrow flip angle (30°) and gradient refocused echoes. Cine MRI has been used to measure ventricular volumes and ejection fraction and regional myocardial wall thickening. It is also sensitive to the detection of valvular regurgitation and can provide quantitation of regurgitant volume. This article reviews the current status of MRI for quantitating cardiac function. Research fellow in magnetic resonance imaging supported by grant SE 441-2 from Deutsche Forschungsgenmeinschaft, Bonn, West Germany. Research fellow in magnetic resonance imaging supported by a grant from the Canadian Heart Foundation.     

Evaluation of regional ventricular wall motion by ECG-gated CT

A conventional whole body CT scanner equipped for electrocardiographic gating was used to evaluate regional left ventricular function and the findings were compared with a corresponding analysis by two-dimensional echocardiography and left ventriculography. Twenty-two patients between the ages of 40 and 77 years with a documented anterior or posterolateral myocardial infarction were studied together with a control group comprising 10 patients. The gated CT studies were obtained using three 1 cm levels selected through the mid, apical, and basal regions of the left ventricle. Qualitative analysis of segmental wall motion (p less than 0.0001) correlated with angiography in 82% and with two-dimensional echocardiography in 86% (p less than 0.0001). Computed tomography correctly identified the location of prior myocardial infarction in all but one patient. The results of this study suggest that gated CT may provide an accurate assessment of regional left ventricular function (for anterior and posterolateral myocardial infarction) and that this technique may prove to be clinically useful if these early results are confirmed by further experience.     

Perfusion and mechanical analysis with technetium-99m 2-methoxy-isobutyl-isonitrile in a case of dilated cardiomyopathy

With technetium-99m 2-methoxy-isobutyl-isonitrile (99mTc-MIBI), regional wall thickening in a patient with dilated cardiomyopathy was analyzed by the first component Fourier method. The regional wall thickening was compared with thallium-201 and 99mTc-MIBI SPECT imaging. Thallium-201 SPECT images showed mildly reduced perfusion in the posterior wall and redistribution in the septum, whereas 99mTc-MIBI images showed heterogeneous accumulation around the left ventricular circumference. By means of phase analysis, diffusely decreased wall thickening and discontinuity of percent wall thickening in neighboring segments were observed throughout the left ventricle. Regional wall motion and wall thickening correlated roughly. However, discrepancies between the mechanical function and myocardial perfusion, and discrepancies in regional myocardial perfusion between thallium-201 and 99mTc-MIBI were observed.     

Computed tomographic evaluation of morphological and functional condition of left ventricle in heart aneurysm

Computed tomography is a valuable method for the diagnosis of post-infarction aneurysm of the left ventricle of the heart. It gives additional information concerning the morphological and functional condition of the left ventricle. The suggested method of layer-by-layer scanning improves the diagnostic efficiency of CT during examination of patients with heart aneurysm and is noninvasive. Precise individual calculation of the peak concentration of contrast medium, defined by dynamic scanning, optimises the process of gated CT. CT makes it possible to study changes in cavity configuration, left ventricle wall thinning, induration and calcification of the myocardium, changes in left ventricle wall mobility, decreased thickening of the myocardium at systole and left ventricle cavity thrombosis--all changes characteristic of left ventricular aneurysm. CT provides important additional information about the condition of the inter-ventricular septum. EDV, ESV and EF data obtained using CT produce important information about the functional state of the left ventricle. Computed tomography can be used as an independent method of left ventricle aneurysm detection, especially in those institutions where more complicated investigation methods are not used and interventional cardiac procedures are not practised. Complex use of computed tomography and left ventriculography in cardiosurgical institutions makes it possible to improve significantly the diagnosis of cardiac aneurysm. Calculation of integral data about left ventricle pumping function based on CT and LVG data gives proper evaluation of the indications for operative intervention in left ventricular aneurysm.     

Parametric visualization methods for the quantitative assessment of myocardial motion

RATIONALE AND OBJECTIVES: The authors performed this study to evaluate three-dimensional (3D) and four-dimensional (4D) techniques for quantifying and visualizing myocardial motion. MATERIALS AND METHODS: The 4D method was performed by using 3D reconstructions of the complete, in vivo, canine heart before and after acute myocardial infarction. Images were obtained with the Dynamic Spatial Reconstructor (1-3) at 15 time points throughout one cardiac cycle. The authors used 0.75-mm-thick sections to allow creation of deformable models at each time point. For the 3D method, electron-beam computed tomographic reconstructions were obtained in anesthetized pigs from eight adjacent short-axis sections of the left ventricle. Data were acquired before and after selective microembolization of the left anterior descending coronary artery at 11 time points throughout one complete cardiaccycle. The authors used 8-mm-thick sections, which did not enable the use of the volumetric 4D approach with deformable models. For the 3D method, images were processed by radially dividing the tomographic images into small circumferential sectors. Color encoding was used for the derived local magnitudes of wall dynamics. RESULTS: The 4D method provided endocardial peak velocities, excursions, and strains throughout systole and diastole. The 3D method provided regional thickness or regional rates of left ventricular wall thickening throughout the cardiac cycle. CONCLUSION: Functional parametric maps of disturbances in regional contractility and relaxation facilitate appreciation of the effect of altered structure-to-function relationships in the myocardium.     

Functional assessment of the right ventricle with gated myocardial perfusion SPECT

BACKGROUND: The evaluation of right ventricular function can provide valuable information in a variety of cardiac and noncardiac conditions. Functional assessment of the right ventricle is difficult because of its anatomy and geometry. The authors describe a method for assessing right ventricular function using gated myocardial perfusion SPECT. METHODS: In 20 patients, right and left ventricular ejection fractions (RVEF, LVEF) were determined using gated blood-pool scintigraphy (GBPS) and gated myocardial perfusion SPECT (GSPECT). To avoid contamination with right atrial activity, the two-frame method was adopted for gated blood-pool data when RVEF was measured. In nine patients with normal right ventricles, an index of wall thickening for the right ventricle was derived from the peak systolic and diastolic counts in the free wall. RESULTS: Linear correlation between the two methods adopted for calculation of LVEF and RVEF was good. Bland-Altman analysis revealed good agreement between the two methods with no specific bias. The mean LVEF was 47.9 +/- 12% (GBPS) and 47.3 +/- 12.4 (GSPECT). The mean RVEF was 43.2 +/- 9.6% (GBPS) and 44.2 +/- 8.5% (GSPECT). In both cases, the values were not significantly different. The mean wall motion index was 35%. There was no correlation between the wall thickness index and ejection fraction, but the index was greater in patients with a normal right ventricle compared with those with reduced RVEF. CONCLUSIONS: Gated SPECT offers an alternative to GBPS for the functional assessment of the right ventricle. Using GSPECT will allow the simultaneous assessment of both the right and left ventricles.     

Model-based analysis of electrocardiography-gated cardiac (18)F-FDG PET images to assess left ventricular geometry and contractile function.

This study presents and evaluates a model-based image analysis method to calculate from gated cardiac (18)F-FDG PET images diastolic and systolic volumes, ejection fraction, and myocardial mass of the left ventricle. The accuracy of these estimates was delineated using measurements obtained by MRI, which was considered the reference standard because of its high spatial resolution. METHODS: Twenty patients (18 men, 2 women; mean age +/- SD, 59 +/- 12 y) underwent electrocardiography-gated cardiac PET and MRI to acquire a set of systolic and diastolic short-axis images covering the heart from apex to base. For PET images, left ventricular radius and wall thickness were estimated by model-based nonlinear regression analysis applied to the observed tracer concentration along radial rays. Endocardial and epicardial contours were derived from these estimates, and left ventricular volumes, ejection fraction, and myocardial mass were calculated. For MR images, an expert manually drew contours. RESULTS: Left ventricular volumes by PET and MRI were 101 +/- 60 mL and 112 +/- 93 mL, respectively, for end-systolic volume and 170 +/- 68 mL and 189 +/- 99 mL, respectively, for end-diastolic volume. Ejection fraction was 44% +/- 13% by PET and 46% +/- 18% by MRI. The left ventricular mass by PET and MRI was 196 +/- 44 g and 200 +/- 46 g, respectively. PET and MRI measurements were not statistically significant. A significant correlation was observed between PET and MRI for calculation of end-systolic volumes (r = 0.93, SEE = 23.4, P < 0.0001), end-diastolic volumes (r = 0.92, SEE = 26.7, P < 0.0001), ejection fraction (r = 0.85, SEE = 7.4, P < 0.0001), and left ventricular mass (r = 0.75, SEE = 29.6, P < 0.001). CONCLUSION: Model-based analysis of gated cardiac PET images permits an accurate assessment of left ventricular volumes, ejection fraction, and myocardial mass. Cardiac PET may thus offer a near-simultaneous assessment of myocardial perfusion, metabolism, and contractile function.     

Right ventricular mural thrombus caused by myocardial infarction diagnosed by computed tomography

Thrombi of the left ventricle are common sequelae to acute anterior myocardial infarctions that involve the apex of the heart and produce akinetic or dyskinetic wall thickening patterns. While infarctions of the right ventricle are being increasingly recognized in the setting of inferior myocardial infarcts, little data on in vivo clot formation in the right ventricle of the heart are available in these patients. In the current study we were able to demonstrate a right ventricular mural thrombus using gated computed tomography of the heart. Although an abnormality in the right ventricle extending from the septal margin of the ventricle into the outflow tract could be identified with standard blood pool computed tomographic images and from cross sectional echocardiograms, only with cardiac gating could the relationship between the mass (thrombus) and the noncontractile section of the right ventricular myocardium be clearly identified. We conclude that cardiac gating may help in the evaluation of cardiac masses, and in particular cardiac thrombi. This will be particular valuable in the setting of recent or remote infarction, as the relationship between wall-motion abnormalities and thrombus formation has been well documented.     

Regional wall motion and wall thickening visual scores from gated SPECT in anterior and infero-lateral myocardial infarctions

BACKGROUND: The relationship between the visual scores for wall motion (WM) and wall thickening (WT) of different left ventricular regions in patients with anterior and infero-lateral myocardial infarctions was evaluated using gated SPECT. METHODS: Ninety consecutive patients (79 men and 11 women; mean age 56 +/- 9 years) with previous myocardial infarction (33 anterior and 57 infero-lateral) were included. Left ventricular volumes and ejection fractions (EFs) were calculated from quantitative rest gated SPECT 99mTc tetrofosmin images by using the QGS automatic algorithm. Global and regional (anterior, septal, inferior and lateral) wall motion and wall thickening scores were calculated by consensus of three experienced observers. RESULTS: The correlation between EFs and wall motion and wall thickening scores was better for WM scores in anterior (r=0.904, P<0.0001) than infero-lateral infarctions (r=0.674, P<0.0001). Correlation between wall motion and wall thickening scores was also better for anterior (r=0.898, P<0.0001) than for infero-lateral infarctions (r=0.750, P<0.0001). Except in septal regions, WT scores of the different regions were higher than WM scores (P<0.05) but the statistical significance was higher (P<0.001) in inferior and lateral regions of infero-lateral infarctions. CONCLUSION: Visual global wall motion and wall thickening scores obtained by gated SPECT showed good correlation between them and with the EF, but differences were observed between regional wall motion and wall thickening, especially in inferior and lateral regions of patients with infero-lateral infarctions.     

Unique contraction pattern in patients after coronary bypass graft surgery by gated SPECT myocardial perfusion imaging

PURPOSE: Although left ventricular systolic function seems to be accurately represented on gated SPECT myocardial perfusion imaging, specific patterns of wall motion (WM) and thickening after coronary bypass graft surgery (CABG), demonstrated by other imaging methods, have not been characterized for gated SPECT myocardial perfusion imaging. METHODS: Gated SPECT myocardial perfusion imaging was studied in 30 consecutive patients after CABG (group 1) and 40 non-CABG patients-30 with normal stress perfusion studies (group 2) and 10 with known previous anterior wall infarction (group 3). Two expert readers evaluated epicardial and endocardial systolic WM. Regional WM and the thickening percentage were obtained using CEQUAL 20 segment bull's eye analysis and compiled into regional values. RESULTS: Qualitatively, the post-CABG patients had hypokinetic septum, a hyperdynamic lateral wall, and preservation of anterior WM. In 25 of 30 (83.3%) patients, an anterior systolic epicardial "swing" was evident and was different from the inward endocardial and epicardial motion seen in groups 2 and 3. Septal WM was decreased in group 1 compared with group 2 (2.9 vs. 6.0 mm, < 0.001), with no significant difference in septal thickening. This was not different from the reduced septal motion seen in group 3 (4.1 mm), which was accompanied by both reduced thickening and abnormalities of anterior WM. Lateral WM was increased in group 1 compared with group 2 (9.9 vs. 8.2, < 0.001), with no significant difference in lateral wall thickening (34.6% vs. 39%). CONCLUSIONS: There is a characteristic contraction pattern on gated SPECT myocardial perfusion imaging in post-CABG patients distinguished by apparent septal hypokinesis with preservation of septal wall thickening, apparent increase in endocardial lateral WM, and an anterior epicardial "swing," different from the contraction pattern seen in normal patients and those with previous anterior wall infarction. The related perfusion pattern aids in evaluation of the mechanism of these findings.     

Quantification of regional myocardial wall thickening on electrocardiogram-gated SPECT imaging

BACKGROUND: Current assessment of regional left ventricular function with electrocardiogram (ECG)-gated single photon emission computed tomography (SPECT) imaging is generally performed by visual inspection. The objective of this study was to develop and validate a new computer algorithm for quantifying regional left ventricular wall thickening on ECG-gated SPECT images. METHODS: Regional wall thickening was measured from count density changes during the cardiac cycle observed in 24-sector circumferential count distribution profiles generated from each of 8 frames of an ECG-gated SPECT study. Wall thickening was expressed as the percent count increase during systole relative to end diastole. The program was tested in a phantom simulation and in patient studies consisting of a pilot study (n = 40) and a validation study (n = 33). In the phantom study varying degrees of wall thickening were simulated. The pilot study included 20 normal subjects with low likelihood (<3%) of coronary disease and 20 patients with prior myocardial infarction. Mean wall thickening - 2 standard deviations, measured in normal subjects, defined the lower limit of normal wall thickening. This criterion was tested in the validation study in 13 normal subjects and 20 patients with prior myocardial infarction. Abnormal wall thickening was characterized by extent (percent of circumferential profile) and severity (minimal thickening). RESULTS: The phantom study showed excellent linear correlation between wall thickening computed by the new software and actual wall thickening (r = 0.98). Interobserver and intraobserver reproducibility of quantitative assessment of minimal wall thickening were excellent (r = 0.98 and 0.99, P < .001). Regional wall thickening varied considerably from apex to base in the same ventricle among normal subjects. The average lower limit of normal wall thickening was 25% to 30% at the apex, 19% to 24% in the mid-ventricle, and 13% to 20% at the base of the left ventricle. In the validation study 11 of 13 normal subjects had wall thickening profiles within the pre-defined normal range. All 20 patients with prior myocardial infarction had abnormal regional wall thickening. Minimal regional wall thickening in the infarct areas was 5.4% +/- 5.5%, compared with 30.1% +/- 9.1% wall thickening in comparable anatomic areas in normal subjects (P < .001). CONCLUSION: Regional wall thickening can be quantified reliably from regional count density changes during the cardiac cycle on ECG-gated SPECT images. The new software measured the extent and severity of abnormal regional wall thickening relative to normal files. The method is highly reproducible. Clinical validation showed good differentiation between normal subjects and patients with prior infarction. Quantification of regional wall thickening may enhance diagnostic accuracy and reproducibility of interpretation of gated SPECT imaging.     

Left ventricular mass in hypertrophic cardiomyopathy: assessment by three-dimensional and geometric MR methods.

PURPOSE: The goals of this work were to evaluate the practical utility of MRI to quantify myocardial mass in patients with hypertrophic cardiomyopathy (HCM), define the differences in myocardial mass measurements obtained with three-dimensional and geometric MR methods in patients with normal left ventricular morphology and in patients with wall thickening, and establish the correlation between the two MR methods and the geometric echocardiographic method (GEM). METHOD: The same protocol was followed to conduct prospective MR examinations on 72 patients. In 60 of the subjects suspected to have HCM, imaging was performed to confirm or rule out the preliminary clinical diagnosis; the other 12 were healthy volunteers. Multislice SE, single slice multiphase, and multislice multiphase GRE sequences were performed in all cases. Left ventricle mass was calculated using formulas that assume an ellipsoid geometry for the left ventricle (geometric method), and the results were compared with the mass found using the three-dimensional method and subsequent application of Simpson rule. Tests were run to evaluate intraobserver variability in the MR data obtained with the three-dimensional method. The measurements obtained with the two MR methods were compared with the results obtained with GEM. RESULTS: Although the mean left myocardial mass values obtained using the three-dimensional MR method were smaller than the mean values found with the geometric MR method in all patients, the difference was significant only in patients with HCM. The correlation between the geometric MR method and GEM was very good both in patients with HCM and in those with normal wall thickening. The correlation between the three-dimensional MR method and GEM was good in patients whose left ventricle morphology was normal and poor in patients with HCM. Intraobserver agreement for three-dimensional mass values was excellent. CONCLUSION: MR examinations should be a standard technique for calculating myocardial ventricular mass. In patients with normal ventricle wall thickness, the geometric method can be used to calculate myocardial mass because it is less time consuming. However, in patients with abnormal morphology of the left ventricle and/or asymmetric wall thickening such as found in HCM, in whom the geometric method overestimates myocardial mass, measurements should be made using the three-dimensional method.     

Validation of a new counts-based gated single photon emission computed tomography method for quantifying left ventricular systolic function: Comparison with equilibrium radionuclide angiography

Background  Because myocardial wall thickness is smaller than the spatial resolution of single photon emission computed tomography (SPECT) imaging, changes in myocardial wall thickness are related to changes in maximum pixel counts via the partial volume effect, allowing for quantification of regional systolic wall thickening. We have developed a new gated SPECT method for computing the global left ventricular ejection fraction (LVEF) based entirely on changes in maximum regional myocardial counts during systolic contraction. This new method is independent of endocardial edge detection or other geometric measurements. Methods and Results  In 23 patients the gated SPECT method was validated by comparison with radionuclide angiography. The correlation between computed LVEFs was excellent (slope=0.97, r=0.91). The measurement of LVEF by gated SPECT was highly reproducible, with minimal intraoperator (slope=0.97, r=0.97) or interoperator (slope=1.00, r=0.97) variability. Measurements of regional thickening indexes were also reproducible, with a mean intraoperator correlation coefficient of 0.89±0.05 (range 0.79 to 0.95) for the 14 myocardial regions. Finally, the measurement of LVEF was not significantly influenced by changes in reconstruction filter parameters over a range of cutoff frequencies from 0.16 to 0.28. Conclusions  This new counts-based gated SPECT method for measuring global left ventricular systolic function correlates well with radionuclide angiography, is highly reproducible, and has theoretic advantages over geometric methods. Supported by a grant from the American Heart Association, Virginia Affiliate, Inc., and by a grant from DuPont Pharma Radiopharmaceuticals, N. Billerica, Mass.