Left ventricular volumes measured by MR imaging

We assessed the potential of proton magnetic resonance (MR) imaging for accurately measuring left ventricular volumes using 15 latex casts of excised human left ventricles. The casts were submerged in water to stimulate the endocardial left ventricular cavity interface in in vivo imaging conditions. Tomographic image sections perpendicular to the long axis of the cast were obtained, spanning each cast from apex to base. Simpson's rule was used to calculate the cast volumes. Correlation between the actual cast volumes (as measured by the displacement method) and the calculated volumes using MR imaging for the 15 casts was excellent. Our data demonstrate that MR imaging accurately measures cardiac chamber volumes in this in vitro model.     

X射线心室造影计算左室容积三种方法的比较

目的评价X射线心室造影计算左心室容积的3种方法单平面面积-长度法、双平面面积-长度法和单平面Simpson法的相对准确性.方法对人的左心室铸型(12只)进行X射线摄影,分别用单平面面积-长度法、双平面面积-长度法和单平面Simpson法3种方法计算左心室容积;左心室铸型的实际容积由铸型排出水的体积来测定.结果左心室铸型的实际容积为(61.17±26.49)ml;单平面面积-长度法计算的容积为(97.50±35.56)ml;双平面面积-长度法计算的容积为(90.51±36.33)ml;单平面Simpson法计算的容积为(65.00±23.63)ml.单平面和双平面面积-长度法的计算值明显大于左心室铸型的实际容积值和单平面Simpson法的计算值(P均＜0.05);而单平面Simpson法的计算值与左心室铸型的实际容积差异无显著性(P＞0.05);单平面和双平面面积-长度法的计算值之间差异无显著性(P＞0.05).相关分析表明,单平面面积-长度法、双平面面积-长度法和单平面Simpson法的容积计算值均与左心室铸型的实际容积高度相关(r均＞0.98),但单平面和双平面面积-长度法对左心室容积的高估程度均较单平面Simpson法更高,单平面法为(36.34±17.98)ml,双平面法为(29.34±15.59)ml,单平面Simpson法为(3.83±8.48)ml,P＜0.01.结论X射线心室造影计算左室容积方法、单平面Simpson法较单平面和双平面面积-长度法更精确,但对于不具有分析软件的电影摄影设备,面积-长度法亦可用于计算左心室容积.     

Assessment of human right ventricular cast volume by CT and angiocardiography

Angiocardiographic methods available for cardiac chamber volume measurements have been shown to be less accurate although more practical than CT for the evaluation of the LV. To explore the capability of CT for RV volume measurements, silastic casts of seven normal RV were measured by a displacement method, conventional angiocardiographic biplane methods, and CT. The displacement method used degassing beneath vacuum to remove air trapped in the casts, and the actual volumes, which varied between 62 and 188 cc, were measured by Archimedes' principle. Cast volumes measured by biplane angiogram methods displayed a varying degree of spread around the regression line, caused by the chamber's irregular shape and its variation in orientation relative to the x-ray beams. CT measurements were in all aspects significantly more accurate.     

Fusion of computed tomography data and optical 3D images of the dentition for streak artefact correction in the simulation of orthognathic surgery

OBJECTIVE: To determine the limits of accuracy of fusion of optical three-dimensional (3D) imaging and computed tomography (CT) with and without metal artefacts in an experimental setting and to show the application of this hybrid system in 3D orthognathic surgery simulation. METHODS: Ten plaster casts of dental arches were subjected to a CT scan and optical 3D surface imaging. Subsequently, the first molars in the plaster casts were supplied with metal restorations, bilaterally, and new CT scans and optical surface images were assessed. The registration of the surface data of the two imaging modalities of the study models without and with metal restorations was carried out. The mean distance between the two data sets was calculated. From a patient a CT scan of the skull as well as optical 3D images of plaster casts of the dental arches were acquired. Again the two imaging modalities were registered and virtual orthognathic surgery simulation was carried out. RESULTS: The mean distance between the corresponding data points of CT and optical 3D surface images was 0.1262+/-0.0301 mm and 0.2671+/-0.0580 mm, respectively, for the plaster casts without and with metal restorations. The differences between these data were statistically significant (P<0.0005). For the patient case a mean difference of 0.66+/-0.49 mm and 0.56+/-0.48 mm for mandible and maxilla, respectively, was calculated between CT and optical surface data. CONCLUSION: The accuracy of the fusion of 3D CT surface data and optical 3D imaging is significantly reduced by metal artefacts. However, it seems appropriate for virtual orthognathic surgery simulation, as post-operative orthodontics are performed frequently.     

Two- and three-dimensional CT ventriculography: a new application of helical CT

OBJECTIVE: We propose a new application of helical CT, CT ventriculography, which can produce two-dimensional (2D) and three-dimensional (3D) images of different cardiac phases (plus animation). We sought to determine the accuracy of CT ventriculography for assessing left ventricular volumes. MATERIALS AND METHODS: With a single breath-hold, the patient's entire heart was scanned with an ECG-gating technique (3-mm-thick collimation, 2 mm per rotation table speed, 0.8 sec per rotation, and 50 rotations through 10 cm in total). Using a 0.2-mm (0.08-sec) interval (10 slices per rotation) overlapping reconstruction, about 500 axial slices were obtained and reordered to separate different cardiac cycles. Then, 2D cardiac axes and 3D images were reconstructed and animated movies of the 2D and 3D images were produced. In 21 patients, the left ventricular end-diastolic volume, end-systolic volume, and ejection fraction were assessed and compared with left ventriculography. Correlations and agreements between CT and left ventriculography were determined. RESULTS: Close correlations between CT and left ventriculography were obtained (r = 0.95, 0.98, and 0.91, for end-diastolic volume, end-systolic volume, and left ventricular ejection fraction, respectively; p < 0.0001 for all values). The limits of agreement between CT and left ventriculography were 44.3 to -44.5 ml for end-diastolic volume, 19.8 to -29.0 ml for end-systolic volume, and 19.7% to -9.5% for left ventricular ejection fraction. CONCLUSION: This cardiac application of helical CT provides a clear morphology along the cardiac axes and 3D images and an assessment of left ventricular volumes (end-diastolic volume, end-systolic volume, and left ventricular ejection fraction).     

Non-invasive measurement of left ventricular volumes and function by gated positron emission tomography

To date cardiac positron emission tomography (PET) studies have focussed on the measurement of myocardial blood flow, metabolism and receptors while left ventricular (LV) function and dimensions have been derived from other modalities. The main drawback of this approach is the difficulty of data co-registration, which limits clinical interpretation. The aim of this study was to evaluate whether it is possible to measure absolute cardiac volumes, and consequently LV function parameters such as ejection fraction, and wall motion with gated PET. Nineteen patients underwent a PET scan and planar radionuclide ventriculography (MUGA) within 9±9 days. A 9-min scan (16 gates/cardiac cycle) was acquired after inhalation of 3 MBq/ml of oxygen-15 labelled carbon monoxide at the rate of 500 m1/min over 4 min using a multislice PET camera. Noise reduction was performed on the gated image to enhance the definition of the ventricles before reslicing to the short-axis view. A threshold value was used to detect the edge of the LV at each gate. LV volumes at each gate were estimated by summing the volume of voxels within the LV boundary. PET measurements of LV volumes were as follows: LV end-diastolic volume ranged from 72 to 233 ml and LV end-systolic volume ranged from 24 to 203 ml. Phantom experiments supported the validity of this approach for estimating volumes. LV ejection fraction measured with MUGA was 38.4%±16.3% (range 15%–71%) and that measured with PET was 39.6%±17.7% (range 9%–72%) (P=NS). The LV ejection fraction measurements were highly correlated (r ²=0.824). These results indicate that: (1) absolute enddiastolic and end-systolic volumes can be quantified using gated PET and (2) LV ejection fraction can be accurately measured by gated PET simultaneously with the other physiological PET parameters.     

Right and left ventricular volumes and wall measurements: determination by computed tomography in arrested canine hearts.

Computed tomographic (CT) images of in vitro hearts filled with iodinated contrast medium have delineated right and left ventricular cavities, papillary muscles, major trabeculae, pulmonary artery, and the aorta. Because of relatively good structural definition, this study was undertaken to determine the potential use of CT in the measurement of cardiac dimensions and cavity volumes. Ten isolated arrested canine hearts were filled with an iodinated oil-paraffin mixture and scanned transversely from base to apex. Measurements of the thickness of the interventricular septum and of the left ventricular posterior wall (indexes of cardiac hypertrophy) had a high degree of correlation to similar measurements of corresponding heart specimens. Using serial tomographic images, the cavity volumes of individual tomographic scans were totaled. The volume of each scan of given thickness was obtained either by the use of planimetry or from a numerical computer printout. Both the planimetric and computer methods gave right and left ventricular volumes which correlated well (P less than .05) with the volumes of paraffin casts. Unlike other techniques widely used for ventricular volume measurement, the method described does not depend on an assumption that the chamber resembles a specific geometric model. This method of volume measurement is applicable to both the left ventricle, regardless of its shape, and to the concave irregularly shaped right ventricle.     

Quantitative comparison of analytic and iterative reconstruction methods in 2- and 3-dimensional dynamic cardiac 18F-FDG PET.

The aim of this work was to compare the quantitative accuracy of iteratively reconstructed cardiac (18)F-FDG PET with that of filtered backprojection for both 2-dimensional (2D) and 3-dimensional (3D) acquisitions and to establish an optimal procedure for imaging myocardial viability with (18)F-FDG PET. METHODS: Eight patients underwent dynamic cardiac (18)F-FDG PET using an interleaved 2D/3D scan protocol, enabling comparison of 2D and 3D acquisitions within the same patient and study. A 10-min transmission scan was followed by a 10-min, 25-frame dynamic 3D scan and then by a series of 10 alternating 5-min 3D and 2D scans. Images were reconstructed with filtered backprojection (FBP) or attenuation-weighted ordered-subsets expectation maximization (OSEM), combined with Fourier rebinning (FORE) for 3D acquisitions, applying all usual corrections. Regions of interest (ROIs) were drawn in the myocardium, left ventricle, and ascending aorta, with the last 2 being used to define image-derived input functions (IDIFs). Patlak graphical analysis was used to compare net (18)F-FDG uptake in the myocardium, calculated from either 2D or 3D data, after reconstruction with FBP or OSEM. Either IDIFs or arterial sampling was used as the input function. The same analysis was performed on parametric images. RESULTS: A good correlation (r(2) > 0.99) was found between net (18)F-FDG uptake values for a myocardium ROI determined using each acquisition and reconstruction method and blood-sampling input functions. A similar result was found for parametric images. The ascending aorta was the best choice for IDIF definition. CONCLUSION: Good correlation and no bias of net (18)F-FDG uptake in relation to that based on FBP images, combined with less image noise, make 3D acquisition with FORE plus attenuation-weighted OSEM reconstruction the preferred choice for cardiac (18)F-FDG PET studies.     

Comparison of cine MR imaging with Doppler echocardiography for the evaluation of aortic regurgitation

Regurgitant blood flow is associated with localized signal loss of the blood pool within the recipient chamber on cine MR images, which may be useful for assessing regurgitant valvular disease. To evaluate the potential of this technique for determining the severity of aortic regurgitation, multilevel cine MR imaging was performed in 10 normal volunteers and in 25 patients with aortic regurgitation documented and graded for severity by Doppler echocardiography. Cine MR images were analyzed to obtain cardiac chamber volumes and to measure the extent of the signal loss associated with regurgitation. All regurgitant lesions were visualized on cine MR images as areas of diastolic signal loss extending from the aortic valve into the left ventricle. The extent of signal loss and the regurgitant volume determined from analysis of MR images correlated with the echocardiographic severity of the lesion. The total area of diastolic left ventricular signal loss was 0 cm2 in 10 normal volunteers, 24 +/- 13 (+/- SD) cm2 in eight patients with mild aortic regurgitation, 49 +/- 11 cm2 in nine patients with moderate aortic regurgitation, and 62 +/- 20 cm2 in eight patients with severe aortic regurgitation (p less than .05 for moderate and severe vs mild). Left ventricular volumes calculated from MR images correlated well with echocardiographic volumes (r = .92, SEE = 30 ml, p less than .0001). Regurgitant fraction calculated from analysis of cine MR images was 4 +/- 7% in normal volunteers and 31 +/- 8% in mild, 45 +/- 11% in moderate, and 56 +/- 9% in severe aortic regurgitation (p less than .05 for moderate and severe vs mild and normal). Thus, cine MR imaging can provide useful qualitative and quantitative data regarding cardiac dimensions and regurgitant valvular flow in patients with aortic regurgitation.     

The estimation of the volume of sheep mandibular defects using cone-beam computed tomography images and a stereological method

Objective: The Cavalieri principle of stereological methods is widely used to estimate the volume of structures. Recently in clinical practice, it has become common to use this approach for daily routine purposes. The Cavalieri principle provides quantitative and unbiased volume estimates which are independent of the observer. In the present study, the efficacy of using the Cavalieri principle to estimate the volume of sheep mandibular defects on cone beam CT (CBCT) scans was tested.Methods: 24 differently sized defects were created on 4 sheep mandibles. Before the defects were created, the outer boundaries of the defects were determined using plaster casts. CBCT scans of the defects were taken. The scans were reconstructed in the coronal plane and sections of 0.2 mm thickness with 0.2 mm and 0.4 mm intervals were obtained. The volume of each defect was estimated using the Cavalieri principle. The models were created using light-body silicone for the estimation of the actual volume of each defect. They were immersed in water using a pycnometer and the actual volumes were obtained on the basis of the Archimedean principle. The actual and estimated volumes of the defects were compared using the Wilcoxon signed-rank test.Results: The results showed that the volumes from the Cavalieri estimates did not differ from the actual volumes of the defects (P > 0.05).Conclusion: We concluded that the volume of mandibular defects can be accurately estimated using the Cavalieri principle on images from a CBCT scan.     

High-resolution three-dimensional in vivo imaging of atherosclerotic plaque.

The internal structure of atherosclerotic-plaque lesions may be a useful predictor of which lesions will rupture and cause sudden events such as heart attack or stroke. With lipid and flow suppression, we obtained high-resolution, three-dimensional (3D) images of atherosclerotic plaque in vivo that show the cap thickness and core size of the lesions. 3D GRASE was used because it provides flexible T(2) contrast and good resistance to off-resonance artifacts. While 2D RARE has similar properties, its resolution in the slice-select direction, which is important because of the irregular geometry of atherosclerotic lesions, is limited by achievable slice-excitation profiles. Also, 2D imaging generally achieves lower SNR than 3D imaging because, for SNR purposes, 3D image data is averaged over all the slices of a corresponding multislice 2D dataset. Although 3D RARE has many of the advantages of 3D GRASE, it requires a longer scan time because it uses more refocusing pulses to acquire the same amount of data. Finally, cardiac gating is an important part of our imaging sequence, but can make the imaging time quite long. To obtain reasonable scan times, a 2D excitation pulse was used to restrict the field of view. Magn Reson Med 42:762-771, 1999.     

Assessment of fetal anatomy in the first trimester using two- and three-dimensional ultrasound

The objective of this study was to perform a complete anatomical survey of the fetus at 12-13 weeks gestation using stored volumes acquired by a three-dimensional (3D) scanner. 159 consecutive women at 12-13 weeks gestation who had a routine early pregnancy scan in our unit were recruited. A complete survey of the fetal anatomy was attempted by two-dimensional (2D) transabdominal and, if needed, transvaginal ultrasound. Then, using a 3D transvaginal probe, two volumes of the whole fetus were acquired. A complete anatomical survey (excluding anatomy of the heart) was attempted using the stored data. A complete anatomical survey was achieved in 93.7% (149) of cases with 2D ultrasound compared to 80.5% (128) of cases with 3D volume acquisition (p<0.001). The nuchal translucency was measured with 2D scanning in 98.7% of cases and in 91.8% of cases using 3D volumes. The mean time to perform a 2D scan was 12.2 min standard deviation (SD 3.4 min) while the mean time to obtain and examine the stored volumes was 8.4 min (SD 1.45 min, p<0.001). Real-time 2D ultrasound is still the best way to examine fetal anatomy in the first trimester. However, 3D ultrasound can be a useful addition to clinical practice, providing views not easily obtained by conventional 2D ultrasound. It can potentially minimize actual scanning time and provides an excellent way to store scanned data.     

OSEM子集及迭代次数对PET图像质量的影响

目的 :探讨有序子集最大期望重建算法 (OSEM )中子集及迭代次数对PET图像质量的影响。材料和方法 :圆柱模型 (长 18.5cm ,直径 2 1.5cm)内灌注比活度为 1.2 5kBq/ml18F 水溶液形成本底 ,平行内置的 7个不同直径空心小圆柱内灌注18F 水溶液 (比活度 12 5kBq/ml)形成热灶 ,以 2D方式采集数据、OSEM算法重建图像 ,子集水平 3 2、16,迭代次数 1～10。在图像横断面对应外围 7个热灶画与其同大小的ROI及本底ROI ,由此计算CV等参数。结果 :相同条件下 3 2子集重建图像的热灶活度比 16子集更接近真实值。变异系数CV ,在较小热灶及背景区中 3 2子集的大于 16子集 ,较大的热灶中 3 2子集的则小于 16子集。结论 :OSEM重建方式选择 3 2子集 2～ 3次迭代 ,或 16子集 3～ 4次迭代的图像质量较好。     

Fast measurement of intracardiac pressure differences with 2D breath-hold phase-contrast MRI.

Intracardiovascular blood pressure differences can be derived from velocity images acquired with phase-contrast (PC) MRI by evaluating the Navier-Stokes equations. Pressure differences within a slice of interest can be calculated using only the in-plane velocity components from that slice. This rapid exam is proposed as an alternative to the lengthy 3D velocity imaging exams. Despite their good spatial coverage, the 3D exams are prone to artifacts and errors from respiratory motion and insufficient temporal resolution, and are unattractive in the clinical setting due to their excessive scan times (>10 min of free breathing). The proposed single-slice approach requires only one or two breath-holds of acquisition time, and the velocity data can be processed for the calculation of pressure differences online with immediate feedback. The impact of reducing the pressure difference calculation to two dimensions is quantified by comparison with 3D data sets for the case of blood flow within the cardiac chambers. The calculated pressure differences are validated using high-fidelity pressure transducers both in a pulsatile flow phantom and in vivo in a dog model. There was excellent agreement between the transducer and PC-MRI results in all of the studies.     

Feedback-assisted three-dimensional reconstruction of the left ventricle with MRI

PURPOSE: To develop and test a new technique for rapid, accurate three-dimensional (3D) reconstruction of the left ventricle (LV) and calculation of its volume parameters, with images from multiple orientations and interactive feedback. MATERIALS AND METHODS: The ventricular surface was fit to a number of user-placed guide points in magnetic resonance (MR) images using bivariate smoothing splines. A 3D model was reconstructed and the LV volumes were calculated at both end diastole (ED) and end systole (ES). This technique was validated using a phantom, and applied to studies of 18 patients and four volunteers (N = 22) imaged on a 1.5-T clinical scanner. The results of the 3D method were compared to the standard 2D short-axis slice summation technique, which is widely used for the analysis of cardiac function. RESULTS: There was excellent agreement between the computed volume of the phantom using the 3D modeling method and the actual volume (190.50 mL +/- 3.06 mL, and 191.0 mL +/- 2.5 mL, respectively). There was good correlation between the volumes calculated with our 3D model and the slice summation technique (ED volume (EDV) difference, 6.36% +/- 8.99% [mean +/- SD]; ES volume (ESV), 0.92% +/- 14.75%; stroke volume (SV), 10.54% +/- 13.95%; ejection fraction (EF), 4.22% +/- 9.16%). The 3D method was found to be more accurate than the slice summation technique for calculating LV volumes and mass from images of different slice orientations. Variations in the parameters between the two separate orientations using the 3D model vs. the slice summation method were as follows: EDV: 2.11% +/- 1.52% vs. 10.36% +/- 9.33%; ES volume: 2.76% +/- 1.64% vs. 6.39% +/- 3.62%; SV, 3.02% +/- 4.38% vs. 18.84% +/- 15.30%; EF, 2.03% +/- 2.16% vs. 8.58% +/- 6.73%; and LV mass: 4.77% +/- 2.41% vs. 24.59% +/- 6.41%. Differences in the ES volume due to the inclusion or exclusion of the most basal slice were found to be lower with the 3D model (6.90% +/- 3.83%) compared to the slice summation method (25.04% +/- 6.15%). CONCLUSION: 3D models can be used to accurately determine ventricular volume parameters. Results can be obtained using images from a variety of orientations, providing greater flexibility during image acquisition and possibly reducing the number of images needed for analysis. Feedback is provided to assist the analysis by providing a continuous update of the LV shape and volume. This feature allows the user to determine LV parameters to a predefined accuracy or to terminate the analysis when the parameters are not changing. This method is not restricted to multislice cine imaging in a single or prescribed slice orientation, and can be used for quick, accurate, and interactive analysis of cardiac function.     

Volumetric cardiac quantification by using 3D dual-phase whole-heart MR imaging

This study was approved by the local institutional ethics committee, and informed consent was obtained from all volunteers and patients. The purpose of the study was to assess ventricular volumes by using three-dimensional (3D) whole-heart data sets acquired during end-systolic and end-diastolic phases during one free-breathing magnetic resonance imaging examination. In five healthy volunteers and 10 patients, 3D dual cardiac phase data sets, short-axis multisection breath-hold images, and through-plane flow images of the great vessels were acquired. Within these data sets, statistic analyses were performed to compare stroke, end-systolic, and end-diastolic volumes for the left ventricle (LV) and the right ventricle (RV). Results showed that the breath-hold multisection approach, the flow measurement approach, and the new dual-phase 3D approach delivered comparable results for quantification of cardiac volumes and function. High correlation values greater than 0.95 were found when these methods were compared, and no significant differences were recognized for stroke, end-systolic, or end-diastolic volumes in either the LV or the RV.     

长管状骨骨折移位X线表现的校正方法探讨

目的 探讨常规X线摄影(正、侧位)时骨折移位影像表现的校正方法,并用CT验证.方法 根据X线摄影几何学原理设计出移位的校正方法.取一枚中段骨折的肱骨标本构成一定程度的侧方移位和成角移位后,将标本沿横轴多角度旋转并分别行前后(正位)、左右(侧位)方向X线拍摄,然后利用CT进行整个标本的容积扫描,并将容积扫描数据进行多维平面重建(MPR)及表面遮盖显示(SSD).对X线图像的移位程度及校正数据、MPR及SSD后的移位程度、标本实际移位程度分别进行比较分析.结果 经X线图像求得的校正数据、MPR及SSD后所得的数据与标本实际设置移位方向、程度误差较小,位置差异＜1.5 mm,角度差异＜1.5°.结论 常规X线摄影显示的骨折移位的影像表现经坐标图测量校正,方法真实可靠,可以显著提高X线诊断骨折移位程度的准确性.     

Volumes of chronic traumatic frontal brain lesions measured by MR imaging and CBF tomography

The volumes (ml) of chronic traumatic frontal brain lesions were compared measured "morphologically" with MR imaging (T1 and T2 weighted images) and "functionally" with a tomographic rCBF technique (SPECT with 133Xe i.v.). The T1 volumes varied between 11 and 220 ml. The correlation between T1 and T2 volumes was 0.95, the T2 volumes being 33% larger than T1 volumes (p less than 0.001). The functional SPECT volumes were considerably larger (range 16-324 ml) than the MR volumes. The mean volume difference was 81% between T1 and SPECT images (p less than 0.001), and 35% between T2 and SPECT images (p less than 0.001). Correlations between the MR and SPECT volumes were also higher for T2 than T1 volumes. The volume difference is most likely explained by a functional decrease in regions around the lesion in which no morphologic change visible on MR images had taken place. MR and SPECT volume measurements were positively related to persistent lack of energy and personality changes, but only moderately related to duration of impaired consciousness and neuropsychologic outcome.     

Feasibility of automatic assessment of four-chamber cardiac function with MDCT: Initial clinical application and validation

Background

The ability to perform a simultaneous analysis of ventricular and atrial volumes may provide clinically useful information for diagnosis and prognosis. We aimed to evaluate the feasibility and clinical value of a novel algorithm that performs fully automatic evaluation of the four cardiac chambers and myocardium from gated CT datasets.

Methods

50 patients were studied—Group 1: 30 consecutive unselected patients, Group 2A: 10 patients after myocardial infarction and Group 2B: 10 normal controls. Fully automatic, segmentation of the heart was performed with a model-based segmentation algorithm requiring no user input other than loading the datasets. Qualitative and quantitative evaluation of segmentation quality was performed. Left ventricular (LV) and right ventricular (RV) stroke volumes (SV) were compared.

Results

Overall, segmentation succeeded in all patients although 11/500 (2.2%) cardiac chambers achieved poor segmentation grading. Correlation coefficients between automatic and manually derived volumes were excellent (r > 0.98) for all chambers. Bland-Altman analysis showed minimal bias (−1.0 ml, 0.4 ml, −1.8 ml) for the LV and RV, and right atria, respectively, with mild overestimation of LV myocardial volume (5.2 ml). Significant, yet consistent, overestimation of left atrial volume (23.6 ml) due to inclusion of proximal pulmonary veins was observed. LV and RV ejection fraction (r = 0.91 and 0.98) and SV (r = 0.98 and 0.99) also correlated closely with minimal bias (<2%). Most significantly, LV SV (91.0 ± 21.6 ml) correlated highly with RV SV (81.7 ± 18.2 ml, r = 0.86). Outliers could usually be explained by valvular regurgitation.

Conclusions

Fully automatic segmentation of all cardiac chambers can be achieved with high accuracy over multiple cardiac phases, enabling reliable comprehensive evaluation of four-chamber cardiac function.     

Effect of patient imaging angle on apparent cardiac volumes and the potential impact on measurement of valvular regurgitant fractions

The accurate measurement of cardiac chamber volume is of major importance in assessing cardiac performance. Accurate equilibrium radionuclide volume estimations are difficult to obtain, due to the geometry of the chambers, and the physical characteristics of the imaging system. The purpose of this study was to examine the effects of imaging projections on relative cardiac chamber volumes, indexes, and stroke volume ratios. Twenty-two male patients, free of clinical evidence of disease, were studied. A series of four 2-minute acquisitions were made with the patient successively imaged in the anterior, 30 degrees left anterior oblique (LAO), 45 degrees LAO, and 60 degrees LAO projections with 15 degrees of caudal inclination. Filtered stroke volume and original images were used by the operator to assign right ventricular (RV), left ventricular (LV), and a combined right and left ventricular (TOT) regions-of-interest. From the data we determined end-diastolic counts (EDC), end-systolic counts (ESC), stroke counts (SC), ejection fractions (EF), and R/L stroke count ratios. The following changes were observed as the projection was moved from the anterior to 60 degrees LAO: 1) all RV parameters decreased in value, including, RVEDC (P less than .001), RVESC (P less than .01), RVESC (P less than .01) and RVEF (P less than .001); 2) LVEDC and LVESC (both P less than .01) increased while LVEF decreased (P less than .004); and 3) the R/L stroke count ratio decreased (P less than .001). Variability could be explained by 1) chamber overlap and geometry; 2) patient variability; and 3) intrachamber, interchamber and chest wall photon attenuation and scatter. We suggest that close attention to detail, with computer assistance, to optimally position the patient may reduce the effect of inherent limitations in radionuclide volumetric measurements, thus improving the reliability and usefulness of existing studies.