Improved reproducibility of right ventricular volumes and function estimation from cardiac magnetic resonance images using level-set models

Quantification of Right and Left Ventricular Function in Cardiac MR Imaging: Comparison of Semiautomatic and Manual Segmentation Algorithms

The purpose of this study was to evaluate the performance of a semiautomatic segmentation method for the anatomical and functional assessment of both ventricles from cardiac cine magnetic resonance (MR) examinations, reducing user interaction to a “mouse-click”. Fifty-two patients with cardiovascular diseases were examined using a 1.5-T MR imaging unit. Several parameters of both ventricles, such as end-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (EF), were quantified by an experienced operator using the conventional method based on manually-defined contours, as the standard of reference; and a novel semiautomatic segmentation method based on edge detection, iterative thresholding and region growing techniques, for evaluation purposes. No statistically significant differences were found between the two measurement values obtained for each parameter (p > 0.05). Correlation to estimate right ventricular function was good (r > 0.8) and turned out to be excellent (r > 0.9) for the left ventricle (LV). Bland-Altman plots revealed acceptable limits of agreement between the two methods (95%). Our study findings indicate that the proposed technique allows a fast and accurate assessment of both ventricles. However, further improvements are needed to equal results achieved for the right ventricle (RV) using the conventional methodology.

Cardiac MRI assessment of right ventricular function in acquired heart disease: factors of variability

RATIONALE AND OBJECTIVES

To evaluate intra- and inter-observer variability of right ventricular (RV) functional parameters as evaluated by cardiac magnetic resonance imaging (MRI) in patients with acquired heart disease (AHD), and to identify factors associated with an increased variability.

MATERIALS AND METHODS

Sixty consecutive patients were enrolled. Right and left ventricular (LV) volumes, ejection fraction, and mass were determined from short-axis cine sequences. All analyzes were performed twice by three observers with various training-degree in cardiac MRI. Intra- and inter-observer variability was evaluated. The impact on variability of each of the following parameters was assessed: observer's experience, basal and apical slices selection, end-systolic phase selection, and delineation.

RESULTS

Mean segmentation time ranged 9.8-19.0 minutes for RV and 6.4-9.2 minutes for LV. Variability of RV functional parameters measurement was strongly influenced by previous observer's experience: it was two to three times superior to that of LV, even for the most experienced observer. High variability in the measurement of RV mass was observed. For both ventricles, selection of the basal slice and delineation were major determinants of variability.

CONCLUSION

As compared to LV, RV function assessment with cardiac MRI in AHD patients is much more variable and time-consuming. Observer's experience, selection of basal slice, and delineation are determinant.

Diagnostic accuracy and variability of three semi-quantitative methods for assessing right ventricular systolic function from cardiac MRI in patients with acquired heart disease

OBJECTIVES

To evaluate the diagnostic accuracy and variability of 3 semi-quantitative (SQt) methods for assessing right ventricular (RV) systolic function from cardiac MRI in patients with acquired heart disease: tricuspid annular plane systolic excursion (TAPSE), RV fractional-shortening (RVFS) and RV fractional area change (RVFAC).

METHODS

Sixty consecutive patients were enrolled. Reference RV ejection fraction (RVEF) was determined from short axis cine sequences. TAPSE, RVFS and RVFAC were measured on a 4-chamber cine sequence. All SQt analyses were performed twice by 3 observers with various degrees of training in cardiac MRI. Correlation with RVEF, intra- and inter-observer variability, and receiver operating characteristic (ROC) curve analysis were performed for each SQt method.

RESULTS

Correlation between RVFAC and RVEF was good for all observers and did not depend on previous cardiac MRI experience (R range = 0.716-0.741). Conversely, RVFS (R range = 0.534-0.720) and TAPSE (R range = 0.482-0.646) correlated less with RVEF and depended on previous experience. Intra- and inter-observer variability was much lower for RVFAC than for RVFS and TAPSE. ROC analysis demonstrated that RVFAC <41% could predict a RVEF <45% with 90% sensitivity and 94% specificity.

CONCLUSIONS

RVFAC appears to be more accurate and reproducible than RVFS and TAPSE for SQt assessment of RV function by cardiac MRI.

Measuring the heart in pulmonary arterial hypertension (PAH): implications for trial study size

PURPOSE

To calculate the sample size for a theoretical pulmonary arterial hypertension (PAH) randomized controlled trial (RCT) by using cardiovascular magnetic resonance (CMR) imaging to determine the repeatability of measures between two scans.

MATERIALS AND METHODS

Two same-day examinations from 10 PAH patients were analyzed manually and semiautomatically. Study size was calculated from the standard deviation (SD) of repeatability. Different approaches to right-ventricle (RV) mass were investigated, agreement between methods tested and interobserver reproducibility measured by Bland-Altman analysis to explore how the PAH heart might be best measured.

RESULTS

Repeatability was good for almost all manually-measured indices but poor for semiautomated measurement of RV mass and left-ventricle (LV) end-diastolic volume (EDV). Thus, for an RCT (power, 80%; significance level, 5%) analyzing "outcome" indices (RVEDV, LVEDV, RV ejection fraction, and RV mass; anticipated change: 10 mL, 10 mL, 3%, and 10 g, respectively) manually, 34 patients are required compared to 78 if analysis is semiautomated. RV mass was repeatable if the interventricular septum was divided between ventricles or if wholly apportioned to the LV. Limits of agreement between manual and semiautomated analyses were unsatisfactory for RV measures and interobserver reproducibility was worse for semiautomated than manual analysis.

CONCLUSION

Manual is more robust than semiautomated analysis and at present should be favored in RCTs in PAH as it leads to lower sample size requirements.

Intra-observer and interobserver variability of biventricular function, volumes and mass in patients with congenital heart disease measured by CMR imaging

Cardiovascular magnetic resonance (CMR) imaging provides highly accurate measurements of biventricular volumes and mass and is frequently used in the follow-up of patients with acquired and congenital heart disease (CHD). Data on reproducibility are limited in patients with CHD, while measurements should be reproducible, since CMR imaging has a main contribution to decision making and timing of (re)interventions. The aim of this study was to assess intra-observer and interobserver variability of biventricular function, volumes and mass in a heterogeneous group of patients with CHD using CMR imaging. Thirty-five patients with CHD (7-62 years) were included in this study. A short axis set was acquired using a steady-state free precession pulse sequence. Intra-observer and interobserver variability was assessed for left ventricular (LV) and right ventricular (RV) volumes, function and mass by calculating the coefficient of variability. Intra-observer variability was between 2.9 and 6.8% and interobserver variability was between 3.9 and 10.2%. Overall, variations were smallest for biventricular end-diastolic volume and highest for biventricular end-systolic volume. Intra-observer and interobserver variability of biventricular parameters assessed by CMR imaging is good for a heterogeneous group of patients with CHD. CMR imaging is an accurate and reproducible method and should allow adequate assessment of changes in ventricular size and global ventricular function.