BackgroundCommercially available software for cardiovascular image analysis often has limited functionality and frequently lacks the careful validation that is required for clinical studies. We have already implemented a cardiovascular image analysis software package and released it as freeware for the research community. However, it was distributed as a stand-alone application and other researchers could not extend it by writing their own custom image analysis algorithms. We believe that the work required to make a clinically applicable prototype can be reduced by making the software extensible, so that researchers can develop their own modules or improvements. Such an initiative might then serve as a bridge between image analysis research and cardiovascular research. The aim of this article is therefore to present the design and validation of a cardiovascular image analysis software package (Segment) and to announce its release in a source code format.ResultsSegment can be used for image analysis in magnetic resonance imaging (MRI), computed tomography (CT), single photon emission computed tomography (SPECT) and positron emission tomography (PET). Some of its main features include loading of DICOM images from all major scanner vendors, simultaneous display of multiple image stacks and plane intersections, automated segmentation of the left ventricle, quantification of MRI flow, tools for manual and general object segmentation, quantitative regional wall motion analysis, myocardial viability analysis and image fusion tools. Here we present an overview of the validation results and validation procedures for the functionality of the software. We describe a technique to ensure continued accuracy and validity of the software by implementing and using a test script that tests the functionality of the software and validates the output. The software has been made freely available for research purposes in a source code format on the project home page http://segment.heiberg.se.ConclusionsSegment is a well-validated comprehensive software package for cardiovascular image analysis. It is freely available for research purposes provided that relevant original research publications related to the software are cited.

Previous studies using echocardiography in healthy subjects have reported conflicting data regarding the percentage of the stroke volume (SV) of the left ventricle (LV) resulting from longitudinal and radial function, respectively. Therefore, the aim was to quantify the percentage of SV explained by longitudinal atrioventricular plane displacement (AVPD) in controls, athletes, and patients with decreased LV function due to dilated cardiomyopathy (DCM). Twelve healthy subjects, 12 elite triathletes, and 12 patients with DCM and ejection fraction below 30% were examined by cine magnetic resonance imaging. AVPD and SV were measured in long- and short-axis images, respectively. The percentage of the SV explained by longitudinal function (SV(AVPD%)) was calculated as the mean epicardial area of the largest short-axis slices in end diastole multiplied by the AVPD and divided by the SV. SV was higher in athletes [140 +/- 4 ml (mean +/- SE), P = 0.009] and lower in patients (72 +/- 7 ml, P < 0.001) when compared with controls (116 +/- 6 ml). AVPD was similar in athletes (17 +/- 1 mm, P = 0.45) and lower in patients (7 +/- 1 mm, P < 0.001) when compared with controls (16 +/- 0 mm). SV(AVPD%) was similar both in athletes (57 +/- 2%, P = 0.51) and in patients (67 +/- 4%, P = 0.24) when compared with controls (60 +/- 2%). In conclusion, longitudinal AVPD is the primary contributor to LV pumping and accounts for approximately 60% of the SV. Although AVPD is less than half in patients with DCM when compared with controls and athletes, the contribution of AVPD to LV function is maintained, which can be explained by the larger short-axis area in DCM.

The total heart volume variation (THVV) during systole has been proposed to be caused by radial function of the ventricles, but definitive data for both ventricles have not been presented. Furthermore, the right ventricle (RV) has been suggested to have a greater longitudinal pumping component than the left ventricle (LV). Therefore, we aimed to compare the stroke volume (SV) generated by radial function to the volume variation of the left, right, and total heart. To do this, we also needed to develop a new method for measuring the contribution of the longitudinal atrioventricular plane displacement (AVPD) to the RVSV (RVSV(AVPD)). For our study, 11 volunteers underwent cine MRI in the short- and long-axis planes and MRI flow measurement in all vessels leading to and from the heart. The left, right, and total heart showed correlations between volume variation from flow measurements and radial function calculated as SV minus the longitudinal function (r = 0.81, P < 0.01; r = 0.80, P < 0.01; and r = 0.92, P < 0.001, respectively). Compared with the LV, the RV had a greater AVPD (23.4 +/- 0.8 vs. 16.4 +/- 0.5 mm), center of volume movement (13.0 +/- 0.7 vs. 7.8 +/- 0.4 mm), and, RVSV(AVPD) (82 +/- 2% vs. 60 +/- 2%) (P < 0.001 for all). We found that THVV is predominantly caused by radial function of the ventricles. Longitudinal AVPD accounts for approximately 80% of the RVSV, compared with approximately 60% for the LVSV. This difference explains the larger portion of THVV found on the left side of the heart.

Carlsson M, Heiberg E, Toger J, Arheden H. Quantification of left and right ventricular kinetic energy using four-dimensional intracardiac magnetic resonance imaging flow measurements. Am J Physiol Heart Circ Physiol 302: H893-H900, 2012. First published December 16, 2011; doi:10.1152/ajpheart.00942.2011.-We aimed to quantify kinetic energy (KE) during the entire cardiac cycle of the left ventricle (LV) and right ventricle (RV) using four-dimensional phasecontrast magnetic resonance imaging (MRI). KE was quantified in healthy volunteers (n ϭ 9) using an in-house developed software. Mean KE through the cardiac cycle of the LV and the RV were highly correlated (r 2 ϭ 0.96). Mean KE was related to end-diastolic volume (r 2 ϭ 0.66 for LV and r 2 ϭ 0.74 for RV), end-systolic volume (r 2 ϭ 0.59 and 0.68), and stroke volume (r 2 ϭ 0.55 and 0.60), but not to ejection fraction (r 2 Ͻ 0.01, P ϭ not significant for both). Three KE peaks were found in both ventricles, in systole, early diastole, and late diastole. In systole, peak KE in the LV was lower (4.9 Ϯ 0.4 mJ, P ϭ 0.004) compared with the RV (7.5 Ϯ 0.8 mJ). In contrast, KE during early diastole was higher in the LV (6.0 Ϯ 0.6 mJ, P ϭ 0.004) compared with the RV (3.6 Ϯ 0.4 mJ). The late diastolic peaks were smaller than the systolic and early diastolic peaks (1.3 Ϯ 0.2 and 1.2 Ϯ 0.2 mJ). Modeling estimated the proportion of KE to total external work, which comprised ϳ0.3% of LV external work and 3% of RV energy at rest and 3 vs. 24% during peak exercise. The higher early diastolic KE in the LV indicates that LV filling is more dependent on ventricular suction compared with the RV. RV early diastolic filling, on the other hand, may be caused to a higher degree of the return of the atrioventricular plane toward the base of the heart. The difference in ventricular geometry with a longer outflow tract in the RV compared with the LV explains the higher systolic KE in the RV.four-dimensional phase-contrast magnetic resonance imaging; cardiovascular magnetic resonance; energy; cardiac function; heart failure CARDIAC PUMPING DELIVERS A pressurized blood volume to the systemic and the pulmonary circulation. The amount of external work required to deliver the volume and pressure can be divided into kinetic energy (KE) and stroke work. Total work of the heart also includes internal work not delivered to the system. Stroke work stands for the vast majority (99%) of the external energy at rest in the left ventricle (LV) (29, 31) and somewhat less in the right ventricle (RV, 94%) (31). The structure of the looped heart has been proposed to direct the momentum or KE of the inflowing blood toward the aorta (18), which may be of specific importance during exercise (17). The magnitude and significance of maintenance of KE of blood in the looped heart has recently been under debate (16, 39 -40). KE is linked to inertia, an important physiological concept (37,41). Inertia is a physical concept describing the maintenance of the forward velocity of a medium (e.g., blood) after a force has...