Accelerating global left-ventricular function assessment in mice using reduced slice acquisition and three-dimensional guide-point modelling

Abstract

BackgroundTo investigate the utility of three-dimensional guide-point modeling (GPM) to reduce the time required for CMR evaluation of global cardiac function in mice, by reducing the number of image slices required for accurate quantification of left-ventricular (LV) mass and volumes.MethodsFive female C57Bl/6 mice 8 weeks post myocardial infarction induced by permanent occlusion of the left coronary artery, and six male control (un-operated) C57Bl/6 mice, were subject to CMR examination under isoflurane anaesthesia. Contiguous short axis (SAX) slices (1 mm thick 7-9 slices) were obtained together with two long axis (LAX) slices in two chamber and four chamber orientations. Using a mathematical model of the heart to interpolate information between the available slices, GPM LV mass and volumes were determined using full slice (all SAX and two LAX), six slice (four SAX and two LAX) and four slice (two SAX and two LAX) analysis protocols. All results were compared with standard manual volumetric analysis using all SAX slices.ResultsInfarct size was 39.1 ± 5.1% of LV myocardium. No significant differences were found in left ventricular mass and volumes between the standard and GPM full and six slice protocols in infarcted mice (113 ± 10, 116 ± 11, and 117 ± 11 mg respectively for mass), or between the standard and GPM full, six and four slice protocols in control mice, (105 ± 14, 106 ± 10, 104 ± 12, and 105 ± 7 mg respectively for mass). Significant differences were found in LV mass (135 ± 18 mg) and EF using the GPM four slice protocol in infarcted mice (p < 0.05).ConclusionGPM enables accurate analysis of LV function in mice with relatively large infarcts using a reduced six slice acquisition protocol, and in mice with normal/symmetrical left-ventricular topology using a four slice protocol.

Does reduced myocardial efficiency in systemic hypertensive-hypertrophy correlate with increased left-ventricular wall thickness?

“…Of more import is the extension of this ex vivo study to the in vivo conditions, particularly in the human. Techniques such as echocardiography, magnetic resonance imaging and threedimensional guide-point modelling 28 have been exploited to allow in vivo measurements of ventricular wall thickness and whole-heart mass. In addition, satisfactory measurement of LV hypertrophy could be performed in vivo, combining the techniques of electrocardiography and plasma pro-brain natriuretic peptide assay.…”

Increased cardiac work provides a link between systemic hypertension and heart failure

“…The images were analyzed using the Cardiac Image Modelling software (CIM version 6.1, University of Auckland) (Young et al. ). A 3D finite element model of the LV was interactively customized to each image frame throughout the cardiac cycle for each animal.…”

Imaging the healing murine myocardial infarct in vivo: ultrasound, magnetic resonance imaging and fluorescence molecular tomography

“…Hair removal is not required for MRI, but the chest must be shaved for ultrasound analysis, and optical imaging can require more extensive depilation because hair produces a signal that can interfere with image collection. While optical images can be collected in less than 1 min, a typical ultrasound analysis of function will take 15–20 min, and MRI around 1 h, although new shorter imaging acquisition protocols are being introduced (Young et al 2011). Careful physiological monitoring is crucial, particularly during extended imaging, so that body temperature and anaesthesia are maintained at optimal levels and heart rate is retained within a physiological range (500 beats min −1 ).…”