Evaluation of septal insertion of atrioventricular valves in fetuses by postmortem 4.7 Tesla cardiac MRI: A feasibility study.

PURPOSE: The purpose of this study was to compare non-invasive high-spatial-resolution postmortem cardiac magnetic resonance imaging (MRI) and autopsy findings for evaluating the septal insertion of atrioventricular valves in fetuses. MATERIALS AND METHODS: Five fetal heart specimens including two normal hearts, one heart with complete atrioventricular septal defect (AVSD) and two hearts with linear insertion of atrioventricular valves (LIAVV; gestational age 17 to 34 weeks) were studied with cardiac MRI using a 4.7 T MRI scanner without sample preparation. Three (3D) and two-dimensional (2D) turbo-RARE (rapid imaging with refocused echoes) sequences in four-chamber and left-ventricular long-axis planes were obtained with a minimal isotropic/in-plane resolution of 156µm. Nonparametric tests were performed to compare the distance between insertions of medial leaflets of the atrioventricular valves and the inlet/outlet distance ratio between MRI and autopsy findings in normal, complete AVSD and with linear insertion of atrioventricular valves (LIAVV) fetal hearts. RESULTS: Despite apparent differences between LIAVV/normal hearts, no significant differences were found between differential insertion of medial leaflets and inlet/outlet distance ratios with both techniques. Very good to excellent reliability between both techniques was found for differential insertion (ICC: 87.2%; 95% CI: -21.7%, 99.1%) (P=0.963) and inlet/outlet distance ratio (ICC 98.3%; 95%CI: 85.2%, 99.8%) (P=0.537) measurements. CONCLUSION: Postmortem cardiac MRI could replace autopsy for assessing normal or abnormal septal insertion of atrioventricular valves in fetuses without requiring specific preparation of the heart.

Application of rodes software to experimental biokinetic data for dose assessment in mice and rats.

H Miloudi, M Locatelli, G Autret, D Balvay, A Desbrée, E Blanchardon, J M Bertho: application of RODES software to experimental biokinetic data for dose assessment in mice and rats. In support of experimental studies of chronic, long-term contamination in rodents, voxel-based computer models were built representing adult mice and juvenile, adult and elderly rats of both sexes. RODES software was created to calculate absorbed radiation doses to organs with these specific anatomical models. Absorbed doses were then calculated starting from previously published biokinetic data. Whole body doses showed less than 5% differences between calculation with RODES and calculation with the ICRP Publication 108 model for long term exposure to 90Sr of mice. Similar results were obtained for long term exposure to 137Cs. Dose distribution for 90Sr internal contamination also showed that the dose to the skeleton is six fold more as compared to the whole body dose while radiation dose to other organs is less than the mean whole body dose. These results underline the importance of using specific anatomical models according to the age and the sex of experimental animals.

Shear wave elastography of tumour growth in a human breast cancer model with pathological correlation.

OBJECTIVE: To assess stiffness in a human breast cancer implanted in mice using shear wave elastography (SWE) during tumour growth and to correlate the results with pathology. METHODS: Local ethics committee for animal research approval was obtained. A human invasive ductal carcinoma was implanted subcutaneously in 24 athymic nude female mice. Ultrasound was longitudinally performed in 22 tumours, every 1-2 weeks. Maximum diameter and mean stiffness were collected. Seven tumours were measured both in vivo and ex vivo. Tumours of different sizes were removed for pathological analysis on which the percentages of viable cellular tissue, fibrosis and necrosis were measured. RESULTS: A total of 63 SWE measurements were performed. Stiffness increased during tumour growth with an excellent correlation with size (r = 0.94, P < 0.0001). No differences were found between the values of stiffness in vivo and ex vivo (P = 0.81). There was a significant correlation between elasticity and fibrosis (r = 0.83, P < 0.0001), a negative correlation with necrosis (r = -0.76, p = 0.0004) but no significant correlation with cellular tissue (r = 0.40, p = 0.1). CONCLUSION: Fibrosis plays an important role in stiffness as measured by SWE, whereas necrosis is correlated with softness. KEY POINTS: • In a breast cancer model, ultrasound tumour stiffness is correlated with size. • Stiffness changes with tumour growth are correlated with pathological changes. • Stiffness is very well correlated with proportion of tumour fibrosis. • Stiffness is inversely correlated with proportion of tumour necrosis. • Tumour stiffness measurements are similar in vivo and ex vivo.

In vivo 2D magnetic resonance spectroscopy of small animals.

Localized in vivo NMR spectroscopy, chemical shift imaging or multi-voxel spectroscopy are potentially useful tools in small animals that are complementary to MRI, adding biochemical information to the mainly anatomical data provided by imaging of water protons. However the contribution of such methods remains hampered by the low spectral resolution of the in vivo 1D spectra. Two-dimensional methods widely developed for in vitro studies have been proposed as suitable approaches to overcome these limitations in resolution. The different homonuclear and heteronuclear sequences adapted to in vivo studies are reviewed. Their specific contributions to the spectral resolution of spectroscopic data and their limitations for in vivo investigations are discussed. The applications to experimental models of pathological processes or pharmacological treatment in mainly brain and muscle are presented. According to their combined sensitivity, acquisition duration and spatial resolution, the heteronuclear 2D experiments, which are mainly used for 1H detected-13C spectroscopy after administration of 13C-labeled compounds, appear to be less efficient than 1H detected-13C 1D methods at high field. However, the applications of 2D proton homonuclear methods show that they remain the best tools for in vivo studies when an improved resolution is required.