Report No xxxx - Instytut Fizyki JÄ drowej PAN

ASSESSMENT OF CARDIAC FUNCTION IN MICE IN VIVO
BY MRI – PRELIMINARY RESULTS
S. Heinze-Paluchowska ∗ , T. Skórka ∗ , K. Majcher ∗ , Ł. Drelicharz ∗∗ , S. Chłopicki ∗∗ ,
A. Jasiński ∗
∗
H. Niewodniczański Institute of Nuclear Physics, Polish Academy of Sciences, Kraków,
Poland; ∗∗ Chair of Pharmacology, Medical College of Jagiellonian University, Kraków,
Poland
Introduction
The purpose of our study was to assess the feasibility of MRI to characterize cardiac
function in mice in vivo. Transgenic mice are gaining widespread popularity in cardiovascular
research. Indeed, numerous genetic models of mice with altered expression of variety of genes
have been developed and used in studies on the physiology and pathology of cardiovascular
system. The use of genetically-modified mice offer opportunities for better understanding of
cardiovascular diseases [1,2] . This has provided motivation for the current study. Here we
present our preliminary results on the measurements of cardiac function in mice in vivo. This
technique was set-up for future assessment of functional progression of heart failure in
transgenic mice with cardiac-specific overexpression of Glafaq protein (Mende JACC).
Materials and Methods
Mice were anesthetized with Avertin, injected i.p 12 mg/100g body weight. During the
experiment, the mouse was positioned supine on a nonmagnetic pad to maintain constant
body position and temperature throughout the MR study. Heart rates were 250-350 beats/min.
All animal experimental procedures were in accordance with institutional guidelines.
Experiments were performed on a 4,7T MR scanner with MARAN DRX console. The
scanner was equipped with a gradient system (MAGNEX) capable of 10mT/m maximum
gradient strength. For NMR signal transmission and reception an 8-rung homebuilt birdcage
coil with inner diameter of 36mm was used. For exact ECG triggering, an ECG trigger unit
(RAPID Biomedical ECG TRIGGER UNIT HSB) was used, allowing for multiple filtering of
the original surface ECG signal to sufficiently isolate the QRS signal from noise generated by
the magnet and the gradient coils. The trigger point was set on the R wave. ECG trigger unit
was connected to the oscilloscope (Tektronix, TDS 3000).
MR imaging was performed using an ECG triggered fast gradient echo [3] (FLASH
with multiphase option) sequence with the following imaging parameters: Echo time (TE)
3,8 ms; repetition time (TR) depends on the distance between R-R waves, acquisition matrix
128×128; slice thickness 1,1 mm, number of scans (NS) 4, and a flip angle was set to achieve
the best contrast between myocardium and blood pool (about 50 degrees).
After the image plane orientation from saggital and coronal LV long-axis images was
positioned, MRI data acquisition was performed in multiple contiguous short-axis slices to
cover the entire left ventricle (LV).
Results
Good quality MR images of the mouse heart in vivo were obtained. Measurements of
the multiple slice images in different phases of the cardiac cycle, with a good contrast
between myocardium and flowing blood, give the opportunity to calculate the end-diastolic
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