Biology Reference
In-Depth Information
Transthoracic echocardiography can be performed with an
instrument for clinical use on conscious, previously trained mice
with the use of a 12-15 MHz linear transducer at high frame rate
imaging (102 Hz) and a 7.5 MHz phased array probe for pulsed-
wave Doppler measurements. An echocardiograph, especially design
for mice, is used to examine anesthetized (0.5-1.5% isoflurane) ani-
mals. High frequency of its probes, 30 MHz, allows higher spatial
resolution. The rat cannot be easily trained, therefore, needs to be
evaluated under sedation, with ketamine and imidazolam for exam-
ple, or under anesthesia with 0.5-1.5% isoflurane.
Short and long-axis two dimensional (2D) views and M-mode
at the level of infarction is analyzed in real time and recorded on
magneto-optic disk for off-line analysis by a sonographer blind to
study groups. Left atrial diameter, end-diastolic and end-systolic
wall thicknesses and left ventricular internal dimensions are mea-
sured, as recommended by the American Society of Echocardiography
(see Note 1).
As for echocardiography, more than one model and set up for
MRI exist on the market. Since the detailed description of the
instrumental settings goes far beyond the aims of the present chap-
ter, the setting used in the laboratory of one of the authors (RL) is
described (see Note 2).
1. All animals are anesthetized by facemask with isoflurane (induc-
tion in chamber at 3-5%, maintenance 0.5-1.5%) and 0.3 L/
min O
2
.
2. Animals are positioned in a purpose-built cradle and ECG elec-
trodes are attached to the front paws. NOTE: ad hoc properly
shielded ECG leads and cables must be purchased in order to
avoid the instrument-derived noise that would completely
mask the ECG signal.
3. A pressure-transducer for respiratory gating is positioned above
the abdomen.
4. A fiber optic probe is used for monitoring the rectal temperature.
5. ECG and respiratory signals are processed and displayed using
a gating device and temperature is maintained at 37±0.5°C
during the whole exam (60-90 min).
6. After the image plane orientation from coronal, axial and
oblique LV long-axis, a 2 chamber long-axis view is obtained
and orthogonal to it a 4 chamber long-axis is acquired fol-
lowed by 1 mm serial short-axis slices covering the entire LV
length. Seven to ten short-axis slices are acquired from base to
apex. Sixteen frames per slice for one cine sequence are saved.
Images are exported in DICOM format and analyzed off-line.
7. End-diastolic and end-systolic variables are measured in
selected frames according to the visual estimation of the maxi-
mal and minimal ventricular cavity respectively.
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