Biomedical Engineering Reference
In-Depth Information
Camera
Recorder
Microscope
TV monitor
Animal preparation
with isolated
vascular bed
FIGURE 15.1
Schematic of a typical intravital microscopy system. The key parameters are the microscope,
which is coupled to a live-feed imaging system, and a real-time data acquisition component. Intravital microscopy
can be used to monitor disease progression, therapeutic efficacy, clearance, and distribution of blood cells within
the microvasculature.
Other benefits of this approach are that relatively long
effects can be monitored
because the animal preparation can be maintained for at least 6 hours. Therefore, clearance
of new therapeutics can be investigated in tandem with the local effects of the therapeutic
agent.
in vivo
15.2 DOPPLER ULTRASOUND
Before we discuss the Doppler mode associated with ultrasound image acquisition, we
will first discuss the general procedures involved with three-dimensional ultrasound tech-
nology. The first device necessary to acquire ultrasound images is the ultrasound scanner,
which is used to emit and collect sound waves aimed at specific tissue locations. Standard
probes are equipped with a transducer that emits a frequency in the range of 1 MHz to
10 MHz. Ultrasound technology also requires the use of an electromagnetic position and
an orientation measurement device, which normally consists of a component that is
located within the examination table and a second component located within the ultra-
sound probe. This device records the spatial location of the probe in relation to the fixed
examination table position. The angle of the probe in relation to the fixed axis is also
recorded by this device, because an ultrasound probe has 6 degrees of freedom and an
accurate distance and angle of incidence is needed to analyze the data properly. By sweep-
ing the ultrasound probe over a tissue bed, multiple images can be obtained to observe
the tissue from different locations.
There are multiple imaging modes that can be used in conjunction with the ultrasound
probe. The one of most interest to this textbook is the Doppler mode, which can obtain a
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