TELEMED ClarUs User Guide, REV 4.0 2013.12.04
18
4.
SYSTEM OVERVIEW
The
ClarUs
system handles the multi-element probes.
4.1.
Principle of operation
The ultrasound diagnostic
system is based on the effect of ultrasound wave
reflection from the tissue edges with different acoustic impedance levels. Ultrasound
waves sent out by the probe head are emitted into the patient’s body. Reflections
from the specific types of tissue and their external surface/edges cause partial
reflections of the propagating sound wave. The return echo comes back to the probe
head and after being detected and amplified is displayed on the monitor screen as a
pixel combination with various shades of brightness creating an ultrasound image.
4.2.
Components & Modifications
4.2.1. Basic unit/Beamformer
Basic unit functions are:
excite electric pulses to fire the probe;
ultrasound echo signals pre-amplification;
compensation of the ultrasound attenuation due to travel depth;
re-ordering the receiving signal sequence and focusing by applying the
appropriate time delays;
shifting the center frequency of BPF (band pass filter) to follow the frequency
shift that occurs according to the travel depth;
the ultrasound signal compression by means of Log Amplifier, detection of the
echo signal envelope
4.2.2. Probe Unit
The probe unit is a piezoelectric transformer which provides the acoustical
pulse used to examine the medium and is used for both transmission and reception
(the transducer is used in pulse-echo mode). A voltage waveform is applied to the
transducer and then converted into an acoustic waveform (inverse piezoelectric
effect). An acoustic pulse is then partially transmitted and partially reflected by the
intervening soft tissues structures in the body. The reflected acoustic waveform is
received by the same transducer and is converted into a voltage waveform (direct
piezoelectric effect). The probe unit consists of piezoelectric elements. The probe
enclosure has a relief to affix the scanning direction.
