Introduction; Features; Principles Of Operation - Hitachi S21 Instruction Manual

1. Introduction

1.1 Features

S21 probe is a phased array sector scanning type probe.
The acoustic output of this probe when connected to ultrasound
scanner was measured according to the IEC60601-2-37 standard.
The table of measured acoustic output data is contained in the
operation manual of each ultrasound scanner.
This probe is categorized in class IIa according to Directive
93/42/EEC.
According to IEC60601-1 the probe is classified as type BF.

1.2 Principles of operation

This probe and the ultrasound diagnostic scanner enable image
diagnosis using ultrasonic waves. This system operates under the
principles described below.
1) When an electric pulse signal is applied from the transmitter
to the transducer of the probe, the transducer converts
electric signals into mechanical vibration energy for
emitting pulse-shaped ultrasonic waves into the body part,
liquid or other medium contacting the transducer.
2) The emitted ultrasonic waves are reflected by boundaries with
different acoustic characteristics (acoustic impedance)
within the body.
3) The transducer is also used to receive reflected ultrasonic
waves. The transducer vibrates mechanically due to the
received ultrasonic waves and converts mechanical vibrations
into electric energy. Electric signals are converted to shades
of brightness by brightness modulation to obtain an image.
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