SOUND AND ULTRASOUND IN MEDICINE Prof. Dr. Moustafa. M. Mohamed Vice Dean Faculty of Allied Medical Science Pharos University Alexandria Dr. Yasser Khedr Department of Medical Biophysics Pharos University

Sound Sound is energy traveling though matter as a wave. Sound is a mechanical, longitudinal wave that travels in a straight line. The wave travels by compressing and rarefacting matter. Sound requires a medium through which to travel. Depending on the matter- the wave will travel at different velocities or directions.

B  P P x A C animation

4 SOUND TRAVELS TO YOUR EAR The air vibrates but does not travel from the alarm to the ear. Sound

a- Sound is produced by vibrations Sound source vibrates. Surrounding air vibrates. Vibrations travel in air. Ear drum vibrates and sound heard. b- Sound can travel through solids, liquids and gases You can hear sound when swimming underwater. Floors, ceilings and brick walls also transmit sound.

c- Sound cannot travel through a vacuum

7 Connected to the space ship by a line Why? NASA picture

Speed of sound It increases with the temperature. It varies with the medium:

Sound and light waves compared Difference between Sound and Light waves.

Sound and light waves compared Sound wavesLight waves Travelling speed in Air330 m/s3*10^8 Wave CompositionLongitudinalTransverse Transmitting MediumAll Substances Empty Space And All Substances Except Opaque Materials Relation of Transmitting Medium Velocity to Velocity The Denser The Medium, The Greater The Speed The Denser The Medium, The Slower The Speed Sensations ProducedHearingSeeing

11 Telephones -- Are like a sound system The electrical signal is amplified A microphone changes sound to an electrical signal. A loudspeaker changes the electrical signal to sound.

12 Telephones -- The message travels through miles of wires as an electrical signal. microphone loudspeaker electrical signal

13 Radio signal Mobile phones use radio Sound - electrical signal - radio signal - electrical signal - sound In one phone the sound is changed into an electrical signal then into a radio signal. Sound - electrical signal - radio signal - electrical signal - sound In the second phone the radio signal is changed into an electrical signal then into sound. Mobile phone beacons

Audible sound and ultrasound a Audible sound Human beings can hear sound of frequency from about 20 Hz to 20 kHz. It is called audio frequency range. Many animals can hear sound waves within a wider range of frequencies.

Audible sound and ultrasound B- Ultrasound Audio freq. range: 20 Hz - 20 kHz f sound > 20 kHz (ultrasonic waves) Dolphins and bats can emit ultrasonic waves.

Ultrasound This is sound with a higher frequency than we can hear, i.e. above Hz. Uses include: industrial cleaning, breaking down kidney stones, industrial quality control, scanning of unborn babies and SONAR.

INDUSTRIAL CLEANING

Uses of Ultrasound Ultrasound has many uses, especially in medicine where: it is used to scan the foetus. Measuring blood flow. Viewing organs and other tissues for abnormalities or information. Mapping and injecting drugs into the brain.

What is Ultrasound? Ultrasound is a mechanical, longitudinal wave with a frequency exceeding the upper limit of human hearing, which is 20,000 Hz or 20 kHz. Medical Ultrasound 2MHz to 16MHz. High Frequency High frequency (5-10 MHz) greater resolution less penetration Shallow structures vascular, abscess

Low Frequency Low frequency (2-3.5 MHz) greater penetration less resolution Deep structures Aorta, renal

ULTRULTRASOUND – How is it produced? Produced by passing an electrical current through a piezoelectrical crystal (probe) U/S probes emit and receive the energy as waves to form pictures.

The Machine

The basic components of the Ultrasound machine are: A computer/CPU unit Transducer Controls Transducer

The Transducer is the main probe which sends and receives the sound waves. Can come In many different shapes and sizes, single- element, multiple-element, surface or insertion

Ultrasound Process The ultrasound can be external or internal depending on what is being examined If external, then the skin is prepared with a mineral-oil based jelly to maximize contact of transducer to skin and allow better conduction for the waves The Transducer or patient can be moved to obtain more images and angles of the subject

Ultrasound Production Transducer contains piezoelectric elements/crystals which produce the ultrasound pulses. These elements convert electrical energy into a mechanical ultrasound wave

The Returning Echo Reflected echoes return to the scanhead where the piezoelectric elements convert the ultrasound wave back into an electrical signal The electrical signal is then processed by the ultrasound system

Piezoelectric Crystals The thickness of the crystal determines the frequency of the scanhead

Frequency vs. Resolution The frequency also affects the QUALITY of the ultrasound image –The HIGHER the frequency, the BETTER the resolution –The LOWER the frequency, the LESS the resolution A 12 MHz transducer has very good resolution, but cannot penetrate very deep into the body. A 3 MHz transducer can penetrate deep into the body, but the resolution is not as good as the 12 MHz.