Ultrasound therapy uses high frequency sound waves to treat various medical conditions. It can be used for diagnosis, tissue destruction, and therapy. The document discusses ultrasound frequencies used in physiotherapy between 0.75-3.3 MHz, with deeper penetration at lower frequencies. It also covers the production of ultrasound waves using piezoelectric crystals, their propagation through tissues based on density and velocity, and how varying the voltage controls intensity.

1. ULTRASOUNDTHERAPY

2. INTRODUCTION
Ultrasound is the modality that is used for a number of purposes
• diagnosis,
• destruction of tissues
• therapy
Ultrasound refers to mechanical vibrations which are essentially the same as sound
waves but of a higher frequency. Such waves are beyond the range of human hearing
and therefore also be called ultrasonic.
Frequency- above audible range 20-20000 HZ
A generator that can be set between 1 and 3 MHz affords the therapist the treatment
flexibility.

3. Depth of penetration
• Ultrasonic energy generated at 1 MHz is
transmitted through the more superficial
tissue and absorbed primarily in the deeper
tissues at depths of 3 to 5 cm.
• Suitable for person with high fat content
• 3 MHz, the energy is absorbed in the more
superficial tissues with a depth of pene-
tration between 1 and 2 cm

4. Medical frequency of Ultrasound
• Physiotherapy Equipment -0.75 MHZ , 1 MHZ , 1 MHZ, 1.5 MHZ and 3.3 MHZ
• Dignostic – 1 MHZ-10 MHZ
• Surgical Eq1uipment- 1 MHZ-5 MHz

5. PROPERTY OF SOUND WAVE
• Sonic waves are a series of mechanical
compression and rarefactions in the
direction of travel of the wave, hence they
are called longitudinal waves

6. PROPOGATION AND SPEED OF ULTASOUND
Z ∝ 𝜌𝑉
Z = impedance ofTissue
𝜌 = 𝐷𝑒𝑛𝑠𝑖𝑡𝑦
V =Velocity Of Propagation
Velocity
Velocity of ultrasound Is the rate of successive zone of compression travel through
medium
Propagation occur as a result of oscillation of particle about their mean position
which transfer energy through medium
Density
Propagation is controlled by density of medium
Air- 344ms−1
Water – 1410ms-1
Muscles – 1540 ms-1

7. PRODUCTION OF ULTRASOUND
For 1 MHz machine a vibrating source with a frequency of one million cycles per second is needed
. This is achieved by using
• a quartz crystal
• barium titanate crystal
• lead zirconate crystal
• nickel-cobalt ferrite crystal
These crystals deform when subjected to a varying potential difference, this is called piezoelectric
effect

8. PRODUCTION OF ULTRASOUND
• Power supply on
• Energy to oscillator circuit
• Produces oscillating voltage
• Cystal inside transducer embedded between
the link electrode and metal front plate
respond to oscillating voltage which fed
through coaxial cable
• Crystal expand and contract at same frequency
at which the current changes polarity
• Metal front plate of the treatment head moves
backward and forward generating a stream of
compression waves that form sonic beam

9. PRODUCTION OF ULTRASOUND
• Intensity controller controls the amplitude of
alternating voltafge thereby controls
amplitude of sonic waves
• Intensity is expressed in watts per square
centimeter (W/cm2 )
Mark space ratio
Mark-space ratio, or mark-to-space ratio, is
another term for the same concept, to
describe the temporal relationship between
two alternating periods of a waveform
Mark space ratio=
Both PW is duration of alternating period
𝑃𝑊𝑂𝑁
𝑃𝑊 𝑂𝐹𝐹

10. TRANSMISSION OF ULTRASOUND