Ultrasound The Professional Development Service for Teachers is

Ultrasound The Professional Development Service for Teachers is funded by the Department of Education and Science under the National Development Plan 1

Ultrasound 2

Ultrasound This unit explores ultrasound. By the end you should understand be able to explain the following ideas Some background information about ultrasound. Ø Some of the physics ideas behind ultrasound. Ø Some uses of ultrasound in medicine. Ø Perform some simple experiments Ø Solve simple problems using formulae and calculations Ø Have the basic knowledge needed for Expert Group tasks 3

What is a ultrasound? Ultrasound or ultrasonography is a medical imaging technique that uses high frequency sound waves and their echoes. These frequencies are between 1 MHz and 10 MHz (mega, M, is one million or × 106) and such frequencies cannot be heard by humans The technique is similar to the method of location used by bats, whales and dolphins, as well as SONAR used by submarines. 4

When and why is it used? • There are many occasions when ultrasound is a favourable method of viewing inside the body • An obstetrician can use ultrasound to check the development of an unborn baby • Doppler ultrasound can be use to view blood flow through the heart and diagnose circulation problems • Ultrasound is a ‘non-invasive’ imaging method with instant results, relatively inexpensive, with little or no health risks • Recent advances, including 4 D with surface rendering have increased the resolution and detail of ultrasound scans 5

Physics principles: Waves l crest l Amplitude mean or zero position l l l trough Frequency (f) – number of waves per second (in Hz) Wavelength (l) – distance between any point on one wave and the corresponding point on the next wave Velocity v = fl 6

Physics Principles Ultrasounds are sound waves whose frequency is above the range of normal human hearing. Audible sound frequencies extend from about 20 to 20, 000 hertz (1 Hz = 1 cycle per second). SONAR stands for Sound Navigation and Ranging; it was developed during World War I for submarine detection. It relies on the reflection of ultrasonic pulses bouncing off an object. By timing how long it takes for the signal to return, the depth of the object can be calculated. It has been used to map the ocean floor, as well as finding shoals of fish by fishermen. 7

SONAR Applications Click on the picture for the video on SONAR 8

From the Beginning 9

How does an ultrasound machine work? Ø The ultrasound machine transmits high-frequency (1 to 5 megahertz) sound pulses into the body using a probe. Ø The sound waves travel into the body and hit different tissue, fluid or bone Ø Some of the sound waves get reflected back to the probe, (A) while some travel on further until they reach another boundary and then get reflected. (B) Ø The reflected waves are picked up by the probe and relayed to the machine. Ø Using speed = distance x time the machine calculates the distance from the probe to the tissue or organ. Ø The machine displays the distances and intensities of the echoes on the screen, forming a two dimensional image 10

How is an ultrasound machine operated? Ø The patient must remove clothing around the area to be examined. Ø A gel is applied to the areathis removes any air which would affect the signal. Ø The probe or transducer is placed on the skin. Ø A computer monitor displays the image which can be stored or printed 11

Ultrasound Simulation Different depths or densities produce different intensities boundaries 12

Ultrasound in Action Click on the picture for video on ultrasound (requires video file) 13

Experiment Using the apparatus shown, design an experiment to find the upper frequency that you can hear signal generator loudspeaker microphone Cathode ray oscilloscope Hz 14

Student Activity Try to find out if your mother had an ultrasound scan while she was pregnant with you or a brother or sister See if she received a printout It may still exist! If you have a scanner make a copy of it rather than bringing the original to school Your first picture is very precious! 15

Student Activity- Problem An ultrasonic pulse has a speed of 1500 ms-1 in a sample of soft tissue. If the frequency is 10 MHz, find its wavelength using. . . speed = frequency × wavelength v = fl 16

Student Activity- Solution v = 1500 ms-1 f = 10 000 Hz l = ? speed = frequency x wavelength v = f×l 1500 = (10 000000)(l) 1500/(10 000000) = l 0. 00015 m = l 17

The Doppler Effect • Discovered by Christian Doppler (1803 – 1853) • The sound of an approaching car appears to be higher pitched than when it is going away. • The apparent change in pitch is due to the Doppler effect and can be calculated using fc f'= c±u Use negative u as source approaches f '= f= apparent frequency c= u= speed of wave actual frequency speed of source Use positive u as source departs 18

As the object moves the waves are stretched here As the object moves the waves are compressed here Hear the Doppler Effect Again Click here for web simulation http: //www. phy. ntnu. edu. tw/ntnujava/viewtopic. php? t = 38 19

The Doppler Effect • The Doppler Effect is used by the Gardaí in their speed guns. • When light undergoes a Doppler shift, it’s colour changes. The “Red Shift” of distance stars is evidence that the Universe is expanding 20

Student Activity / Demo • Place a buzzer connected to a battery into a small net (a washing powder net is ideal) • Carefully swing around your head • The rest of the class will hear the Doppler Effect • Your will not hear any change in pitch Why? 21

Student Activity /Problem A fire engine travelling at 30 ms-1 passes a man standing on the footpath. The siren emits a note of frequency 1 k. Hz. If the speed of the sound in the air is 336 ms-1, what is the frequency heard by the man as the fire engine (a) approaches (b) departs 22

Student Activity /Solution approaches u f c f' f' ms-1. = 30 = 1000 Hz. = 336 ms-1 =? = 1000(336) 336 -30 f' = 1098 Hz departs u = 30 ms-1. f = 1000 Hz. c = 336 ms-1 f' =? f' = 1000(336) 336+30 f' = 918 Hz 23

Doppler Ultrasound • As the ultrasound reflects off the flowing blood there is a Doppler Shift. • This can be used to analyse the flow of blood in an artery or through the heart. • A Doppler ultrasound, also known as a echocardiogram , can be used to diagnose coronary heat disease (artery blockages) and other heart problems with the valves or the hearts rhythm Ultrasound flow in a spleen. Colour is added to the image; red is flow away from the probe and blue is flow towards the probe. 24

Student Activity Determine Heart Rate by Pulse Taking Rest two fingers against the inside of your wrist You will feel a pulse as the blood gushes in your radial artery Count the number of pulses in 10 seconds and multiply by 6 to calculate the heart rate per minute Repeat this 3 times and calculate your average Exercise by doing standing squats for 5 minutes Take your pulse again until it returns to your rest pulse You can plot a graph of pulse against time What conclusions can you draw from your ‘recovery time’? 25

Portable Doppler Ultrasound Click the icon 26

3 D Ultrasound Recent advances in electronics and computing power have led to the development of 3 D scanning which shows greater detail such as perspective 27

4 D Ultrasound If many images are recorded in the scan and merged together a movement can be seen and so a movie can be made Computers can also add ‘ a skin effect’ this is called surface rendering Click on picture for 4 D scan of twins in the womb 28

Research from Ultrasound Recent advances in imaging have lead to new discoveries about the behaviour of the unborn. It is now known that the unborn baby opens its eyes, cries, yawns and even scratches! 29

Student Activity Ultrasound scans have always been able to determine the sex of the baby. Some parents do not wish to know the gender of their baby What do you think? It is also now possible to diagnose many more foetal abnormalities Could this lead to increased numbers of terminations? -this is a complex medical ethics issue What are your opinions? Maybe you would like to do further research, write an essay or debate the issue? 30

Ultrasound Treatments Ultrasound is the best form of heat treatment for soft tissue injuries. It is used to treat joint and muscle sprains, and tendonitis. Ultrasound treatment is used to: • relieve pain and inflammation • speed healing • reduce muscle spasms • increase range of motion Ultrasound uses high frequency sound waves. The sound waves vibrate tissues deep inside the injured area. This creates heat that draws more blood into the tissues. The tissues then respond to healing nutrients brought in by the blood and the repair process begins. 31

Lithotripsy LITHO = Stone , TRIP = To Break Lithotripsy (also called ESWL- Extra-Corporeal Shock Wave Lithotripsy) is a method is breaking up kidney stones in the kidneys or tract , using ultasound shock waves. A kidney stone(2 cm diameter) formed from build up of calcium A Lithotripter machine 32

Lithotripsy - Advantages Lithotripsy was developed in the early 1980 s. Before this, surgery was the usual treatment. It is estimated that more than one million patients are treated annually in the USA alone. VIRTUALLY NO PAIN! NO ANESTHESIA! NO SURGERY! NO HOSPITAL STAY 33

Some Other Ultrasound Treatments Ø Treating benign and malignant tumors and other disorders, via a process known as Focused Ultrasound Surgery (FUS) Ø Ultrasound sources may be used to clean teeth in dental hygiene Ø Focused ultrasound sources may be used for cataract treatment Ø Low intensity pulsed ultrasound is used for therapeutic tooth and bone regeneration. Ø As a guidance tool for ‘key hole surgery’ Ø Detecting prostate cancer early 34

Possible Dangers of Ultrasound There have been many concerns about the safety of ultrasound. Because ultrasound is energy there may be some side effects, particularly due to high doses or many scans. There have been some reports of low birthweight babies being born to mothers who had frequent ultrasound examinations during pregnancy The two problems with ultrasound are : The development of heat - tissues or water absorb the ultrasound energy which increases their temperature locally The formation of bubbles when dissolved gases within the body come out of solution due to local heat caused by ultrasound. However, there have been no substantiated ill-effects of ultrasound documented in studies in either humans or animals. This being said, ultrasound should still be used only when necessary 35

The Future of Ultrasound machines will most likely get smaller, producing even higher resolution images. One new area of research is the development of a machine with a ‘heads up real time’ display that will allow a doctor to "see" inside you as he/she is performing a procedure 36