Basics Of Ultrasound Imaging PDF

12/2/24 Basics of Ultrasound Imaging Bryan John Magoling, PhD Batangas State University TNEU 1 1 Learning objectives Present an introduction to medical ultrasonography at the level of a th...

12/2/24 Basics of Ultrasound Imaging Bryan John Magoling, PhD Batangas State University TNEU 1 1 Learning objectives Present an introduction to medical ultrasonography at the level of a third or fourth year medical student. After the brief course, the student should be able to: – Understand basic physics and terminology of ultrasound – State the advantages and disadvantages of ultrasound – Understand how the images are obtained – Begin to interpret simple ultrasound images. 2 1  12/2/24 Outline Brief history of ultrasound technology Advantages, disadvantages What is ultrasound? Physics Probes, controls, machine, Doppler Terminology What structures look like Abdominal ultrasound Example of liver/gallbladder Quick review questions 3 History Medical use – 1940s Developing technology – 1950s Advancements – 1960s/1970s Real time ultrasound – 1980s 3D and 4D images – 1990s 4 2  12/2/24 Advantages Lack of radiation Quick, adaptable Looking at different layers/planes High resolution in low fat areas Portable Less expensive 5 Disadvantages Operator-dependent Depends on area to view Depends on body habitus of patient Artifact Location 6 3  12/2/24 What is ultrasound? Sound waves Waves have amplitude and frequency Frequency – measured in Hz Pulse-echo principle – crystals respond to sound waves Ultrasound waves – transmitted well through fluids and poorly through gases 7 What is Ultrasound? Ultrasound or ultrasonography is a medical imaging technique that uses high frequency sound waves and their echoes. The technique is similar to the echolocation used by bats, whales and dolphins, as well as SONAR used by submarines. 8 4  12/2/24 In ultrasound, the following events happen: The ultrasound machine transmits high-frequency (1 to 5 megahertz) sound pulses into your body using a probe. The sound waves travel into your body and hit a boundary between tissues (e.g. between fluid and soft tissue, soft tissue and bone). Some of the sound waves get reflected back to the probe, while some travel on further until they reach another boundary and get reflected. The reflected waves are picked up by the probe and relayed to the machine. The machine calculates the distance from the probe to the tissue or organ (boundaries) using the speed of sound in tissue (5,005 ft/s or1,540 m/s) and the time of the each echo's return (usually on the order of millionths of a second). The machine displays the distances and intensities of the echoes on the screen, forming a two dimensional image like the one shown below. 9 The Ultrasound Machine Transducer probe - probe that sends and receives the sound waves Central processing unit (CPU) - computer that does all of the calculations and contains the electrical power supplies for itself and the transducer probe Transducer pulse controls - changes the amplitude, frequency and duration of the pulses emitted from the transducer probe Display - displays the image from the ultrasound data processed by the CPU Keyboard/cursor - inputs data and takes measurements from the display Disk storage device (hard, floppy, CD) - stores the acquired images Printer - prints the image from the displayed data 10 5  12/2/24 Transducer probe Is the main part of the ultrasound machine. The transducer probe makes the sound waves and receives the echoes. The mouth and ears of the ultrasound machine. The transducer probe generates and receives sound waves using a principle called the piezoelectric (pressure electricity) effect, which was discovered by Pierre and Jacques Curie in 1880. In the probe, there are one or more quartz crystals called piezoelectric crystals. When an electric current is applied to these crystals, they change shape rapidly. The rapid shape changes, or vibrations, of the crystals produce sound waves that travel outward. Conversely, when sound or pressure waves hit the crystals, they emit electrical currents. Therefore, the same crystals can be used to send and receive sound waves. The probe also has a sound absorbing substance to eliminate back reflections from the probe itself, and an acoustic lens to help focus the emitted sound waves. 11 Physics Speed of ultrasound – average 1,540 m/second, but depends on tissue Acoustic impedance – density of tissue multiplied by velocity of sound; harder substances (like bone) usually have higher acoustic impedance (than substances like water or fat) 12 6  12/2/24 Terminology Echogenicity – measure of jumps in impedance of an organ (NOT density) Hyperechoic – bright; many echos Hypoechoic – dark; few echos Anechoic – black; no echoes Shadowing 13 Frequencies Higher frequencies – better resolution but less penetration [useful for thyroid, testes, superficial blood vessels] Lower frequencies – better penetration but worse resolution [useful for the abdomen, aorta] 14 7  12/2/24 Orientation of probe Head Head Feet Transverse/axial Head Feet Coronal Longitudinal Feet 15 Different probes Linear probes Convex probes Marker on right side of screen used to show scale 16 8  12/2/24 Ultrasound probe Where pizoelectric Connects probe to cable, crystal is internally which is connected to ultrasound machine 17 How to hold an ultrasound probe 18 9  12/2/24 Types of probes – linear 19 Linear probes Probe Direction of waves 20 10  12/2/24 Linear Image from UCMC 21 Types of probes – convex 22 11  12/2/24 Convex probes (also known as ‘curved’) Probe Direction of waves 23 Large convex Large curved probe Images from UCMC 24 12  12/2/24 Small convex Small curved probe – similar to sector probe; used to picture a baby’s head Images from UCMC 25 Ultrasound machine 26 13  12/2/24 Ultrasound machine - portable 27 4 main controls Doppler Gain Depth Freeze 28 14  12/2/24 Doppler Tells you direction of flow, and its magnitude Color Doppler – blue and red show Spectral Doppler – waveform showing flow of blood flow (same as color, but quantitative) Images from UCMC 29 Doppler A little more detail Color Doppler – kidney , showing Spectral Doppler – right testicle with segmental arteries and veins low impedance arterial waveform Images from UCMC 30 15  12/2/24 What structures look like... 31 Pleural effusion - anechoic Image from UCMC 32 16  12/2/24 Pleural effusion - anechoic Skin/abdo minal wall Pleural effusion Liver Image from UCMC 33 Coronal view neonatal brain hydrocephalus – anechoic Image from UCMC 34 17  12/2/24 Coronal view neonatal brain hydrocephalus – anechoic Mid-line Lateral ventricles Sylvian fissure Third ventricle Posterior lateral horns Skull Image from UCMC 35 Conus medullaris – hypoechoic Image from UCMC 36 18  12/2/24 Conus medullaris – hypoechoic Spinal cord in spinal canal Posterior process Image from UCMC Vertebral body 37 Kidneys – parenchyma hypoechoic to liver Image from UCMC 38 19  12/2/24 Kidneys – parenchyma hypoechoic to liver Cortex Liver Kidney Fat Calyx Liver- kidney interface Image from UCMC 39 Gallstones – hyperechoic and shadowing underneath Image from UCMC 40 20  12/2/24 Gallstones – hyperechoic and shadowing underneath Liver Gallstone Gallbladder Kidney Shadowing Image from UCMC 41 Liver/gallbladder example Now – try to think of an ultrasound from start to finish; we will take the example of a liver/gallbladder ultrasound Liver parenchyma Ducts Vascular system Gallbladder, stones 42 21  12/2/24 Indications Hernia Tumors/cancers/metastasis Ascites Organomegaly Free peritoneal fluid s/p trauma Gallbladder or kidney stones Evaluation of liver anatomy and ducts Pancreatitis Abscess Appendicitis Ultrasound guided biopsy 43 Liver/gallbladder example NPO 4-6 hours – gallbladder distended and bowel gas minimal Longitudinal, transverse, and coronal scans in supine and left posterior oblique positions Subcostal approach good for most of liver, but may need intercostal approach for most superior part Use Doppler to distinguish blood vessels and ducts 44 22  12/2/24 Abdominal ultrasound Layperson description (what your patient gets told): http://www.nlm.nih.gov/medlineplus/ency/ar ticle/003777.htm Example of how to do an abdominal ultrasound: http://www.youtube.com/watch?v=7Y6wFXf muvg 45 Liver/gallbladder anatomy Stomach Middle hepatic vein Gallbladder Small bowel with contrast Distended bladder Image from UCMC 46 23  12/2/24 Liver/gallbladder anatomy IVC coursing through liver Portal vein formed by SMV and splenic vein, going Aorta passing to liver anterior to IVC and bifurcating into right and left Branches of SMA common iliac and SMV arteries Image from UCMC 47 Liver/gallbladder anatomy Liver Spleen Left kidney Right kidney Bowel Image from UCMC 48 24  12/2/24 Liver/gallbladder CT – sagittal cut U/S – longitudinal orientation Liver Gallbladder Right kidney Liver Right kidney Images from UCMC 49 Liver/gallbladder CT – axial cut U/S – transverse orientation Right, middle, and left hepatic veins Right, middle, and left hepatic veins Draining into the IVC Draining into the IVC Images from UCMC 50 25  12/2/24 Liver/gallbladder CT – axial cut U/S – transverse orientation Liver Kidneys Gallbladder Liver Right kidney Gallbladder Splenic vein Images from UCMC 51 Liver/gallbladder CT – axial cut U/S – transverse orientation Splenic vein Right portal vein Aorta Spleen IVC IVC Pancreas Left kidney Images from UCMC Left lobe of liver 52 26  12/2/24 Summary You should now understand ultrasound basics Physics, orientation, probes Terms, anatomy Much more to learn 53 Quick review questions 1. What is ultrasound? What types of tissues does it travel well through? Poorly through? 54 27  12/2/24 Quick review questions 2. How does the frequency of the ultrasound affect resolution and penetration? 55 Quick review questions 3. Name some types of hyperechoic, hypoechoic, and anechoic tissues. Can you picture them as they would appear on an ultrasound image? 56 28  12/2/24 Quick review questions 4. What are some pros and cons of using ultrasound? 57 Quick review questions 5. What shapes do the probes come in? Can you describe a few of the differences of the probe types? 58 29  12/2/24 Quick review questions 6. What are the three main ways in which the ultrasound probe can be held (i.e. the orientations of the probes)? 59 Quick review questions 7. Name at least three indications for an abdominal ultrasound. What are some of the things you could tell a patient when they are preparing for an abdominal ultrasound and orders you might need to write? 60 30  12/2/24 Quick review questions 8. (Difficult) What are these ultrasound images of? What do they show? 61 References Pediatric Sonography, by Siegel, 4th edition Ultrasound Teaching Manual, by Hofer: Thieme medical publishers Abdominal Ultrasound: Step by Step, by Block, Thieme medical publishers ACS Ultrasound for Surgeons, 1998 http://www.ultrasound-images.com/liver.htm http://www.ultrasoundcases.info/ http://www.genesis.net.au/~ajs/projects/medical_physics/ult rasound/index.html http://www.radiologytoday.net/archive/rt_120108p28.shtml http://www.ultrasoundpaedia.com/ 62 31