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129 Cards in this Set
- Front
- Back
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Propagation of energy by a mechanical wave through matter |
Sound |
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Acoustic velocity of various tissue |
Air (lowest) Bone (highest) |
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Measure of the strength of a sound wave Power per cross sectional area and expressed in watt per square cm |
Intensity |
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Frequency range of ultrasound |
Above 20,000 Hz |
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Used to locate delineate deep tissues or structures by measuring the transmission or reflection of ultrasonic waves |
Ultrasonography |
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Production of an image of the internal body by transmission of a beam of high frequency sound through the body and recording on a screen the echoes returning from the internal organs and structures |
Ultrasonic imaging |
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Ultrasonography is relatively |
Safe, rapid, non-invasive With high penetration and resolution |
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Diagnostic ultrasound uses frequencies ranging |
1-10 MHz |
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Used to image superficial structures such as the eyes, teat, skin, etc |
7.5 and 10 MHz |
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Used to image deeper structures such as liver, kidneys, lungs, spleen, gall bladder etc |
1, 3.5, 5 MHz |
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Characteristics of ultrasonography |
1. Real time image 2. absence radiation 3. Portable 4. Rapid procedure |
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Advantages of ultrasonography |
1. Noninvasive 2. Enable evaluation of dynamic function 3. Does not require general anesthesia or sedation 4. Permits accurate fine needle aspiration |
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Disadvantages of ultrasonography |
1. Cannot be used in the presence of air or bone 2. Needs direct contact 3. Artifacts (misinterpretation) 4. Variability 5. expensive equipment |
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Applications of ultrasonography |
1. Fat and lean meat evaluation. 2. Detect fluids, fibrosis and tumors 3. Detect foreign bodies 4. Pregnancy diagnosis 5. Biopsy 6. measure blood flow 7. Echocardiography |
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Any attempt to improve resolution by increasing the frequency will |
Decrease penetration |
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Intensity of a sound beam constantly decreases as it travels through tissue. Decrease in intensity is called |
Attenuation |
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Product of the tissues density and the sound velocity within the tissue is known as |
Tissue's acoustic impedance |
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Used to refer to the reflection or transmission characteristics of tissue |
Acoustic impedance |
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Proportional to the difference in acoustic impedance |
Amplitude of the returning echo |
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Acoustic impedance of tissues Low High |
Low- air (0.0004) High- bone (7.8) |
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Altering the beam's direction |
Refraction |
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Parts of the ultrasound machine |
1. Transducer probe or scanner 2. CPU 3. Transducer pulse controls 4. Display 5. Keybord/cursor 6. Disk storage device 7 image recorders |
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Probe that send and receives the sound waves |
Transducer probe or scanner |
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Changes the amplitude, frequency and duration of thenpulses emitted from the transducer probe |
transducer pulse control |
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Ultrasound machine settings and labels |
1. On-off switch 2. Transducer selection 3. display mode selection 4. Power output 5. Time gain compensation (TGC) 6. Pre- and post- processing controls 7. Freeze frame 8. Electronic calipers 9. Magnification or zoom 10. Beam angle 11. Frame rate 12. Split frame 13. ECG |
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This regulates the amount of sound emitted by the transducer and hence the strength of the returning echoes, alteringbthe overall brightness of the image |
Power output |
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Allow electronic amplication of the returning echoes to compensate for reduction in the signal strenght with depth |
Time gain compensation (TCG) |
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Used to alter the omage by accentuating different levels of echoes and so wnhancibg organ boundaries or fine architectural details |
Pre- and post processing controls |
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Allows measurement of the distancr between two points and the circumference and area of an object |
Electronic calipers |
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Option of altering the angle of thr sector imaged. Wider angle = larger field of view |
Beam angle |
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Allowing slower rate for improved resolution or a faster rate to allow full appreciation of moving structures |
Frame rate |
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Device that converts one form of energy into another |
Transducer |
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Avtual transducer of the ultrasonics Converts sonic energy into electric energy and vice versa |
Peizoelectric crystals |
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Main part of the ultrasound machine |
Transducer probe |
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Have the advantage that ultrasound beam can be steered |
Multiple element probes |
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Small dogs and cats can be examines with |
7.5 or 10 MHz transducers |
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Medium sized dogs require frequencies |
5.0 MHz |
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Large breed dogs require |
3.0 or 3.5 transducer |
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Scanners can be classified as follows |
1. Static scanner 2. Real time scanner |
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Older articulated arm scanner which displays a single frozen image |
Static scanner |
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Display a moving gray-scale image of cross sectional anatomy |
Real time scanner |
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Types of real time scanner |
1. Sector scanner -mechanical sector scanner -Electronic (phased array) sector scanner 2. Linear array scanner 3. Convex array scanner |
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Beam shape and resulting screeen imagr are sector shaped or triangular |
Sector scanner |
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Electric scanner with multiple crystals arranged in a line within a bar shaped transducer Rectangular field of view |
Linear array scanner |
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Gives mildly diverging field of view |
Convex array scanner |
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Applied between the transducer and the skin to facilitate contact between two |
Coupling gel |
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Decrease reverberation artifacts and view the structures more accurately |
Standoff pads |
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Fast the patient for how many hours to minimize gas production |
12 |
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Make assessment of the lumen impossible and may obscure surrounding structures |
Food and gas in stomach |
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An area of the body surface should be choses ovelying the organ of interest and avoiding intervening bone and structures containing gas |
Acoustic window |
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To minimize air interposition between the tranducer and the skin |
Shaving |
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Diagnostiv ultrasound visualization method |
1. Operator control 2. Transducer drive 3. Ultrasound pulse 4. Acoustic information 5. Electric information 6. Visual information |
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A good ultrasound image is |
uniform brightness TGC adjusted properly |
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Always scan in |
Dimly lighted room |
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Always scan each organ in at least |
Two planes ( longitudinal and sagittal) |
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When too many echoes generally |
1. Turn down the gain (power) 2. Use TCG controls to supress the image 3. change to a higher frequency transducer |
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Too many echoes proximally |
1. Add or increase slope delay 2. Decrease slope 3 use stand off |
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Too many echoes distally |
1. Decrease slope 2. Use higher frequency transducer |
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Too few echoes generally |
1 check is adequate gel 2 check slope and slope delay 3 increase gain or power 4 lower frequency |
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Too few small amplitude echoes |
1 check to ensure adequate gel 2 check slope and slope delay 3. Increase gain power 4. Use lower frequency |
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Too few echoes proximally |
1 reduce slope delay 2 increase slope |
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Image display modes |
1. A- MODE (AMPLITUDE) 2. B- MODE (BRIGHTNESS) 3. M-MODE OR TM MODE (MOTION OR TIME-MOTION) |
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mode ised for ophthalmic examinations Simplest mode Single fixed beam is used |
A mode |
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Displays the returning echoes as dots Multiple beams used |
B mode |
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Used in echocardiography along with B mode to evaluate heart Motion of dots is recorded with respect of time Single ultasound beam |
M or TM mode |
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Top of the image usally represents the |
Skin surface |
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Abdominal scanning the animal should be positioned on the table in |
Dorsal recumbency with the head oriented away from the sonographer |
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Refers to the section through the entire body |
Plane |
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Refers to the organ itself |
Reference to an axis or a view |
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Attributed to the differences in acousticvimpedence and absorption capacity between tissue |
Different sahes of gray scale formed |
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Decription of echoes |
1. Hyperechoic, echogenic, high echo intensity, echo rich 2. Hypoechoic or echo poor 3. Anechoic, echolucent, sonolucent or transonic 4. isoechoic |
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Having relatively strong echoes which appear white . Highly reflectice interfaces Ex bones, gas, collagen |
Hyperechoic |
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Relatively weak or sparse echoes which appear grey to dark gray Intermediate reflection/transmission Ex. Many soft tissues |
Hypoechoic |
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No echoes and appear black Complete transmission of sound Ex. fluid |
Anechoic |
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Having echoes comparable with surrou ding tissues |
Isoechoic |
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Echogenicity of tissues |
1. Bile, urine (anechoic) 2. Renal medulla (hypoechoic) 3. Muscle 4. Renal cortex 5. Liver 6. Storagr fat 7. Spleen 8. Prostate 9. Renal sinus 10. Fat, vessel walls 11. Bone, gas, organ boundaries (hyperechoic) |
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Bone or gas appear dark on the image becase of |
Shadowing |
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Artifacts can be divided into two categories |
Useless Useful |
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Refers to the production of spurious echoes due to two or more reflectors in the sound path |
Reverberation |
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Common causes of reverberation |
Bones or gas |
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Type or reverberation produced by smaill highly reflective interfaces such as metal or gas bubbles |
Comet tail artifacts |
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Occurs when large rounded, strongly reflective surface such as the diaphragm-lung interface is encountered |
Mirror inage artifact |
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Lateral dispalcement of structures not aligned with the sound beam |
Side lobe artifact |
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Occurs whem the incident sound wave traverses tissues of different acoustic impedances |
Refration of the sound beam |
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Appears as an area of low amplitude echoes (hypoechoic to anechoic) created by structures of high attenuation Gas or bone |
Acoustic shadowing |
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Occasionally seen distal to the lateral margins of cystic structures Fat, tumor, bone, gas, edge of gut |
Acoustic shadow |
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Regularly seen at the edges of a rounded structure such as bladder, gallbladder and kidney |
Edge shadowing |
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Represents a localized increase of echo amplitude occuring distal to a structure of low attenuation Area of increased brightness |
Acoustic enhancement |
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Artifacts related to scanning technique and parient preparation |
Manipulation artifacts |
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Highest practical transducer frequency used for small parts scanning |
10 MHz |
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Common carotid artery is imaged by placing the transducer in |
Jugular furrow directed along long axis of neck at 45 degree angle between parasagital and dorsal planes |
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Common carotid and bifurcation identification |
Anechoic lumina Hyperechoic arterial walls Pulsations |
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Jugular vein appearance |
Thin Anechoic lumen Hyperechoic wall |
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How to image thyroid gland |
Locate common carotid in cranial cervical region Scanning plane is then rotated ventrally and medially |
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Salivary glands is best visualize by |
Identify the carotid bifurcation Rotate transducer 10-20deg |
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Esophagus is best imaged on |
To the left of midline Central, star shaped, hyperechoic pattern |
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Esophagus can be confirmed by |
Identifying esophageal movement after swallowing |
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Trachea image in tranverse and sagittal |
Well demarcated ventral margin with reverberation artifact Distict ventral wall with reverberation echoes and far field shadowing due to air |
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Well suited for ovular examination |
7.5- 10 MHz |
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Position during eye examination |
Sitting or standing position |
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2 basic techniques on eye ultrasound |
Corneal technique Eyelid technique |
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Position during ultrasonography of general abdomen |
Dorsal recumbency Left or right recumbency Standing positon |
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Apperance of normal diaphragm |
Hyperechoic line adjacent to the cranial border of the liver |
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Ultrasonography of the liver indications |
Ascites Hepatomegaly Icterus Fever unkown cause Jaundice |
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Liver imaging technique and position of dog |
1. Patient is starved 2. Shave ventral abdomen 3. Position: right lateral, left lateral or dorsal recumbency |
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Liver apperance |
Cranial: convex outline, contact with diaphragm Caudal: contact with right kidney, cranial flexure of dupdenum and stomach |
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Liver transducer position |
Placed directly under the sternum near xiphoid process |
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Liver normal structure |
Parenchyma- coarsened to fine grained texture Homogenous with portal and hepatic veins easily visualized Portal veins- echogenic walls Hepatic veins- no walls |
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Gall bladder appearance |
Anechoic and ovoid in shape with tapered neck Walls- very fine echogenic line |
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Slpeen indications |
1. Splenomegaly 2. Anemia 3. Mass lesions 4. Abdominal distention 5. Hemoperitoneum |
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Spleen image technique |
Ventral of lateral to left kidney and caudal to the liver Left 11th or 12th intercostal space 7.5 MHz (dogs) 10 MHz (cats) |
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Spleen normal structure |
Fine grained texture and wholly homogenous, granular, speckled |
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Kidneys image tecnique |
Bean shaped in appearance Located in the retroperitoneal space in the cranial abdomen Examined from ventral abdomen 5.0 MHz |
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Kidney normal structure |
Bean shaped
Spleen as an acoustic window Renal outline- smooth and well defined Capsule- hyperechoic line Medulla- almosr anechoic Cortex- higher echogenicity |
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Urinary bladder imaging technique |
Examined when distended with urine Lie partially within pelvis 5.0 MHz |
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Urinary bladder normal |
Round or ovoid appearance Wall- 2 distinct hyperechoic lines Content- anechoic |
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GIT image technique |
Dorsal recumbency Right lateral- pyloric region Left later- fundus Standing- ventral aspect of pylorus and body of stomach Real time sector scanner 5.0 MHz |
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GIT normal structures |
Hyperechoic inner layer Hypoechoic layer mucosa Hyperechoic middle layer Hypoechoic layer muscle Hyperechoic outer layer Intestinal motility |
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Pancreas image technique |
1-2cm thick Isoechoic granular texture V shaped 11th or 12th intercostal space 5.0 or 3.0 |
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Female reproductive organs image technique |
Ovaries & uterus- 7.5 Mid to late term pregnancy - 5.0 |
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Ovary normal |
Oval to round |
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Image technique of heart |
3.5 large 5.0-7.5 most dogs
Apwx beat usually 4-6th ICS |
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Cardiac chambers |
Atria- right of screen Ventricles- left Right atrium and ventricles- closest to transducer Right ventricular wall- closest to transducer IVS- horizontally Left ventricular free wall- farthest from trensducer *hyperechoic rim |
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Fractional shortening (FS) |
Dog- 28-45% Cat- 29-55% |
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Testicle appearance Epididymis |
Homogenous Less echoic |
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Prostate |
Homogeneous parenchymal pattern with a medium to fine texture |
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Non cardiac image technique |
Intercostal approach Fluids and liver as acoustic window |
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Normal structure lung |
Hyperechoic smooth line moving to and fro (pleural lung interface) |
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Normal diaphragmatic outline |
Curvef, smooth, hyperechoic linear structure cranial to liver |
