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49 Cards in this Set
- Front
- Back
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Pulse Wave Transducer |
Most common; A short burst of sound is emitted; The transducer waits until the echo comes back before sending another one; One piezoelectric transducer crystal alternately transmits and receives echoes |
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Continuous Wave Transducer |
Contains two piezoelectric crystals; One constantly sends sound waves; The other constantly receives |
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Mechanical Sector |
Consists of one or more crystals mechanically steered to produce a pie shaped image; Most common in veterinary medicine |
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Linear Array |
Small row of crystals sequentially pulsed; Produce parallel lines and allow the image to be rectangular; Ideal for transrectal and equine tendon exams |
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Phased Array Sector Scanner |
Contains about 20 crystals; Echocardiography; Small and expensive |
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Broad Bandwidth Transducer |
Light weight and lower acoustic impedance (ability of tissue to resist or impede the transmission of sound); Most efficient transmission of sound waves; Piezoelectric ceramic epoxy materials; Wide frequency bandwidths |
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Transducer Crystals |
This is the active element required to promote the conversion of electrical energy to U/S; The produce sound by vibrations through the piezoelectric effect; After pulses are sent, crystals are damped to stop vibrations; Struck by the echoes returning they start to vibrate again; Crystals convert echoes into electrical energy |
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Acoustic Impedance |
This is the relationship between density or stiffness of the tissue and the velocity of sound within the tissue; Example: If two separate tissue types are 1cm thick does the sound wave necessarily travel through them at the same speed?- liver vs. kidney |
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Piezoelectric Effect |
The conversion of electrical energy to pressure energy (vibrations) |
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Bandwidth |
Entire range of frequency; A transducer can produce more than one frequency above or below its center frequency |
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Wavelength |
Distance a wave must travel in one cycle; U/S has shorter wavelengths than those of audible sounds; Determined by the characteristics of the transducer; Shorter the wavelength the higher the frequency transducer which provides a better quality image |
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Frequency |
Number of cycles per unit of time (seconds); As this increases, wavelength decreases |
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Velocity |
Speed at which sound travels through an object; Frequency X wavelength=velocity; When sound wave returns, computer records the time; Computer uses the time taken for the echo to return to calculate the depth at which the sound was reflected; Amplitude: intensity or loudness of a wave; Period (T): time needed to produce one cycle |
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Brightness and Contrast |
Should be adjusted so that black, white and all different shades of grey can be seen |
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Gain and Power |
Affects brightness of the whole image; The higher the power/gain, the brighter the image; Increasing power increases intensity of the sound leaving the transducer and the waves returning to it |
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Time-Gain Compensations |
TCG increases electronic gain of the more distant echoes; Enables returning echoes from different depths to have the same brightness when imaging one tissue type; TCG consists of a series of slide pods to control the brightness in different depths of the image |
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Resolution |
Ability to separately identify small structures on the U/S image or the detail of the image; Frequency of transducer dictates the resolution; Higher the frequency, shorter the wavelength and better the resolution |
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Lateral Resolution |
The ability of the U/S beam to separate two structures lying perpendicular to the sound beam: depends on the beam diameter (width); Distance between two interface must be greater than the beam width for each interface to be identified separately |
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Axial Resolution |
Ability of the U/S beam to separate two structures lying along the path of the beam; Depends on the wavelength of the sound for frequency used; The higher the frequency, the shorter the wavelength, the better the resolution |
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Displaying the Image |
How the returning echo or the image appears on the screen: rectangular or sector |
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A-Mode Display Format |
Amplitude mode; One dimensional graphic display; Returning echoes or viewed as a series of peaks on a graph; Greater the intensity, the higher the peak |
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B-Mode Display Format |
Brightness mode; Depicts dots or pixels on a screen as a two dimensional image; Brightness of the pixel depends on the intesity of the returning echo; The higher the intensity, the brighter the pixel |
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M-Mode Display Format |
Motion mode; Two dimensional display of a reflector over a time oriented baseline; Position of a reflector is displayed on the vertical axis, time is displayed on the horizontal axis; Stationary objects result in straight lines, whereas moving object produce wavy lines; Cardiology |
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Doppler Imaging |
Diagnosing moving structures or fluids (blood flow); Received frequency is either higher or lower than the source; Depends on whether the source is moving away or towards the receiver; Provides information about the velocity of the structure; Can help determine if a lesion is a mass or vessel; Helps detect portal systemic shunts; Provides data on cardiac output and structural abnormalities |
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Sonolucent |
Tissue permits majority of sound to pass through to deeper tissues, only a few echoes return; Appears dark grey on the monitor; Ex: lymph nodes |
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Isoechoic |
Is a term used to describe a tissue that is equal in appearance to that of surrounding tissue |
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Scanning |
Organs should be scanned on two planes: Sagittal or long axis: transducer marker should be constantly positional to the cranial or caudal end of the animal; Transverse or short axis: transducer marker should be 90 degrees to the longitudinal plane |
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Heart |
M-mode and B-mode obtaining both long axis and short axis; Doppler imaging is used to assess turbulence and velocity of blood flow; Examined between 4th and 5th ribs; Right lateral recumbency |
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Cardiac Ultrasound |
Ultrasound can also determine blood flow in the heart; Blue signifies blood moving away from the transducer; Red signifies blood moving towards the transducer |
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Spleen |
Most hyperechoic of all organs; Uniform, granular appearance; Seen best on left side of patient; The spleen is more densely textured than the liver and so generally appears more echogenic; The spleen is variable in position and may be difficult to find in the normal animal, especially in cats |
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Liver |
Less echogenic than the spleen; Texture is coarse; Contains gallbladder; Liver lies immediately behind the diaphragm, which appears on the ultrasound image as a curved, hyperechoic on the ultrasound image as a curved, hyperechoic line, which will move in time with the animals respiration |
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Ballbladder |
Anechoic with bright wall; Sometimes contains echogenic debris; Large in animals that have been fasted; This image shows gallbladder wall edema which can be induced by sepsis |
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Kidneys |
Lateral recumbency- kidney bean shaped; Dorsal recumbency- oval shaped; Surrounded by bright capsule; Cortex is hypoechoic; Medulla is anechoic; Sagittal view is used to measure size |
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Bladder |
Anechoic with hyperechoic wall; Debris often seen |
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Prostate |
Visualize by following urethra into pelvic inlet; Surrounds urethra and is bilobed with a bright appearance; Large and more echogenic in intact males |
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Uterus |
If enlarged, can be seen between the bladder and the colon; Wall is hypoechoic; Pregnancy detection at 20 days in small animals, 11 days in horses |
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Stomach and Bowels |
Difficult to image due to gas; Walls can be seen as alternating black and white layers; Rugal folds can be visualized in the stomach |
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Pancreas |
Adjacent to duodenum on the right side and between the stomach, spleen and colon on the left side |
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Adrenal Gland |
Hypoechoic; Uniformly grey; Found medial and cranial to or beside the cranial pole of the kidneys; Caudal pole of the adrenal gland is next to the renal artery where it joins the aorta |
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Identification of Lesions |
Disease can appear as an alteration in echo texture; Appearance: focal changes, readily identified, affect one specific area; Diffuse changes: subtle changes, can affect whole organ |
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Classification of a Lesion |
Cystic: well defined borders, no internal echoes; Solide: contains many echoes; Mixed: contians cystic and solid lesions, borders may be irregular |
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Artifacts |
An artifact is something that is seen on an ultrasound but anatomically does not exist: propagation artifacts, attenuation artifacts, and other artifacts |
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Reverberations |
Propagation artifact; Many linear echoes; Occurs when sound is reflected constantly between a strong reflector |
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Refraction |
Propagation artifact; Organ appears in different positions, occurs when sound beam changes direction as it passes from one medium to another |
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Mirror Image |
Propagation artifact; Organ appears to be present on both sides of the reflector; When organ lies next to a relfector on the image, usually occurs in region of diaphragm and liver |
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Acoustic Shadowing |
Attenuation artifact; When sound is totally reflected or absorbed by an object; Prevents sound from traveling to a greater depth; Calculi and bowel gas can cause this |
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Distance Enhancement |
Attenuation artifact; Echoes from a fluid filled structure will not be as strong as the echoes from behind it; Enhancement occurs because sound transmitted through fluid is less attenuated than tissue beside it; This artifact can be used to determine if a lesion is a hypoechoic mass or cyst |
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Ring Down |
Similar to reverberation; Produces many parrallel echoes; Associated with gas bubbles |
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Comet Tail |
Similar to reverberation; Caused by strong reflector; Consist of thin lines with close echoes |
