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Flashcards in Rad3 Deck (31):


• Ultrasonography is a non invasive diagnostic imaging modality that uses high frequency sound waves to produce an image of internal body structures
• Sound waves are mechanical oscillations in pressure transmitted through a medium (solid, liquid, or gas)


Creation of an ultrasound image

1. An ultrasound pulse is created by a transducer (probe)
2. The sound wave travels through the body until it reaches a reflective surface (tissue)
3. The sound wave is bounced back to the transducer as an echo where it is converted into an electronic signal that is processed by a computer to create an image



• The transducer keeps track of the time that elapses from the beginning of the pulse to the time the echo is received.
• Reflected sound waves create white areas on the computer monitor- more or less reflection= black and white
White is where it is bouncing of stuff, and black is passing through it.


Ultrasound Sounds (echos)

• Ultrasound images are created by differences in how tissues reflect sound waves (i.e. its acoustic properties or echogenicity)


Some tissues reflect few no echoes:

o examples include a fluid-
o filled urinary bladder and
o gallbladder


Some tissues reflect a few echoes examples

o visceral organs - kindey
o and fat tissue


Some tissues reflect many echoes examples

o bladder stones,
o bone, metal


The acoustic properties

o Air: Scatters sound
o Liquid: Transmits sound with little attenuation leading to distant enhancement
o Bone/Uroliths/Metal: Reflects sound and cause acoustic shadowing



How the sound waves interact with tissues.



o Machine
o Transducer


Ultrasonography Machines

o Small and large units available
o Larger machines allow greater manipulation of the ultrasound image


Ultrasonography Transducers

• Produce the ultrasound pulse during an ultrasound study
• The pulse is created by a piezoelectric crystal inside the transducer (probe)
• The crystal oscillates at several million Hertz per second to produce high frequency sound waves


Ultrasonography- how the image is formed

• Many pulses per second are sent out and echoes received to produce the image
• The data collected by the transducer is stored in the computer and then transmitted at 15 to 30 images per second to produce a real time, moving image
• The image can be saved and sent as an electronic file; it can also be stored on a DVD, video tape; or it can be printed on photo paper


High frequency probes

o 5 to 7.5 MHz
o Most common in small animals
o Provide good resolution and detail
o Limited depth of penetration


Low frequency probes

o 2.5 to 3 MHz
o Used in large animals
o Greater depth of penetration but poor detail


Linear probes

o Produce rectangular-shaped image
o Used for high resolution scanning of small animal abdomen, equine reproductive tract and tendons


Curvilinear (convex) sector probes

o Produce pie-shaped image
o Most commonly used probe
o Used for scanning small animals, including the heart


position of the transducer

• Reference mark on transducer should be oriented cranially when scanning in the sagittal plane and to the right side of the animal’s body if scanning in the transverse plane- only on one side
• Transducer should be directed perpendicular to object being scanned


Patient preparation

o Area to be imaged is clipped and cleaned
o Ultrasound gel is used to eliminate the air artifact between the probe and the skin



o Hair can be wetted with alcohol instead of clipping
o Use diluted alcohol to prevent damage to the probe (50% alcohol & 50% water)


Abdominal ultrasound

o Used to image the organs of the abdominal cavity
o Best if patients are fasted for 12 hrs.
o Hair is normally clipped from caudal aspect of ribcage to pelvic brim
o Animal is positioned in ventrodorsal or lateral recumbency


Reproductive ultrasound

• Allows detection and measurement of pregnancy
• Optimum time for pregnancy detection using ultrasound:
• Dogs = 30 days
• Horses = 11 days


Things you can detect on reproductive ultrasound

• Can be used to detects viability of embryos by looking at the heart beat
• Can be used to look for twins in horses
• Can be used to look for abnormalities (e.g. pyometra, cysts, endometritis)


Ultrasound of extremities

• Used in the equine limbs below the carpus and hock
• Allows diagnosis of:
o Traumatic injury (e.g. “bowed tendons”)
o Infection
o Inflammation


Ultrasound of the eyes

• Allows visualization of the internal structures of the eye
• Can be used to diagnose ocular abnormalities (e.g. cancer, hemorrhage)



ultrasound of the heart
• Used to diagnose and evaluate cardiac disease


Able to visualize on Echocardiography

• Valves
• Chamber sizes
• Wall thickness
• Blood flow via Doppler technology


Long axis view vs Short axis view

• Long axis view- Shows heart from base to apex in the sagittal plane
• Short axis view- Shows heart in the transverse plane



o Normal ultrasound scan that produces a moving two-dimensional image of the heart
o Brightness seen on the screen corresponds to returning echoes



o One-dimensional view of the heart
o Shows a traced display of the movement of heart chamber walls over time
o Used to measure heart chamber size and wall thickness


Doppler echocardiography

o Used to evaluate blood flow
o Allows measurement of blood flow velocity and direction in the heart
o Measurement is based on the shift in frequency of returning echoes