Rad3 Flashcards
Ultrasonography
- 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
- An ultrasound pulse is created by a transducer (probe)
- The sound wave travels through the body until it reaches a reflective surface (tissue)
- 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
Ultrasonography
• 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:
(anechoic),
o examples include a fluid-
o filled urinary bladder and
o gallbladder
Some tissues reflect a few echoes examples
(hypoechoic),
o visceral organs - kindey
o and fat tissue
Some tissues reflect many echoes examples
(hyperechoic),
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
Echogenicity
How the sound waves interact with tissues.
Equipment
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
Ultrasonography
• 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
Cystocentesis
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)
Echocardiography
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
B-mode
o Normal ultrasound scan that produces a moving two-dimensional image of the heart
o Brightness seen on the screen corresponds to returning echoes
M-mode
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
