Ultrasound (US) Flashcards
What range is used in BIOMEDICAL ULTRASOUND?
20kHz-50MHz
What range is used in CLINICAL ULTRASOUND?
1-15MHz
How is SOUND defined?
Periods of compression and rarefaction passing a given point
What is PARTICLE/MEDIUM VELOCITY (u)?
The velocity of a particle/medium caused by sound disturbance
What are the 3 types of ULTRASOUND PROBES?
- Linear: Flat line of elements
- Convex: Curved
- Phased (linear or convex): Sequential activation of elements
What is the LATERAL RESOLUTION of an US system?
Resolution parallel to the surface - the width of an element
What is the AXIAL RESOLUTION of an US system?
Resolution perpendicular to the surface - SPL/2 or nC/2f
* SPL = nC/f
* n = number of pulses, C = speed of sound in medium, f = frequency
What is the FIELD of VIEW of a probe?
Total width of active elements (width of individual element * number of elements)
What is TIME-GAIN COMPENSATION (TGC)?
Adjusts the amplification of received echoes based on their origin depth, makes the final image more uniform and easier to interpret
What is AMPLITUDE MODE ultrasound (A-MODE)?
- Simplest, single line of data with variable peaks
- Hard to find specific details
- Only requires a single transducer
What is BRIGHTNESS MODE ultrasound (B-MODE)?
- Combines multiple A-mode scans
- Processing required to get from A-mode
- Brightness is proportional to penetration depth
- Takes time to create each frame (tf)
What is the DOPPLER EFFECT?
The apparent change in frequency at the receiver of a sound from or reflected from another object – requires at least one object to be moving
What is 3D ULTRASONOGRAPHY?
- Creates a 3D reconstruction formed from 2D images
- Used to aid in early detection of cancerous/bengin tumours
- Offered to new parents to ‘meet’ their child
What affect does FREQUENCY have on ultrasound?
Faster frequency = higher resolution but less penetration
What is PULSE REPETITION FREQUENCY (PRF)?
The number of pulses per unit time, Hz
