quick study guide

Spatial Averaging

• filling in gaps, used to reduce noise by smoothing

• pixel regions are averaged together

• improves spatial resolution

• reduces speckle by averaging pixel values

• improves SNR but slightly reduces detail

• occurs in the scan converter

Pre-Processing

• image adjustments done BEFORE storage

• must be performed during live scanning

• EX: TGC, persistence, spatial compounding, gray maps, write magnification

Post-Processing

• changes made AFTER freeze

• does not affect stored data

• EX: smoothing, calipers, text, read magnification

Shades of Gray

• determined by bit depth

• more bits = more gray shades

• formula: Shades = 2^n

Binary Digit (Bit)

• fundamental digital unit: 0 or 1

• more bits per pixel = more shades of gray

• 8 bits = 256 shades

Panoramic Imaging

• extend the FOV by physically sliding transducer across the patient to build 2D image

• echo data from previous planes are retained while new data is added from planes in other directions

• results in a WIDER FOV

• extends field of view by sliding probe

• stitches sequential frames into one long image

• useful for large organs and MSK structures

Harmonic Imaging

• uses frequencies created in tissue (2nd harmonic)

• reduces noise, artifacts, improves clarity

• great for difficult patients and cystic structures

Dynamic Range

• number of gray shades displayed

• ↑ DR = softer, lower contrast

• ↓ DR = high contrast

the part of the machine responsible for timing the reception of the pulses to determine their location is the

beamformer

the ability to resolve two events related by time is

temporal resolution

receives digital echo voltages from the beam former

Signal Processor

echo information is taken from the memory and converted so it can be shown on the display in the

D to A converter

functions with array transducers during both transmission and reception

beamformer