Beam Former - Principle 1 Flashcards
Where does scanning, focusing, and apodization occur?
The beam former - specifically the pulser and pulse delays
What artifact is reduced via apodization?
Grating lobes/side lobes
What part of the beam former generates voltages that drive the transducer?
Pulser - sequencing and phasing are carried out by the pulser and pulse delays
How does the sonographer adjust for PRF?
Changing the DEPTH of the image
What artifact violates the idea that US assumes that the first pulse sent out is received back to the transducer before the next pulse?
Range Ambiguity
Where is the output power/driving voltage produced?
The pulser
What is the benefit of having an increased number of “channels” within the transducer?
Allows more precise control of the beam
During transmission, the T/R switch opens the path from the pulser to what?
Transducer elements
During reception, the T/R switch opens the path from the elements to what?
Reception amplifiers
The beam former has how many amplifiers for each channel?
One
What do ADC’s convert the analog voltages representing echoes into?
Numbers
In what part of the imaging process includes bandpass filtering, amplitude detection, and compression?
Signal processor
What rejects frequencies above and below the accepted bandwidth?
Bandpass filter
What is amplitude detection also known as?
Demodulation
What is the process of decreasing the smallest and largest echo amplitudes to a useable range?
Compression
What is higher: display dynamic range or visual dynamic range?
Display DR: which is why we need compression
In terms of compression and DR, what setting gives the highest level of contrast resolution?
High compression, low DR
What type of resolution is compression important for?
Contrast
When is an echo stored in image memory?
When it is converted from A mode to B mode during scan conversion
Storing the last several frames acquired before freezing is called?
Cine loop
How do we calculate bit depth?
2 ^ n
How many shades of grey can an ultrasound unit display?
256
Describe acoustic and non-acoustic zoom and if they can be used preprocessing or postprocessing?
Acoustic = write zoom - pre-processing only where new beams are formed in the zoomed display
Non-acoustic = read zoom - NO new sound beams, only magnification of the image
What type of resolution is improved using write zoom?
Detail
