Real Time Imaging
What is temporal resolution
A sonographer adjusts an ultrasound scan to double the depth of view from 5 cm to 10 cm. What happens to the frame rate?
The frame rate will be halved
Which electronic component is required for gray scale imaging?
What is the scan converter
As a general rule, what decreases the more it is processed?
What is the dynamic range of information
What is the preferred method of zoom?
pre-processing or write zoom
What is the time needed to make a single image if the frame rate of an ultrasound system is 20Hz?
0.05 seconds
A sonographer adjusts an ultrasound scan to double the depth of view from 5 cm to 10 cm. The frame rate remains the same, what is narrowed?
What is the sector
How do you determine the number of gray shades that a group of bits can represent?
What is multiply 2 by itself as many times as there are bits. ie: 4 bits represents 16 shades
A method of describing the extent to which a signal can vary and still maintain accuracy
What is dynamic range
An ultrasound pulse is attenuated by 40 dB. Its intensity is reduced by a factor of what?
10000
What is the critical factor in determining frame rate, line density, and imaging depth?
What is time
A sonographer adjusts an ultrasound machine to change the sector size from 90 to 45 degrees. Nothing else changes. What hapens to the frame rate?
The frame rate is doubled
What is the number of shades that can be represented by 3 bits?
8 ie: 2x2x2=8
Dynamic range is reported in units of what?
Decibels (dB)
In ultrasound imaging axial resolution is what at all depths?
the same
The number of lines per frame and the frame rate determine what?
What is the pulse repetition frequency
A sonographer, using a phased array ultrasound system, turns off the multi-focus feature. What is the most likely consequence of this action?
Temporal resolution increases
Where does coded excitation take place?
In the pulser
An uncompressed signal has a dynamic range of 85 dB. The signal undergoes 30 dB of compression. What is the dynamic range of the compressed signal?
55 dB ie: 85 dB-30 dB=55 dB
The maximum PRF that the machine can use when imagine is limited by the what?
What is the depth of penetration
If the imaging depth of a scan is 15 cm and there are 100 lines in the image, then what is the number of pulses making up the scan?
100
A sonographer reduces the sector angle from 90 degrees to 30 degrees. At the same time, the ultrasound system automatically increases the line density from 1 line per degree to 3 lines per degree. No other changes are made. What will happen to temporal resolution?
Temporal resolution is unchanged.
What is DICOM?
DICOM is a set of standards that allow medical imaging systems to communicate over a network.
What is the dynamic range of a transducer?
120 dB
The axial resolution in an ultrasound is determined by the what?
pulse duration