homework 7 review Flashcards
A combination of rows and columns (array) of pixels is called a
matrix
A method of describing the strength of the radiation exposure compared with the amount of noise apparent in the digital image
signal to noise ratio
An example of a scintillator used in an indirect conversion detector is:
gadolinium oxysulfide and cesium iodide
Based on the histogram analysis, consistent image brightness is accomplished through:
automatic rescaling
true/false:
Bit depth is determined by the matrix size.
false; bit depth is determined by the analog to digital converter (ADC)
DR imaging systems briefly store the electrical charge in the
TFT (thin film transistor array)
If the matrix size is increased for a fixed field of view (FOV), the pixel size is ___________
decreased
Immediately before leaving the CR reader unit, the IP is exposed to:
intense white light
Increasing the number of line pairs per millimeter resolved in the imaging system results in:
increased spatial resolution
Overexposing a digital image receptor may result in:
-high SNR
-visible quantum noise
-increased patient exposure
high SNR and increased patient exposure
Pixel bit depth is determined by the
ADC (analog to digital converter)
The histogram is a graphic representation of the ______________
range and incidence of pixel values
The distance between the analog points being sampled is the
sampling pitch
The ability of the detector to accurately capture the variety of photon intensities in the remnant radiation is
dynamic range
true/false: The DR system does not require a separate reader unit.
true
The DR system sends the digital signal __________________
directly to the computer.
The CR phosphor layer is composed of ________________ with ___________
barium fluorohalide, europium
The numerical value indicating the level of radiation exposure to the digital IR is the:
exposure indicator
This material is composed of barium fluorohalide and makes up the primary component of the CR IP
photostimulable phosphor
What factors may influence the exposure indicator (EI)?
-collimation
-focal spot size
-centering
collimation and centering
What is the term generally used to describe the emission of light from a substance as the result of stimulation by radiation?
luminescence
What type of image receptor converts the exit radiation into electrical charges and stores them before readout and digitization?
DR
Which of the following is not a component of a flat-panel detector?
-glass substrate
-TFT array
-x-ray converter
-phosphor layer
phosphor layer
what is the sequence of events for CR reading unit?
- Stored energy is released as visible light,
- PMT converts light energy to electrical signal
- analog electrical signal is sampled and digitized
With CR, trapped electrons are
-proportional to the exit exposure intensity
-released during readout stage
-in a lower energy state
-proportional to the exit exposure intensity
-released during readout stage
