digital systems Flashcards
film-type radiograph
analog
smallest component of the matrix; a greater number of smaller ______ improves spatial resolution; “picture elements”
pixels
image displayed as a combination of rows and columns (array)
matrix
number of bits that determines the precision with which the exit radiation is recorded and controls the exact pixel brightness that can be displayed
pixel bit depth
pixel size is _____ related to the FOV and _____ to the matrix size
directly, inversely
the greater the pixel bit depth, the _________ the digitization of analog signal and the _________ the number of shades of gray available for image display
more precise; greater
increasing pixel bit depth _______ contrast resolution
increases
CR has ___; DR has ____
2 steps, 1 step
the IP in computed radiography layers in a cross section
protective layer
phosphor layer (turbid)
reflective layer
conductive layer
support layer
types of phosphor layers
turbid (random), structured (columnar)
three stages of CR processing
scanning, sampling quantization
what type of laser is the CR reader?
neon helium laser
how often the analog signal is reproduced in its digitized form
sampling frequency
distance between sampling points
sampling pitch
equation for analog to digital conversion
Nyquist frequency
each pixel brightness value is assigned a numerical number
quantization
number of gray shades (contrast resolution)
pixel depth
Laser scanning of the exposed IP converts the released energy (_______) into an electrical signal (______)
visible light, voltage
indirect conversion utilizes a ______________ detector that converts exit radiation to _______; the __________ then converts this to a _________________
scintillator type, visible light, photodetector, electrical charges
direct conversion utilizes ____________________ detector converts exit radiation directly into ____________-
amorphous selenium-coated, electrical charges
which sends electrical signal to an analog to digital converter?
both direct and indirect conversion
solid state IRs that use a large area active matrix array of electronic components
flat panel detectors (FPDs)
for best image quality, you want _____ matrix with ______ pixel size
large, small
graphic representation of a data set
histogram
histogram x-axis
X-axis = range of pixel values
histogram y-axis
y -axis = number of pixels in that range
names for exposure indicators
S number, EI, Z number
this provides a method of processing the image data, based on the reference histogram, to transform the image data into a quality image for display
lookup table (LUTs)
LUTs provide the means to alter the ___________ to improve the brightness and contrast of the displayed image
original pixel values
a post processing technique that can remove superimposed structures so that the anatomic area of interest becomes more visible
dual-energy subtraction
post-processing technique that suppresses image noise (quantum noise)
smoothing
post-processing function whereby underexposed areas (light areas) are made darker and overexposed areas (dark areas) are made lighter
equalization
high-pass filtering is another term for _________
edge enhancement
post-processing technique that improves the visibility of small, high-contrast structure
edge enhancement
post-processing technique that reverses the grayscale from original imaging
inversion
low-pass filtering is another term for __________
smoothing
window level is for ________
brightness
window width is for ______
contrast
HIS stands for
hospital information system
RIS stands for
radiology information system
EHR stands for
electronic health record
PACS stands for
picture archival and communication system
DICOM stands for
digital imaging and communications in medicine
S numbers are (inverse/direct)
inverse
a larger matrix size _____ spatial resolution
Improves
increasing pixel density (increases/decreases) spatial resolution
increases
decreasing pixel pitch (increases/decreases) spatial resolution
decreases
post processing technique that alters pixel values to change contrast
contrast enhancement
what does PACS stand for?
pictural archival and communication system
what does DICOM stand for?
Digital Imaging and Communications in Medicine
material used in phosphor layer in CR plates
barium halide with europium
material used in DR scintillator detectors
cesium iodide OR gadolinium oxide
material used in DR CCD detectors
cesium iodide
material used in DR CMOS detectors
crystalline silicon
material used in DR direct conversion detectors
amorphous selenium
