Test 1 Flashcards
what is CPU?
central processing unit
coordinates all computer operations
what is the RAM?
random access memory
can be overwritten by the user and accessed very quickly
memory stored on a chip or disc
what is ROM?
read-only memory
memory that can’t be changed by user
(foundational programs)
what is BIOS?
basic input/output system
internal/primary ROM that directs the flow of information between CPU & peripherals
what is the motherboard?
houses CPU, RAM, ROM chips and connections for USB/audio
what is LAN?
Local area network
a network contained within a single building or business
what is WAN?
wide area network
extends to multiple businesses or geographical areas
what is teleradiology?
remote transmission of medical images via telephone wire or fiber cable outside a facility to a radiologists home or remote radiologist on the other side of the world
what is a bit?
how many bits become a byte?
small unit for binary numbers
8 bits
Bit units are used for:
binary numbers
convert this binary code: 110011
51
what is the smallest unit of a digital image?
pixel
the smaller the pixel:
the better the spatial resolution
in diagnostic imaging pixel size is limited by:
detector element size (DEL)
what is the field of view? (FOV)
the physical area of an image
what is the matrix?
15 x 15?
a pattern of pixels laid out in rows and columns
225
what is scanning?
what is sampling?
what is quantization?
creating a matrix
measuring the intensity
assigning a value
what is bit depth?
maximum range of pixel values that a computer can measure or store
what is a bit depth of 5?
32 shades of gray
(human eye can distinguish between 32 shades)
what is a bit depth of 8?
256 shades of gray
common for non-medical imaging
what is the bit depth 10?
1024 shades of gray
number of shade of gray in the remnant beam
what is dynamic range?
the range of shades of gray that a system can generate
(diagnostic is large)
what is window leveling?
adjusting the image brightness
increasing the window level decreases the brightness
decreasing the window level increases the brightness
what is window width?
adjusting the images contrast
increasing the width increases the shade of grey in the image (low contrast)
decreasing the width decreases the shade of greys in the image (high contrast)
what is the greatest benefit of digital imaging?
the ability to control contrast resolutions
what is the image matrix of these modalities?
Nuc med:
US:
MR:
CT:
x-ray:
Mammo:
64 x 64
128 x 128
512 x 512
512 x 512
1024 x 1024
3328 x 3328 (bit depth 14 & 27 MB file size)
what is preprocessing?
automatic cleaning up of the raw image before the initial image is visible to us (cleaned up by computer)
pre-processing makes ____
post-processing makes ____
corrections
refinements
what is flat field uniformity?
type of preprocessing that corrects for flaws in the electronics/optics of the image receptor system
what is the noise reduction for del drop-outs?
compensating for malfunctioning DEL’s by taking the surrounding 8 DELs and assigning a value to the malfunctioning one
what can happen to individual detector elements? (DELs)
can malfunctions and return no data
what is segmentation?
this occurs to what only?
error that occurs when the computer sees multiple images as a single image
CR (computed radiography) only
what is exposure field recognition?
error that occurs when the computer analyzes raw radiation outside the anatomy of interest
what is the histogram?
a bar graph created by counting the number of pixels (DELs) at each brightness level
how does a histogram visually appeal?
dark pixels to the right
white pixels to the left
what are the Smax & Smin?
Smax are the maximum pixel values that are used for analysis
Smin are the minium pixel values that are used for analysis
what are the different type of histogram analysis?
Type 1:
Type 2:
Type 3:
detects smax and removes the values to the right (that represent raw radiation) (gets rid of ultra black feeback)
assumes no raw radiation to the right of smax and identifies highest value as smax (abdomen) (assigns a smax)
detects Smin and removes values to the left that represent metal or prothesis (gets rid of ultra white)
what are the VOI?
value of interest
different value ranges within the histogram selected to highlight specific anatomy such as bone or soft tissue
what are the histogram process errors?
segmentation error
exposure field recognition error
unexpected objects in the data set (led apron, large prothesis, lead gloves, etc)
too little/ too much radiation
mispositioning
what is the primary thing that rescaling does?
affects brightness
what is rescaling?
the initial processing to make images appear “normal”
what is the goal of a lookup tables?
adjust input so that the image appears “normal”
what is spatial domain?
processing based on the location of a pixel in the overall matrix
what is intensity domain?
processing based on the greyscale value of an individual pixel
what is the frequency domain?
processing based on the size of an object
what does gradation processing primarily control?
contrast
what is data clipping?
a limited bit depth that can limit our ability to adjust the brightness or contrast as it will “clip” the ends of the processing curve
(we don’t want to data clip for our radiologist)
what is detail processing?
breaks down an image into a larger & smaller object based on how many pixels are used to create it
large objects have ____ ____ & ______ ______
small objects have _____ _____ & ____ _____
large waves & low frequency (large objects are not muted)
short waves & high frequency (small objects are not muted)
high pass filtering mutes:
low pass filtering mutes:
large objects
small objects
what is the rule?
low pass =
high pass=
low pass= low frequency= large objects
high pass= high frequency= small objects
what is edge enchancement?
mutes large objects and enhances smaller objects (including artifacts)
what is a kernel?
small matrix used to apply effects to a small section of an image or overall image
what is speed class?
how sensitive an imaging system is to radiation
increasing the speed (class) reduces:
increasing the speed (class) can increase:
patient dose
quantum mottle
what speed can modern CR & DR systems operate at?
without?
speed class of 400
the appearance of substantial quantum mottle
what do digital images lack?
why is this bad?
visual cues that can indicate correct tecnhical factors
the exposure indicator is not ___
an actual exposure reading taken at the image receptor
(median point between Smin and Smax on the image histogram)
the standardized EI is based on _____ ______ to the image receptor and is measured in?
actual exposure
Micro-gray (siemens only)
what is the target EI? (EIT)
the ideal exposure to the image receptor for a particular projection
what is signal-to-noise- ratio? (SNR)
always greater than?
to produce the highest quality image, the signal should be as high as possible, and noise should be as low as possible
1
what is the deviation index?
indicator of how far away a technique was from ideal
If the index for deviation index were to change by +1 how much increased exposure is that?
and for -1?
25% increase in exposure for +1
20% decrease in exposure for -1
what happens if an x-ray results in -3.0?
automatic repeat as quantum mottle is likely
what is saturation?
what can be a result of this?
extreme overexposure (10x)
can overwhelm the digital detection system, causing a loss of data
what is alternative processing?
how can this affect a radiologist?
processing under incorrect anatomy
(processing a knee as a hand)
affect there ability to window or adjust the image data
what is dark masking?
darkens the collimated areas
what is the minimal spatial resolution when reviewing an image on a workstation?
6 LP/mm
what is the only controlling factor common to film and digital imaging?
distortion
(garbage in, garbage out)
