processing terms Flashcards
raw data
is the exposure information prior to any processing algorithms
-raw data is converted into digital data using the analog to digital converter 
quantization
assigns each pixel number
-each number has an assigned grayscale value.
- when does it happen: the same time as the analog to digital conversion. ( digital part is the number)
bit depth
is the number of shades of gray that can be used to define each pixel higher, the bit depth higher the amount of information 
grayscale 
Digital term for scale of contrast
what is a histogram
A graphical display of the pixel intensity distribution for a digital image. Frequency of recorded exposure values. 
what are VOI
values of interest
they are stored in histogram models
what to VOI determine
The range of the histogram data set that should be included in the displayed image 
look up table
it allows gray scale, values in the recorded image to be remapped to new values to improve the final image in someway, such as appropriate brightness and contrast.
LUT’s are specific to anatomic areas.
LUT is the controller for
digital contrast ***
rescaling
corrects the appearance of an image one small exposure Errors are present.
-compensates for minor over exposure. Errors made by the tech. 
what is a dead pixel? 
A pixel with a malfunction or sensor error. Able to be seen on technologist panel. 
dead pixel correction
using a software technique, dead pixels are identified in the matrix and then removed from all subsequent images. 
flat fielding
Dead pixels are removed from the matrix by making a mask of the dead pixels. 
edge ethancement
increases the contrast along the edges of the structures.
- It improves the visibility of details if excessive edge enhancement is used, it can cause a halo artifact around edges.
equalization 
process by which soft tissue and bone are enhanced so all the information within a region of interest can be seen
example: chest images anatomy above, and below the diaphragm can be seen
**It can’t correct for severe under or over exposure 
smoothing OR noise, suppression, low pass, filtering
is used to mask the quantum noise in an image remove random noise areas.
disadvantage : smoothing causes a loss of spatial resolution
Smoothing can’t correct for significant under exposure *
post processing
when the image appears on the screen
windowing
ability to alter, the brightness and contrast of a digital image following processing.
It is done post processing. 
window width
adjust image contrast in the grayscale representation of the tissue.
- wider width
-narrow width 
wider width
Low contrast/long scale, (more shades of gray)
-elephants are wide**
narrow width
High contrast, short scale, more black and white.
region of interest
A technologist can utilize it during post processing to enhance certain areas of the image
-the ROI determines the average pixel value
shuttering
removes white borders around the radiograph because it can cause eye, fatigue and radiologist, trying to read the image 
electronic cropping or masking
crop and image afterwards
shouldn’t be done!!!
- electronic cropping should never be used to crop out anatomy.
- can use it to remove artifacts or errors (scratch on cr plate or a mat next to them)
image inversion
used often for visualizing tubes or lines, -inverting the image of swap, white/block that is normally seen 
image subtraction
Technique used in interventional radiology to clearly visualize blood vessels in a bony or dense soft tissue environment removes the bones to look for blockages or obstructions. 
annotation
writing on the image
- upright/ erect
-supine
cropping
post exposure
removes areas of the image should not be used in place of collimation at the time of the procedure 
Image stitching
The CR processing system uses a stitching application to connect the two images into one for the radiologist to view. Example.) scoliosis. 
Display monitors 
Digital images are displayed on LCD (liquid crystal display monitors)
-The quality of the image and accuracy of the interpretation depends on the number of factors;
-Spatial resolution
-Luminance
-Contrast resolution 
Monitor viewing conditions
Lumens is the amount of light that is emitted from the monitor lumens is important and detecting structures with low contrast, the brighter, the image, the better the contrast resolution 
Monitor viewing angle 
refers to the maximal angle at which a display monitor can be viewed with acceptable visual performance
- radiologists should be reading it straight on!
Lighting for monitors
ambient lighting, refers to the overall illumination of a room, natural light fluorescent light and lamps
-glare from lighting to bright can lead to an accurate reading, and eye fatigue -glare and reflections on the screen will cause the eyes to refocus. Each time vision is passed over the Brightened area
- remove lights!!
Display monitor quality control test
radiology display monitors are checked as part of the quality control program
- a photometer measures the lumens of the monitor as a part of a quality control test
-SMPTE test pattern *
luminance is measured in
candela per square meter
display monitor what light comes off
luminance
PACS stands for
Picture archival in communication system
- sends x rays to PACS. epic
DICOM
Digital imaging and communications in medicine
enables the integration of scanners servers, workstations, printers in network hardware for multiple manufacturers 
Teleradiology
The practice of a radiologist interpreting medical images, while not physically present in the location where the images are generated 
HIS
hospital information system,
which is patient information stored in the hospital database 
RIS
radiology information system
Radiology, modality, work list, and radiology orders 
EMR
electronic medical record means entering a patient’s chart digitally
- never go looking into a patients chart unless it’s your patient
EHR
electronic health record
includes information from various healthcare providers 
signal to noise ratio
good parts of x rays signals
noise- bad grainy
-ideally high signal, low noise
-compares the good parts of your picture to the bad parts
