Test 1: lecture 5 Flashcards
Technique charts for digital radiography are simple and are based on ___
patient thickness and charts
why is it easier to get a diagnostic radiograph with DR?
wide exposure latitude (wide range you can get a good picture with different kVP and mAs)
which one is overexposed
A is underexposed
B is properly exposed
C is overexposed
example of ___
overexposure
As exposure increases, noise ___ because more photons reach the pixels in the detector
decreases
underexposure= fuzzy image
what is each line?
wide ___ virtually eliminates need for repeating radiographs based on technique problems
exposure latitude
low slope means the contrast of digital starts ___
low contrast, computer fixes it to look better
film-screen has ___ different opacities
5 (metal, bone, soft tissue/fluid, fat, air)
Typical DR systems can have up to 4096 ___ or more!
shades of gray
what happens during pre-processing ?
corrects for dead pixels and detectors non-uniform response to the xray beam
calibration mask
what happens during processing?
- Processing refers to steps taken after exposure that change the raw data in the pixels
- Processing improves contrast resolution among other things
Unsharp mask filtering
Multiscale processing
pre processing and processing are ___
altering of raw data
calibration mask- fix dead pixels
unsharp mask filtering and multiscale processing- improves contrast
post processing
- There is no changing of the raw data – steps just change how an image is displayed
- Includes steps done at the time of, or right after, exposure (in radiograph acquisition room)
- Look-up table
- Also includes steps done at a workstation, where radiographs are formally viewed for diagnostic purposes
Windowing/Leveling
____ •Includes steps done at the time of, or right after, exposure (in radiograph acquisition room) such as the look-up table
post processing
what kind of processing does not change the raw data
post processing
two examples of post processing are
look-up table
windowing/leveling
look-up table
change the grey scale value in each pixel
increase contrast
different tablets for different body regions
why have different LUT?
different regions of the body have different contrast
thorax already high contrast
abdomen already low contrast
Look up table will have to change more for abdomen then for thorax
•So different LUTs for the various anatomic regions takes into account the ___of the region being imaged
inherent contrast
•LUTs are built into the system so it happens___ but they can be manually adjusted if necessary
automatically,
what are some things you can change in post-processing
- Change image contrast and brightness
- Magnify an image
- Pan around an image
- Perform measurements of structures on the image
- Additional labeling of an image
change image contrast: ___
window width
___ = more gray shades displayed so the image therefore has lower contrast
•“Wide window”
___ = less gray shades displayed so the image therefore has higher contrast
“Narrow window”
which would have more contrast, wide or narrow window
narrow = less grey shades= higher contrast
change in image brightness is also called ___
window level
increasing the window level increases the overall ___of the image
brightness
•A___ system refers to the technologies that contribute to the creation, distribution and archiving of digital images – it’s basically how images are stored and retrieved
PACS
•Picture Archiving and Communications System
DICOM
- Digital Imaging and Communication in Medicine
- This is a standard image file format used in the storing and transmitting of images
- It allows different medical devices from different manufacturers to connect and communicate with each other
what is the standard image file format?
DICOM
