Radiation Imaging PPT Flashcards
Faithfully reproducing the object’s structure and tissues
Quality
4 quality characteristics:
Spatial Resolution
Contrast Resolution
Noise
Artifacts
ability to distinguish two separate objects and visually distinguish them from one another
resolution
Spatial resolution is defined by ___
line pairs/mm
property of being noticeably different
contrast
large density difference between lines
high contrast
unwanted, non-useful signal obscures (hides) the useful signal
noise
4 categories of noise:
- Graininess
- Structure mottle
- Quantum mottle
- Scatter Radiation
___ pixel size = More detail = ___ noise
Smaller, less
Irregular arrangement of spots or patches
mottle
2 types of mottle:
- structure mottle
- quantum mottle
What type of mottle?
Spots/smears - similar to graininess; structure of intensifing screen; dependent on imaging system
structure mottle
What type of mottle?
Random nature of radiation interaction with detector. Dependent on number of photons (quanta).
qunatum mottle
More quant (photons), ___ quantum mottle
less
Type of mottle that looks like a photo taken with poor lighting.
quantum mottle
____ mottle happens when x-ray is cut short (not enough photons)
quantum
___ “fogs” the image
scatter radiation
In scatter radiation, the image improves if you ___.
Move the image detector closer to the patient.
irregularity on an image that is not caused by the proper shadowing of tissue by the primary x-ray beam
artifact
3 types of artifacts:
- Image Detector Artifacts
- Software Artifacts
- Object Artifacts
____ artifacts: problems with image receptor, including, Dirt, Scratches, Pixel malfunction, Ghost images
image detector
software artifacts can result from problems with: (3)
- range/scaling
- image compression
- window and level
Solution to image compression software artifact:
lossless compression (all data is retained, redundant data is compressed)
3 types of object artifacts:
- Patient Positioning
- Collimator
- Backscatter
Magnification problem: ___ detail.
loses (gets mottled, so quality decreases)
Mag factor equation:
𝑀𝐹= (𝐼𝑚𝑎𝑔𝑒 𝑆𝑖𝑧𝑒)/(𝑂𝑏𝑗𝑒𝑐𝑡 𝑆𝑖𝑧𝑒)
MF = SID/SOD, what are SID and SOD
SID = source to image distance SOD = source to object distance
Mag factor: Near Objects appear ___, while Far Objects appear ____
larger, smaller
This image illustrates what?
Closer objects appear larger and far objects appear smaller
This image illustrates what?
Closer images appear larger and far images appear smaller
What are the solutions for distortion from magnification? (2)
- adjust distance to detector
- adjust source to object distance
This illustrates the geometric factor ___ that depends on ___. What is the solution?
distortion, thickness, reduce distance to detector
Geometric factors affecting imaging quality: (3)
- magnification
- distortion
- focul spot blur
This illustrates the geometric factor ___ that depends on ___. What is the solution?
distortion, position, get multiple image angles
This illustrates the geometric factor ___ that depends on ___. What is the solution?
distortion, position, get multiple image angles
This illustrates the geometric factor ___ that depends on ___. What is the solution?
distortion, position, get multiple image angles
The best position to resolve geometric distortion is at __.
isocenter
This image illustrates the geometric factor ___. What is the solution?
focal spot blur, small source size, patient close to imager
Patient factors in imaging quality: (2)
Contrast
Motion
The thicker the patient, the __ scatter you will get.
more
What is the solution for patient thickness?
Increase the dose to the detector
Solution for patient motion artifacts causing blurred image: (4)
- shorten imaging time (may be moving bc of pain)
- restrict pt motion
- image detector close to pt
- gating
This picture illustrates a ___ image, due to ___.
blurred, patient motion
EPID is located?
mounted on gantry head
EPID uses ____ technology, is a ___ detector and is ___-based.
amourphous Si, digital, video
