RQF
describe the relationship between body part thickness and magnification.
as anatomical part thickens, magnification increases because the part is further away from the IR.
describe direct image acquisition.
1. photoconductor coverts x-ray directly to electrical signal
2. image manifest on computer.
what is: uses a reference histogram to map the images gray scale values.
look up table
TRUE OR FALSE:
conventional x-ray uses the same equipment that is required for computed radiography, meaning no major renovations are required to convert from conventional x-ray to computed radiography?
TRUE.
how does a destructive pathology affect the image and technique?
1. decreases absorption/PE
2. increases receptor exposure
3. decreases technique.
increase
describe CR (computed radiography) image aquisition.
1. x-rays hit imaging plate, excited electrons in the PSP.
2. electrons move and are trapped in conductive layer.
3. plates goes into reader, read by laser in raster pattern.
4. electrons release, emit visible light.
5. visible light read by photodetector; light turned into signal and sent to analog-to-digital converter.
what is: graphic representation of received x-ray signal that demonstrates the minimal and maximum signal for each exposure.
histogram
what is the main consequence of manipulating an image after it is taken?
loss of information.
what methods would limit scatter radiation?
1. compression
2. collimation/restricting x-ray field
3. lowering kVp
4. beam restricting devices/grids.
describe the relationship between kVp and contrast.
1. high kVp=low contrast=long scale contrast
2. kVp increases, there is less photoelectric effect, allowing more greys and less differentiation.
How is a CR plate erased?
flood the plate with bright light.
what are the 3 components of PAC's?
1. web access
2. multiple interfaces
3. reading stations.
what does window level control?
controls brightness as window level increases
what is the advantage of using a low grid factor versus a high grid factor?
1. lower patient dose
2. has wide centering latitude.
patient does decreases.
describe the sequence for PSP image capture.
1. remnant beam interacts with atoms in phosphor layer of PSP plate.
2. electrons become excited, move into conductive layer where they are trapped.
3. latent image is formed.
what is DICOM?
Digital Imaging and Communication of Medicine.
how does an image appear with an increased window level?
image appears darker
what is the advantage of using a high grid factor?
1. high contrast
2. less scatter
Describe indirect image acquisition?
1. photoscintilator converts x-ray energy to light.
2. pixels convert light to electrical signal
3. image manifest on computer.
what device is used to release the latent image?
focused laser in a raster pattern.
what is the purpose of DICOM?
standard for PACS for multiple modalities to communicate.
how does an additive pathology affect the image and technique?
1. increases absorption/PE
2. decreases receptor exposure
3. increases technique.
what is the disadvantage of using a high grid factor?
1. increased patient dose
2. narrow centering latitude.