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Computed Radiography
CR System
| Question | Answer |
|---|---|
| what is the purpose of the cassette? | to reduce back scatter |
| the back part of the cassette has lead to reduce back scatter, what does the front(tubeside) have? | imaging plate, radiolucent |
| is the image plate mounted on the front or backside of the cassette | back |
| what are the layers of the cassette and imaging plate? | backing,base, antihalo reflective layer, phosphor, protective |
| backing | bar code info |
| base | mechanical support |
| antihalo reflective layer | allows light to be reflected back (Prevents backflow) |
| phosphor(active) | barium fluorohalide, Europium makes it inperfect, psp |
| protective | Clean it |
| once the plate is read by the laser how is it erased? | White light |
| what are the guidelines about erasing | erase it twice(extra Lg patient), if 48hrs erase twice |
| what window post processing can we use to change the contrast | window width |
| whats another term for computed radiography | cassette based |
| what is a pixel | picture element |
| what is a voxel | 3D pixel |
| matrix | rows or columns of pixels |
| what are the 5 factors that effect spatial resolution or recorded detail? | motion blur(time),sid,oid, focal spot size, image receptor |
| for better spatial resolution, do we want Large or Small pixels? | Small |
| would that give you LG or SM pixel pitch? | Small |
| if we have small pixels with small pixel pitch,would that allow a higher or lower pixel packing density? | higher |
| if we have small pixels, would we have a LG or SM matrix | Larger |
| what is the purpose of the exposure index | tells if you underexposed, or overexposed |
| for the CR system we use the S Number which stands for senstivity. so at HMC what is the range of S values that are acceptable | 100-200, below 100 overexposed, over 200 make too much noise and decrease the contrast |
| what is radiolucent | allows xrays to go through |
| radio-opaque | blocks xrays and does not allow them through |
| what is the LUT(look up table) | visible gray scale rendered image,can be adjusted by changing window width or range after initial processing. |
| what is the forumla to calculate Bit depth | 2^n |
| if we buy system with certain bit depth can we change it? | No |
| is the graphical representation of the signal intensity per exposure to the imaging plate | histogram |
| what do we call histogram with CR system | Tag |
| what are some things that can cause histogram error | wrong tag,improper collimation, not centered right, lead |
| what does pacs stand for | Picture Archiving and Communication System |
| what does pacs do? | transport and store images |
| what is the pacs system we have at HMC | DR |
| what is the purpose of HL7(health level 7) | to communicate between RIS and the HIS |
| what information is on the DICOM header | Patient Name, Medical Record Number, Bar coding |
| what is the purpose of DICOM standards | allows us to transfer images from catapult(Tech station) to Radiologist |
| what does IRD stand for | image reader device |
| what does IRD do for us? | A-D Converter(Analog to digital converter)reads the plate and makes the manifest image come up on your table |
| what is a latent image | image captured by the image receptor, Invisible image( after exposure, but before processing) |
| once we run the CR plate throught the IRD and the image comes up on the LUT what is that image called | manifest image |
| PSP | Barium fluorohalide w/ Europium |
| Latent Image Formation | as the exit beam strikes phosphor, at the Europium sites electrons are given off, and the electrons go through conduction band and held at a bound state at the F-center |
| what is the purpose of the low Freq scan in IRD | to set the parameters |
| what is the 2nd scan that is really fast that prevents banding elements | high freq progressive |
| why is High Freq scan better than Low Freq Scan | Better resolution and Contrast |
| when the laser hits the Electrons in the F-center, what does that excess energy make those electrons do? | fall back onto Europium site and then give off light |
| where is that light sent to in an A-D Convert | CCD, Photodiode |
| types of converters in IRD | CCD,Photomultiplier tube, or photodiode |
| what is the HIS at HMC | Meditech |
| what is the purpose of the default pixel shifting | motion fix |
| Turbid or Columnar, which is Cesium Iodide, and which has better spatial resolution | Columnar |
| Turbid is in the form of what? | Powder |
| what type of scintillator uses turbid | G. Oxysulfide |
| which one has higher detection efficency, better absorption of xray photons so you can use less MAs | G. Oxysulfide |
| what is the purpose of stiching | spine Treatment(scoliosis) |
| what is the measurement of spatial resolution where it looks at the bottom information that is available in your object VS. whats actually captured | module transfer function |
| whats the min freq that all scanners have to meet | nyquest |
| what scan gives you better resolution and contrast | High Freq Progressive |
| what is the ROI(region of Interest) | area that it is sampling |
| what can we do post procedure to change density and contrast, is it direct or indirect | window width, indirect |
| window level changes, is it a direct or indirect | brightness, direct |
| what is any unwanted density | artifact |
| how can we prevent grid aliasing or Moire | thin lines |
| what type of scanning do you to prevent banding | progressive scanning |
| what is the purpose of auto-rescaling | match up histogram, apporiate brightness and contrast |
| what is the purpose of the detail smoothing | helps get rid of noise but gets rid of fine detail |
| whats the process of equalization used for | parts with different densities |
| whats the purpose of edge enhancement | artificial enchancment of the bone |
| what does the fourier transformation do | change image |
| what does DQE stand for | detective quantum efficency- how well scintillator picks up radiation |
| what is FOV(field of View), does CR or DR have variable field of view | size of image receptor, CR |
| what is brightness | blackening of image receptor or luminescent of each pixel |
| what is contrast | density difference |
| whats the purpose of shuttering | to reduce radiologist eye strain |
| is collimation important | yes |
| what type of freq or grid do we want to use to prevent grid aliasing | thin, High Freq progressive |
Created by:
johnsoni1986
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