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 |