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CR and DR
| Question | Answer |
|---|---|
| __________ means having no definite shape. | Amorphous |
| Semi-conductor material which means allows some flow of electrons between atoms. | silicon |
| Direct conversion detectors to detect exit radiation and form latent image. | selenium |
| TFT | thin film transistors; electronic switch to allow charges to be collected at each pixel. |
| Automatic rescalling | software that adjusts gray scale values in histogram |
| Number of shades of gray | bit depth |
| How is bit depth calculated? | 2 to the n power; n= 8; 2 to the 8th power = 256 shades of gray |
| Bit depth is also known as ______ _______. | Contrast resolution |
| Dynamic range | range of exposures over which a detector can acquire image data |
| Detective Quantum Efficiency (DQE) | ability to detect or absorbe x rays (dose level required for optimal image) |
| Field of view or detector size | useful acquisition area of imaging device |
| Software must detect collimated edges for proper histogram analysis. | beam part alignment latitude |
| Histogram | identifies all densities on an IP; pattern varies for body part |
| Unwanted density | image noise |
| Spatial resolution | ability to image an object faithfully |
| Measure of the ability of the imaging system to preserve signal contrast as a function of the spatial resolution | modulation transfer function |
| Look Up Table (LUT) | results image with correct contrast and brightness; maps adjusted data through s curve |
| How is the LUT adjusted? | By changing window width or range after initial processing |
| Number of pixels in rows and columns | Matrix size |
| Highest spatial frequency that can be recoreded by a digital detector. | Nyquist Frequency |
| Pixel pitch | distance from the center of one pixel to the center of another pixel |
| Photodiode | electronic element that converts light into electronic charge; indirect |
| photoconductor | TFT detector that converts x ray directly into electrons without photodiode |
| Pixel | picture element |
| Processing algorithm | mathematical codes used by software to provide image |
| 3E picture element of tissue | voxel |
| _____ _____ determines resolution. | pixel size |
| What are the five things that affect spatial resolution? | time, SID, OID, FSS, IR |
| Fourier transformation | mathematical method to convert data |
| What is being described:indirect capture, cassette-based, film less | Computed Radiography |
| What are the five layers of the cassette based image plate? | backing, base, anti-halo/reflective, phosphor, protecftive |
| What is the purpose of the backing layer? | protects from handling artifacts; contains bar code info |
| The base is made of what material? | polyester |
| What is the purpose of the base? | To support the phosphor layer. |
| This layer prevents the IRD laser light from penetrating but allows reflected light to be emitted to strike phosphor to produce latent image | anti-halo/reflective layer |
| What is the PSP layer made of? | barium fluorohalide doped with europrium |
| Which layer captures the latent image? | phospor layer (photostimuable phosphor layer) |
| Image created after exposure but before developing. | latent image |
| What layer provides protection and a cleaning surface? | protective layer |
| What are the steps of the PSP IP luminance? | 1. Stored energy is released to photomultiplier tube and produces light;2. light converted to electrical energy;3.analog to digital conversion;4. digital signal sent to computer |
| Exposed film is ____ more exposable to light. | 8x |
| IRD | image reader device |
| What are some advantages to using an Image Plate for digital radiography? | indefinite life, hold image up to 48 hrs, cassette does not need to be light tight, |
| What is the most common compression ratio? | 1:1-1:3 |
| What happens when the IP is placed within the IRD? | 1. pre-read: sets boundaries of collimation 2. main read: scanned by laser that causes phosphors to emit stored latent image in form of light photons |
| S value # | proper range of exposure ; 100-200 |
| If the s value is over 200 the image is _______, and if the s value is under 100 the image is ________. | Underexposed, overexposed |
| Is the s value # and exposure direct or indirectly related? | indirect |
| Dose Area Product (DAP) | digital radiography systems proper range of exposure |
| Image noise is ________ related to contrast. | inversely |
| Is it beter to have a high or low signal to noise ratio? | high which will decrease noise |
| Window level controls _______ . Their relationship is _______. | density; direct |
| If you increase your window width, what will happen to your contrast? | decrease (indirectly related) |
| Smoothing | software function that reduces noise |
| Edge enhancement | artificial increase in contrast of displayed image at an edge |
| TFT | thin film trnsisistors - collects electronic signal as a matrix |
| DICOM standars | Digital Imaging and Communications in Medicine; system of standards that permits a wide range of digital imaging programs to talk to one another ex. Konica to communicate with GE |
| HL7 | health level 7; standard needed to allow HIS to communicate with RIS (Meditech to PACS) |
| PACS | Picture Archiving and Communication system; sotrage and transmission for digitized images |
| PACS can be manipulated by: | windowing, enlargement, tissue density readings, subtraction |
Created by:
sr4095
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