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Rad Physisics 25
Digital Radiography
| Question | Answer |
|---|---|
| What two groups can digital radiography can be divided into | cassette based or cassette-less |
| What imaging plates do the cassette based imaging use | photostimulable storage phosphor inside the cassette |
| What system uses a reader to process the plate and create the image | computed radiography |
| What are considered cassetteless systems and a cassette is not needed | direct digital radiography (DR) |
| Which acquisitions are used in DR by detector configuratioin | indirect and direct acquisition |
| What acquisition system has two part process involving a scintillator and a photodetector | indirect acquisition |
| What acquisition system use photostimuable storage phospher imaging plates, and charged coupling devices, and Amorphous silicon | direct acquisition |
| What in the indirest acquisition system converts incoming x-ray photons to light | scintillator |
| What in the indirect acquisition system converts light into electronic signal | photodetector |
| What acquisition system direectly converts incoming x-ray photons to an electronic signal | direct acquisition |
| Which acquisition system uses amorphous selenium | direct acquisition |
| What is a rigid sheet to record a beam of ionizing radiation | photostimulable phosphor |
| What are the layers of the photostimuable imaging plates | protective layer, phosphor layer, support layer, conductor layer, and light sheild layer |
| Which layer of the photostimulable imaging plate is made of polyester | support layer |
| What does the cassette that the imaging plate is loaded into looks like | radioigraphic film and intensifying screen cassette |
| What are computed tomography cassettes are sometimes referred to | filmless cassettes |
| What is needed for CR to function | the imaging plate material needs to be able to store and release image information in a usable form |
| What are characteristics favorable for CR | 85% bromide (barium fluorohalide bromides) and 15% iodide (iodides with europium activators) |
| When is the imaging plate more sensitive to scatter | both before and after it is senitized through exposure to the x-ray beam |
| What produces a latent image within the photostimulable fluorohalides that comprise the active layer of the IP | incident x-ray beam |
| What is actually created by eneregy transfer during photoelectric interactions | latent image |
| What is processed by loading the cassette into an image reader device (IRD) | latent image |
| Where is the imaging plate scanned by a helium neon laser | (IRD) imaging reader device |
| What are detected by photosensitive receptors converted to an electrical signal which in turn is converted to a unique digital value | latent image in the form of light photons |
| What happens to the plate aafterit is read | it is erased |
| What begins with x-ray exposure to the imaging plate | image acquisition |
| How can the imaging plate be used | tabletop or with a grid |
| What is the difference of thelatent image stored in the imaging plate and latent image stored on film | wider latitude in the imaging plate |
| What is required in reading the imaging plate | finely focused laser beam that frees the trapped electrons |
| What happens to the light liberated from the imaging plate | emitted in all directions and collected by an optical system |
| Where does the optical system directs the liberated light from the imaging plate | to one or more photomultiplier tubes |
| What converts the visible light into an electronic signal whoseoutput is in analog form | the photomultiplier tubes (PMT) |
| How is the analog signal converted into digital signal | with an analog to digital converter |
| Where does the reading and eraser of the imaging plate occur | in a single processor unit |
| What happens to the spatial resolution when the pixel is small | the spatial resolution is high |
| Why must the analog signal be sampled in order to find the location and size of the signal | to accomplish he task of changing the analog signal into the correct components for digital manipilation |
| During processing, what mus tdetermine the orientation of the part on the plate as well as on the number projections present per plate | CR system |
| Where will the highest values lie | within the collimated field |
| Why does the highest value lie within the collimated field | to allow the sytstem to locate the useful information and disregard the data outside these lines |
| What is known as the exposure data recognition | clinically useful area |
| What are the three modes of the exposure data recognition (EDR) | automatic, semiautomatic, and fixed (auto, semi, fixed) |
| Where should each beam and part be centered | within each pattern |
| How shouldthe collimation be placed | parallel and equidistant from the edges of the imaging plate |
| What is generated by dividing a scanned area into pixels and determining the signal intensity for each pixel | histogram |
| What will coreespond tothe specific anatomy and technique | shape of the histogram |
| What will allow preprocessing of incorrectly run plates | modern CR readers |
| What will show that CR image is extremely grainy and as a result is outside the acceptable range of detail | careful inspection |
| What allows images that were processed with an incorrect anatomical menu to be reprocessed using the correct anatomical menu with no loss of original quality | raw data pre histogram analysis |
| What does the Fugi computed radiography system uses to assist in the evaluating exposure | S value |
| Is the exposure reaching the plate inversely proportional or direct proportional to the imaging plate | inversely proportional |
| What does a high S value indicate | the imaging plate was underexposed |
| What does a low S value indicate | the image plate was overexposed |
| Why is the using more than 80 kVp avoided | higher kVp levels produces excessive fog that will decrease contrast significantly |
| Will using more than 80 kVp produce excessive fog that will decrease contrast significantly more than the same increase with a film/screen imagingreceptor | yes |
| What aer the two types of imaging plates that FUGI uses | 400 relative speed film screen speed system and a 100 film/screen speed system |
| What are the advantages of the CR | wide dynamic range response to the imaging plate detector, response to imaging plate to x-ray is linear, response gives imaging plate increased latitude |
| Why does the extension of the density range occurs with CR with areas of much greater exposure | the imaging plate does not have a D(max) curve |
| What is the great danger that radiographer must realize when using CR | in premitting overexposure of all patients with the intention of the CR system adjusting the histogram ticorrect the exposure |
| What does the practice of overexposure violates and is an unethical practice | ALARA (as low as reasonable achievable) |
| In the CR system what is the multiple benefits inherent in increased latitude | widely attenuation values ex. (chest, and with widely different densities |
| Why do CR has the advantage of the reduction to repeat exposures due to incorrect techniques or image varies densities | the ability to use windowing and leveling in an image |
| How aer the image receptors manufactured | to calibratethe response of their system with different beam qualities |
| Whatis difficult to compare from one system to another | sensitivity |
| What should be the exposure index range for properly exposed images | 1800 to 2200 |
| What is recommeded for all nongrid radiography | that kVp not exceed 80 |
| Why is 80 kVp not used for CR plates | they are sensitive to fogging |
| What must be done to plates to eliminate unwanted noise | erased daily |
| Why don't all CR systems send alll the data required by the image receptor to the post requisiton system | the quantity of data is far graeter than the display system can provide for viewing |
| When do the ARRT recommend plate erasure | every 48 hours or 2 days |
| What is used for radiiographers to justify decreasing mAs during CR exposure as long as setting remain well above quantum mottle/reticulation range | data clipping |
| What can create spectacularly enhanced contrast edges | edge enhancement |
| When should edge enhanced images be viewed | w/o edge enhancement |
| What feature is most commonly applied to high noise images such as quantum mottle/reticulation images to make the sharp edges of the noise blur into the background | using a post algorithm to blur objects |
| What is the CR system look up table | histogram |
| What permit changes in optical density or contrast | look up table |
| How do manufacturers set their system | so that only authorized persons can access the look up table adjustments |
| What allows radiologist to view a normal display of a chest along with a bone enhanced histogram inage, a soft tissue enhanced image | histogram equalization |
| For histogram equalization are digitally enhanced images routine | no |
| What is collimator edge identification related | post acquisition processing |
| What stitch together multiple images form some CR systems | image stitching |
| What rely on overlapping exposures to verfy registration marks and image contrast edges tp align multiply exposures into asingle image | imaging stitching |
| What is used when chest measurements exceed 24 to 26 cm for optimum images | grid use and desired kVp |
| What will be observed if the scan frequency are similar and oriented in the same direction | Moire effect |
| What does direct exposure imaging systems employ that is used on all exposures | stationary high frequency grid |
| What is the charge collected in the direct selenium flat panel imaging plate system transmitted through | thin film transsitor to the computer for processing |
| What cannot directly convert x-rays into an electric charge but does not work as a light detector in indirect silicon flat panel imaging plate systems | amorphous silicon |
| What happens once the light reaches the amorphous silicon | it is converted into an electric signal |
| What device is capable of converting visible light into electric charge | CCD |
| How are CR artifacts classified | according to where they occur in the image processing sequence |
| In acquisition: extremely overexposure may require two erasures cycle to completely remove the image | phantom images |
| What are permanent artifacts caused by damage to imaging plates | scatches (acquisition) |
| What artifacts are created by dust | light spots (acquisition) |
| What are reduction in resolution either overall or in specific areas of the emage | dropout artifacts (acquisition) |
| What is due to imaging plates being much more sensitive than film | fogging (acquisition) |
| What is caused by inadequate exposures (usually insuffiencient mAs) | quantum mottle (acquisition) |
| What is caused from image receptor being exposed to intense heat | heat blur (acquisition) |
| Is algorithm post acquisition or acquisition | post acquisition |
| Is What artifact is limited to problems in laser imaging | dropout artifacts |
| Is laser film transport artifacts post acquisition or acquisition | post acquisitionIs |
| Whatis due to correct preprocessing | histogram error (post acquisition) |
| What does histograms require that collimation edges be parallel to the sides of the imaging plate | nonparallel collimation |
| Is contrast window width adjustments post acquisition, acquisition, or display | display |
| Is density/brightness window levels adjustments post acquisition, acquisition, or display | display |
| Is electronic magnification/magnification adjustments post acquisition, acquisition, or display | display |
| What usually a result of incorrectly set presets for edge enhancement, contrast range, spatial frequency filtration | image enhancemnent artifacts |
| What allows a radiologist to display anormal view of a chest along with bone a enhancement histogram image, | histogram equalization |
| what feature of the CR creates a major imaging dilemma for radiologist because there is no end to the number of modified and enhanced images that can be created from a single image data set | histogram equalization |
| when the software processinfg the data coming from the image receptor is programmed to recognize that some data represents exposure below the diagnostic imaging range while other data represents exposure far above the diagnostic range | data clipping |
| What is directly proportional to the radiation striking tje imaging plate | Kodak CR indicator (exposure index) |
| When is the anatomical menu selected | by body part by the radiographer when the imaging plate is loaded into the reading unit |
| What is also used to eliminate unnecessary information outside the collimated feild, like scatter radiation that degrades the final image | histogram |
| Why should the correct anatomical menu be selected prior to processing the image plate | the image will not process the correct density and contrast |
| What allow preprocessing of incorrectly run plates | modern CR readers |
| What must the reader system be given in order to provide consistent diagnostic quality results | consistent data to analyze |
| How much percentage will the latent image lose of its energy in 8 hours | 25% |
| When the cassettes should the cassettes be processed | shortly after exposure |
| What is lost by cassettes that are stored for several days after exposure and before processing | most of their latent image |
| What causes phosphors to emit the stored latent image in the form of light photons | laser beam scans |
| what does it mean when he absorption efficiency above or below 35 to 50 keV is below that of rare earth intensifying screens | that more exposure is needed in order to have a similar quantum noise outside the optimal energy range |
| What does it mean when the imaging plate will absorb more low energy scatter than the rare earth phospor and film | appropriate kVp and masking must be used to achieve optimal images |
Created by:
rachel43