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Digital Radiography (DR)
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Computed radiography (CR)
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MRO module 6
| Question | Answer |
|---|---|
| Digital Radiography (DR) | A type of digital imaging system in which the image receptor is composed of an array of electronic sensors that "capture" the radiation exiting the patient and send that information in digital format to a computer |
| Computed radiography (CR) | A type of digital imaging system in which the image receptor is composed of an array of electronic sensors that "capture" the radiation exiting the patient and send that information in digital format to a computer |
| Picture Archiving and communication systems (PACS) | System consisting of digital acquisition, display workstations and storage devices interconnected through a network |
| Exposure latitude | The ability of an image receptor to display different shades of gray from light to dark. It is the range of exposures that will produce an acceptable image |
| Dynamic range | The range of gray scale values that can be assigned to each pixel |
| Histogram | A graphic diagram that is used to analyze the pixel values in the digital image |
| Noise | Grainy or mottled appearance of a digital image resulting from electronic signals not related to the image or from statistical variation in x-ray photons (called quantum mottle) caused by lack of mAs (quantum) |
| Lookup table (LUT) | Matrix of data that manipulates the values of gray levels, converting an image input value to different output value. This is what manipulates the contrast of the image |
| Automatic exposure control (AEC) | A system in which the length of the exposure is determined automatically by preprogrammed sensors located between the patient and receptor that terminate exposure when the density is sufficient |
| What controls density in a digital system? | Display computer |
| What is the primary factor influencing contrast in a digital system? | LUT (lookup table) |
| With digital systems, why is it right to use higher kVp and lower mAs by the 15% rule? | Digital has a wider dynamic range |
| Collimation is not important with digital systems. T or F? | False |
| What should kVp selection be based on? | Optimum penetration of the part |
| Which receptor has a wider exposure latitude? 1)Digital or 2)Film/Screen | 1) Digital |
| Which receptor can display the longest grey scale? 1)Digital 2)Film/screen | 1) Digital |
| Photostimulable phosphor | A phosphor that produces light when stimulated by light or x-ray photons (CR) |
| Detector array | Group of detectors and the interspace material used to separate them (DR) |
| PSP (photostimulable phosphor plate) similiar to an intensifying screen of a film/screen system, it has the following layers | 1)Protective layer 2)Phosphor layer 3)Reflective layer 4)Conductive layer 5)Color layer 6)Support layer 7)Backing layer |
| Conduction band | An energy level just beyond the valence shell of an atom where electrons of conductors are free to travel |
| Valence band | The outermost shell of an atom |
| Charged-coupled device (CCD) | A solid-state device that converts visible light photons to electrons |
| X-ray scintillator | A device utilizing a material that absorbs x-ray energy and emits light in response |
| Photodiode | A solid-state device that converts light into an electric current |
| Thin-film transistor (TFT) | An element in a digital image receptor that stores digital information for each pixel-sized radiation detector |
| Photoconductor | Material that conducts electrons when illuminated |
| One problem with the indirect DR system is? | There is the extra step of conversion of x-rays to light and then to electrons, causing a loss of resolution. |
| The direct DR system does not use scintillator, thereby removing the conversion to light step, the direct DR system uses a photoconductor and a TFT array. | |
| When a PSP is exposed to x-rays, which electrons are removed? | Valence shell |
| How are seams between the CCD tiles addressed? | Interpolated by computer |
| Each pixel of a flat-panel indirect DR system contains a photodetector and a TFT. T or F? | True |
| Which causes a PSP to store some energy from x-ray exposure? | Europium |
| Direct DR and one method of indirect DR use a TFT. T or F? | True |
| When the PSP plate is scanned by a laser, the stored energy is emitted as what? | Light |
| Digital imaging and communication in medicine (DICOM) | Standard that enables imaging systems from different manufactures to communicate. First formulated in 1983 |
| What monitor is used for general viewing by non-interpreting physicians and other healthcare workers? | A 1 K (1280x1024)pixel |
| What monitor is used for general interpretation for the radiologist or viewing for QC by the technologist? | A 2 K (1600x1200)Pixel |
| What monitor is necessary for digital mammograms? | A 5 K (2048x2560)Pixel |
| Which storage classification provides the fastest retrieval? 1)online 2)offline 3)nearline | Online |
| Which division of a PACS provides the user interface with the system? | Display station |
| For a PACS to be used in radiography, what is necessary? | Digital version of the images |
| PACS comprises what areas? 1)Acquisition 2)Storage 3)Display | All |
| A RAID system uses which storage medium? | Optical disks |
| Which receptor's useful range of densities is defined by the body of the H&D curve? | Film/Screen |
| A histogram is created to analyze which receptor image? | Digital |
| Insufficient mAs (quanta) exposing a digital receptor will result in what? | Excessive noise |
| What controls contrast in a digital system? | kVp |
| Digital systems are more sensitive to scatter radiation. T or F? | True |
| Digital systems are more likely to record and display scatter and lost contrast as a result. T or F? | True |
| Grids are used with digital systems in the same way as film/screen. T or F? | True |
| A CR system can be used without recalibration of the AEC. T or F? | False |
| At what energy level are electrons trapped following exposure to a PSP? | Conduction band |
| What component of the CR reader converts light to an electronic signal? | Photodetector |
| What is the role of the CCD in indirect DR? | Converts light to electrons |
| Which part of the flat-panel DR converts x-ray to light? | Scintillator |
| Direct DR does not use a scintillator. T or F? | True |
| DICOM serves what purpose in PACS? | Allows different systems to communicate |
| A PACS creates an electronic version of which of the following found in fim/screen department? 1)file room 2)reading room 3)dark room | File room and reading room |
| Which of the following requires the highest resolution monitor? 1)Non-interpreting physician 2)Interpreting physician 3)Technologist 4)Nurse | 2) Interpreting physician |
| Why is storage one of the biggest challenges in PACS? | Rapid increase in use of digital imaging modalities |
| An electromagnet is used to record on what medium? | Tape |
Created by:
volcomgrl12