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RAD142 Final
Fall 2018 Final
| Question | Answer |
|---|---|
| For every cm increase in part thickness, kVp is... | Increased 2kVp |
| Is an exit-type AEC system (detector is behind the IR).. | Photomultiplier |
| Electric current is stored by a capacitor in this type of system... | Photomultiplier AEC |
| The vacuum tube that produces the electric current | Photomultiplier Tube |
| Entrance type system | Ionization Chamber |
| Factors affecting image density produced by an AEC system.. | Pathology, Central ray not centered to the part, Incorrect Bucky or cells selected. |
| Beam Limiting Device Technique Changes | 14x17 to 8x10 = increase mAs by 60% or kVp by 10 14x17 to 10x12 = increase mAs by 40% or kVp by 5 |
| Type of system using a phosphor coated detector to convert radiation to light | Photomultiplier |
| Grid conversion: Grid to non-grid | Change mAs: Divide original mAs by the Bucky Grid Factor Change kVp: Subtract kVp factor from original kVp |
| Grid conversion: Non-grid to grid | Change mAs: Multiply original mAs by the Bucky Grid Factor Change kVp: Add kVp factor to original kVp |
| Phosphors are stimulated w/ x-ray photon energy and fluoresce: CR or DR? | CR |
| Electrons are trapped in proportion to the qty of absorbed radiation: CR or DR? | CR |
| TFT's absorb image-forming radiation: CR or DR? | DR (Flat Panel Detector) |
| Convert x-ray energy into an electrical signals to form the latent image: CR or DR? | DR (FPD) |
| Multiple projections on one IR & Background Radiation Fog | Histogram Analysis Errors |
| Difference between external and internal artifacts | Internal can't be removed, External can be removed. |
| Pediatric Imaging Considerations | Use lower technique |
| Complete program in RAD dept that addresses all aspects of quality including: Customer Service, Image Interpretation, Accuracy of Diagnosis, Distribution of Radiologists' reports. | Quality Assurance |
| Program that specifically addresses safe and reliable operation of equipment | Quality Control |
| Allows imaging of internal structures | Fluoroscopy |
| Electrons are focused by electrostatic lenses and accelerated toward anode, strike output phosphor, and create a brighter image | Image Intensification |
| Increases visualization of smaller structures and increases patient dose | Magnification Mode |
| Type of Fluoro ii distortion w/ pincushion appearance | Shape |
| Type of Fluoro ii distortion w/ loss of brightness around the periphery | Vignetting |
| Type of Fluoro ii distortion w/ insufficient info due to insufficient qty of x-rays, grainy | Noise |
| To view the image from the output phosphor... | It must 1st be converted into an electrical signal via the TV camera |
| Encloses electron gun and photoconductive target assembly | Camera tube |
| light sensitive semiconducting device, no geometric distortion, smaller in size, more sensitive to wider range of light intensities. | CCD (Charge Coupled Device) |
| Dynamic imaging of internal anatomic structures | Image-intensified fluoroscopy |
| Cassette Spot Filming, Film/Photospot Cameras, Videotape/DVD Recording | Recording systems |
| Similar to Image-Intensified Fluoro, but adds ADC & computer between TV camera and monitor | Digital Fluoroscopy |
| Device that takes video (analog) signal and converts it to number bits 1's & 0"s | ADC (Analog to Digital Converter) |
| x-ray exposure continues w/out interruption, increased patient dose | Continuous Fluoro |
| x-ray exposure is not continuous, has exposure gaps, decreased patient dose | Pulsed Fluoro |
| Helium-neon laser or solid state laser diode, scans CR imaging plate to release stored energy/latent image during processing | CR reader laser |
| Collects, amplifies, & converts light to an electrical signal | Photomultiplier tube |
| Compatibility w/existing x-ray equipment, wider exposure latitude/dynamic range compared to film, ideal for mobile imaging | Advantages of CR |
| Excessive amount of time necessary for processing and image readout | Disadvantages of CR |
| Use a cesium iodide scintillator to convert exit radiation into visible light, amorphous silicon converts visible light into electronic charges | Indirect conversion detectors |
| Amorphous Selenium-coated detectors convert exit radiation directly into an electric charge | Direct conversion detectors |
| Sharpness of structural detail in a digital image | Spatial Resolution |
| How is pixel size related to spatial resolution? | Inversely proportional: Smaller pixels = increased spatial resolution & vice versa |
| How is bit depth related to contrast resolution? | Greater bit depth = Greater number of shades of gray the system is capable of displaying. |
| Density or image brightness is determined by... | Pixel numerical value |
| Graph display constructed to show the distribution of pixel values to indicate low, proper, or high exposure | Histogram |
| System with inversely proportional exposure values | Fuji |
| System w/ directly proportional exposure values | Agfa & Kodak |
| Controls brightness post-processing | window level |
| Controls contrast post-processing | window width |
| Images retained after erasure | Ghost Images |
| How often do CR plates need to be erased (if not used) | 24-48 hours |
| To correct for potential artifacts due to dead or unresponsive pixels | computer applies an algorithm and assigns a new digital values to each dead pixel row |
| what is unwanted fluctuations in image brightness called? | noise |
| Cause of noise due to CR reader scan drivers | Mechanical |
| Cause of noise due to laser intensity control, scatter, or light emitted by the imaging plate | Optical Defects |
| Cause of noise due to electronic noise, inadequate sampling (pixels/mm), inadequate quantization (assigned pixel values) | Computer defects |
| 3 Causes of digital imaging artifacts | 1) Dust (due to not cleaning plates), 2) Moire pattern (due to grid and reader alignment), 3) Scatter (due to the increased sensitivity of imaging plates vs screen/film receptors) |
| Protocol and communication standard used for sharing information | DICOM- Digital Imaging and Communications in Medicine |
| Computer system for digital imaging-connects all modalities-CT, MRI, US, CR, & DR | PACS-Picture Archive and Communication System |
| Performed to check the accuracy of time stations in 3 phase or hi-frequency x-ray generators | Synchronous Motor Timer Test (Formula: 360 x Time = Degree of exposure arc) |
| Evaluates relationship between collimator light and actual x-ray field | Beam alignment test (must be within + or - 2% of SID) |
| Used to evaluate the accuracy of the actual kV used during an exposure | Wisconsin Test Tool (must be within 4 kV) |
| Performed to evaluate the focal spot of the x-ray tube, MEASURES the size of the EFFECTIVE focal spot/ ESTIMATES size of the ACTUAL focal spot | Resolution Bar Test Pattern |
| 2 or more objects sharing resources | Network |
| LAN & WAN | LAN= Local Area Network WAN= Wide Area Network |
| Each computer is considered equal and can function as the server or the client | Peer to Peer |
| Centralized computer controls the operations, files, & sometimes programs of other computers (clients) on the network | Server Based |
| Server processes requests and return only the results back to client/ smaller info exchange cuts down on network load | Client Based |
| Formula used to determine the radiation Intensity when SID changes | Indirect Square Law (ISL) I1/I2 = D2 squared/ D1 squared = New Intensity Helpful Hint to Remember it: Intensity=Indirect |
| Formula used to determine new mAs when changing SID and wanting to maintain the same density | Direct Square Law (old mAs-new mAs) mAs1/mAs2= D1squared/D2squared Helpful Hint to remember it: Distance=Direct |
| Factor that most affects Density | mAs directly affects density: Double the mAs=Double the density |
| Factor the most affects Contrast | kVp is inversely related to Contrast: Increase kVp=Decrease the contrast |
| If the intensity of radiation at 24" is 80 mR/hr., what would it be at 40"? Hint: Use ISL | 28.8 mR/hr |
| If the original exposure factors are 40 mAs at 70 Kv, what exposure factors would you use to decrease contrast and maintain density? Hint: 15% rule | 20 mAs at 80.5 kV |
| A supine chest x-ray at 40" requires 3 mAs at 7 kV, what would the new technique be upright at 72"? Hint:Use DSL | 9.72 mAs at 70 kV |
Created by:
som275
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