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RAD142 Final

Fall 2018 Final

QuestionAnswer
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