Term
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Definition
| A high resolution output screen that receives the final processed signal from the fluoro processor |
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Term
| Digital fluoro generators and their functions |
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Definition
1. Achieved through the use of a high-power generator
2. Pulses the x-ray production from the x-ray tube in sync with the detector signal
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Term
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Definition
| The length of time required for the generator to come on and achieve the necessary kVp and mAs levels |
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Term
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Definition
Time that is required to shut the generator down in preparation from the next pulse
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Term
| Thin Film Transistor (TFT) definiton and function |
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Definition
1. A pixelated unit with a photodiode connected to each pixel element
2. TFT is on contact with the Image Intensifier (II) output anode screen. It replaces the II in nondifital fluoro systems
3. Relatively insensitive to x-ray photons |
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Term
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Definition
The electronic noise limits for flat panel amplification
The gain at fluoro levels is around 1-5 μR/frame (adds significant signal-to-noise ratio |
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Term
| Digital fluoro pixels vs. radiography pixels |
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Definition
Digital fluoro- Between 200-300 μm (1-2 lp/mm)
Radiography- Between 100-150 μm (10-12 lp/mm)
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Term
| How many shades of gray are capable in a digital fluoro system |
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Definition
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Term
| Last image hold definiton |
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Definition
| Maintains the last real-time fluoro image until it is replaced by the unit being activated again |
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Term
| List post-exposure image processing functions |
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Definition
1. Window level and width
2. Filtering techniques (edge enhancement, temporal filtering, etc.)
3. Digital subtration technology |
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Term
| Digitization process of digital fluoro |
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Definition
Take signal from CCD and send an analog signal through and analog-to-digital converter microchip
Once converted to a digital signal it can be manipulated as desired and transferred repeatedly
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Term
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Definition
| Should not exceed 10R/min and most should range from 1-3 R/min |
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Term
| Minimum source-to-skin distance for mobile and stationary equipment |
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Definition
Mobile - 12" (30 cm)
Stationary - 15" (38 cm) |
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Term
| Requirement for thickness of lead apron and gloves |
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Definition
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Term
| Lead requirement for bucky slot cover |
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Definition
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Term
| Lead requirement for strips of lead between fluoro unit and radiographer |
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Definition
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Term
| Conventional fluoro produced from |
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Definition
| the transmitted x-ray beam |
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Term
| Digital fluoro produced from |
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Definition
| dynamic images obtained with an area x-ray beam |
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Term
| Difference between conventional and digital fluoro |
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Definition
| The nature of teh image and the manner in which it is digitized |
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Term
| 1024x1024 matrix size= ? line system |
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Definition
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Term
| 1000 line system = ? size matrix |
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Definition
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Term
Spatial resolution determined by?
Spatial resolution limited by? |
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Definition
Determined by the image matrix and by the size of the image instensifier (II)
Limited by pixel size |
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Term
| Formula to determine pixel size? |
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Definition
| Pixel size= Image intensifier size/matrix |
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Term
| Components of a dedicated digital fluoro system |
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Definition
1. Alphanumeric and special function keys
2. Computer-interactive video controls and a pad for cursor and region-of-interest manipulation
3. At least 2 monitors (right-edit patient and exam info and annotate final images, left-display subtracted images)
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Term
| Tube current for digital fluoro |
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Definition
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Term
| Tube current for image intensifying fluoro |
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Definition
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Term
| Images in DF obtained by pulsing x-ray beam called? |
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Definition
| Pulse progressive fluoroscopy |
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Term
| Common image acquisition rates for DF |
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Definition
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Term
| How many ms required to produce a single video frame? |
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Definition
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Term
| How long do interrogation and extinction time need to be for DF |
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Definition
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Term
| Fraction of time that the x-ray tube is energized |
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Definition
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Term
| Does DF use CCD or TV camera tubes? |
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Definition
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Term
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Definition
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Term
| What is the sensitive component of a CCD made of |
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Definition
| layer of cystalline silicon |
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Term
| What happens during the function of a CCD? |
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Definition
| Silicon is illuminated, electrical charge is generated, sampled pixel by pixel, manipulated to produce a digital image |
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Term
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Definition
| on the output phosphor of the II and is coupled through fiberoptics or a lens system |
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Term
| What is the spatial resolution of a CCD determined by? |
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Definition
| It's physical size and pixel count |
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Term
| Does distortion such as "pin cushion" or "barrel" artifact occur with CCD |
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Definition
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Term
| Advantages of CCD devices (11) |
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Definition
1. High spatial resolution
2. High SNR (signal to noise ratio)
3. High DQE (detective quantum efficiency)
4. No warm-up required
5. No lag or blooming
6. No spatial distortion
7. No maintenance
8. Unlimited life
9. Unaffected by magnetic fields
10. Linear response
11. Lower patient radiation dose |
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Term
| What is a FPIR (Flat Panel Image Receptor) composed of? |
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Definition
| Cesium iodide (CsI)/amorphous silicon (a-Si) pixels |
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Term
| Advantages of FPIR over CCDs (6) |
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Definition
1. Distortion-free images
2. Constant image quality over whole image
3. Improved contrast resolution over whole image
4. High DQE (detective quantum efficiency) at all radiation doses
5. Rectangular image area
6. Unaffected by external magnetic fields |
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Term
| What is the line system used by conventional fluoroscopy? |
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Definition
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Term
| Limitations to conventional video that restrict its application in digital techniques (2) |
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Definition
1. Interlaced mode of reading target degrades image
2. Conventional television camera tubes are noisy at an SNR of about 200:1, DF requires 1000:1
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Term
| Interlaced vs Progressive Mode |
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Definition
Interlaced- 2 fields of 262.5 lines were read individually in 1/60s to form a 525 line video frame
Progressive- Eletron beam of the TV camera sweeps the target assembly continuously from top to bottom in 33 ms |
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Term
| Important characteristics of a DF system (3) |
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Definition
1. Image matrix size
2.system dynamic range
3.image acquisition rate |
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Term
| Two principle advantages of DF examinations |
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Definition
1. Image subtraction techniques
2. Enhanced visualization of vasculature that results from venous injection of contrast material |
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Term
| Define temporal subtraction |
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Definition
| An image obtained at one time is subtracted from an image obtained at a later time |
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Term
| What happens in mask mode for DSA (digital subtraction angiography)? |
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Definition
1. Power injector armed and readied to deliver contrast
2. Imaging system changed from fluoro mode to DF mode
3. Injector fired
4. An initial x-ray pulsed exposure is made and stored in primary memory (mask image)
5. More images required, stored in adjacent memory, mask image is subtracted from each |
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Term
| Describe image integration |
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Definition
| Each image in DSA is obtained from 33ms (1 video frame), multiple video frames are summed to create one image |
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Term
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Definition
| If initial image is inadequate, a later image may be used as the mask image |
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Term
Define time-interval difference mode
When is TID mainly used? |
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Definition
Produces subtracted images from progressive masks and following frames
Cardiac evaluations |
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Term
| Define misregistration and how it can be eliminated |
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Definition
When patient motion occurs between the mask image and a subsequent image
Eliminated by reregistration of the mask (shifting the mask by one or more pixels) |
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Term
| Define energy subtraction |
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Definition
| Uses two different x-ray beams alternately to provide a subtraction image that results from differences in photoelectric interaction |
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Term
| Define hybrid subtraction |
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Definition
| Combines temporal and energy subtraction |
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Term
| What happens during roadmapping? |
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Definition
1. Mask image acquired and stored
2. Contract injected and subtraction images acquired
3. As a catheter is advanced undo fluoro, the image is formed by subtraction from the second mask |
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Term
| When was the introduction of fluoroscopy? |
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Definition
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Term
| Components of a typical conventional fluoroscopic imaging chain |
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Definition
X-ray tube
Generator
Spot film device
Image intensifier tube
Optical image distributor
Photospot camera
Video camera coupled to x-ray TV monitor
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Term
| By what percentage can pulsed fluoroscopy reduce patient dose? |
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Definition
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Term
| What type of generator do modern conventional fluoro units use |
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Definition
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Term
| What are common ranges for kVp and mA for fluoro units? |
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Definition
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Term
| What is an example of the material used in early fluorescent screens? |
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Definition
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Term
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Definition
# of light photons at output screen/
#of light photon at input screen |
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Term
Newer formula to measure the light gain at the output screen called the conversion factor (CF)
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Definition
Luminance of the output screen/
Exposure rate at the input screen |
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Term
| Purpose of the optical image distributor |
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Definition
To split the toatl light from the output screen between the video camera (10%) and the photospot film camera (90%)
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Term
| Formula to determine dose from mag mode |
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Definition
| Dose= (Full field diameter)²/(Magnification mode)² |
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Term
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Definition
| The ratio of the image brightness at teh periphery to that at the center of the output screen |
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Term
When does "S" distortion occur?
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Definition
| When an electromagnetic field is close to the intensifier |
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Term
| Steps in a fluoroscopic television chain |
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Definition
1. Video camera coupled to the I.I. by the image distributor
2. Video camera converts light from output screen into an electrical signal
3. Signal sent to TV monitor and converted into a visible image
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