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Digital Fluoroscopy (DF)
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How are DF images obtained?
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Digital Fluoro
| Question | Answer |
|---|---|
| Digital Fluoroscopy (DF) | much the same manner as conventional fluoroscopy but with the addition of a computer, multiple monitors, and a more complex operating console |
| How are DF images obtained? | by pulsing the x-ray beam ( pulse-progressive fluoroscopy ) |
| Thin Film Transistor(TFT) | replaces the image intensifier in conventional fluoro. Also called Flat Panel Image Receptors (FPIRS). Pixilated unit wit a photodiode connected to each pixel element. |
| Photodiode | converts light fromt eh image intensifier to an electronic signal |
| Scintillator | material that emits light when exposed to ionizing radiation. Ex: csl phosphors. They absorb x-ray photons and then emit magnified light to the TFT |
| Advantages of Flat Pannel Image Receptors | smaller, lighter more easily manipulated. Reponse of an FPIR is more uniform over a period of time and doesn’t degrade with age |
| Disadvantages of flat Pannel image receptors | resolution cannot be as high as conventional fluro. Digital fluoro pixel size is larger than radiography pixel size. |
| Charged coupled device (CCD) | a semiconducting device . stores light photon charges and strikes a photosensitive surface. EXTREMELY FAST DISCHARGE TIME- eliminates image lag. |
| Flat Panel Detector | Direct selenium (info TO digital image QUICKLY) Indirect silicon (slower) |
| Video analog to Digital (ADC) | digitizes analog signal and digitizes it. |
| Flat Panel Image Display | replacing cathode ray tube used in CRT. Easier to view/manipulate. Better images. Readily mounted in angiography and Operating rooms. |
| Computer Controlled Characteristics | image matrix size. System dynamic range. Image acquisition range. |
| Output Signal | ADC accepts analog signal and digitizes it. |
| Temporal Subtraction | pre contrast picture+Post contrast Picture – pre contrast stuff that did not change= subtracted image. |
| Mask mode | subtraction that results in successive subtraction imaest of contrast filled vessels. Original mask – each additional image. |
| Time Interval Difference (TID) mode | produces subtracted images from progressive masks and following frames. |
| Energy Subtraction | uses two different x-ray beams alternately to provide a subtraction image from the differences in kVp (photoelectric interaction). @33kVp- iodine absorption UP, soft tissue/bone absorption DOWN. |
| Hybrid Subtraction | Temporal and Energy subtraction. Mask mode used. PRODUCES HIGHEST QUALITY DF IMAGES. |
| REDUCING EXPOSURE | 1.low dose rate (pulse beams)2.static images (better than 200m camera-less frames)3.Spot images- less images if not overused. |
| ADC | Analog to Digital Converter |
| Video Camera Tube | MOST COMMONLY USED FLOURO VIEWER. VIDICON AND PLUBBICON TUBES |
| Video Camera Charge-Couple Device | semiconducting device stores charge from light photons. Stores image in latent form. Video signal emitted raster pattern. MORE SENSITIVE THAN VIDEO TUBES. No image lag. Fast discharge time. |
| Video Monitor (TV Tube) | Cathode ray tube (CRT) Vacuum tube. CATHODE (ELECTRON GUN) IS SOURCE OF THE ELECTRON STREAM. Anode plated onto THE FRONT SCREEN |
| Cine Film Systems (Cineflurography) | DYNAMIC RECORDING SYSTEM has a cinecamera positioned to incercept images produce by output screen of intensifying screen. Needs 90% of image intensity for proper image exposure. |
| Cine film specifications | Uses both 16 and 35mm formats. 30-60 fps. 60hz. Viewed at 16fps. HIGH PATIENT DOSE. |
| Video Recorders | DYNAMIC RECORDING SYSTEM.VCR/VHS recorder |
| Cassette-loaded spot films | STATIC.positioned between patient and image intensifier.HIGH PATIENT DOSE. HIGHER QUALITY. |
| Photospot camera | STATIC. Similar to moview camera but exposes one frame at a time.less than cassette loaded. 70 or 105 mm film. Large film-INCREASED QUALITY/PATIENT DOSE. |
| What is the most commonly used fluoroscopic viewing system? | Video Camera Tube |
| What is similar to a movie camera but exposes one frame at a time? | Photospot camera |
| What size films are used in Cinefluorography? | 16mm and 35mm |
| What size films are used in photospot cameras? | 70 or 105 mm |
| How are images from digital fluoroscopy obtained? | by pulsing the x-ray beam in a manner called pulse-progressive fluoroscopy” |
| What are the advantages of the FPIR? | 1.smaller, lighter and more easily manipulated than image intensifiers. Response more uniform and does not degrade with age |
| What are the disadvantages of the FPIR? | resolution not as high (less patient dose) |
| What is the type of video acquisition of “video analog to digital”(ADC)? | accepts continuously varying signal, the analog signal, and digitizes it. |
| What is the function of the Charged Coupled device (CCD)? | a semiconductor device capable of storing a charge from light photons and striking a photosensitive surface. Can store freed electrons. Extremely fast discharge time. |
| What are the advantages of digital fluoroscopy techniques? | The speed of image acquisition and post-processing to enhance image contrast. |
Created by:
bcmoody