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Who invented the fluoroscope and when?
What is the primary function of fluoroscopy?
To perform dynamic studies that show motion of circulation or hollow internal structures
By what means are permanent images of fluoroscopic exams made?
- Radiographic spot film
- Video Imaging
- Digital Imaging
How are the x-ray tubes and the image intensifier normally positioned for a fluoroscopic exam?
The x-ray tube is under the table, and the image intensifier is over the table
What mA is typically used in conventional fluoroscopy?
How is the fluoroscopic image normally displayed?
On a television monitor
What primary factor determines the kVp setting for a fluoroscopy exam?
Body part being examined
What three terms are used for the electronic component that automatically selects the brightness level?
- Automatic brightness control
- Automatic brightness stabilization
- Automatic gain control
What is the principal advantage of the image-intensified fluoroscopy over earlier versions?
Increased image brightness
Compare characteristics of and cones located in the human eye.
Cones- In center area of retina, Less sensitive to light, Primarily daylight vision, Can perceive small objects
Rods-On periphery of retina, Sensitive to low light levels, Used in night vision, Less capable of perceiving small objects, Less capable of detecting differences in brightness levels, Color blind
Regarding fluoroscopic technique, what determines the brightness of an image?
In conventional image-intensified fluoroscopy, what general technique is used?
List and describe the five image intensifier tube components?
- 1) Input phosphor-Cesium Iodide, Converts x-rays into visible light
- 2). Photocathode- Bonded to input phosphor, Emits electrons when illuminated, # of electrons controlled by x-ray beam & light intensity.
- 3). Electric focusing lenses- Focuses electrons toward anode, Electrons arrive w/high energy & minified image
- 4). Anode- Circular plate w/hole in middle, Directs electrons to output phosphor
- 5). Output Phosphor- Converts electrons back to light, much brighter than original light
What is flux gain?
Ratio of number of light photons at output phosphor to the number of x-rays striking the input phosphor .
What is minification gain?
Ratio of square of input phosphor diameter to square of output phosphor diameter.
What is brightness gain?
Ability of image intensifier to increase the illumination level of the image; varies from 5000-30,000 light photons; decreases with age increasing patient dose; product of flux gain times magnification control.
What is the conversion factor?
Ratio of illumination intensity at output phosphor to intensity striking input phosphor; normally 0.01 times the brightness control.
Explain the concept of multiplied image intensifiers?
Has capability of more than one focusing point-normally two or three. Most conventional image intensifiers and all digital intensifiers are multified. When going from a large field, the focal point is moved out reducing FOV and magnifying image. Results in dimmer image that is adjusted by the automatic brightness control thus increasing spatial resolution and contrast resolution but increasing patient dose as well. Only the central region of the input phosphor is used during magnification.
In regard to the television monitoring of fluoroscopic exams, explain how the image intensifier is connected to the monitoring system?
Output phosphor of image intensifier is coupled to television camera tube either by fiber optics or lens coupling.
What is the most prevalent television camera used in fluoroscopy?
What are the three advantages of fluoroscopy television monitoring?
- Brightness and contrast levels can be controlled electronically
- Several observers can view screen at the same time
- Allows for archiving of images in electronic form for later playback and manipulation
Describe the television camera used in fluoroscopy?
Cylinder-shaped containing television camera tube and electromagnetic coils for steering electronic beam. Glass envelope maintains vacuum and provides mechanical support. Internal elements include cathode/electron gun, accelerator grids, target assembly (anode).
Describe the television monitor used in fluoroscopy?
Monitor and camera form close-circuit television system. Has contrast and brightness controls. Cathode ray tube (CRT) is heart of monitor. Video signal received by CRT and modulated by received light intensity. Weakest link of fluoroscopy system because spatial resolution is less than the intensifier.
What two methods are used to record conventional fluoroscopic images?
- Cassette loaded spot film
- Photospot camera