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Fluoroscopy I

Physics of Image production I

QuestionAnswer
_________ is a _________ radiographic examination which makes possible the visualization of internal organs ___ ______. Fluoroscopy,dynamic, in motion
What device did Thomas A. Edison invent to visualize the motion of internal organs? and when? Fluoroscope, 1896
What does a first generation fluoroscope consist of? x-ray tube, table and fluoroscopic screen
What is first generation fluoroscopy referred to as? Conventional fluoroscopy
What did radiologists have to do when performing conventional fluoroscopy? Dark Adapt their eyes for 20-30 minutes.
How would radiologists dark adapt their eyes? wearing red goggles or sitting in the darkened room 20-30 minutes prior to exam start
How do the red goggles work? The red filters out the blue and green wavelengths which make the rods more sensitive of low levels of illumination.
What protective equipment covered the fluorescent screen so that the radiologist could look at it directly? Lead glass
What are the two types of receptors located in the retina of the eyes? Cones and Rods
What portion of the retina is densely covered with cones? Fovea Centralis
Where is the fovea centralis located within the eye? Posterior portion of the retina
Cones function most efficiently in _____________ ___________ Bright light
Phototopic vision is __________ __________ Daylight vision
Outside the Fovea Centralis, cones are sparsely scattered and used for ________ _______ ______. Daylight Peripheral Vision
Although they are located around the periphery of the retinal there are no _______ in the fovea centralis Rods
Rods funtion best with _____ _______ of illumination. Low Levels
Rods are used primarily for ______ _____ or _______ vision. Night vision, peripheral
Night vision is called ________ _________. scotopic vision
Which light wavelengths are rods most sensitive to? blue and green.
What led to the development of the image intensifier? poor visual acuity, poor abilito detect contrast (shades of gray) and need to produce bright light image for cone vision viewing w/out excessive radiation exposure.
What is an image intensifier? An electronic vaccuum tube that converts the pattern of xray beam to a bright light image
What are the basic components of the image intensifier? Input Phosphor, Photocathode, Electrostatic focusing lens, Accelerating Anode, output phosphor.
What are modern input phosphors made of? Cesium Iodide (CsI)
List the advantages of modern input phosphors to older input phosphors. Increases image quality, decreases phosphor thickness and increases resolution
Older input phosphor screens were made of what material? Zinc Cadmium Sulfide
What results from the Input Phosphor being struck with xrays? Bright Light
What is the Photocathode? A photoemissive material that is on top of the Input Phosphor.
What is the response of the Photocathode to the light from the Input Phosphor? And what is this effect called? it emits electrons. Photoemission.
What is the relationship between the number of electrons produced by the Photocathode and the intensity of light hitting the Photocathode? The more light hits the photocathode, the more electrons are produced.
What prevents a chemical reaction between the PC and IP? Thin transparent layer.
Why are the PC and IP both curved? How does it affect the distance the electrons travel? to prevent focusing distortion. All electrons from pc to op travel same distance.
What are electrostatic focusing lenses? Series of electrically charged electrodes on the inside surface of the tube.
What component of the Image Intensifier focuses the electron beam as it flows toward the OP? Electrostatic focusing lens.
What is the nature of the image when it arrives at the OP? At what point does this happen? inverted and reversed. focal point.
Where is the accelerating anode located? The neck of the tube.
What is the function of the accelerating anode? Accelerates the Electrons toward the OP
What is the difference in voltage between the Accelerating Anode and the PC. AA is 25-35 KV higher in positive direction
What material is the Output Phosphor made of? Zinc Cadmium Sulfide
What is the diameter of the Output Phosphor? 1/2-1 inch.
Describe the size of the image that arrives at the OP from the IP. minified.
Why does the OP produce ~50x's more light than the IP? The electron beam is arriving at the op with high kinetic energy.
T or F. The image from the OP, in the form of light photons, is the same image that was carried to the ip via the remnant x-ray beam. True
Why is video viewing of the fluoroscopic image is advantageous? The image is brighter
What is the purpose of angiography? Visualize vessels
Fluoroscopy normally requires a tube current of ___ to ___ mA 1, 5
In general, during fluoroscopy as compared with radiography what technical factor will be lower? mA
With what type of vision are radiographs viewed? Photopic vision
During a fluoroscopic examination, what are static images obtained on? Spot Film
In a modern fluoroscope, where can the x ray tube located? Either over or under the table
Automatic brightness stabilization (ABS) is designed to compensate for what change during a procedure? patient composition.
Visual acuity is the ability to do what? Perceive fine detail
What is the fluoroscopic system designed to maintain a constant image intensity called? Automatic brightness stabilization (ABS) or Automatic brightness control(ABC)
What does the photocathode do? Converts visible light into electrons
At what stage of image intensified fluoroscopy is the number of image forming photons lowest? Entering the input phosphor
If an image intensifier is described as a 25/12 tube, 25/12 refers to which of the following? The diameter of the input phosphor in centimeters
In a 10/7/5 image intensifier, in what mode is the field of view the largest? 10 mode
When a multifocus image intensifier is operated in the magnification mode where is the focal point relative to when the intensifer is in a normal mode. The focal point is closer to the ip in mag mode.
What is the range of brightness gain for most image intensifiers. 5,000-30,000
What is Photoelectric emission? the emission of electrons from an illuminated surface.
Image intensifier brightness gain increases with increasing what two major factors? Minification Gain and Flux Gain
What is emitted from the output phosphor? Bright Light
The ability of an image intensifier to enhance image illumination is called _________ _______. Brightness Gain
What is the component of the image intensifier responsible for focusing the electron beam? The electrostatic lens
What main factor causes the minification gain of an image intensifier to increase? Increasing the input phosphor size
What changes in image quality result from magnification made? Better spatial and contrast resolution
Reduction in brightness at the perphery of the image is termed ________. Vignetting
Place the following in order: 1. Electric signal to light 2. Electrons-to-light 3. Light-to-electric signal 4. Light-to-electrons 5. X-rays to light 5,4,2,3,1
Why does minification gain happen? The same number of light photons coming off of the ip are compressed to the small area of the op.
What is the size range for input Phosphors 4"-20" in diameter
If an output diameter is not given, what is the assumed size? 1" Diameter
T or F. Flux gain is the ratio of the number of light photons @ OP and the xrays @ the IP True
The further away the Focal Point is from the OP, the more ________ the image is. Magnified
Early image monitoring systems were ____ _____ _____. Which consisted of _____ and _____. Mirror optical systems; mirrors and lenses
What are the disadvantages of Mirror Optical Systems? One viewer system. Significant amount of light loss from OP.
What are the two most commonly used TV cameras? vidicon and plumbicon
What are some advantages of tv monitoring systems? Brightness and contrast adjusted electronically. Several observers at one time. Monitors can be placed outside the area for others to view
TV monitoring allows for storing the ______ on _____ or _______ for future playback. image, disks, tapes
What are the two methods of TV cameral tube coupling? Fiber Optics and Lens system
What's the advantage and disadvatange of fiber optic coupling? small, compact and easy to manipulate tower; cannot accomidate auxiliary imaging equipment.
Lens monitoring system splits the beam to divert image to ______ ______ and __ _______. auxiliary system (spot film camera) and tv camera.
What is the film size for the spot film camera? 105mm
What was the standard cassette size for the spot film recorder? 9 1/2" x 9 1/2"
In the park position the cassette is shielding by ________. Lead
List the 3 reasons why there is a time delay when using the spot film recorder? 1. time required to move cassette into position and make it stationary. 2. Increase mA from the usual low value (.5-5) for fluoro to 200-300 for spot films(increases filament heating). 3. Rotor needs to speed up.
What controls the length of the exposure when taking images with a spot film recorder? phototimer in II
Where does the spot film camera receive its images from? OP via mirrors
T or F the spot film camera can take one to several frames/sec. True
List the advantages of using a spot film camera. less exposure to patient. shorter exposure time. Shorter delay in taking exposure b/c no cassette has to be moved into place.
What is the process of recording fluoscopic images onto a movie camera called? Cinefluorography
What is the film size used in cinefluorography? 16mm or 35mm
Name 2 applications for cinefluorography. Angiography and Cardiac Cath lab
Name and briefly describe the 5 parts of the cine camera. Shutter: opens & closes aperture for light to come in. Apertue: opening for light. Lens: direct narrow light beam to film. Pulldown arm: move film from one frame to the next. Pressure plate: holds film steady.
What is the advantage and disadvantage of using the cine camera? Increases image quality. Increases patient dose.
Created by: aldo.banos
 

 



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