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Ch.25 Fluoroscopy
Equipment. Chap 25. Flouroscopy
| Question | Answer |
|---|---|
| Who invented the fluoroscope, and in what year? | Thomas A. Edison, 1896. |
| Visualization of vessels is called? | angiography |
| During fluoro, the tube is operated at less than _____mA. | 5mA |
| What is ABC? | Automatic brightness control. Rad can change image brightness level by varying the kVp, mA, or both. |
| Illumination levels are measured in units of | lumen per square meter, or lux |
| Structures of the eye responsible for vision are | rods and cones |
| Light on the eye must first pass through the ____, a transparent covering, then through the _______, which focuses the light. | cornea, lens |
| Between the cornea and lens is the _____, which controls the amount of light. | iris |
| Retina does what? | senses light and converts it to electrical impulses? |
| What is the fovea centralis? | a concentration of cones at the center of the retina |
| Where are rods located? | periphery |
| cones or rods are more sensitive to low light? | rods |
| Rods have a threshold of approx _____, and cones is about ________. | 2 lux, 100 lux. |
| _____ are used for daylight vision, aka _____. | cones, photopic |
| ______ are used for nighttime vision, aka _____. | rods, scotopic |
| _____ perceive small objects better. This is called | cones, visual acuity |
| _______ are better at detecting differences in brightness levels. This is called | cones, contrast perception |
| _______ perceive color | cones |
| Order of eye: | Cornea, Iris, lens, retina. |
| Image intensifier tube was created in ______ by _______. | 1940 by John Colton? |
| _________ receives the x-ray beam and converts it into a visible light image of high intensity. | image intensifier tube |
| x-rays that exit the patient and are incident on the ii tube are transmitted through the glass envelope and interact with the ______. | input phosphor |
| The input phosphor is made of ___________. | cesium iodide (CsI) |
| When an x-ray interacts with the input phosphor, what happens? | its energy is converted into visible light. |
| After the input phosphor, the next element of the ii tube is the ______. | photocathode |
| The photocathode is made of ________. | cesium and antimony compounds |
| The photocathode does what when illuminated by the input phosphor? | emits electrons |
| Photoemission vs thermionic emission? | photoemission is electron emission that follows light stimulation, thermionic is electron mission that follows heat stimulation. |
| The # of electrons emitted by the photocathode is directly proportional to | the intensity of light that reaches it. (consequently, # of electrons emitted is proportional to the intensity of the incident image forming x-ray beam.) |
| ii tube has a potential difference of about ______V across the tube between photocathode and anode. (to accelerate the photoemission e-) | 25,000 Volts |
| The _______ has a hole in the middle for e- to pass to the output phosphor. | anode |
| The anode is made of | zinc cadmium sulfide |
| The ___________ is the site where accelerated e- interact and produce light | output phosphor |
| The engineering aspects of maintaining proper e- travel are called | electron optics. (e- from large cathode end of ii tube must be reduced to small output phosphor) |
| e- from large cathode end of ii tube must be reduced to small output phosphor. Devices responsible for this control are called _________. | electrostatic focusing lenses |
| E- arrive at output phosphor with high kinetic energy and contain the image of the input phosphor in ____ form | minified |
| Each photoelectron that arrives at the output phosphor produces ______-_____ times as many light photons as were necessary to create it. | 50-75x. |
| Ratio of the # of light photons are the output phosphor to the # of x-rays are the input phosphor is the_______. | flux gain. |
| ** Flux gain = | # of output light photons / # of input x-ray photons |
| The ability of the image intensifier to increase the illumination level of the image is called | brightness gain. |
| ** Brightness gain is simply the product of _____ and ______ | the minification gain and the flux gain. (BG = Minification gain x Flux gain) |
| _____________ is the ratio of the square of the diameter of the input phosphor to the square of the diameter of the output phosphor. | minificaiton gain |
| ** Minification gain = | (di/do)^2 (di is diameter of input, do is diameter of output) |
| Output phosphor size is fairly standard at ____ or ___ cm. Input varies from ____-____ cm. | 2.5 or 5. 10-40. |
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ What is the brightness gain for a 17 cm image intensifier tube with a flux gain of 120 and a 2.5 cm output phosphor? | Brightness gain = (17/2.5)^2 x 120. = 46 x 120 = 5520. |
| Brightness gain for most image intensifiers is | 5,000-30,000. (and decreases with tube age and use) |
| Internal scatter radiation can reduce the contrast of image intensifiers through a process called | veiling glare |
| Most image intensifiers are the _________type | multifield. |
| Most popular trifield tube size | 25/17/12 cm. (numeric dimensions refer to the diameter of the input phosphor) |
| In the 25 cm mode, photoelectrons from the entire input phosphor are accelerated to the output phosphor. This creates a brighter or darker image? | brighter |
| When switching from 25 to 17 cm mode, the voltage on the electrostatic focusing lenses increases, this causes the electron focal point to move......... | farther from the output phosphor. |
| Use of smaller dimension of a multifield ii tube always results in a ______ image. | magnified |
| Use of a smaller dimension of a multifield ii tube results in an image with a magnification factor in direct proportion to the | ratio of diameters. (25/17/12 tube operated in the 12 cm mode produces an image that is 25/12=2.1 times larger than the image produced in 25 cm mode) |
| ~~~~~~~~~~~~~~~~~~~~~~~~~ how magnified is the image of a 25/17/12 ii in the 17 mode compared with that produced in the 25 cm mode? | MF= 25/17 = 1.5 magnification. |
| In the magnified mode the minification gain is ______, and _______ photoelectrons are incident on the output phosphor. (a ____ image results) | reduced, fewer. (DIMMER image) |
| To maintain the same level of brightness, (in mag mode..) the x-ray tube mA is ______ by the ABC. | increased. (this increases the pt dose.. better image quality) |
| _________ mode results in better spatial and contrast resolution, and higher patient dose. | magnification mode |
| Portion of any image that results from the periphery of the input phosphor is inherently unfocused and suffers from | vignetting. (reduction of brightness at periphery) |
| Because ONLY the central region of the input phosphor is used in the mag mode, ____________ resolution is improved. | spatial |
| Better spatial resolution is associated with with a higher ______ value. | lp/mm |
| @ what time does fluoro sound an alarm? | 5 min |
| The _____ is the TV camera tube that is most often used in television fluro. | vidicon |
| ________________ converts the light image from the output phosphor of the image intensifier into an electrical signal, that is sent to the _____________, where is is reconstructed as an image on the TV screen. | TELEVISON CAMERA TUBE converts the light image from the output phosphor of the image intensifier into an electrical signal that is sent to the TELEVISION MONITOR, where is is reconstructed as an image on the TV screen |
| Significant advantage of tv monitoring is that _______ and _______ can be controlled electronically. | brightness level and contrast. (also allows for storage of the image for later playback and manipulation) |
| Two methods are used to electronically convert the visible image on the output phosphor of the image intensifier into an electric signal. These are : | thermionic TV camera tube and solid state charge-coupled device (CCD) |
| a TV camera tube or CCD do what? | convert the light signal from the output phosphor to an electronic signal |
| (vidicon TV camera tube) the __________ is a heated filament that supplies a constant e- current by thermionic emission | electron gun |
| (vidicon TV camera tube) the electrons are formed into an e- beam by the ________, which also helps accelerate e- to the anode. | control grid |
| (vidicon TV camera tube) the electron beam is further accelerated and focused by additional ______________. | electrostatic grids |
| (vidicon TV camera tube) the size of the e- beam and its position are controlled by | magnetic coils. (deflection, focusing, alignment coils) |
| (vidicon TV camera tube) At the anode end of the tube, the beam interacts with the target assembly. This consists of what 3 layers? | Window (outside), signal plate (inside of window, thin metal/graphite), target (photoconductive layer). {Light from output phosphor of the ii tube strikes the WINDOW, it is transmitted through the SIGNAL PLATE to the TARGET} |
| The magnitude of the video signal is _____________ to the intensity of light from the output phosphor. | proportional |
| What 2 methods are commonly used to couple the TV camera tube to the ii tube? | bundle of fiberoptics (simplest method, more compact), or Lens coupling. |
| What is the advantage of using fiberoptics as the way to couple the TV camera tube to the ii tube? disadvantage? | It is simpler, more compact, can withstand rough handling. Disadvantage is cannot accommodate additional optics like cine or photospot cameras |
| To accept a cine or photospot camera, ___________ is required. | lens coupling. (a way to couple the TV camera tube to the ii) |
| The video signal is amplified, and is transmitted by cable to the __________________, where it is transformed back into a visible image. | television monitor |
| The Television monitor forms one end of a closed circuit television system. The other end is the _____________ or ___________. | TV camera tube or CCD. |
| The heart of the television monitor is the ____________ or _________. | tv picture tube or the cathode ray tube |
| What is the difference between a TV camera tube and a TV picture tube? | Picture tube is larger, its anode assembly consists of a fluorescent screen and a graphite lining. |
| Video signal receive by the TV picture tube is ____________, that is, its magnitude is directly proportional to the __________ received by the TV camera tube. | modulated. light intensity. (Camera tube is constant not modulated) |
| Different from the TV camera tube, the electron beam of the TV picture tube varies in intensity according to the ___________ of the video signal. | modulation |
| ___________ is a change in a quantity of signal in response to another quantity or signal. | modulation |
| The intensity of the electron beam is modulated by a ________, which is attached to the electron gun. (TV picture tube) | control grid |
| Television image on the monitor is formed in a complex way... | Visible light image of the output phosphor of the ii tube into an electrical signal created by a constant beam in TV camera tube. Video signal then modulates the e- beam of TV PIC tube & transforms that e- beam into image @ fluorescent screen of PIC tube. |
| What electron beam pattern occurs in the TV camera and picture tubes? | Raster pattern |
| The vertical resolution is determined by _______________, the horizontal resolution is determined by ____________. | # of scan lines, bandpass (# of lines per sec that the e- beam can be modulated) |
| The higher the bandpass, the ____________ the horizontal resolution. | better |
| Electron beam begins in the left corner, moves to upper right, then is turned off and returns to the left side. This is the ______ retrace | horizontal |
| Two interlaced television fields form a single _________ | television frame |
| video monitoring uses a rate of ______ frames per second | 30 |
| In the TV __________ tube, as the e- beam reads the optical signal, the signal is erased. In the TV _______ tube, as the e- beam creates the optical signal, it immediately fades. | camera, picture |
| Photospot camera exposes how many frames when activated? | one |
| ___________ requires less pt exposure than is required by the cassette-loaded spot film. | photospot |
| Entrance skin dose (ESD) for an adult averages _________ - _____ during fluoro. This can easily result in a skin dose of ______________. | 30-50 mGyt/min (3-5 R/m). 100 mGyt (10 rad) |
| Federal law states that under normal operation, ESD rate shall not exceed what? | 100 mGyt/min (10 R/min). Interventional Rad is 200 mGyt. |
| Cassette ESD: _______ mR per spot. Photofluoro ESD: ________ mR per spot. | 200. 100. |
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