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Physics Ch21
T2
| Question | Answer |
|---|---|
| The flouroscope is used primarly for ___ studies. | dynamic |
| The flouroscope is used for examination of ___ and ___. | moving internal structures and fluids. |
| Flouroscopy is actually a routine xray examination except for its application in the visualization of vessels, called | Angiography |
| Thamas A Edison invented the flouroscope in | 1896 |
| During flouroscopy, the radiologist views a continuous image of the motion of ____ while the xray tube is energized. | internal structures |
| ___ is a small static image on a small format image receptor | Spot Film |
| Angiography is now referred to as | interventional radiology |
| During flouroscopy, the xray tube is operated at less than | 5 mA |
| The kVp of operation depends entirely on | the section of the body that is being examined |
| Flouroscopic equipment allows the radiologist to select an image | brightness level. (maintained automatically by varying the kVp, the mA, or sometimes both) |
| The ability to select the image brightness level | Automatic Brightness Control (ABC) |
| The principal advantage of image intensified flouroscopy over earlier types of flouroscopy is | increased image brightness. |
| Illumination levels are measured in | Lumen per quare meter OR Lux |
| Radiographs are visualized under illumination levels of | 100 to 1000 Lux |
| The structures in the eye that are responsible for the sensation of vision are called __ and __ | rods and cones |
| Light incident on the eye must first pass through the __, a transparent protective covering, and then through the __, where the light is focused onto the ___ | Cornea, Lens, Retina |
| Between the cornea and the lens is the | Iris |
| Iris behaves similarly to the diaphragm of a photographic camera in | controlling the amount of light that is admitted to the eye. |
| Rods and cones are small structures; more than ____ of them are found per square millimeter of retina | 100,000 |
| The CONES are concentrated at the center of the retina in an area called the | fovea centralis |
| Rods are most numerous on the | periphery of the retina |
| No RODS are found at the fovea cetralis | true |
| Rods are sensitive to low light levels, approx 2 lux | Cones respond to intense light levels, approx 100 lux |
| Cones are used primarily for daylight vision called | Phototopic Vision |
| Rods are used for night vision called | Scoptopic Vision |
| Cones perceive small objects much better than rods do. This ability to percieve fine detail is called | Visual Acuity |
| Cones are also much better at detecting differences in brightness levels. This property of vision is called | Contrast Perception |
| Cones percieve color and rods are essentially color blind | True |
| The brightness of the flouroscopic image depends primarily on the __, __ and ___ | anatomy that is being examined, the kVp, and the mA |
| Xrays that exit the pt and are incident on the image intensifier tube are transmitted through the glass envelope and interact with the | input phosphor (CsI) |
| When an xray interacts with the input phosphor, its energy is converted into | visible light |
| The CsI crystals are grown as tiny needles and are tightly packed in a layer of approx ___. Each Crystal is approx __ in diameter | 300 um, 5 um |
| CsI crystals result in microlight pipes with little ___ and improved ___ ___ | dispersion, spatial resolution |
| The Photocathode is bonded directly to the input phosphor with a thin | transparent adhesive layer |
| The photocathode emits electrons when illuminated by the | input phosphor |
| Photoemission is electron emission that follows | light stimulation |
| The number of electrons emitted by the photocathodeis directly proportional to the | intensity of the light that reaches it |
| The number of electrons emitted by the photocathode is proportional to the | intensity of the incident image forming xray beam |
| The image intensifier tube is approx ___ long | 50cm |
| A potential difference of about ____ is maintained across the tube between __ and __ so that electrons produced by photoemission will be accelerated to the anode. | 25,000 V, photocathode and anode |
| The anode is a circular plate with a hole in the middle though which electrons pass to | Output Phosphor (zinc cadmium sulfide) |
| The output phosphor is the site where | electrons interact and produce light |
| The devices responsible for this control, calle ___ ___ __, are located along the lenghth of the image intensifier tube | Electrostatic focusing lenses |
| Each photoelectron that arrives at the output phosphor produces __ to __ times as many light photons as were necessary to create it | 50-75 times |
| This ratio of the number of light photons at the output phosphor to the number of xrays at the input phosphor is the | Flux gain |
| The ability of the image inensfier to increase the illumination level of the image is called its | brightness gain |
| The brightness gain is simply the product of the | minification gain and the flux gain |
| Output phosphor size is fairly standard at | 2.5 to 5cm |
| Input phosphor size varies from __ to __ and is used to identify image intensifier tubes | 10-35cm |
| The brightness gain of most image intensifiers is __ to ___ and it decreases with tube age and use | 5,000 to 30,000 |
| The conversion factor is approx ___ times the brightness gain | 0.01 |
| Image intensifiers have conversion factors of __ to ___. These correspond to brightness gains of ___ to ___ | 50 to 300, 5000 to 30,000 |
| The spot film camera uses ___ film | 105mm |
| The ___ ___ is used almost exclusively in cardiac catheterization | cineradiography camera |
| The internal scatter radiation in the form of xrays, electrons and particularly light can reduce the contrast of image intesifier tubes through a process called | Veiling glare |
| A veiling glare signal is produced ___ a lead disc that is positioned on the input phosphor | behind |
| The numeric dimensions refer to the ___ of the input phosphor of the image intensifier tube | diameter |
| Use of the smaller dimension of a multified image intensifier tube always results in a magnified image, with a magnification factor in ____ ___ to the ratio of the diamters | Direct Proportion |
| To maintain the same level of brightness, the xray tube mA is increased by the ABC, which increases the | pt dose |
| The pt dose is higher bc more xrays per unit area are required to form the image. This results in lower noise and improved | contrast resolution. |
| Magnification Mode results in | Better spatial resolution, Better contrast resolution, Higher pt dose |
| The portion of any image that results from the periphery of the input phosphor is inherently unfocused and suffers from | vignetting, reduction in brightness at the periphery of the image |
| BC only the central region of the input phosphor is used in the magnification mode, __ ___ is also improved | spatial resolution |
| Internal elements include the cathode, its __, assorted ___ ___, and a ___ __ that serves as an anode | electro gun, electrostatic grids, target assembly |
| The electron gun is a heated filament that supplies a constant electron current by | thermionic emission |
| The size of the electron beam and its position are controlled by external electromagnetic coils known as | deflection coils, focusing coils, and alignment coils |
| Coated on the inside of the window is a thin layer of metal or graphite called | the signal plate |
| Antimony trisulfide is photoconductive because, | when illuminated, it conducts electrons; when dark, it behaves as an insulator |
| The magnitude of the video signal is proportional to | the intensity of light |
| The simplest method to couple the tv camera to the image intensifier tube is to use a bundle of | Fiber Optics |
| Advantage of Fiber Optic coupling | its compact assembly makes it easy to move the image intensifier tower |
| The principal disadvantage of the Fiber Optic coupling | it cannot accomodate the additional optics required for devices such as cine or photospot cameras. |
| The __ __ accepts light from the output phosphor and verts it into a __ __ | objective lens, parallel beam |
| When an image is recorded on film, this beam is interrupted by a __ __ __ so that only a portion is transmitted to the tv camera | beam splitting mirror |
| These __ __ are the most critical elements in the optical chain in terms of alignment | camera lenses |
| The heart of the tv monitor is the | television picture tube or the cathode ray tube (CRT) |
| The video signal received by the picture tube is __, its magnitudedirectly proportional to the light intensity received by the tv camera tube. | modulated |
| The intensity of the electron beam is modulated by a __ __, which is attached to the electron gun | control grid |
| The movement of the electron beams produce a __ __ on the screen of a tv picture tube | raster pattern |
| The electron beam begins in the upper left corner of the screen and moves to the upper right corner creating a line of varying intensity of light as it movies called | active trace |
| The electron beam is ___ or turned off and it returns to the left side of the screen. This is __ __ | blanked, horizontal trace |
| Video monitoring uses a rate of __ frames per second | 30 |
| Standard broadcast and closed circuit televisions are called ___ line systems bc they use ___ of active trace per frame | 525-line |
| Other special purpose systems have ___ or ___ lines per frame and therefore have better spatial resolution | 875, 1024 |
| The conventional __-___ __ __ is one item that is used with image-intensified flouroscopes | cassette-loaded spot film |
| The __ __ receives its image from the output phosphor of the image intensifier tube and therefore requires less pt exposure than is required by the cassette-loaded spot film | photospot camera |
| The photospot camera uses film sizes of __ and ___. | 70 and 105mm |
| Larger film format results in better image quality but at increased pt dose. T/F | True |
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Darla1083