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fluoroscopy
| Question | Answer |
|---|---|
| What is the primary function of the fluoroscope? | To provide real-time dynamic viewing of atomic structures. |
| Who invented the fluoroscope and in what year? | Thomas A. Edison in 1896. |
| What are dynamic studies in fluoroscopy? | Examinations that show the motion of circulation or the motion of internal structures. |
| What is a spot film in fluoroscopy? | A small static image on a small-format image receptor. |
| What is the typical patient dose during fluoroscopy compared to radiographic examinations? | The patient dose is considerably higher during fluoroscopy. |
| What does automatic brightness control (ABC) do in fluoroscopy? | Automatically varies the kVp and mA to maintain a selected image brightness level. |
| What are illumination levels in fluoroscopy measured in? | Units of lumen per square meter or lux. |
| What is the threshold for rod vision? | Approximately 2 lux. |
| What is the threshold for cone vision? | 100 lux. |
| What type of vision do rods provide? | Night vision, also known as scotopic vision. |
| What type of vision do cones provide? | Daylight vision, also known as photopic vision. |
| What is visual acuity? | The ability to perceive fine detail. |
| What is brightness gain in an image intensifier? | The ability to convert x-ray energy into light energy and increase the brightness of the image. |
| What are the five basic parts of an image intensifier? | Input Phosphor, Photocathode, Electrostatic focusing lenses, Accelerating Anode, Output Phosphor. |
| What material is the input phosphor made of? | Cesium iodide. |
| What is the process called when the photocathode emits electrons in response to light? | Photoemission. |
| What is the function of the accelerating anode in an image intensifier? | Maintains a constant potential of approximately 25 kV to accelerate electrons. |
| What is the output phosphor made of? | Silver activated zinc cadmium sulfide. |
| What is the purpose of the electrostatic focusing lenses in an image intensifier? | To focus the electron stream on the small output phosphor. |
| What is the typical length and diameter of an image intensifier? | Approximately 50 cm in length and 15 to 58 cm in diameter. |
| What is the significance of the fovea centralis in human vision? | It is the center of the retina where cones are concentrated, providing high visual acuity. |
| What is the main advantage of modern image-intensified fluoroscopy? | Increased image brightness. |
| What is the difference between brightness gain and conversion factor? | Brightness gain traditionally refers to the ability to increase image brightness, while conversion factor is a modern term for the same concept. |
| What is the role of the image intensifier in fluoroscopy? | To convert the remnant beam to light, then to electrons, and back to light while increasing light intensity. |
| What is the typical kilovolt peak for a barium enema examination? | 110-120 kVp. |
| What is the typical kilovolt peak for a gallbladder examination? | 65-75 kVp. |
| What does the fluoroscopic chain consist of? | X-ray tube, Image Intensifier, Recording System, Viewing System. |
| What happens to light emitted from the input phosphor? | It exposes the photocathode, which emits electrons in proportion to the light intensity. |
| What is flux gain in image intensification? | Flux gain is the ratio of the number of light photons at the output phosphor to the number of light photons emitted in the input phosphor, indicating the tube's conversion efficiency. |
| How is minification gain defined? | Minification gain is the degree to which the image is made smaller from input phosphor to output phosphor, which increases brightness due to concentration of electrons on a smaller area. |
| What is the formula for calculating minification gain? | Minification gain = (input phosphor diameter)² / (output phosphor diameter)². |
| What is the typical range for input and output phosphor diameters? | Input phosphors range from 10 to 40 cm, while output phosphors are typically 2.5 cm or 5 cm. |
| Define conversion factor in the context of image intensification. | The conversion factor is the luminance at the output phosphor divided by the input exposure rate, measured in cd/m²/mR/s. |
| What is the typical conversion factor range for image intensifiers? | Image intensifiers have conversion factors ranging from 50 to 300, corresponding to brightness gains of 5000 to 30,000. |
| What effect does aging have on image intensifiers? | As image intensifiers age, more radiation is needed to achieve the same output brightness, resulting in increased patient dose. |
| What is veiling glare in image intensification? | Veiling glare is a reduction in image contrast caused by internal scatter radiation, including x-rays, electrons, and light. |
| What is Automatic Brightness Control (ABC)? | ABC maintains the fluoroscopic image's overall appearance by automatically adjusting kVp, mA, or both based on monitored output intensity. |
| What is the principal function of multifield image intensification? | Multifield image intensification provides flexibility in fluoroscopic exams by allowing different field sizes and magnification options. |
| How does the magnification mode affect the image? | In magnification mode, the focal point shifts farther from the output phosphor, resulting in a magnified image but reduced brightness. |
| What is the magnification factor (MF) formula? | Magnification factor (MF) = full-size input diameter / selected input diameter. |
| What is distortion in image intensification? | Distortion is a misrepresentation of size or shape in the image due to inaccurate electron control at the photocathode's periphery. |
| What is noise in fluoroscopy? | Noise is the result of insufficient information to create an image, often caused by inadequate x-ray quantity, leading to a grainy appearance. |
| What viewing system is commonly used today for image intensifier images? | Today, images from the output phosphor are converted to an electric signal and viewed on a television monitor. |
| What is a vidicon camera tube? | A vidicon is a type of camera tube used in fluoroscopy, enclosing an electron gun and photoelectric target assembly. |
| What components are involved in the operation of a vidicon camera tube? | The vidicon camera tube includes a cathode with an electron gun, control grid, and alignment coils to manage the electron beam. |
| How does the electron beam in a vidicon tube operate? | The electron beam is swept back and forth in a raster pattern, approximately 1,000,000 sweeps per second. |
| What is the role of the photoelectric surface in a vidicon tube? | The photoelectric surface converts light from the output phosphor into an electric signal for image processing. |
| What happens to the image brightness when using a smaller input diameter in multifield image intensification? | Using a smaller input diameter reduces minification gain, resulting in fewer photoelectrons at the output phosphor and a dimmer image. |
| What is the significance of adjusting x-ray beam collimation in magnification mode? | Adjusting x-ray beam collimation in magnification mode prevents unnecessary irradiation of tissues not displayed in the image. |
| What is the effect of increased mA during magnification mode? | Increased mA compensates for reduced brightness in magnification mode, leading to a higher patient radiation dose. |
| What is vignetting in image intensification? | Vignetting is the loss of brightness around the periphery of the image, often resulting from distortion. |
| What is the relationship between spatial resolution and magnification? | Magnification improves the ability to see small structures (spatial resolution) but increases patient dose. |
| What is the function of the anode in a Vidicon tube? | The anode acts as a target assembly for the electron beam. |
| What is the purpose of the control grid in a Vidicon tube? | It decelerates and aligns the electron beam for proper interaction with the anode. |
| What happens when the electron beam and light from the output phosphor are incident on the same place? | Electrons are transmitted through the target to the signal plate, creating an electronic signal. |
| How does light intensity affect the electronic signal in a Vidicon tube? | Greater light intensity results in more electrons transmitted, increasing the electronic signal and variations in brightness. |
| What is a Charged-Coupled Device (CCD)? | A light-sensitive semiconducting device that generates and stores an electrical charge proportional to light intensity. |
| What is the role of a fiberoptic bundle in viewing systems? | It couples devices to the image intensifier, allowing light transmission without spot filming. |
| What is the disadvantage of using an optical lens system for image coupling? | It is easier to cause maladjustment of the mirror and lenses, resulting in a blurred image. |
| What are the main components of a television monitor? | Electron gun, control grid, focusing and deflecting coils, anode, and fluorescent screen. |
| How does the electron gun in a television monitor function? | It is modulated by the signal from the camera or CCD and moves in the same pattern as the camera tube. |
| What is the raster pattern in a television monitor? | The electron beam sweeps the screen line by line, creating a television frame. |
| What is a typical resolution for television monitors? | 525-line systems are common, while high-resolution monitors can have 1024 lines/frame. |
| What is the principle behind Liquid Crystal Display (LCD) monitors? | Liquid crystals organize to block or allow light to pass through when an electric current is applied. |
| How do plasma monitors produce visible light? | Gas-filled pixels release ultraviolet radiation when ionized, stimulating a phosphor coating to produce light. |
| What is the function of a cassette spot film in radiography? | It is a static imaging process that allows for multiple exposures on one cassette. |
| What is the exposure rate limit for fluoroscopy under federal law? | The ESD rate shall not exceed 100 mGyt/min under normal operation. |
| What is the purpose of performance monitoring in Automatic Exposure Systems (AES)? | To ensure constant radiation exposure to the input phosphor regardless of patient thickness. |
| What is the role of the medical physicist in quality control for fluoroscopy? | They perform tests and interpretation to ensure equipment performance and patient safety. |
| What is the recommended frequency for operational inspections of radiographic equipment? | At least every six months. |
| What is the significance of the American College of Radiology Technical Standards? | It recommends evaluations and monitoring of 18 aspects of radiographic equipment by a medical physicist. |
| What is the function of the focusing and deflecting coils in a television monitor? | They control the electron beam and direct it to the fluorescent screen. |
| What happens during the horizontal and vertical retrace in a television monitor? | The beam blanks and returns to the left side and top to start the next line of the image. |
| What is the purpose of the signal plate in a Vidicon tube? | It carries the current as an electronic signal to the TV monitor. |
| What is the impact of using a beam-splitting mirror in optical lens systems? | It allows for spot filming by diverting some light to the desired filming device. |
| What is the typical radiation dose required by film cameras or photospot cameras? | They require half the radiation dose of spot-filming systems. |
| What is the role of filters in fluoroscopy quality control? | They determine the adequacy of the automatic brightness stabilization (ABS) system. |
| What is the significance of the input exposure rate measured in Automatic Exposure Systems? | It should be in the range of 0.1 to 0.4 Gya/s for effective performance. |
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