DR: Fluoroscopy Vocab

Image Intensifier

electronic vacuum tube that amplifies the brightness of the fluoroscopic image

Input Screen

cesium iodine phosphor coated onto a curved surface of glass, titanium, or steel. Converts incident xray to light

Photocathode

device made of photoemissive metals (cesium and anitomy compounds) that absorbs light and emits electrons in a process called photoemission (signal is amplified in this process)

Electrostatic Lenses

series of bands or rings of metal which have varying positive voltages. These bands pull the elections across the tube toward the output phosphor (accelerate and focus electron stream)

Accelerating Anode

small ring of metal located in neck of the ii. Device has a positive charge that accelerates electrons across ii tube causing them to strike output screen with 50-75x more kinetic energy than they had leaving the photocathode. Hole in center allows electrons to pass through anode to output screen

Output Screen

Glass base coated with zinc cadmium sulfide phosphor which accepts electrons and emits green light. Only 1"

Minification Gain

gain in brightness due to energy from large input screen being compressed to very small output screen

Total Brightness Gain

minification gain x flux gain

Conversion Efficiency

a ratio of the intensity of output phosphor to input exposure rate. Intensity output phosphor/mR per sec at input screen

ABC (automatic brightness control)

maintains image brightness by automatically adjusting exposure factors (adjusts technical factors as tissue thickness and density change)

Magnification Mode

Increasing the voltage supplied to focusing lenses moves focal point closer to input screen, which magnifies the image at the output screen. This is accompanied by using the ii in the smallest mode. Resolution improves, but the patient dose also increases. Image may be magnified between 1.5 to 4 times its original size

Quantum Mottle

grainy image due to insufficient radiation

Coupling Device

devices that convert light from output screen to electrons, which can then be sent on to viewing devices. CCD/CMOS/Vidicon and plumbicon tubes are all coupling devices

CCD (charge coupled device)

couples output screen to viewing devices. A flat, compact light sensing device that accepts light and converts it to electrons. More sensitive than video tubes, operate at lower voltages, acceptable resolution, not as fragile. More commonly used than CMOS (better quality)

CMOS (complimentary metal-oxide semi conductor)

can be used instead of CCD to convert light to electrons at the output screen. (cheaper than CCD, uses less power, but bad quality)

TV Camera Tube

Vidicon and Plumbicon Tubes (cathode xray tubes that accept light and emit electrons. Had been used at output screen to convert signal to electrons which can then be sent on to viewing devices

Flux Gain

Increase in brightness due to the acceleration of electrons across the ii tube. Increase in light photons due to conversion efficiency of the output screen

Veiling Glare

distortion caused by light scatter at the output screen that adds background signal degrading contrast

Pincushion Distortion

Type of distortion where the outer portion of image is magnified more than central portion because the input screen is curved and the output screen is flat

Vignetting

type of image distortion. Brightness is greater at the center of the image and falls off toward the edges. Occurs as a consequence of pincushion distortion, or from scattered light near the coupling device

Pulsed Fluoro

exposure is pulsed at specific number of exposures per second, rather than a continuous screen (digital flour), which saves patient dose

Last Image Hold

after a short exposure, a continuous image is held on the viewing monitor using digital memory capabilities. This minimizes exposure and reduces patient dose

Multi-field Intensifier

Intensifies with more than one field of view selection (size of inout screen). Dualmode has two selections (7/10), trimmed has three options (6/7/9)