Fluoroscopy

What is fluoroscopy?

Sequence of images taken in quick succession to obtain a moving image

What is a scintillator?

Material that emits visible light when it absorbs radiation

How is emitted visible light converted into images?

Light flashes are captured by a photodetector which converts them into electrical signal

What are the two modifications of image intensifiers in fluoroscopy?

Higher heat storage

Faster cooling rate

What two filters are used in fluoroscopy?

Copper filter

AERC controlling brightness

What is the function of wedge filters in fluoroscopy?

Take away the glare from anatomical structures with different attenuations

What are the four image principle components in fluoroscopy?

Input screen

Electron optics

Output screen

Vacuum housing

What are the three components of the input screen?

Input window

Input phosphor

Photocathode

What is the structure of the input window?

Curved titanium sheet

Protects electronics

What is the function of the input phosphor?

Sodium activated caesium iodide acts as a scintillator converting x-rays into light

What is the function of the photocathode?

Converts light photons into electrons

What is the function of the electron optics?

Creates electrical field to add energy to emitted photons

What is the function of the anode?

Accelerates electrons

What is the function of the focusing electrodes?

Focuses electrons to the output screen

What is the structure of the output screen/phosphor?

Layer of silver activated zinc cadmium sulphide coated onto a glass or fibre optic output layer

What is the function of the output screen/phosphor?

Converts electrons into light photons

What are the two factors that intensify the output image?

Electron acceleration

Image magnification

What is the function of the output window?

Where light photons are released

What is the function of the vacuum envelope?

Provide an unobstructed path for electrons to not interact with other molecules

What is an optical distributor?

Couples image intensifier to video camera using optical lens system or fibre optic plate

What are flat panel detectors?

What are dexels?

Individual detector elements arranged in a square or rectangular area

What are the three parts of the dexels?

Light sensitive area

Detector element

Electronic components

What is indirect x ray conversion in flat panel detectors?

X-rays hit a scintillator which changes X-rays into light and then into electrical signal

What is direct x-ray conversion in flat panel detectors?

X-rays hot amorphous selenium layer changing them into electrical charge

What are the two components of a dexel?

Capacitor

Transistor

What is the function of a capacitor in a dexel?

Stores signal as electrical charge

What is the function of a transistor in a dexel?

Serves as a switch

What are the three components of an electronic switch in a thin film transistor?

Gate

Source/photodiode

Drain

What is the purpose of the automatic exposure rate control?

Deliver constant x ray intensity to the receptor and automatically adjusts X-ray factors, focal spot and beam filtration to obtain optimal signal

What are the three modes in AERC which determine allowable dose?

Minimum patient dose rate

Standard patient dose rate

High patient dose rate

What is the pulse rate?

Number of X-ray pulses per second

What is the purpose of the pulse rate?

Reduces radiation dose compared to continuous exposure

What are low pulse rates and what are they used for?

3-7 pps

Barium swallow

What are high pulse rates and what are they used for?

15-30 pops

Cardiac pacing

What is frame rate?

Number of images displayed per second can differ from pulse rate if processed differently

What is the relationship between brightness and magnification in image intensifiers?

Brightness gain decreases as magnification increases

How do the AERC compensate for low signal?

Increases x ray exposure rate

What is fluoroscopy mode?

Real time imaging

Not recorded

Low dose

What is fluorography?

Uses pulsed radiographic mode to record relevant temporal sequences

What are the five components of modern fluoroscopic systems?

Flat panel detector

Noise reduction image processing

Zoom and roam

Auto/manual contrast co tell

Last image hold

What are three image processing techniques in fluoroscopy?

Digital subtraction angiography

Road mapping

Ct acquisition