The Production Of X-Rays And Image Quality

Front 1

The X-ray tube is made of:

Back 1

A pyrex tube surrounding the anode and cathode

Front 2

Tube contains a vacuum preventing:

Back 2

Unwanted interactions during the production ofX-rays.

Front 3

The anode and cathode both have a high tensionelectrical supply:

Back 3

Providing the direct current necessary togenerate the X-rays

Front 4

Pyrex tube is surrounded by oil to:

Back 4

Prevent build-up of heat

Front 5

The Cathode

Back 5

The negativepart of the X-ray tube, and is made up of the filament and the focusingcup.

Front 6

The filament

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Is a small piece of wire made of tungsten that is heated to produceelectrons

Front 7

The focusing cup

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Surrounds the filament and its function is tostream the electrons in a narrow band towards the anode when an exposure ismade

Front 8

The Anode

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The positivepart of the X-ray tube. One of the functions is to helpremove excess heat from the tube

Front 9

The target

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Is the area that the electrons strike in theanode. Is made of tungsten alloy embedded in a copperanode

Front 10

The focalspot

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The area hit by the electrons.

Front 11

This window has a small aluminum filter to:

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Remove any low energy x-rays from the primarybeam, improving its quality.

Front 12

First stage

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‘Preps’ the machine, heating the cathode andstarting the rotation of the anode

Front 13

Wavelength

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Is the distance from the peak of one wave to thepeak of the next

Front 14

Frequency

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Is the number of peaks passing a set point everysecond. Measured in hertz (Hz)

Front 15

Inverse square law

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When electromagnetic radiation is emitted theintensity will decrease as the distance from the source increases

Front 16

kV

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Controls the penetrating power of the primarybeam. Affects the scale of contrast on the image andthe radiographic density. Should be increased as tissue thickness anddensity increased

Front 17

Increasing the kV

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Will cause greater penetration of all tissuesand hence a blacker film

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Too high a kV

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Will over penetrate tissues resulting in a darkimage with few different shades. Low contrast

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Too low a kV

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Will not penetrate the tissues enough which willappear white on a black or dark grey backgroundFragment. High contrast

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mA

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Determines the tube current (quantity ofelectrons produced) and the quantity of x-rays per second in the emergentprimary beam - its intensity

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FFD

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The distance between the focal spot and thesurface of the x-ray film

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Inverse square law film

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States that the intensity of the primary beamprojected onto an x-ray film is reduced to one quarter by doubling the distanceto the x-ray film

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Latitude

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The range of exposures that will ensure adiagnostic image is possible.

Front 24

Density

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Refers to the degree of blackening on theradiograph

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High mAs

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= increased film density

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Low mAs

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= decreased film density

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Contrast

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The difference in density, i.e. degree ofblackening, between two adjacent structures

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Low contrast

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Lots of grey but very little black and white

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High contrast

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Little grey but lots of black and white

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Contrast is influenced by

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Tissuespecific gravity and atomic number. Voltage. Objectshape and thickness. Filmfogging

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Increase in specific gravity and atomic number

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Morex-ray photons being absorbed. A higher voltage will ensure adequate penetrationand an overall increase in contrast.

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Low voltage

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High contrast.

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Increased Voltage

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Amount of contrast increases. A greater range of greys andless black and white.

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Filmfogging

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Results in an overall greyness and a reduction in contrast.This may be due to poor film storage, incorrect processing, scatter radiationor exposure to light.