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Related Experiment Video

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Dependence of Laser-induced Breakdown Spectroscopy Results on Pulse Energies and Timing Parameters Using Soil Simulants

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Contrast reduction using energy dependent intensifying screens

G A Shah¹, G Hassam, D L Newman

¹Department of Radiologic Sciences, Kuwait University.

The British Journal of Radiology

|June 1, 1996

Summary

This summary is machine-generated.

Rare earth screens used in X-ray imaging show reduced contrast with increasing beam energy. This occurs because the aluminum disc filters X-rays, leading to an effective gamma lower than individual film-screen gammas.

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Phase Contrast and Differential Interference Contrast DIC Microscopy

Phase Contrast and Differential Interference Contrast DIC Microscopy

Published on: August 6, 2008

Area of Science:

Medical Imaging
Radiography
Physics

Background:

Intensifying screen speed, particularly with rare earth screens, is known to increase with beam energy.
Measured contrast in radiography can deviate from theoretical calculations based on film-screen properties.

Purpose of the Study:

To investigate the discrepancy between measured and calculated contrast for an aluminum disc using rare earth screens across a range of X-ray tube potentials.
To explain the observed contrast reduction effect and develop a model for accurate contrast prediction.

Main Methods:

Utilized an aluminum disc as a test object with optical densities in the linear region of the characteristic curve.
Employed a film-screen combination with rare earth intensifying screens.
Varied X-ray tube potentials from 40 to 140 kVp.

Main Results:

Measured contrast was consistently lower than calculated contrast across all tested tube potentials (40-140 kVp).
The contrast reduction is attributed to the filtering action of the aluminum disc, which alters the effective beam energy.
An 'effective gamma,' lower than the individual gammas of the film-screen combination at different energies, was identified as the key factor.

Conclusions:

The filtering effect of objects in radiography leads to exposure of the film-screen system to X-rays of varying effective energies.
An effective gamma, which accounts for the different speeds of the film-screen combination at these varying energies, accurately predicts measured contrast.
Accurate contrast calculation in radiography requires considering the effective gamma, not just the standard gamma of the film-screen combination.