The Effect of Atomic Number and Mass Density on the Attenuation of X-rays. Boyes, J.
abstract   bibtex   
The interaction between radiation and matter is of prime importance in Diagnostic Radiology. This project examines the interaction between the photons in an x-ray beam and the electrons in target materials of various mass densities and atomic numbers. In the photon energy range used in Diagnostic Radiology, the primary interactions are Compton Scatter and the Photoelectric Effect. The goal of this experiment was to document the attenuation of the x-ray beam by targets of increasing atomic numbers. Ten salts were chosen that collectively exhibited a range of effective atomic numbers from about 7 to 50, and four aqueous solutions were made of each salt. Each of the forty solutions were subjected to x-ray beams using a General Electric CT scanner. It was found that, at low atomic numbers, attenuation was roughly proportional to mass and electron density. As atomic number increased, however, attenuation increased beyond what would be expected from the target’s density. Attenuation per unit mass density increased linearly with effective atomic number, and overall attenuation varied exponentially with effective atomic number. In conclusion, CT numbers are only proportional to the mass and electron density of targets with low atomic numbers. As atomic number increases, the number of photoelectric interactions increases, causing overall attenuation to increase greatly.
@article{boyes_effect_nodate,
	title = {The {Effect} of {Atomic} {Number} and {Mass} {Density} on the {Attenuation} of {X}-rays},
	abstract = {The interaction between radiation and matter is of prime importance in Diagnostic Radiology. This project examines the interaction between the photons in an x-ray beam and the electrons in target materials of various mass densities and atomic numbers. In the photon energy range used in Diagnostic Radiology, the primary interactions are Compton Scatter and the Photoelectric Effect. The goal of this experiment was to document the attenuation of the x-ray beam by targets of increasing atomic numbers. Ten salts were chosen that collectively exhibited a range of effective atomic numbers from about 7 to 50, and four aqueous solutions were made of each salt. Each of the forty solutions were subjected to x-ray beams using a General Electric CT scanner. It was found that, at low atomic numbers, attenuation was roughly proportional to mass and electron density. As atomic number increased, however, attenuation increased beyond what would be expected from the target’s density. Attenuation per unit mass density increased linearly with effective atomic number, and overall attenuation varied exponentially with effective atomic number. In conclusion, CT numbers are only proportional to the mass and electron density of targets with low atomic numbers. As atomic number increases, the number of photoelectric interactions increases, causing overall attenuation to increase greatly.},
	language = {en},
	author = {Boyes, Jeff},
	pages = {4},
}

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