Physics • How Radiology Works

X-ray attenuation of tissues [thickness, atomic number] for Radiologic Technologists

In x-ray imaging (radiography and CT) the contrast between the tissues in the image is generated by the difference between the x-ray attenuation (influenced by density and atomic number). In this post we demonstrate the material dependence for x-ray attenuation. For all radiographers, radiologic technologists and students understanding the basic principles of x-ray interactions, which […]

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Interactive X-Ray Transmission Calculator for Radiologic Technologists (Beer’s Law Equation)

Calculators, Physics

This is a calculator the transmission, (fraction of the x-ray beam), that will penetrate different thickness of materials such as water, bone, air and lead. This calculator is useful to get a sense of what fraction of the x-ray beam will pass through different objects. The calculator has the option for a few energies of

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Magnification and Blurring Effects for Radiographers and Radiologic Technologists (with Focal Spot Blur Formula)

Physics, X-Ray

Magnification occurs in x-ray imaging because the x-rays are divergent or spread out from the x-ray source. Therefore, the object will appear larger on the detector than the true object size. Magnification in radiography is defined as (Image Size/Object Size) and is equal to the (SID/SOD) which is the source to image distance divided by

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Beam Quality, Beam Quantity (mA, kVp, HVL) for Radiologic Technologist

Physics, CT, X-Ray

Beam Quality describes the shape of the energy spectrum (i.e. the energy distribution of the x-rays) and beam quantity describes the total intensity of the spectrum (i.e. the area under the x-ray spectrum curve). In this post we describe the factors affecting beam quality including: kVp, target material, and pre-patient collimation. We also discuss the

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5 reasons why Gonad Shielding will soon be extinct, and motivations for why it was introduced.

Physics, CT, Dose, X-Ray

The motivation for gonad shielding is to reduce the hereditary specific risks of radiation, and it is still common practice at many institutions. The reasons that shielding will soon be phased out include: hereditary risk in humans has not been demonstrated even at high doses, the radiation doses have reduced greatly from the 1950s (orders

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Radiation Biology Illustrated Introduction [ionization DNA breaks, LD50, stochastic vs deterministic] for Radiologic Technologists

Physics, Dose

The body is composed of individual cells wherein the genetic information is stored in DNA (deoxyribose nucleic acid). This DNA can be damaged by ionizing radiation, i.e. radiation which has sufficient energy to remove electrons from atoms. The DNA damage can be either direct (i.e. the electron hits the DNA directly) or indirect (i.e. the

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X-ray/CT radiation doses [7 anatomies] compared to background radiation for Radiologic Technologists/Radiographers.

Physics, Dose

The radiation dose for x-ray radiography and CT is compared with the background radiation dose levels (average in United States of 3mSv). The different exams Abdomen, Bone, Head and Neck, Chest, Cardiac, and Mammography are presented. For reference the sources of background radiation of cosmic radiation and Radon are presented. Background Radiation Overview To provide

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X-Ray Interactions, Illustrated Summary (Photoelectric, Compton, Coherent) for Radiologic Technologists and Radiographers

Physics, CT, X-Ray

The x-ray interactions are Photoelectric, Compton and Coherent. Photoelectric is mainly responsible for image contrast, Compton contributes to artifacts in the images, and Coherent scattering has little influence in most diagnostic (x-ray/CT) procedures. Overview of the Physics Behind X-Ray Interactions When x-rays interact with the human body during an x-ray exposure, they form an image

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X-Ray Properties (Energy, Wavelength, Inverse Square Law) For Radiologic Technologists

Physics, X-Ray

Basics of x-ray properties for radiographers and radiologic technologists include: wave and particle models for x-rays, relationships between Energy, wavelength and frequency, and 1/R^2 effect. Radiation Radiation is energy emitted/transmitted as a wave or particle that travels through a medium (such as the air or a patient). A brief comparison of the different types of

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X-ray scatter (collimation, kVp, air gap, thickness, anti-scatter grids) factors every technologist should know.

Physics, CT, X-Ray

X-ray scatter due to Compton Scatter generates background haze in x-ray images and there is a desire to reduce the scatter impact on image quality. X-ray scatter depends on several physical factors including: body habitus (increases with increased habitus), kVp, collimation (increases with increased kVp), air gap (decreases with increased air gap), and anti-scatter grids

X-ray scatter (collimation, kVp, air gap, thickness, anti-scatter grids) factors every technologist should know. Read More »