What factors affect subject contrast?

Subject contrast is caused by the range of absorption of radiation by the subject, i.e., the material being radiographed. This is affected by (a) the mass of the subject, including the atomic number and the thickness, and (b) the penetrating power of the radiation source, which is the wavelength of the radiation used.

How would you increase the contrast of a radiographic image?

The viewer of radiographic images can obtain increased contrast simply by increasing the distance between the view box and the radiograph, since this results in more parallel incident light. The authors found a contrast increase of more than 40\% when x-ray film was positioned 4 m from a view box.

What is radiographic contrast controlled by?

If any of these three factors are not correct, the film will be undiagnostic because it will not have the proper level of density or contrast. The mechanism which controls radiographic contrast is the kilovolts peak.

What might a radiographer consider when trying to achieve higher film contrast?

Generating x-rays using a low kilovoltage will generally result in a radiograph with high contrast. This occurs because low energy radiation is more easily attenuated. Therefore, the ratio of photons that are transmitted through a thick and thin area will be greater with low energy radiation.

How does filtration affect contrast?

Our experiments showed that appropriate filtrations could reduce certain low- and high-energy components of X-ray spectra which have limited contributions to image contrast. At the same time, such filtration could improve the contrast-detail detectability, particularly at relatively low kVp and high filtration.

What affects image contrast?

In conventional radiography, the contrast depends on the size of the grains, the development time, the concentration and temperature of the developing solution, and overall film density.

What factors affect radiographic density?

Radiographic Density

• Radiographic density is reflected by radiographic image darkness. In conventional film radiography, it is called “transmitted density” because it is a measure of the light transmitted through the film.
• Change in kVp.
• Change in Source to Object Distance.
• Thickness of the Absorber.

Does kVp control contrast?

kVp also controls the amount of contrast (the difference between whites and blacks on an image) seen on an x-ray. The amount of contrast visible in an image is referred to as gray scale.

How does beam restriction affect contrast?

Beam Restriction and Scatter Radiation In addition to decreasing patient dose, beam-restricting devices reduce the amount of scatter radiation that is produced within the patient, reducing the amount of scatter the IR is exposed to, and thereby increasing the radiographic contrast.

What affects brightness in radiography?

However, there are several factors that affect x-ray image quality. Brightness – intensity of light representing individual pixels in an image. Contrast – differences in brightness between light and dark areas of image.

What factors affect contrast on a radiograph?

Influencing factors can also effect contrast. These include mAs, Focal spot size, anode heel effect, distance, filtration, beam restriction, anatomical part, image receptor, processing, and the use of grids. The 15\% rule. In order to make a visible difference in contrast on a radiograph you must adjust the kVp between 4\%-12\% .

How does kilovoltage affect contrast in radiography?

Contrast control Kilovoltage. Radiographic contrast is dependent on the technical factors of the radiographs taken. The kilovoltage (kV) during the radiographic examination will determine the primary beams’ energy; higher energy effects increased penetrating power.

What is the difference between high and low radiographic contrast?

Radiographic contrast is the density difference between neighboring regions on a plain radiograph. High radiographic contrast is observed in radiographs where density differences are notably distinguished (black to white). Low radiographic contrast is seen on radiographic images where adjacent regions have a low-density difference (black to grey).

What are the possible adverse effects of contrast media?

Awareness of different risk factors and screening for their presence before the use of contrast agents allow for early recognition of adverse reactions and their prompt treatment. The most important adverse effects of contrast media include hypersensitivity reactions, thyroid dysfunction, and contrast-induced nephropathy [3]. Go to: 2.