A sharp difference between the light and dark areas of a radiographic image is termed:

Contrast is the difference in density or the degree of grayness between areas of the radiographic image.7 The radiographic contrast depends on the following three factors:

Inhaltsverzeichnis Show

Cited by (0)
What refers to how sharp a light or dark area is differentiated?
What term describes the degree of differences between light and dark areas visualized on a displayed image?
What is the difference between high and low contrast radiography?
What refers to the portion of a processed radiograph that is dark or black?

Subject Contrast: it refers to the difference in the intensity transmitted through the different parts of an object. For example, in an intraoral radiograph, the enamel will attenuate x-rays more than dentin. Subject contrast is affected by the following factors:

Thickness difference: when two different thicknesses of the same material attenuate an x-ray beam, the thicker part will attenuate more x-rays than the thinner part. 1,4,5,12
Density difference: this is also known as the mass per unit volume. It is the most critical factor contributing to subject contrast. A higher density material will attenuate more x-rays than a lower density material.5,6,10,11
Atomic number difference: A higher atomic number material will attenuate more x-rays than a lower atomic number material.2,6,7
Radiation quality or kVp: this has a significant effect on subject contrast. A lower kVp will make the x-ray beam less penetrating. It will result in a more substantial difference in attenuation between the different parts of the subject, leading to higher contrast. A higher kVp will make the x-ray beam more penetrating. It will also result in less difference in attenuation between the different parts of the subject, leading to lower contrast.1,3,4,12

Receptor Contrast: It refers to a receptor's ability to adequately show the information that the photons transmitted through the subject. 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.2,4,7,12As there is limited usage of conventional film, we will not discuss the details of these factors. In digital imaging, contrast depends on the bit-depth of the receptor. Bit-depth refers to the number of possible grey values stored in an image. The higher the bit-depth, the more gray values it can show. A 1-bit image can only show two colors, black and white. 1-bit can only store one of two values, 0 (white) and 1 (black). An 8-bit image can store 256 possible gray values, while a 12-bit image can display 4096 gray values.1,4,9

Factors that Affect Radiographic Contrast: Scattered radiation will increase the image noise and decrease the radiographic image's contrast. Radiographic collimation can reduce the amount of scattered radiation and improve the radiographic contrast.1,4,7,8

PDFView PDF

Under a Creative Commons license

Open access

Abstract

Chest X-rays are one of the most commonly performed procedures for diagnosing conditions affecting the chest and its contents. It's also represents the change of actual human body to compare the image produced by using different parameters. And comparing the image characteristics of a particular x-ray system with different techniques. The aim of this experiment is to obtain the best quality radiograph by evaluating the optimum parameters such as kVp, mA, exposure time, and distance associated with the film characteristic and to find the difference in optical density (OD) of air stepwedge with different thicknesses. The comparison of the image produced in terms of exposure assessment was made by using the Toshiba KXO 50R X-ray Machine. The RMI Radiographic Chest Phantom, Model 170B, was used as the subject matter in this experiment. Radiographic film KONICA MG-SR PLUS, which is green-sensitive film, was used and inserted into a cassette. It was placed right below the RMI Radiographic Chest Phantom, Model 170B and then was exposed by using different kVp, which were 60, 70, and 80 kVp with 2, 2.5, 3.2, and 4 mAs for each kVp. The source-to-image distance, which was 183 cm, was kept constant in this study. The film was then processed by using an automatic processor in the darkroom. From the observations, 80 kVp with 2 mAs provides a better image quality as compared to others, and the optical density (OD) of air stepwedge increases with increasing thickness.

Keywords

X-ray films

Optical density (OD)

RMI Radiographic, and Chest Phantom

Cited by (0)

What refers to how sharp a light or dark area is differentiated?

Contrast. how sharply dark and light areas are differentiated or separated on an image; the difference in the degrees of blackness between adjacent areas on a dental radiograph. high contrast. a term describing an image with many very dark areas and very light areas and few shades of gray. low contrast.

What term describes the degree of differences between light and dark areas visualized on a displayed image?

The amount of contrast visible in an image is referred to as gray scale. - If an image has high contrast, there will be white and black areas on the film, but very few grays in between. - When a film has low contrast, there are numerous shades of grays ranging from very light to very dark.

What is the difference between high and low contrast radiography?

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 refers to the portion of a processed radiograph that is dark or black?

Radiolucent: Radiolucent refers to that portion of a processed radiograph that is dark or black. A structure that appears radiolucent on a radiograph lacks density and permits the passage of the X-ray beam with little or no resistance.