What happens to the radiographic image when the object film distance is increased?

What happens to the radiographic image when the object film distance is increased?

When the source to object distance increases, the intensity of the x-ray beam decreases following the inverse square law. This will result in decrease in the intensity of the beam reaching the object, and this results in a decrease in image density (Figure 4).

How does distance affect image quality in the radiograph?

The source image receptor distance (SID), is the distance of the tube from the image receptor, affecting magnification. The greater the SID, the less magnification the image will suffer.

Why should the object tooth be as close to the image receptor as possible?

The object in this principle refers to the tooth or structures being radiographed. Placing the object close to the receptor reduces magnification and improves image sharpness.

What causes distortion in radiography?

Size distortion is magnifying the anatomical structure and is usually caused by an increased object-to-image receptor distance or decreased distance between the source of radiation and the image receptor. This phenomenon causes the object to look larger than it is in reality.

Which of the following factors will affect the definition of the radiographic image?

The radiographic contrast depends on the following three factors: Subject Contrast: it refers to the difference in the intensity transmitted through the different parts of an object. Radiation quality or kVp: it has a great effect on subject contrast. A lower kVp will make the x-ray beam less penetrating.

Why are radiographic images magnified?

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.

What are the factors affecting radiographic image quality?

Acquisition geometry-Image acquisition geometric factors affecting image quality include a source to image receptor distance, orientation, the amount of magnification, and size of the focal spot.

What factors affect radiographic quality?

Various factors affect the diagnostic quality of radiographs: overexposure, underexposure, and poor positioning (these three factors can be controlled by the radiographer or medical imaging scientist); motion by the patient (from the patient’s condition); and processing conditions and x-ray machine (equipment) …

How are radiographic images formed in computed radiography?

Imaging plates are inserted in a radiographic table’s cassette holder and images are acquired using the x-ray system. When exposed to x-rays, electrons in the phosphor plate are excited into a higher energy state, forming a latent image. An image reader scans the phosphor plate with a laser spot.

What does computed radiography use as its image receptor?

Computed radiography (CR) is the use of photostimulable phosphor as an image receptor. The image receptor is held in a similar casing (cassette) to that of the traditional film screen.

What is radiographic image distortion?

It refers to the non-proportional increase in the dimensions of a radiographed object relative to the actual dimensions of that object. It can be seen when there is a change in the angle of the incidence x-ray beam or when the receptor is not parallel to the object (Figure 10).

What causes distortion on a film?

Perspective distortion is influenced by the relationship between two factors: the angle of view at which the image is captured by the camera and the angle of view at which the photograph of the subject is presented or viewed.

When is the radiographic density of an image optimum?

When the radiographic density is optimum, the image is both dark enough and light enough for you to see the anatomic details clearly on the viewbox. In conventional film / screen system, density is controlled by the exposure factors, primarily the mAs.

What causes shape distortion in a radiographic image?

When the SID is shorter, the rays that define the subject are those that diverge at a greater angle, increasing the magnification. The closer the object to the receptor, the less magnification there will be. Shape distortion is the result of unequal magnification of various parts of the subject.

How is the visibility of a radiographic image determined?

The more exposure received by a specific portion of the image receptor, the darker that portion of the image will be. The visibility of the radiographic image depends on two factors: the overall blackness of the image and the differences in blackness between the various portions of the image.

What is the definition of magnification in radiography?

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 the source to object distance. Table Of Contents Magnification