Anti-scatter grid

Anti-scatter grid

An anti-scatter grid is a device used in radiography to improve the quality of X-ray images. It is designed to reduce the amount of scattered radiation that reaches the X-ray detector, thereby enhancing image contrast and detail.

Diagram of a lead collimator, a component of an anti-scatter grid

Function

The primary function of an anti-scatter grid is to allow primary radiation (the X-rays that pass directly from the X-ray tube to the detector) to pass through while absorbing scattered radiation. Scattered radiation is produced when X-rays interact with matter, such as the patient's body, and are deflected in different directions. This scattered radiation can degrade the quality of the image by reducing contrast.

Construction

Anti-scatter grids are typically constructed from alternating strips of a radiopaque material, such as lead, and a radiolucent material, such as aluminum or plastic. The lead strips are aligned in such a way that they allow the primary X-rays to pass through while absorbing the scattered rays.

Types

There are several types of anti-scatter grids, including:

• Parallel grids: These have lead strips that are parallel to each other. They are simple in design but can cause grid cutoff at the edges of the image.
• Focused grids: These have lead strips that are angled to match the divergence of the X-ray beam. This design minimizes grid cutoff and is commonly used in clinical practice.
• Crossed grids: These consist of two sets of parallel grids placed at right angles to each other. They provide better scatter reduction but require higher exposure.

Usage

Anti-scatter grids are used in various radiographic procedures, particularly those involving thicker body parts, such as the abdomen or chest. They are essential in computed tomography (CT) and mammography to ensure high-quality images.

Limitations

While anti-scatter grids improve image quality, they also increase the required radiation dose to the patient. This is because some of the primary radiation is absorbed by the grid, necessitating a higher exposure to achieve the same image brightness.

Related pages

• Radiography
• X-ray
• Computed tomography
• Mammography