Grid

Grid is a term used in various fields, including mathematics, computing, and geography, to refer to a network of lines that cross each other to form a series of squares or rectangles. In the context of medicine, a grid can refer to a device used in radiology to improve the quality of images by absorbing scattered radiation.

Overview

In radiology, a grid is a device placed between the patient and the X-ray film to absorb scattered radiation, thereby improving image contrast. The grid is made up of thin lead strips separated by radiolucent material such as aluminum or plastic. The lead strips absorb the scattered radiation, while the radiolucent material allows the primary radiation to pass through to the film.

Grids are used in various types of radiographic examinations, including chest radiography, abdominal radiography, and mammography. They are particularly useful in examinations of large or dense body parts, where the amount of scattered radiation is high.

Types of Grids

There are several types of grids used in radiology, including:

• Linear grids: These grids have lead strips that run in one direction. They can be used with the tube angled in the direction of the strips.

• Crossed grids: These grids have lead strips that run in two directions, forming a grid pattern. They cannot be used with the tube angled.

• Focused grids: These grids have lead strips that are angled to match the divergence of the x-ray beam. They must be used at a specific distance from the tube.

• Parallel grids: These grids have lead strips that run parallel to each other. They can be used at any distance from the tube, but they may cause some image distortion.

Grid Ratio

The grid ratio is a measure of the height of the lead strips relative to the distance between them. It is a key factor in determining the amount of scattered radiation that a grid can absorb. Higher grid ratios absorb more scattered radiation, but they also absorb more primary radiation, which can reduce image quality.

Grid Use and Image Quality

The use of a grid can significantly improve image quality in radiographic examinations. However, it also increases the dose of radiation to the patient. Therefore, grids should be used judiciously, taking into account the benefits and risks in each individual case.

See Also

• Radiology
• X-ray
• Radiographic examination

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