The grid factor depends on which characteristics?

• A. Grid ratio and lines per centimetre
• B. Film speed and processing temperature
• C. Tube voltage and current
• D. The age of the radiographic table

Answer: (A)

When a radiographic grid is used, the grid factor tells you how much to increase exposure to compensate for the grid’s attenuation of the primary beam. This depends on how the grid is constructed: the grid ratio, which is the height of the lead strips relative to the width of the spaces between them, directly affects how much primary radiation is absorbed—the higher the ratio, the more absorption, and the larger the grid factor. The lines per centimetre (grid frequency) also influences the amount of primary radiation that can pass through and how efficiently the grid removes scatter, which in turn affects the exposure needed. So both grid ratio and line density determine the grid factor. Choices involving film speed, processing temperature, tube voltage, current, or the age of the radiographic table don’t define how much exposure must be adjusted for the grid’s attenuation.