Radiologic Technologist Practice Exam

An increase in patient exposure is likely when which factor is increased?

1. Decreasing mAs

2. Decreasing object-to-imaged distance (OID)

3. Increasing grid ratio

4. Increasing focal spot size

The correct answer is: Increasing grid ratio

Increasing the grid ratio is associated with a higher patient exposure due to the way grids function in radiographic imaging. Grids are used to improve image quality by reducing scatter radiation that reaches the image receptor. When the grid ratio is increased, it effectively enhances the ability of the grid to absorb scattered radiation. However, this also means that more primary radiation is required to penetrate the grid and reach the receptor, leading to an increase in the required technique factors, particularly mAs (milliamperes per second). Consequently, to maintain image quality, the technician must increase the mAs, which directly correlates with higher radiation exposure to the patient. Decreasing mAs would lead to lower radiation exposure, while decreasing OID generally reduces the amount of scatter reaching the image receptor, thereby improving image quality and reducing needed exposure. The focal spot size primarily affects image resolution and does not directly correlate with patient exposure in the way that grid ratio does. Therefore, the increase in grid ratio results in a corresponding increase in primary exposure, making it the factor linked to greater patient exposure.