American Registry of Radiologic Technologists (ARRT) Practice Exam

When utilizing an 8:1 grid, the necessary mass (or exposure) for the radiographic procedure is influenced by the grid's ability to absorb scattered radiation. The primary function of a grid is to enhance image quality by reducing the amount of scatter that reaches the imaging plate or detector, resulting in clearer and more defined images.

When a grid is employed, particularly one with an 8:1 ratio, the image receptor is shielded from the effects of scatter, which means that the amount of primary radiation that needs to be directed toward the receptor increases. An 8:1 grid typically requires an increase in exposure in order to compensate for the grid's absorption of some of the useful photons. In practice, using an 8:1 grid can often imply that the necessary mass (or amount of radiation exposure) is approximately multiplied by a factor of four. This multiplier reflects the heightened need for mass to ensure sufficient exposure, which in this case is attributed to the grid’s absorption properties.

Thus, the correct response indicates that the use of an 8:1 grid generally necessitates an increase in exposure mass to maintain adequate image quality, validating why the mass would be multiplied by four.