American Registry of Radiologic Technologists (ARRT) Practice Exam

The moire effect in radiography is best described as an aliasing artifact. This phenomenon occurs when a grid is used in conjunction with digital imaging systems, particularly when the grid lines and the pixel structure of the imaging detector do not align properly. The misalignment creates an interference pattern that results in unwanted wavy lines or bands in the image, which can obscure important details and diagnostic information.

This effect is typical in digital radiography because it involves the sampling of data. If the grid frequency is close to the imaging system's sampling frequency, aliasing occurs, leading to the characteristic moire pattern. Understanding this artifact is crucial for radiologic technologists to ensure they can minimize its occurrence and improve the quality of the diagnostic images they produce.

While the other choices mention aspects related to image quality, they do not specifically capture the nature of the moire effect. Film fog refers to unwanted exposure on film leading to a clouded image, while a digital imaging artifact describes any undesirable feature that detracts from the image quality, and a type of exposure error pertains to incorrect settings impacting image exposure. However, these do not specifically define the unique patterning seen with the moire effect.