Final answer:
In fluoroscopy, a larger beam size does not exclusively determine image brightness, but it generally provides more photons for image formation. Other factors like detector sensitivity also influence brightness.
Step-by-step explanation:
The question relates to the influence of beam size on the brightness of a fluoroscopic image. In fluoroscopy, a larger beam size generally means that more photons are available to create the image.
However, brightness is not solely determined by beam size; it also depends on other factors such as the sensitivity of the fluoroscopic detector and the settings used. The NA (numerical aperture) mentioned refers to the ability of a lens in a microscope to gather light; a larger NA means a larger cone of light can enter, collecting more diffraction modes and thus providing more information to form a clearer image with higher resolving power.
The fluoroscopic image will be brighter with a larger beam size. When using a larger beam size in fluoroscopy, more X-ray photons are allowed through, resulting in a higher intensity of the image. This increased intensity makes the image appear brighter.