The light intensity of the output phosphor is measured in what units?

The light intensity of the output phosphor in fluoroscopy systems is measured in candelas, which are abbreviated as "cd." The candela is a basic unit of photometry in the International System of Units (SI) that quantifies the amount of light emitted by a source in a particular direction. It is defined based on the luminous intensity of a light source that emits monochromatic radiation at a frequency of 540 terahertz with a radiant intensity of 1/683 watt per steradian.

Using candelas as the unit of measure is crucial in evaluating the performance of imaging systems, as it provides a standardized way to quantify how much light is produced by the output phosphor and subsequently impacts the image quality. This is particularly important in medical imaging, where adequate light output is essential for accurate diagnostics and safety.

The other units mentioned are not appropriate for measuring light intensity in this context. Lumens are a measure of luminous flux, which is different from measuring the intensity of light in a specific direction. Roentgens are units used to measure exposure to ionizing radiation, and do not pertain to the measurement of light intensity. Therefore, the use of candelas for measuring light output from the phosphor is the correct choice