In normal fluoroscopy mode, how much exposure time is needed to induce early transient erythema?

To induce early transient erythema during fluoroscopy, a significant amount of exposure time to radiation is required. Early transient erythema is a radiological effect characterized by a temporary reddening of the skin due to radiation exposure. This effect typically occurs after a threshold dose of ionizing radiation has been absorbed by the skin.

In general, the time required to induce this erythema can vary depending on the dose rate of the fluoroscopy equipment being used, but in this case, the option that specifies 1 hour and 42 minutes aligns closely with the known data indicating that a longer exposure time is necessary to reach the required dose threshold for producing such an effect.

The other options suggest much shorter time intervals, which are generally insufficient for inducing early transient erythema. Radionuclide exposures at these shorter durations would typically be associated with much lower skin dose levels, thereby not reaching the threshold necessary for the visible effects of erythema. Therefore, the correct answer reflects the appropriate exposure duration needed to observe early transient erythema, emphasizing the importance of understanding dose-response relationships in radiological practice.