Which factors influence the occurrence and severity of deterministic effects such as erythema or cataracts?

• A. Dose magnitude, dose rate, exposure duration, and tissue sensitivity.
• B. Thresholds only.
• C. Dose rate and tissue type only.
• D. Exposure duration only.

Answer: (A)

Deterministic effects are tissue reactions that have a threshold, and once that threshold is surpassed, the damage and its severity grow with how the dose is delivered and how sensitive the tissue is. The total amount of energy absorbed (the dose magnitude) sets whether you cross that threshold at all and, after crossing it, larger doses produce more severe damage. How fast that dose is delivered (the dose rate) matters because cells have limited time to repair between events; a higher dose rate delivers energy quickly, leaving less opportunity for repair and tending to lower the threshold and worsen the reaction for a given total dose. The exposure duration also influences outcomes by affecting how the dose is distributed over time; spreading the same total dose over a longer period (lower dose rate) generally allows more repair and reduces severity, while delivering it in a short, intense burst increases severity. Finally, tissue sensitivity dictates how much dose is needed to trigger a reaction and how severe that reaction will be; some tissues, like the eye lens, are especially radiosensitive, so even smaller doses can lead to cataracts, whereas others may require higher doses to produce erythema.