During a prolonged barium enema under fluoroscopy the radiologist asks for ongoing skin injury risk assessment, the table display shows fluoroscopy time, dose rate, cumulative air kerma, and DAP, and the patient has had prior therapeutic radiation. Which dose monitoring indicator should the radiographer track to estimate peak skin dose?

Cumulative air kerma at the reference point is correct because it accumulates incident air kerma corrected for distance and approximates energy delivered to the small skin area where the beam enters, correlating best with deterministic skin effects such as erythema during prolonged fluoroscopy. The dose-area product approach fails because DAP integrates dose over total beam area and reflects overall stochastic energy imparted, so a tightly collimated high-skin-dose field can show low DAP while skin is injured. The instantaneous dose rate approach fails because rate describes intensity at one moment and does not accumulate, so brief high rates may be safe and prolonged low rates may still injure skin. The beam-on time approach fails because time ignores kV, mA, pulse rate, magnification, and patient thickness that strongly modulate output, making it a poor surrogate for absorbed dose. Exam caveat is that air kerma estimates peak skin entry while DAP estimates total population risk, and questions often swap them. Practical check is to announce cumulative values at intervals, collimate tightly, vary beam angle, and document the final cumulative air kerma and DAP in the record.