Which factors influence entrance skin exposure (ESE) and patient dose?

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Entrance skin exposure and patient dose come from how the X-ray beam is produced and delivered. The projection chosen affects which tissues the beam must pass through and how much attenuation occurs before it reaches the skin. The kilovoltage peak (kVp) and the exposure value (mAs) set the beam’s energy and intensity; higher mAs raises dose, while kVp changes the penetrating power of the beam and, together with mAs, influences the dose required to obtain a quality image. The source-to-image distance (SID) follows the inverse square law, so moving closer to the patient increases skin dose. Patient size and body habitus change how much tissue attenuates the beam and how much scatter is produced, often requiring adjustments in technique and exposure that affect ESE. Shielding directly reduces skin dose by blocking the beam to sensitive areas. Technique, including precise positioning, proper collimation, and correct beam alignment, minimizes unnecessary exposure and concentrates the dose on the area of interest. Diet, exercise, age, and time of day do not meaningfully influence entrance skin exposure in a standard radiographic exam.