Assessment of air kerma–area product in computed tomography using small solid-state dosemeters

Technological advances in computed tomography (CT) have highlighted limitations of traditional dose descriptors such as computed tomography dose index_vol and dose-length product, particularly for wide-beam and modulated acquisitions. This study investigates a CT-specific, operational air kerma–area product derived from time-resolved measurements using small solid-state dosemeters mounted at the gantry aperture. A mathematical framework is presented that accounts for tube rotation, bow-tie filtration, beam geometry, and the longitudinal dose profile. Model validation was performed using measured air-kerma rate waveforms under free-in-air and phantom conditions, demonstrating that a reproducible kerma–area quantity can be derived from fixed-detector measurements. By excluding the kerma–area contribution associated with radiation that does not intersect the object, the proposed approach yields a quantity that is more closely related to patient-incident radiation than conventional output-based KAP concepts in CT. The methodology provides a practical tool for system characterization and quality control in CT dosimetry.