SU-GG-I-52: Kerma Area Product and Energy Incident on Patients in X-Ray Imaging

Abstract

Purpose: To quantify the total x‐ray energy incident on a patient undergoing an x‐ray exposure using the Kerma Area Product. Method and Materials: Knowledge of the x‐ray beam spectrum permits the total energy in the x‐ray beam (mJ) and the corresponding Kerma Area Product (KAP, unit: Gy‐cm2) to be determined. For each x‐ray beam spectrum, conversion factors between the total energy incident on the patient and the KAP were determined (mJ/Gy‐cm2). We investigated mono‐energetic x‐ray beams and x‐ray spectra of interest in diagnostic x‐ray imaging. For the latter, we determined the importance of x‐ray tube voltage (kV), x‐ray beam filtration (mm Al), x‐ray tube anode angle (°), and voltage ripple (%). Results: Energy incident per unit KAP increases from 6.71 mJ per Gy‐cm2 for 30 keV photons to 43.5 mJ per Gy‐cm2 for 100 keV photons. For 3 mm Al filtration beams, increasing the x‐ray tube voltage from 50 kV to 100 kV increased the energy incident per unit KAP from 7.0 mJ per Gy‐cm2 18.5 mJ per Gy‐cm2. At 80 kV, increasing the x‐ray tube filtration from 1 to 5 mm Al increased the energy incident per unit KAP from 9.0 mJ per Gy‐cm2 17 mJ per Gy‐cm2. The x‐ray tube anode angle and voltage ripple had very little effect (< 20%) on energy incident per unit KAP conversion coefficients. Conclusion: Energy incident on the patient, determined from the Kerma Area Product, can be combined with absorbed fraction values to quantify energy imparted to patients.