Work

Influence of radiation field size on half-value layer measurements in mammography

Year: 2026

Type: article

Abstract: INTRODUCTION: Mammography measurements are commonly conducted in a radiation field of standard size without additional collimation of the primary beam. International standards, protocols and guidelines propose half-value layer (HVL) measurements under narrow beam conditions, which are not applied in clinical measurements. METHODS: The HVL was measured using an ionization chamber and X-ray multimeters (XMMs) in different field collimations in radiation qualities commonly encountered in mammography. The impact of field size on measured HVL was examined for Mo/Mo, Mo/Rh, W/Rh and W/Ag anode/filter combinations, for X-ray tube voltages of 25 kV, 28 kV, 30 kV and 35 kV. RESULTS: Field size has a significant influence on the HVL measured with the ionization chamber. Up to 5 % differences were observed and it was impacted by irradiation geometry (field shape and usage of compression paddle) and radiation quality. The XMMs do not have similar behaviour. CONCLUSION: With ionization chambers, the HVL should be measured following the definition in a narrow beam without scatter. The XMMs are not so sensitive to scattered radiation but they should have a traceable calibration in terms of HVL for specific radiation qualities in use.

Source: Physica Medica

DOI: 10.1016/j.ejmp.2026.105862