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Modelling the effect of lead and other materials for shielding of the fetus in CT pulmonary angiography

¹ Department of Medical Physics & Engineering, Leeds Teaching Hospitals NHS Trust, Leeds General Infirmary, Leeds LS1 3EX, ² Academic Unit of Medical Physics, University of Leeds, Leeds LS2 9JT, UK

Correspondence: D S Brettle, Department of Medical Physics & Engineering, Leeds Teaching Hospitals NHS Trust, Leeds General Infirmary, Leeds, LS1 3EX, UK. E-mail: gri{at}medphysics.leeds.ac.uk

The aim of this work is to construct and validate a model to describe the variation in fetal dose as a function of the thickness of abdominal lead shielding used during CT pulmonary angiography and to determine the optimal shielding material. An anthropomorphic phantom was modified to contain a 15 cm³ ionization chamber at the site of the uterus. Fetal dose was measured with varying thicknesses of lead shielding at four values of tube potential (kV_p). Data generated by the proposed model were compared with experimental data to determine the validity of the model. The effect of lead shielding has been modelled accurately and results have shown that, although alternative materials could be used, lead is an effective and practical shielding material. In conclusion, lead remains a suitable shielding material and a pair of conventional lead aprons provides significant shielding for the fetus; we recommend that aprons should be reserved specifically for this purpose. However, it is possible that a dedicated and specifically designed lead shield could reduce fetal dose more effectively whilst also reducing patient discomfort.