Relative response of dosimeters to variations in scattered X-ray energy spectra encountered in interventional radiology

Abstract

Purpose: The new lower eye lens dose limit is of relevance in interventional radiology, where higher dose procedures result in increased scattered radiation to staff. The eye lens dose may be monitored using the directional dose equivalent at 3 mm depth, H_p(3), or through H_p(10) or H_p(0.07) measurements and using conversion factors. However, there are a considerable range of factors which contribute to measurement uncertainties, one of which is the incident photon energy. This study investigated the energy spectra of scattered radiation in interventional radiology, and the dosimetry accuracy of dosimeter types, evaluating their energy dependence.

Methods: Scatter X-ray energy spectra were recorded under varied conditions in a fluoroscopy imaging suite. Dosimetry accuracy of eye dosimeters, including TLDs (100 s, 100Hs), Landauer H_p(3), John Caunt ED3 and Electronic Personal dosimeters (EPDs) were compared to air kerma measurements across a range of tube voltages.

Results: The variation of energy spectra with changing phantom thickness, spectrometer angulation and filtration are presented. The 100 and 100H TLDs, and EPDs showed a consistent air kerma response (within 10%) with changes in energy. The real-time silicon diode detectors showed a variable over response of between 10 and 25% across the energies investigated while Landauers dedicated H_p(3) eye dosimeters showed considerable variation between dosimeters for similar conditions, a 17% variation at 50 kV_p.

Conclusion: The work aimed to validate the scattered energy spectra typically encountered in interventional radiology and to further determine the accuracy of eye dosimeters in relation to energy response variations.

Keywords: Energy spectra; Eye dosimetry; Interventional radiology.