Affiliations: [a] Ionizing and Non-Ionizing Radiation Protection Research Center, Shiraz University of Medical Sciences, Shiraz, Iran | [b] Medical Imaging Research Centre, Shiraz University of Medical Sciences, Shiraz, Iran
Correspondence:
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Corresponding author: Mahdi Saeedi-Moghadam, Medical Imaging Research Centre, Shiraz University of Medical Sciences, Shiraz, Iran. E-mail:m_saeedimoghadam@yahoo.com
Abstract: BACKGROUND: Over the past few years, because of high attenuation
and lightweight, non-toxic, lead-free aprons (LFAs) have been replaced by
lead aprons (LAs). Lots of studies declared that this fact was based on the
interactions of diagnostic X-ray with material such as the photoelectric
effect (PE) and Compton scattering. These studies have demonstrated that in
these types of aprons, due to the presence of different K-edge absorption,
PE has a wide absorption in various metals with divers K-edges. The
measurement geometry in most of these studies was narrow beam geometry, i.e.
a collimated source and a collimated detector with a large source-detector
distance.
OBJECTIVE: The present study intended to evaluate the attenuation
of radiology scattered radiations in LAs and LFAs in both narrow and broad
beam geometries, which is a more realistic situation, in order to check
whether or not the higher attenuation is valid.
METHODS: In this study, a lead apron contains (Pb + EPV) and two
non-lead compounds of (W + Sn + EPVC) with different weight percent (Wt%) were evaluated in the energy range of diagnostic radiology (100 kVp).
The MCNPX code was applied to simulate broad - and narrow-beam measurement
geometries. The evaluations have been performed in three situations: 1st) the
same density thickness of LA and LFAs 2nd) same line thickness of LA and
LFAs 3rd) considering the thickness of LFAs which has the same
attenuation with LAs i.e. lead equivalent thickness for LFAs in the narrow
beam. Finally, the x-ray transmission ratio (I/I_0) of LAs and LFAs was
compared in 100 kVp for three mentioned conditions.
RESULTS: Our results indicated that LFAs had more radiation
attenuation rather than LA in the 1st and 2nd conditions with both
geometries. However, LFAs had lower attenuation in comparison to LAs in the
3rd condition with broad beam geometry. More importantly, the
transmission ratio (I/I_0) of LFAs in the broad beam condition was more
significant than LA.
CONCLUSION: The scattered radiations produced by LFAs are more than
LAs because of the production of characteristic radiations resulted from
K-edge absorption in composited aprons. Consequently, the LFAs should be
evaluated in both narrow and broad beam situation using the lead equivalent
thickness of LFAs to make sure that the non-lead aprons do not increase the
radiation dose of the user.
Keywords: Lead-free aprons, lead aprons, diagnostic radiology, MCNPX, narrow and broad beam
