Technical note: Characteristics of the energy spread kernels of scattered radiation in an x‐ray room

Abstract

To describe the scattered radiation spectra inside an x-ray room for different scattering conditions. Methods: Monte Carlo simulations of an x-ray room using phantoms of different size, varying field sizes, and a range of mono-energetic beams were carried out. For each energy, the particle fluence spectrum of scattered photons was collected at different spherical zones to describe the radiation reaching the different boundaries of the x-ray room. The effect on the scattered spectrum of the room floor was also considered. Results:The scattered spectra for mono-energetic primary beams at a given spherical zone give rise to oriented energy spread kernels (OESKs) that can be used to calculate the scattered spectrum for any poly-energetic beam at that zone. Despite the large differences, which can be seen in the OESKs when the scattering conditions vary, an important invariance is also observed: the position of the broad scatter peak for a given primary energy and zone. Conclusions: The result of breaking down the calculation of the scattered radiation spectrum into the different factors that influence it allows estimating the spectrum in a wide range of situations. The invariant position of the broad scatter peak can be used to estimate the highest energy of the scattered photons for a given primary energy and zone, which may determine radiation shielding needs.

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“…It's worth noting the increase in the secondary-to-primary ratio as the thickness of the barrier increases, the monotonically decreasing behavior of the SPR with energy in the case of concrete, and the sharp discontinuities due to the absorption edges of lead observed in the relationship of SPR with energy in the case of lead. The directions are lateral-inferior (LI), back-scatter (BS), and forward-scatter (FS) [5].…”

“…In a previous study [5], secondary radiation spectra were determined in water phantoms simulating patients. The method was similar to that used in the present study, collecting photons scattered in different directions and grouping them according to their energy and direction.…”

“…The procedure for calculating spectra at the barrier's exit can be fed with any type of input spectrum found within the diagnostic radiology range. In particular, spectra from beams calculated in situations similar to those encountered in clinical practice can be used [5]. For some of these cases, the radiation spectra after the barrier are analyzed, including representative cases from interventional radiology and conventional radiology.…”

“…The differences are due to the absorption edges observed in lead, which modify the monotonic behavior of the curves. Figure 3 shows, in its left column, spectral fluences generated in water phantoms [5] and directed towards personnel in an interventional radiology suite (figure 3(a)), and towards the ceiling (figure 3(c)) and floor (figure 3(e)) of the room. In its right column, spectral fluences attenuated by lead thicknesses similar to those present in lead aprons 3(b) and concrete thicknesses similar to those found in ceilings 3(d) and floors 3(f) of the rooms are shown.…”

“…Right: Fluence spectra after being attenuated by 0.3 mm lead shielding and 15 cm concrete shielding. The directions are lateral-inferior (LI), back-scatter (BS), and forward-scatter (FS)[5].…”