Characterization of Tissue-Equivalent Materials Through Measurements of the Linear Attenuation Coefficient and Scattering Profiles Obtained With Polyenergetic Beams

In this work seven tissue-equivalent materials (Nylon, Polyacetate, Polymethylmethacrylate (PMMA), water, muscle-equivalent, bone-equivalent and adipose-equivalent) were characterized, through their attenuation (linear attenuation coefficient) and scattering (scattering profile) properties. An energy dispersive X-ray system (EDXS) was used to analyze these properties simultaneously. The EDXS consisted of a tungsten anode X-ray tube operating at 60 kVp, a goniometer, and two detectors: a Cadmium Telluride (CdTe) detector, positioned at 7 degrees with relation to the incident beam, used for detecting the energy distribution of the scattered photons, and a Silicon Drift Detector (SDD), positioned at zero degree with relation to the incident beam, used for detecting the energy distribution of the transmitted beam (with the sample) or the incident beam (without the sample). The preliminary results obtained in this work show the potential of combining the linear attenuation coefficient and the scattering profile for characterizing and choosing the most suitable tissue-equivalent materials to simulate human tissue. Our results show that adipose-equivalent, water and bone-equivalent would be adequate to simulate adipose, muscle and bone tissue respectively.

I. Introduction

Radiographic techniques, such as mammography, radiology and bone densitometry, are based on differences of attenuation coefficient between the biological tissues that compose the body or a specific organ. Therefore, the accurate knowledge of the attenuation properties of those tissues is fundamental to optimize the image quality, and at same time minimizing the absorbed dose in the patient. In practice, tests of quality control in radiographic clinical equipments are performed by using tissue-equivalent materials. For a material to be considered tissue equivalent, it must have similar radiological proprieties as that of tissue (soft-tissue, muscle, bone, or fat). These proprieties include physical density, relative electron density and effective atomic number as well as similar absorption and scattering of radiation [1]–[3]. For image quality assessments in diagnostic radiology, the ICRU Report 44 [2] recommends that tissue-equivalent materials should have linear attenuation coefficients within of these for a given body tissue over the required photon energy interval. Furthermore, it would be expected that their scattering properties could also be similar to those of human tissues [4].