Analysis of 80 kV WAXS Measurements with a CdTe Breast Biopsy Diffractometer

Abstract

Measurements to test the ability of using a higher kV with a custom built breast biopsy CdTe diffractometer were performed. 80 kV 3.2 mm diameter beams of 3 min duration interrogated 5 mm diameter, 2 to 5 mm thick samples of polymethyl methacrylate (PMMA) and polycarbonate as well as a 5 mm thick water sample. Scattered spectra Ns(E) were measured at θ=6∘ with a 25 mm² × 1 mm thick CdTe detector which subtended a solid angle of detection Ω = 4.9×10^− 5 sr at the sample center. The probed momentum transfer x range was from 0.3 nm^− 1 to 3.38 nm^− 1. Linear differential scattering coefficients (μ _s ) of water and PMMA were calculated using Ns, an estimate of the incident spectrum (N₀) and a semianalytical model. For μ _s water, N₀ spectra were estimated using Ns from PMMA and polycarbonate plastics of varying thicknesses while only the latter for μ _s PMMA. A detector response function was applied to correct for florescence escape and hole tailing.

The μ _s of H₂O matched fairly well with literature between 0.42 nm^− 1 < x < 1.68 nm^− 1, however, above this region discrepancies occurred. No significant effects were observed when using different sample thicknesses to obtain N₀. The results of μ _s PMMA matched well with literature over the whole x range. The detector response function did not have a significant effect on the μ _s curves.

It is anticipated that some of the pinhole scatter interacted with the Pb sample holder and then contaminated the Ns spectra. The contamination would be similar for both plastics because of their similar μ values. Regardless, if the μ of the sample being analyzed are similar to those of the sample used to get N₀, the system is capable of probing a wider x range using an 80kV beam.