Evaluation of external beam hardening filters on image quality of computed tomography and single photon emission computed tomography/computed tomography

Abstract

This study was undertaken to evaluate the effect of external metal filters on the image quality of computed tomography (CT) and single photon emission computed tomography (SPECT)/CT images. Images of Jaszack phantom filled with water and containing iodine contrast filled syringes were acquired using CT (120 kV, 2.5 mA) component of SPECT/CT system, ensuring fixation of filter on X-ray collimator. Different thickness of filters of Al and Cu (1 mm, 2 mm, 3 mm, and 4 mm) and filter combinations Cu 1 mm, Cu 2 mm, Cu 3 mm each in combination with Al (1 mm, 2 mm, 3 mm, and 4 mm), respectively, were used. All image sets were visually analyzed for streak artifacts and contrast to noise ratio (CNR) was derived. Similar acquisition was done using Philips CT quality control (QC) phantom and CNR were calculated for its lexan, perspex, and teflon inserts. Attenuation corrected SPECT/CT images of Jaszack phantom filled with 444–555 MBq (12–15 mCi) of 99mTc were obtained by applying attenuation correction map generated by hardened X-ray beam for different filter combination, on SPECT data. Uniformity, root mean square (rms) and contrast were calculated in all image sets. Less streak artifacts at iodine water interface were observed in images acquired using external filters as compared to those without a filter. CNR for syringes, spheres, and inserts of Philips CT QC phantom was almost similar to Al 2 mm, Al 3 mm, and without the use of filters. CNR decreased with increasing copper thickness and other filter combinations. Uniformity and rms were lower, and value of contrast was higher for SPECT/CT images when CT was acquired with Al 2 mm and 3 mm filter than for images acquired without a filter. The study suggests that for Infinia Hawkeye 4, SPECT/CT system, Al 2 mm, and 3 mm are the optimum filters for improving image quality of SPECT/CT images of Jaszack or Philips CT QC phantom keeping other parameters of CT constant.

Mechanical and morphological properties of additively manufactured SS316L and Ti6Al4V micro-struts as a function of build angle

“…The source voltage and current were 100 kV and 100 µA respectively. A 0.11 mm Cu beam hardening filter was used to improve the image contrast and remove streak artifacts [46] . The volume reconstruction from X-ray images was calculated using NRecon 1.7.1.0.…”

Artifacts and quantitative biases in neutron tomography introduced by systematic and random errors

“…Dozens of correcting solutions have 2021 JINST 16 P01023 been developed including both beamline components and software methods for the suppression of such unwanted effects in the projections, sinograms and reconstructed images. These include blackbody corrections, physical anti-scatter grids, external beam hardening filters, simulation of missing data, instrumental minimisation of parasitic scattering and incorporation of calculated scattering contributions [3][4][5][6].…”