X-ray imaging using photon-counting detectors (PCDs) allows for the calculation of quantitative images such as the effective atomic number (Zeff). However, physical phenomena such as characteristic X-ray emission and charge sharing can cause incomplete total absorption events during signal generation, which reduces the accuracy of X-ray penetration analysis. To solve the problem, an anti-coincidence mode (ACM) has been developed, but complete correction has not been established. We aimed to investigate the accuracy of Zeff image when the proposed software-based corrections, namely beam hardening and response function corrections, are added to the hardware-based correction of the ACM. The response function was calculated using the Monte-Carlo simulation code. In a simulation study, we analyzed a phantom composed of virtual materials with Zeff values of 4–16. While sufficient accuracy cannot be achieved by applying only the ACM, it was demonstrated that low-noise Zeff images can be obtained by applying our correction. Furthermore, it was demonstrated that Zeff images of food samples can be generated by using actual non-destructive testing equipment with a 10 m/min transportation speed. In conclusion, our correction procedure can maximize the performance of PCDs, and our findings are essential for promoting imaging techniques concerning quantitative images.
BACKGROUND:Conventional CT assessment of lung lesions is based mainly on morphological features. CT values represent relative X-ray attenuation that does not directly reflect tissue composition and/or physical density. Quantitative imaging using photon-counting CT (PC-CT) has the potential to provide quantitative parameters, such as effective atomic number (Zeff) and effective physical density (ρeff). PURPOSE:The purpose is to develop and demonstrate the potential of an algorithm that generates both the Zeff and ρeff images, derived directly from virtual monoenergetic images (VMIs) acquired with a clinical PC-CT system. METHODS:The ρeff image was generated by fitting a database of mass attenuation coefficients (μ/ρ) to the measured linear attenuation coefficients (μ), which were obtained from two VMIs at 70 and 100 keV. As an effective material, Zeff information was also determined and fed back into the ρeff calculation. An in-house low-density phantom was scanned for quantitative evaluation of ρeff. In addition, to demonstrate the applicability of our procedure to actual clinical imaging, representative chest PC-CT images from patients were analyzed. RESULTS:In experiments using low-density phantoms, the CT values did not necessarily correlate with Zeff values, but they showed a very good correlation with the ρeff values. The ρeff values calculated using our procedure correlated well with the correct values of ρ. A relative root mean square error of ρeff calculation was 5.5%. Furthermore, we found that in pulmonary diagnosis, image contrast information from ρeff makes it easier to identify and distinguish lesions compared to that from Zeff. CONCLUSIONS:The proposed procedure directly generated Zeff and ρeff images from PC-CT data and enabled quantitative interpretation of CT value in terms of elemental composition and physical density. In this study, the feasibility of generating Zeff and ρeff images was demonstrated.
It has been suggested that non-fasting triglyceride (TG) concentrations may be useful in predicting various diseases. However, current epidemiological evidence focuses mainly on the effects of fasting TG concentrations. The aim of this study was to investigate the effect of fasting and non-fasting TG levels on new-onset hyperuricemia (HUA) in the general Japanese population. This is a population-based retrospective cohort study (ISSA-CKD study); it included 5,576 participants without HUA at baseline between 2008 and 2019. Participants were categorized into gender-specific tertile groups of serum TG levels: group 1 (< 83 mg/dL [0.94 mmol/l] in male and < 77 mg/dL [0.87mmol/l] in female), group 2 (83-129mg/dL [0.94–1.46mmol/l] in male and 77-114 mg/dL [0.87–1.29mmol/l in female), and group 3 (≥ 130mg/dL [1.47 mmol/l] in male and ≥ 115 mg/dL [1.30mmol/l] in female). Outcome of this study was new-onset HUA (serum uric acid > 7 mg/dL [0.42 mmol/l]). During the 5.4-year follow-up period, 552 male and 146 female participants developed new-onset HUA. Incidence rates (per 1,000 person-years) of HUA were 18.2 in group 1, 21.9 in group 2 and 31.0 in group 3 among male, and 2.1 in group 1, 4.0 in group 2 and 7.4 group 3 among female. These associations remained significant after adjustment for confounders (p trend < 0.0001 among male and 0.0004 for female). There was no clear difference in effect of non-fasting and fasting TG levels on the development of new HUA (P interaction = 0.546 for male and 0.886 for female). Non-fasting and fasting TG concentrations were significantly associated with new-onset HUA among general Japanese men and women.
