MATERIALS AND METHODS: The elemental composition of tungsten carbide was analysed using Field-Emission Scanning Electron Microscopy (FESEM) with energy dispersive X-ray (EDX). The purity of tungsten carbide was 99.9%, APS: 40-50 µm. Three discs of tungsten carbide was fabricated with thickness of 0.1 cm, 0.5 cm and 1.0 cm. Three lead discs with similar thickness were used to compare the attenuation properties with tungsten carbide discs. Energy calibration of gamma spectroscopy was performed by using 123I, 133Ba, 152Eu, and 137Cs. Gamma radiation from these sources were irradiated on both materials at energies ranging from 0.160 MeV to 0.779 MeV. The experimental attenuation coefficients of lead and tungsten carbide were compared with theoretical attenuation coefficients of both materials from NIST database. The half value layer and mean free path of both materials were also evaluated in this study.
RESULTS: This study found that the peaks obtained from gamma spectroscopy have linear relationship with all energies used in this study. The relative differences between the measured and theoretical mass attenuation coefficients are within 0.19-5.11% for both materials. Tungsten carbide has low half value layer and mean free path compared to lead for all thickness at different energies.
CONCLUSION: This study shows that tungsten carbide has high potential to replace lead as new lead-free radiation shielding material in nuclear medicine.
Objective: To compare the real-world effectiveness of EHRZ and FDC treatment groups on a cohort registry by investigating the sputum conversion rate and treatment outcomes of both groups.
Methods: A total of 11,489 patients' data were extracted from the Sabah TB registry between January 2012 and June 2016, including EHRZ (n = 4188) and FDC (n = 7301) patients. Then, 1:1 propensity score matching was adopted to reduce the baseline bias. Caliper matching was conducted with maximum tolerance score set at 0.001. Confounders included in the propensity score matching were gender, nationality, diabetes, HIV status, smoking status, and chest X-ray status. Successful matching provided 4188 matched pairs (n = 8376) for final analysis.
Results: In this matched cohort of 4188 pairs, the 2-month sputum conversion rate of FDC group was significantly higher than the EHRZ group (96.3% vs. 94.3%; P < 0.001) whereas 6-month sputum conversion of both groups showed no significant difference. Treatment outcomes such as noncompliance rate, failure rate, and success rate have no significant difference (P > 0.05) in both the treatment groups. There was an incidental finding of reduced death rate among FDC group compared to the EHRZ group (0.2% vs. 0.5%; P = 0.034).
Conclusion: The FDC formulation has better sputum conversion rate at 2 months compared to conventional EHRZ regime as separate-drug formulation. It was also observed that FDC has a slight protective effect against all-cause death among TB patients. This protective effect of FDC, however, still needs to be proven further.