Determination of radon gas and respirable ore dust concentrations in the underground merelani Tanzanite mines

This study has estimated the concentrations of radon gas and respirable ore dust in the Merelani underground tanzanite mines. Two different portable monitors were used to measure the radon gas and respirable ore dust concentrations respectively. The mean radon gas concentration (disintegrations per second per cubic meter) ranges from 40.1 Bq/m3 to 4.2x103 Bq/m3 with the geometric mean of 118.4 Bq/m3 which is below the ICRP workplace guidance level of 500 - 1500 Bq/m3. The estimated mean annual effective dose (D) was 1.6 mSv which is significantly lower than the external exposure annual effective dose of 20 mSv and the annual organ dose limit of 2.4 mSv. The overall concentrations of respirable ore dust arithmetic mean was 18.2 g/m3 and the geometric mean of 2.1 g/m3 which is very high compared to the guidance level of 2 g/m3. The respirable dust was mainly produced during drilling and blasting of rocks, under normal conditions the geometric mean of respirable gas concentrations was 0.8 g/m3. It is recommended that immediate intervention such as providing proper ventilation during the two processes to dilute radon levels in underground mines and the monitoring should be done regularly

Effect of Lowering Tube Potential and Increase Iodine Concentration of Contrast Medium on Radiation Dose and Image Quality in Computed Tomography Pulmonary Angiography Procedure: A Phantom Study

The aim of the study was to examine the effect of lowering tube potential and increase iodine concentration on image quality and radiation dose in computed tomography pulmonary angiography procedure. The pulmonary arteries were simulated by three syringes. The syringes were filled with 1:10 diluted solutions of 300 mg, 350 mg and 370 mg of iodine per millilitre concentration in three water-filled phantoms simulating thin, intermediate and thick patients. The phantoms were scanned at 80 kVp, 110 kVp and 130 kVp and 0.6 second rotation time using a 16 slice computed tomography (CT) scanner. The tube current was either fixed at 80, 100, 200, 250 and 300 mA or automatically adjusted with quality reference tube current-time product (mAsQR). In comparison with 130 kVp, images acquired at 80 kVp and 110 kVp, respectively, showed 76.2% to 99% and 19% to 26% enhancement in CT attenuation of iodinated contrast material. A volume CT dose index (CTDIvol) reduction by 35.3% was attained in small phantom with the use of 80 kVp, while in the medium phantom, a CTDIvol reduction by 29.9% was attained with the use of 110 kVp instead of 130 kVp. In light of the above, lowering tube potential and increase iodinated CM could substantially reduce the dose to small-sized adults and children