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[en] This paper examines the feasibility of detecting strontium 90 in groundwater directly with photodiodes and considers the physical parameters which maximise radiation absorption within the detector. Geant4 simulations were used to draw comparisons between silicon, gallium arsenide and cadmium telluride detectors of varying surface area and thickness. Detectors were compared in their ability to absorb point and scattered sources of radiation. The results indicate that a detector, of 10 mm2 surface area, and 1 mm thickness offered the highest detection efficiency in a contaminated groundwater simulation. 1 mm thick and 100 mm2 detectors cadmium telluride and gallium arsenide detectors were modelled in a groundwater borehole scenario. Each material offered similar detection efficiency, but the greater backscattering effect in cadmium telluride resulted in a greater peak at lower energies compared to that observed in gallium arsenide.
[en] Current echocardiographic data reporting the impact of concomitant mitral regurgitation (MR) on outcome in patients who undergo transcatheter aortic valve replacement (TAVR) are conflicting. Using cardiovascular magnetic resonance (CMR) imaging, this study aimed to assess the impact of MR severity on cardiac reverse remodeling and patient outcome. 85 patients undergoing TAVR with CMR pre- and 6 m post-TAVR were evaluated. The CMR protocol included cines for left (LV) and right ventricular (RV) volumes, flow assessment, and myocardial scar assessment by late gadolinium enhancement (LGE). Patients were dichotomised according to CMR severity of MR fraction at baseline (‘non-significant’ vs ‘significant’) and followed up for a median duration of 3 years. Forty-two (49%) patients had ‘significant MR’ at baseline; they had similar LV and RV size and function compared to the ‘non-significant MR’ group but had greater LV mass at baseline. In those with significant MR at baseline, 77% (n = 32) had a reduction in MR post-TAVR, moving them into the ‘non-significant’ category at 6-months, with an overall reduction in MR fraction from 34 to 17% (p < 0.001). Improvement in MR was not associated with more favourable cardiac reverse remodeling when compared with the ‘non-improvers’. Significant MR at baseline was not associated with increased mortality at follow-up. Significant MR is common in patients undergoing TAVR and improves in the majority post-procedure. Improvement in MR was not associated with more favourable LV reverse remodeling and baseline MR severity was not associated with mortality.