RESUMEN
The study presented in this paper aims to explain the influence of scintillation detector size on spectrometric parameters. For this purpose, a setup composed of 1.5"×1.5", 2"×2" and 3"×3" NaI(Tl) detectors from the same manufacturer was performed. Furthermore, the linearity of detector response to gamma-ray energy was examined for all detectors. Our results show that the energy resolution presents a remarkable dependency to detector size, governed by a second order polynomial function. Thus, the energy resolution shows a significant decrease for almost all energies. As expected, full-energy peak efficiency and Peak-to-Total coefficients have a notable correlation with NaI(Tl) crystal size. In order to study a larger range of crystal sizes, we have developed a Monte Carlo (MC) simulation model using Geant4 (V 10.05). The obtained results were presented using ROOT (V 6.14/08) data analysis framework. The statistical uncertainties were below 4% for all obtained spectra. The comparison of simulated and measured results shows an excellent agreement. The accuracy of our model and the real detector responses has been quantified by applying statistical tests. In this context, a negligible deviation within 4.1% and 3.96% was found, for the obtained response functions and efficiency curves, respectively. An important improvement of intrinsic efficiency and photoelectric effect probability was observed for larger crystals. However, our study shows that CPU-time increases with increasing the active volume of the detector.
RESUMEN
BACKGROUND AND AIM: Little information is available on healthcare costs for patients with very severe chronic obstructive pulmonary disease. The aim of the current work was to evaluate Italian healthcare costs in these patients. METHODS: Prospective 1-year analysis was assessed in three subgroups of patients; non-invasively ventilated (n=30); invasively-ventilated (n=12) and on long-term oxygen therapy (n=41). Acute costs for care were a sum of fees for doctor's consultations, admissions to hospital (ward and intensive care units) and emergency drugs. Chronic costs were the sum of costs for pharmacotherapy and home ventilation and/or oxygen care. RESULTS: Mean cost/day/patient was 96 +/- 112 Euro (range 9-526 Euro), with acute costs accounting for 72% and chronic costs for 28% of the total cost burden, with no significant differences in costs associated with the three subgroups. Acute costs had a non-normal distribution (range 0 to 510 Euro) being cost for hospitalisation the highest cost burden with more than 30% of acute care costs attributed to only a small segment of patients. Chronic care costs were also unevenly distributed among the various groups (ANOVA p = 0.006), being home oxygen supply the highest cost burden. CONCLUSIONS: The current Health Care System is in urgent need for a reassessment of the high cost burden associated with hospitalisations and home oxygen supply.