Dosimetry of microbeam radiotherapy by flexible hydrogenated amorphous silicon detectors.

Objective.Detectors that can provide accurate dosimetry for microbeam radiation therapy (MRT) must possess intrinsic radiation hardness, a high dynamic range, and a micron-scale spatial resolution. In this work we characterize hydrogenated amorphous silicon detectors for MRT dosimetry, presenting a novel combination of flexible, ultra-thin and radiation-hard features.Approach.Two detectors are explored: an n-type/intrinsic/p-type planar diode (NIP) and an NIP with an additional charge selective layer (NIP + CSC).Results.The sensitivity of the NIP + CSC detector was greater than the NIP detector for all measurement conditions. At 1 V and 0 kGy under the 3T Cu-Cu synchrotron broadbeam, the NIP + CSC detector sensitivity of (7.76 ± 0.01) pC cGy-1outperformed the NIP detector sensitivity of (3.55 ± 0.23) pC cGy-1by 219%. The energy dependence of both detectors matches closely to the attenuation coefficient ratio of silicon against water. Radiation damage measurements of both detectors out to 40 kGy revealed a higher radiation tolerance in the NIP detector compared to the NIP + CSC (17.2% and 33.5% degradations, respectively). Percentage depth dose profiles matched the PTW microDiamond detector's performance to within ±6% for all beam filtrations except in 3T Al-Al due to energy dependence. The 3T Cu-Cu microbeam field profile was reconstructed and returned microbeam width and peak-to-peak values of (51 ± 1)µm and (405 ± 5)µm, respectively. The peak-to-valley dose ratio was measured as a function of depth and agrees within error to the values obtained with the PTW microDiamond. X-ray beam induced charge mapping of the detector revealed minimal dose perturbations from extra-cameral materials.Significance.The detectors are comparable to commercially available dosimeters for quality assurance in MRT. With added benefits of being micron-sized and possessing a flexible water-equivalent substrate, these detectors are attractive candidates for quality assurance,in-vivodosimetry and in-line beam monitoring for MRT and FLASH therapy.

Cost/utility ratio in chronic heart failure: comparison between heart failure management program delivered by day-hospital and usual care.

OBJECTIVE: This study compared the effectiveness and cost/utility ratio between a heart failure (HF) management program delivered by day-hospital (DH) and usual care in chronic heart failure (CHF) outpatients. BACKGROUND: Previous studies showed that about 50% of readmissions for CHF can be prevented by a multidisciplinary approach. However, the performance, effectiveness, and cost/utility ratio of a process of HF outpatient management related to evidence-based medicine have not been considered. METHODS: A total of 234 prospective patients discharged by a HF Unit were randomized to two management strategies: 122 patients to usual community care and 112 patients to a HF management program delivered by the DH. Management (rate of readmissions, therapeutic interventions), functional parameters (New York Heart Association [NYHA] functional class, left ventricular diameters, and ejection fraction, deceleration time of early diastolic mitral flow, peak oxygen uptake, and mitral regurgitation) and hard outcomes (cardiac death and urgent cardiac transplantation) were evaluated. The cost/utility ratios of the two strategies were compared. RESULTS: After 12 +/- 3 months of follow-up, the individual rate access in DH was 5.5 +/- 3.8 days. The DH subjects were readmitted to the hospital less frequently than were the usual-care group patients (13 vs. 78, p < 0.00001). Patients allocated to usual-care management showed heterogeneous changes in NYHA functional class (13% improved and 16% worsened p = NS); In contrast, the DH group showed significant changes in NYHA functional class (23% improved and 11% worsened, p < 0.009). Hard cardiac events in the one-year follow-up occurred in 25/234 (10.6%) patients; cardiac death occurred in 21/122 (17.2%) of the community group and in 3/112 (2.7%) in the DH group (p < 0.0007). One DH patient underwent urgent transplantation. Comparison of the two managerial models by Cox regression analysis showed that DH management significantly protected against the appearance of hard events (relative risk [RR] 0.17; confidence interval [CI] 0.06 to 0.66). The cost/utility ratio of the two management strategies was similar (usual care $2,409 vs. DH $2,244). The incremental analysis revealed a cost savings of $1,068 for each quality-adjusted life year gained. The cost/utility ratio for the integration of DH management of CHF was $19,462 (CI $13,904 to $34,048). CONCLUSIONS: A heart failure outpatient management program delivered by a DH can reduce mortality and morbidity of CHF patients. This management strategy is cost-effective and has an equitable value from a societal point of view.