The clinical translation of plastic scintillation dosimetry

Contemporary radiotherapy focuses on achieving the best patient outcomes by delivering highly targeted treatments that often include small fields and high dose gradients. Plastic scintillators outperform traditional dosimeters in these fields as they are close to water-equivalent. However, the translation of scintillation dosimeters into the clinic has been limited by three roadblocks. The generation of Cerenkov radiation in an optic fibre irradiated by megavoltage radiation contaminates the scintillation signal. Two Cerenkov removal methods (spectral discrimination and air core) were found to be accurate in accounting for Cerenkov radiation and their clinical robustness was improved. The light readout system is often the limiting factor for the accuracy of scintillators. PMTs outperform camera-based systems, though their implementation for array dosimetry is complex. A novel system with a multianode PMT was constructed and enabled multiple light signals from an array to be simultaneously measured. Arrays of scintillation dosimeters are difficult to create due to the complex arrangement of detectors and their optical pathways. Two innovative approaches (square waveguides and 3D printing) were used to build prototype scintillation dosimeter arrays. These arrays showed that scintillation dosimeters can measure dose distributions with high spatial and temporal resolution. Addressing these roadblocks has enabled the clinical translation of scintillation dosimeters. In small field dosimetry, an air core dosimeter was used as a reference to calculate and predict correction factors for existing dosimeters. For brachytherapy, an array of scintillators provided real-time dose measurements that improved the safety of the treatment. For rotational treatments, a cylindrical array was used to verify the dose delivered during simulated stereotactic treatments. Traditional dosimeters cannot be used in these applications and this demonstrates the potential of scintillation dosimetry

Measurement of event-shape observables in Z→ℓ+ℓ− events in pp collisions at √ s=7 TeV with the ATLAS detector at the LHC

Event-shape observables measured using charged particles in inclusive $Z$-boson events are presented, using the electron and muon decay modes of the $Z$ bosons. The measurements are based on an integrated luminosity of $1.1 {\rm fb}^{-1}$ of proton--proton collisions recorded by the ATLAS detector at the LHC at a centre-of-mass energy $\sqrt{s}=7$ TeV. Charged-particle distributions, excluding the lepton--antilepton pair from the $Z$-boson decay, are measured in different ranges of transverse momentum of the $Z$ boson. Distributions include multiplicity, scalar sum of transverse momenta, beam thrust, transverse thrust, spherocity, and $\mathcal{F}$-parameter, which are in particular sensitive to properties of the underlying event at small values of the $Z$-boson transverse momentum. The Sherpa event generator shows larger deviations from the measured observables than Pythia8 and Herwig7. Typically, all three Monte Carlo generators provide predictions that are in better agreement with the data at high $Z$-boson transverse momenta than at low $Z$-boson transverse momenta and for the observables that are less sensitive to the number of charged particles in the event.Comment: 36 pages plus author list + cover page (54 pages total), 14 figures, 4 tables, submitted to EPJC, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2014-0

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Muscle strength and exercise kinetics in COPD patients with a normal fat-free mass index are comparable to control subjects.

Item does not contain fulltextSTUDY OBJECTIVE: This study was designed to investigate the extent of clinical muscle dysfunction in stable patients with COPD who were attending an out-patient pulmonary clinic compared with that of age-matched control subjects without COPD. Design and subjects: Respiratory muscle and hand grip strength, steady-state O(2) kinetics, and body composition were measured in 32 patients with COPD (19 women) [mean (+/- SD) FEV(1), 38 +/- 11% predicted] and 36 age-matched control subjects (13 women). RESULTS: Measurements of handgrip force (mean, 97 +/- 32% vs 106 +/- 26% predicted, respectively), maximal expiratory pressure (mean, 57 +/- 33% vs 61 +/- 22% predicted, respectively), steady-state O(2) kinetics (mean tau, 72 +/- 34 s vs 78 +/- 37 s, respectively) and steady-state CO(2) kinetics (mean tau, 77 +/- 38 s vs 65 +/- 32 s, respectively) at submaximal exercise were similar in patients and control subjects. All the subjects, except for one female COPD patient, had a normal fat-free mass index (FFMI), although on average the FFMI was lower in male patients (19.8 +/- 2.8) than in male control subjects (23.0 +/- 2.8; p < 0.01). CONCLUSIONS: In patients with COPD who were attending a regular outpatient pulmonary clinic, there was no evidence of reduced upper extremity and expiratory muscle strength or prolonged O(2) and CO(2) kinetics during isowork submaximal cardiopulmonary exercise compared to healthy, age-matched control subjects. Also, a normal body composition was found in nearly all COPD patients. This argues against the existence of a clinically significant systemic myopathy in most stable patients with severe COPD and normal FFMI

Terrorism risks for bridges in a multi-hazard environment

The paper will assess terrorist threats to new and existing bridges and the cost-effectiveness of protective counter-terrorism measures. This analysis will consider threat likelihood, cost of security measures, risk reduction and expected losses to compare the costs and benefits of protective measures to bridges to decide which protective measures are cost-effective. In this paper, a break-even cost-benefit analysis determines the minimum probability of an attack, absent the protective measures, that is required for the benefit of the protective measures to equal their cost for new and existing bridges. It was found that unless terrorist threat probabilities are high, then typical protective measures are not cost-effective. Bridges and other critical infrastructure are subject to a range of natural and man-made hazards, and terrorism is most likely not as important a threat as natural hazards. It was found that economic risks to bridges from floods, earthquakes, and ship impact are higher than threats from terrorism