PurposeCherenkov light during MV radiotherapy has recently found imaging and therapeutic applications but is challenged by relatively low fluence. Our purpose is to investigate the feasibility of increasing Cherenkov light production during MV radiotherapy by increasing photon energy and applying specialized beam-hardening filtration. MethodsGAMOS 5.0.0, a GEANT4-based framework for Monte Carlo simulations, was used to model standard clinical linear accelerator primary photon beams. The photon source was incident upon a 17.8cm(3) cubic water phantom with a 94cm source to surface distance. Dose and Cherenkov production was determined at depths of 3-9cm. Filtration was simulated 15cm below the photon beam source. Filter materials included aluminum, iron, and copper with thicknesses of 2-20cm. Histories used depended on the level of attenuation from the filter, ranging from 100 million to 2 billion. Comparing average dose per history also allowed for evaluation of dose-rate reduction for different filters. ResultsOverall, increasing photon beam energy is more effective at improving Cherenkov production per unit dose than is filtration, with a standard 18MV beam yielding 3.3-4.0x more photons than 6MV. Introducing an aluminum filter into an unfiltered 2400cGy/min 10MV beam increases the Cherenkov production by 1.6-1.7x, while maintaining a clinical dose rate of 300cGy/min, compared to increases of similar to 1.5x for iron and copper. Aluminum was also more effective than the standard flattening filter, with the increase over the unfiltered beam being 1.4-1.5x (maintaining 600cGy/min dose rate) vs 1.3-1.4x for the standard flattening filter. Applying a 10cm aluminum filter to a standard 18MV, photon beam increased the Cherenkov production per unit dose to 3.9-4.3x beyond that of 6MV (vs 3.3-4.0x for 18MV with no aluminum filter). ConclusionsThrough a combination of increasing photon energy and applying specialized beam-hardening filtration, the amount of Cherenkov photons per unit radiotherapy dose can be increased substantially.

Background. The number of adults referred to high-volume centers for extracorporeal membrane oxygenation (ECMO) is increasing. Outcomes of patients requiring transport are not well characterized, and referral guidelines are lacking. This study describes the experience and outcomes of a single high-volume center.& para;& para;Methods. A retrospective study was performed that included adults undergoing ECMO between June 2009 and December 2015. Patient characteristics and outcomes were acquired from the medical record. Logistic regression was used to identify predictors of survival to hospital discharge. The Kaplan-Meier method was used to depict rates of survival.& para;& para;Results. Of 133 patients, 77 (57.9%) underwent venoarterial (VA) ECMO and 56 (42.1%) underwent venovenous (VV) ECMO. Median transport distance was 88.8 miles (range 0.2-1,434 miles). Median duration of support was 6 days (range, 1-32.5 days). Age older than 60 years, pulmonary hypertension, and body mass index (BMI) greater than 30 were associated with worse survival to discharge for VA ECMO; a history of hypertension and presence of left ventricular (LV) vent were associated with better survival. Age older than 60 years and diabetes were associated with worse survival to hospital discharge for VV ECMO. Survival to decannulation was 66.2% and 76.8%, and to hospital discharge it was 48.1% and 69.6% for VA and VV ECMO, respectively. Of hospital survivors, Kaplan-Meier estimates of 1-year survival were 82.4% and 95.5% for VA and VV, respectively.& para;& para;Conclusions. Outcomes are favorable after transport to high-volume ECMO centers. Guidelines and infrastructure for short- and long-distance ECMO transport is imperative for the efficient and successful management of these patients. (C) 2017 by The Society of Thoracic Surgeons

X-ray psoralen activated cancer therapy (X-PACT) is a new therapeutic approach that has been shown to induce tumor cell apoptosis and cytotoxicity in vitro, and slow tumor growth in BALB/c mice with syngeneic 4T1 tumors. X-PACT is accomplished by injection of co-incubated psoralen and phosphors; the phosphors emit UV to activate psoralen, and are activated by an external kV source. Here we describe application of a kV x-ray source mounted on board a medical linear accelerator for X-PACT in preparation for a phase I clinical trial of X-PACT for spontaneous tumors in pet dogs. We commissioned a 80 kVp beam at 50-80 cm from the source with varied blade settings to achieve rectangular collimated beams. Commissioning included dosimetry measurements, developing a formalism for absolute dose calculation in water, FLUKA Monte Carlo based planning and evaluation, and verification measurements. Dosimetry measurements included AAPMTG-61 absolute dose calibration, depth dose curves, backscatter and collimator scatter factors, heel effect, and leakage. Reasonable agreement was achieved between measurement and Monte Carlo, and between calculated dose and verification measurements. Finally, we demonstrate the X-PACT treatment process for an example dog with a 3-5 cc left hip sarcoma located at a 2 cm depth. The absolute dose formalism indicated 21 pulses of 160 mAs were required to deliver the prescription dose of 0.6 Gy to 2.8 cm depth. The dose distribution was calculated with the Monte Carlo planning tool and visualized at 1 x 1 x 2 mm(3) spatial resolution. A dose enhancement in the hip bone of up to 4.5 Gy was observed. This work demonstrates that X-PACT is feasible utilizing diagnostic kV sources such as those mounted on a clinical linear accelerator, and reports commissioning and treatment planning data and formalism respectively.

INTRODUCTION:Surgical skills training varies greatly between institutions and is often left to students to approach independently. Although many studies have examined single interventions of skills training, no data currently exists about the implementation of surgical skills assessment as a component of the medical student surgical curriculum. We created a technical skills competition and evaluated its effect on student surgical skill development. METHODS:Second-year medical students enrolled in the surgery clerkship voluntarily participated in a surgical skills competition consisting of knot tying, laparoscopic peg transfer, and laparoscopic pattern cut. Winning students were awarded dinner with the chair of surgery and a resident of their choice. Individual event times and combined times were recorded and compared for students who completed without disqualification. Disqualification included compromising cutting pattern, dropping a peg out of the field of vision, and incorrect knot tying technique. Timed performance was compared for 2 subsequent academic years using Mann-Whitney U test. RESULTS:Overall, 175 students competed and 71 students met qualification criteria. When compared by academic year, 2015 to 2016 students (n = 34) performed better than 2014 to 2015 students (n = 37) in pattern cut (133s vs 167s, p = 0.040), peg transfer (66s vs 101s, p < 0.001), knot tying (28s vs 30s, p = 0.361), and combined time (232s vs 283s, p = 0.009). The best time for each academic year also improved (105s vs 110s). Fundamentals of Laparoscopic Surgery proficiency standards for examined tasks were achieved by 70% of winning students. CONCLUSIONS:Implementation of an incentivized surgical skills competition improves student technical performance. Further research is needed regarding long-term benefits of surgical competitions for medical students.

To ensure reliability and reproducibility of radiobiological data, it is necessary to standardize dosimetry practices across all research institutions. The photoelectric effect predominates over other interactions at low energy and in high atomic number materials such as bone, which can lead to increased dose deposition in soft tissue adjacent to mineral bone due to secondary radiation particles. This may produce radiation effects that deviate from higher energy photon irradiation that best model exposure from clinical radiotherapy or nuclear incidences. Past theoretical considerations have indicated that this process should affect radiation exposure of neighboring bone marrow (BM) and account for reported differences in relative biological effectiveness (RBE) for hematopoietic failure in rodents. The studies described herein definitively estimate spatial dose distribution and biological effectiveness within the BM compartment for (137)Cs gamma rays and 320 kVp X rays at two levels of filtration: 1 and 4 mm Cu half-value layer (HVL). In these studies, we performed: 1. Monte Carlo simulations on a 5 μm resolution model of mouse vertebrae and femur derived from micro-CT images; 2. In vitro biological experiments irradiating BM cells plated directly on the surface of a bone-equivalent material (BEM); and 3. An in vivo study on BM cell survival in irradiated live mice. Simulation results showed that the relative dose increased in proximity to bone at the lower radiation energies and produced averaged values of relative dose over the entire BM volume within imaged trabecular bone of 1.17, 1.08 and 1.01 for beam qualities of 1 mm Cu HVL, 4 mm Cu HVL and (137)Cs, respectively. In accordance with Monte Carlo simulations, in vitro irradiation of BM cells located on BEM and in vivo whole-body irradiation at a prescribed dose to soft tissue of 6 Gy produced relative cell killing of hematopoietic progenitors (CFU-C) that significantly increased for the 1 mm Cu HVL X rays compared to radiation exposures of higher photon energies. Thus, we propose that X rays of the highest possible kVp and filtration be used to investigate radiation effects on the hematopoietic system, as this will allow for better comparisons with high-energy photon exposures applied in radiotherapy or as anticipated in a nuclear event.

PURPOSE:Accurate dosimetry is essential when irradiating mice to ensure that functional and molecular endpoints are well understood for the radiation dose delivered. Conventional methods of prescribing dose in mice involve the use of a single dose rate measurement and assume a uniform average dose throughout all organs of the entire mouse. Here, the authors report the individual average organ dose values for the irradiation of a 12, 23, and 33 g mouse on a 320 kVp x-ray irradiator and calculate the resulting error from using conventional dose prescription methods. METHODS:Organ doses were simulated in the Geant4 application for tomographic emission toolkit using the MOBY mouse whole-body phantom. Dosimetry was performed for three beams utilizing filters A (1.65 mm Al), B (2.0 mm Al), and C (0.1 mm Cu + 2.5 mm Al), respectively. In addition, simulated x-ray spectra were validated with physical half-value layer measurements. RESULTS:Average doses in soft-tissue organs were found to vary by as much as 23%-32% depending on the filter. Compared to filters A and B, filter C provided the hardest beam and had the lowest variation in soft-tissue average organ doses across all mouse sizes, with a difference of 23% for the median mouse size of 23 g. CONCLUSIONS:This work suggests a new dose prescription method in small animal dosimetry: it presents a departure from the conventional approach of assigninga single dose value for irradiation of mice to a more comprehensive approach of characterizing individual organ doses to minimize the error and uncertainty. In human radiation therapy, clinical treatment planning establishes the target dose as well as the dose distribution, however, this has generally not been done in small animal research. These results suggest that organ dose errors will be minimized by calibrating the dose rates for all filters, and using different dose rates for different organs.

Using the South Pole Acoustic Test Setup (SPATS) and a retrievable transmitter deployed in holes drilled for the IceCube experiment, we have measured the attenuation of acoustic signals by South Pole ice at depths between 190 m and 500 m. Three data sets, using different acoustic sources, have been analyzed and give consistent results. The method with the smallest systematic uncertainties yields an amplitude attenuation coefficient alpha = 3.20 \pm 0.57 km^(-1) between 10 and 30 kHz, considerably larger than previous theoretical estimates. Expressed as an attenuation length, the analyses give a consistent result for lambda = 1/alpha of ~1/300 m with 20% uncertainty. No significant depth or frequency dependence has been found.

We report on the search for electromagnetic and hadronic showers (“cascades”) produced by a diffuse flux of extraterrestrial neutrinos in the AMANDA neutrino telescope. Data for this analysis were recorded during 1001 days of detector livetime in the years 2000–2004. The observed event rates are consistent with the background expectation from atmospheric neutrinos and muons. An upper limit is derived for the diffuse flux of neutrinos of all flavors assuming a flavor ratio of νe:νμ:ντ = 1:1:1 at the detection site. The all-flavor flux of neutrinos with an energy spectrum Φ ∝ E−2 is less than 5.0 × 10−7 GeV s−1 sr−1 cm−2 at a 90% C.L. Here, 90% of the simulated signal would fall within the energy range 40 TeV to 9 PeV. We discuss flux limits in the context of several specific models of extraterrestrial and prompt atmospheric neutrino production.

IceCube Collaboration Contributions to the 2009 International Cosmic Ray Conference

Over 5,000 PMTs are being deployed at the South Pole to compose the IceCube neutrino observatory. Many are placed deep in the ice to detect Cherenkov light emitted by the products of high-energy neutrino interactions, and others are frozen into tanks on the surface to detect particles from atmospheric cosmic ray showers. IceCube is using the 10-inch diameter R7081-02 made by Hamamatsu Photonics. This paper describes the laboratory characterization and calibration of these PMTs before deployment. PMTs were illuminated with pulses ranging from single photons to saturation level. Parameterizations are given for the single photoelectron charge spectrum and the saturation behavior. Time resolution, late pulses and afterpulses are characterized. Because the PMTs are relatively large, the cathode sensitivity uniformity was measured. The absolute photon detection efficiency was calibrated using Rayleigh-scattered photons from a nitrogen laser. Measured characteristics are discussed in the context of their relevance to IceCube event reconstruction and simulation efforts.

Reference EPFL-ARTICLE-154501doi:10.1088/0004-637X/708/1/911View record in Web of Science Record created on 2010-11-05, modified on 2017-05-12

We investigate the discovery potential of cubic-kilometer neutrino observatories such as IceCube to set stringent limits on the forbidden decays $\ensuremath{\eta}\ensuremath{\rightarrow}{\ensuremath{\nu}}_{e}{\overline{\ensuremath{\nu}}}_{e}$ and $\ensuremath{\eta}\ensuremath{\rightarrow}{\ensuremath{\nu}}_{\ensuremath{\tau}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}}$. The signatures for these decays are cascade events resulting from the charged-current reactions of ${\ensuremath{\nu}}_{e}$, ${\ensuremath{\nu}}_{\ensuremath{\tau}}$, ${\overline{\ensuremath{\nu}}}_{e}$, and ${\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}}$ on nuclei in such detectors. Background cascade events are mainly due to ${\ensuremath{\nu}}_{e}$'s from atmospheric $\ensuremath{\mu}$, ${K}^{+}$, and ${K}_{S}^{0}$ decays and to a lesser extent from atmospheric ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ neutral-current interactions with nuclei. A direct upper limit for the branching ratio $\ensuremath{\eta}\ensuremath{\rightarrow}{\ensuremath{\nu}}_{e,\ensuremath{\tau}}{\overline{\ensuremath{\nu}}}_{e,\ensuremath{\tau}}$ of $6.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ at 90% CL can be achieved.

The objective of this paper is threefold: (1) to establish sensitivity of XRQA and EBT radiochromic films to fast neutron exposure; (2) to develop a film response to radiation dose calibration curve and (3) to investigate a two-dimensional (2D) film dosimetry technique for use in establishing an experimental setup for a radiobiological irradiation of mice and to assess the dose to the mice in this setup. The films were exposed to a 10 MeV neutron beam via the (2)H(d,n)(3)He reaction. The XRQA film response was a factor of 1.39 greater than EBT film response to the 10 MeV neutron beam when exposed to a neutron dose of 165 cGy. A film response-to-soft tissue dose calibration function was established over a range of 0-10 Gy and had a goodness of fit of 0.9926 with the calibration data. The 2D film dosimetry technique estimated the neutron dose to the mice by measuring the dose using a mouse phantom and by placing a piece of film on the exterior of the experimental mouse setup. The film results were benchmarked using Monte Carlo and aluminum (Al) foil activation measurements. The radiochromic film, Monte Carlo and Al foil dose measurements were strongly correlated, and the film within the mouse phantom agreed to better than 7% of the externally mounted films. These results demonstrated the potential application of radiochromic films for passive 2D neutron dosimetry.

We present the results of searches for high-energy muon neutrinos from 41 gamma- ray bursts (GRBs) in the northern sky with the IceCube detector in its 22-string con- figuration active in 2007/2008. The searches cover both the prompt and a possible precursor emission as well as a model-independent, wide time window of -1 h to +3 h around each GRB. In contrast to previous searches with a large GRB population, we do not utilize a standard Waxman?Bahcall GRB flux for the prompt emission but calcu- late individual neutrino spectra for all 41 GRBs from the burst parameters measured by satellites. For all three time windows the best estimate for the number of signal events is zero. Therefore, we place 90percent CL upper limits on the fluence from the prompt phase of 3.7 x 10-3 erg cm-2 (72TeV - 6.5 PeV) and on the fluence from the precursor phase of 2.3 x 10-3 erg cm-2 (2.2TeV - 55TeV), where the quoted energy ranges contain 90percent of the expected signal events in the detector. The 90percent CL upper limit for the wide time window is 2.7 x 10-3 erg cm-2 (3TeV - 2.8 PeV) assuming an E-2 flux.

We have measured the speed of both pressure waves and shear waves as a function of depth between 80 and 500 m depth in South Pole ice with better than 1% precision. The measurements were made using the South Pole Acoustic Test Setup ({SPATS}), an array of transmitters and sensors deployed in the ice at South Pole Station in order to measure the acoustic properties relevant to acoustic detection of astrophysical neutrinos. The transmitters and sensors use piezoceramics operating at $\sim$5-25 kHz. Between 200 m and 500 m depth, the measured profile is consistent with zero variation of the sound speed with depth, resulting in zero refraction, for both pressure and shear waves. We also performed a complementary study featuring an explosive signal propagating from 50 to 2250 m depth, from which we determined a value for the pressure wave speed consistent with that determined with the sensors operating at shallower depths and higher frequencies. These results have encouraging implications for neutrino astronomy: The negligible refraction of acoustic waves deeper than 200 m indicates that good neutrino direction and energy reconstruction, as well as separation from background events, could be achieved.

A search for muon neutrinos from Kaluza-Klein dark matter annihilations in the Sun has been performed with the 22-string configuration of the IceCube neutrino detector using data collected in 104.3 days of live-time in 2007. No excess over the expected atmospheric background has been observed. Upper limits have been obtained on the annihilation rate of captured lightest Kaluza-Klein particle (LKP) WIMPs in the Sun and converted to limits on the LKP-proton cross-sections for LKP masses in the range 250 -- 3000 GeV. These results are the most stringent limits to date on LKP annihilation in the Sun.

We investigate the discovery potential of cubic-kilometer neutrino observatories such as IceCube to set stringent limits on the forbidden decays eta -> nu(e)(nu) over bar (e) and eta -> nu(tau)(nu) over bar (tau). The signatures for these decays are cascade events resulting from the charged-current reactions of nu(e), nu(tau), (nu) over bar (e), and (nu) over bar (tau) on nuclei in such detectors. Background cascade events are mainly due to nu(e)'s from atmospheric mu, K+, and K-S(0) decays and to a lesser extent from atmospheric nu(mu) neutral-current interactions with nuclei. A direct upper limit for the branching ratio eta -> nu(e,tau)(nu) over bar (e,tau) of 6.1 x 10(-4) at 90% CL can be achieved.

The muon and anti-muon neutrino energy spectrum is determined from 2000-2003 AMANDA telescope data using regularised unfolding. This is the first measurement of atmospheric neutrinos in the energy range 2 - 200 TeV. The result is compared to different atmospheric neutrino models and it is compatible with the atmospheric neutrinos from pion and kaon decays. No significant contribution from charm hadron decays or extraterrestrial neutrinos is detected. The capabilities to improve the measurement of the neutrino spectrum with the successor experiment IceCube are discussed.