Comparative dosimetry in intracavitary balloon catheter brachytherapy with I-125 and in Cf-252 brachytherapy combined with BNCT for brain tumors

Objective Comparative analysis of dosimetry in intracavitary balloon catheter brachytherapy with I-125 and in Cf-252 brachytherapy combined with BNCT for treatment of brain tumors. Materials and Methods Simulations of intracavitary balloon catheter brachytherapy with I-125 and in Cf-252 brachytherapy combined with BNCT were performed with the MCNP5 code, modeling the treatment of a brain tumor on a voxel computational phantom representing a human head. Absorbed dose rates were converted into biologically weighted dose rates. Results Intracavitary balloon catheter brachytherapy with I-125 produced biologically weighted mean dose rates of 3.2E-11, 1.3E-10, 1.9E-11 and 6.9E-13 RBE.Gy.h-1.p-1.s, respectively, on the healthy tissue, on the balloon periphery and on the I 1 and I 2 tumor infiltration zones. On the other hand, Cf-252 brachytherapy combined with BNCT produced a biologically weighted mean dose rate of 5.2E-09, 2.3E-07, 8.7E-09 and 2.4E-09 RBE.Gy.h-1.p-1.s, respectively on the healthy tissue, on the target tumor and on the I 1 and I 2 infiltration zones. Conclusion Cf-252 brachytherapy combined with BNCT delivered a selective irradiation to the target tumor and to infiltration zones, while intracavitary balloon catheter brachytherapy with I-125 delivered negligible doses on the tumor infiltration zones.

Balloon-based adjuvant radiotherapy in breast cancer: comparison between 99mTc and HDR 192Ir

Abstract Objective: To perform a comparative dosimetric analysis, based on computer simulations, of temporary balloon implants with 99mTc and balloon brachytherapy with high-dose-rate (HDR) 192Ir, as boosts to radiotherapy. We hypothesized that the two techniques would produce equivalent doses under pre-established conditions of activity and exposure time. Materials and Methods: Simulations of implants with 99mTc-filled and HDR 192Ir-filled balloons were performed with the Siscodes/MCNP5, modeling in voxels a magnetic resonance imaging set related to a young female. Spatial dose rate distributions were determined. In the dosimetric analysis of the protocols, the exposure time and the level of activity required were specified. Results: The 99mTc balloon presented a weighted dose rate in the tumor bed of 0.428 cGy.h-1.mCi-1 and 0.190 cGyh-1.mCi-1 at the balloon surface and at 8-10 mm from the surface, respectively, compared with 0.499 and 0.150 cGyh-1.mCi-1, respectively, for the HDR 192Ir balloon. An exposure time of 24 hours was required for the 99mTc balloon to produce a boost of 10.14 Gy with 1.0 Ci, whereas only 24 minutes with 10.0 Ci segments were required for the HDR 192Ir balloon to produce a boost of 5.14 Gy at the same reference point, or 10.28 Gy in two 24-minutes fractions. Conclusion: Temporary 99mTc balloon implantation is an attractive option for adjuvant radiotherapy in breast cancer, because of its availability, economic viability, and similar dosimetry in comparison with the use of HDR 192Ir balloon implantation, which is the current standard in clinical practice.

Atherosclerosis and acute arterial thrombosis in rabbits: a model using balloon desendothelization without dietary intervention

Acute thrombosis can be induced in rabbits by a triggering protocol using Russell's viper venom and histamine given after 8 months of a 1% cholesterol diet and balloon desendothelization. In the present study, we tested the hypothesis that aortic desendothelization performed 4 months before the triggering protocol without a high cholesterol diet is a highly effective and less expensive way of producing arterial atherosclerosis and thrombosis. Nineteen male New Zealand white rabbits on a normal diet were studied. The control group (N = 9) received no intervention during the 4-month observation period, while the other group (N = 10) was submitted to aortic balloon desendothelization using a 4F Fogarty catheter. At the end of this period, all animals were killed 48 h after receiving the first dose of the triggering treatment. Eight of 10 rabbits (80%) in the balloon-trauma group presented platelet-rich arterial thrombosis while none of the animals in the control group had thrombus formation (P<0.01). Thus, this model, using balloon desendothelization without dietary manipulation, induces arterial atherosclerosis and thrombosis and may provide possibilities to test new therapeutic approaches

Évaluation de la valeur pronostique de la lactatémie lors de dilatation à droite de la caillette ou de volvulus abomasal chez la vache laitière

Dans les élevages laitiers d’aujourd’hui, les déplacements de la caillette sont parmi les conditions chirurgicales les plus souvent rencontrées. Le pronostic pour ces pathologies est cependant très différent que l’on soit en présence d’une dilatation de la caillette à droite (DCD) ou d’un volvulus de la caillette (VC). En pratique, la distinction en période préopératoire entre ces deux conditions est difficile. Afin de limiter les pertes économiques associées aux DCD/VC, l’identification et la réforme précoce des animaux ayant le plus grand risque d’avoir une mauvaise évolution postopératoire deviennent des enjeux de premier plan. Les objectifs de cette étude étaient de déterminer la valeur pronostique de la L-lactatémie (LAC) mesurée à la ferme en préopératoire à l’aide d’un appareil portatif chez des vaches souffrant de DCD ou VC et de suggérer des seuils de LAC cliniquement significatifs. Nos résultats indiquent que la LAC est un bon indicateur pronostique lors de DCD/VC. Une LAC ≤ 2 mmol/L est un bon indicateur de succès chirurgical et s’avère très utile pour appuyer la décision d’opérer l’animal (sensibilité, spécificité, valeurs prédictives positive et négative de respectivement 76.2, 82.7, 53.3 et 93.1%). Par ailleurs, il n’y a aucun avantage économique à effectuer une chirurgie chez des vaches commerciales souffrant de DCD/VC qui ont une LAC ≥ 6 mmol/L (sensibilité, spécificité, valeurs prédictives positive et négative de respectivement 28.6, 97.5, 75 et 84%). Par conséquent, ces animaux devraient, dans la plupart des cas, être réformés en raison de la probabilité élevée qu’ils aient une mauvaise évolution postopératoire.

The balloon.

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A three-dimensional magnetometer for motion sensing of a balloon-carried atmospheric measurement package

An instrument is described which carries three orthogonal geomagnetic field sensors on a standard meteorological balloon package, to sense rapid motion and position changes during ascent through the atmosphere. Because of the finite data bandwidth available over the UHF radio link, a burst sampling strategy is adopted. Bursts of 9s of measurements at 3.6Hz are interleaved with periods of slow data telemetry lasting 25s. Calculation of the variability in each channel is used to determine position changes, a method robust to periods of poor radio signals. During three balloon ascents, variability was found repeatedly at similar altitudes, simultaneously in each of three orthogonal sensors carried. This variability is attributed to atmospheric motions. It is found that the vertical sensor is least prone to stray motions, and that the use of two horizontal sensors provides no additional information over a single horizontal sensor

A double-Gerdien instrument for simultaneous bipolar air conductivity measurements on balloon platforms

A bipolar air conductivity instrument is described for use with a standard disposable meteorological radiosonde package. It is intended to provide electrical measurements at cloud boundaries, where the ratio of the bipolar air conductivities is affected by the presence of charged particles. The sensors are two identical Gerdien-type electrodes, which, through a voltage decay method, measure positive and negative air conductivities simultaneously. Voltage decay provides a thermally stable approach and a novel low current leakage electrometer switch is described which initiates the decay sequence. The radiosonde supplies power and telemetry, as well as measuring simultaneous meteorological data. A test flight using a tethered balloon determined positive (σ+) and negative (σ−) conductivities of σ+ = 2.77±0.2 fS m−1 and σ− = 2.82±0.2 fS m−1, respectively, at 400 m aloft, with σ+/σ− = 0.98±0.04.

A lightweight balloon-carried cloud charge sensor

Despite the importance of microphysical cloud processes on the climate system, some topics are under-explored. For example, few measurements of droplet charges in nonthunderstorm clouds exist. Balloon carried charge sensors can be used to provide new measurements. A charge sensor is described for use with meteorological balloons, which has been tested over a range of atmospheric temperatures from -60 to 20 degrees C, in cloudy and clear air. The rapid time response of the sensor (to >10 V s(-1)) permits charge densities from 100 fC m(-3) to 1 nC m(-3) to be determined, which is sufficient for it to act as a cloud edge charge detector at weakly charged horizontal cloud boundaries.

Comparison of balloon-carried atmospheric motion sensors with Doppler lidar turbulence measurements

Magnetic sensors have been added to a standard weather balloon radiosonde package to detect motion in turbulent air. These measure the terrestrial magnetic field and return data over the standard uhf radio telemetry. Variability in the magnetic sensor data is caused by motion of the instrument package. A series of radiosonde ascents carrying these sensors has been made near a Doppler lidar measuring atmospheric properties. Lidar-retrieved quantities include vertical velocity (w) profile and its standard deviation (w). w determined over 1 h is compared with the radiosonde motion variability at the same heights. Vertical motion in the radiosonde is found to be robustly increased when w>0.75 m s−1 and is linearly proportional to w. ©2009 American Institute of Physics

A method for estimating the turbulent kinetic energy dissipation rate from a vertically pointing Doppler lidar, and independent evaluation from balloon-borne in situ measurements

A method of estimating dissipation rates from a vertically pointing Doppler lidar with high temporal and spatial resolution has been evaluated by comparison with independent measurements derived from a balloon-borne sonic anemometer. This method utilizes the variance of the mean Doppler velocity from a number of sequential samples and requires an estimate of the horizontal wind speed. The noise contribution to the variance can be estimated from the observed signal-to-noise ratio and removed where appropriate. The relative size of the noise variance to the observed variance provides a measure of the confidence in the retrieval. Comparison with in situ dissipation rates derived from the balloon-borne sonic anemometer reveal that this particular Doppler lidar is capable of retrieving dissipation rates over a range of at least three orders of magnitude. This method is most suitable for retrieval of dissipation rates within the convective well-mixed boundary layer where the scales of motion that the Doppler lidar probes remain well within the inertial subrange. Caution must be applied when estimating dissipation rates in more quiescent conditions. For the particular Doppler lidar described here, the selection of suitably short integration times will permit this method to be applicable in such situations but at the expense of accuracy in the Doppler velocity estimates. The two case studies presented here suggest that, with profiles every 4 s, reliable estimates of ϵ can be derived to within at least an order of magnitude throughout almost all of the lowest 2 km and, in the convective boundary layer, to within 50%. Increasing the integration time for individual profiles to 30 s can improve the accuracy substantially but potentially confines retrievals to within the convective boundary layer. Therefore, optimization of certain instrument parameters may be required for specific implementations.