Sonographic evaluation of maternal uterine artery from 11 - 30 weeks 6 days of gestational age in a Nigerian population: A predictive index for pre-eclampsia and intrauterine growth restriction.

INTRODUCTION: Uterine artery (UtA) Doppler sonography is a potential screening tool for pregnancy complications in placental insufficiency. Evaluation of the maternal and fetal vessels in pregnancy ensures accurate identification and prediction of pregnancy complications, such as preeclampsia (PE) and intrauterine growth restrictions (IUGR). The study aims to establish local reference values for UtA in a Nigerian population. METHODS: This prospective longitudinal study was conducted among 230 pregnant women. All participants had their left (Lt) and right (RT) UtAs evaluated with a Doppler ultrasound from 11 to 30 weeks 6 days of gestational age. Peak systolic velocity (PSV), End diastolic Velocity (EDV), Systolic/Diastolic ratio (S/D), Pulsatility Index (PI), and Resistivity Index (RI) were measured and documented. RESULTS: The mean values of UtA at 11-30 weeks 6 days of GA ranged as follows: 0.79-0.53 (RI), 1.83-0.79 (PI), 5.16-2.23 (S/D), 96.37-98.00 (PSV) & 26.07-44.14 (EDV). While the mean values of the Rt. & Lt. UtA 's ranged as follows: 0.79-0.50 (RI. Rt), 0.78-0.56 (RI. Lt), 2.05-0.80 (PI. Rt), 1.61-0.78 (PI. Lt), 6.03-2.13 (S/D. Rt), 4.29-2.33 (S/D. Lt), 89.79-99.23 (PSV. Rt), 102.76-96.71 (PSV. Lt) & 23.31-45.25 (EDV. Rt), 28.83-43.02 (EDV. Lt) respectively. CONCLUSION: UtA Doppler reference range was established in the study population. These reference ranges will be of clinical value in daily obstetric practice. IMPLICATION FOR PRACTICE: Obstetricians and sonographers will apply these values for early prediction of pregnancies at risk of complications in the locality.

A CAD interface for GEANT4.

Often CAD models already exist for parts of a geometry being simulated using GEANT4. Direct import of these CAD models into GEANT4 however, may not be possible and complex components may be difficult to define via other means. Solutions that allow for users to work around the limited support in the GEANT4 toolkit for loading predefined CAD geometries have been presented by others, however these solutions require intermediate file format conversion using commercial software. Here within we describe a technique that allows for CAD models to be directly loaded as geometry without the need for commercial software and intermediate file format conversion. Robustness of the interface was tested using a set of CAD models of various complexity; for the models used in testing, no import errors were reported and all geometry was found to be navigable by GEANT4.

Radiotherapy Monte Carlo simulation using cloud computing technology.

Cloud computing allows for vast computational resources to be leveraged quickly and easily in bursts as and when required. Here we describe a technique that allows for Monte Carlo radiotherapy dose calculations to be performed using GEANT4 and executed in the cloud, with relative simulation cost and completion time evaluated as a function of machine count. As expected, simulation completion time decreases as 1/n for n parallel machines, and relative simulation cost is found to be optimal where n is a factor of the total simulation time in hours. Using the technique, we demonstrate the potential usefulness of cloud computing as a solution for rapid Monte Carlo simulation for radiotherapy dose calculation without the need for dedicated local computer hardware as a proof of principal.

A method for the inter-calibration of a matrix of sensors.

We present a quick and easy method for the calibration of a matrix of sensors. The algorithm is based on a three-step irradiation procedure which relies only on the constancy of the delivered fluence at each step. With this method the gain of each sensor is derived relative to a reference detector. The algorithm has been applied to a matrix of (32 x 32) ionization chambers. After the calibration coefficients have been applied, by comparing the response of the matrix of chambers to a reference detector over a large field, we determined that the fluence measurement of individual chambers is better than 0.7%. The algorithm solves the cumbersome problem of the relative gain calibration of a matrix of a large number of sensors.

Miniature semiconductor detectors for in vivo dosimetry.

Silicon mini-semiconductor detectors are found in wide applications for in vivo personal dosimetry and dosimetry and microdosimetry of different radiation oncology modalities. These applications are based on integral and spectroscopy modes of metal oxide semiconductor field effect transistor and silicon p-n junction detectors. The advantages and limitations of each are discussed.

Charge collection imaging of a monolithic DeltaE-E telescope for radiation protection applications.

The development of microdosimeters and particle telescopes is important for risk assessment in space and aviation applications. The charge collection properties of a monolithic particle telescope, suitable for both microdosimetry and fluence based approaches, were studied using an ion microprobe.

Absorbed dose-to-water protocol applied to synchrotron-generated x-rays at very high dose rates.

Microbeam radiation therapy (MRT) is a new radiation treatment modality in the pre-clinical stage of development at the ID17 Biomedical Beamline of the European synchrotron radiation facility (ESRF) in Grenoble, France. MRT exploits the dose volume effect that is made possible through the spatial fractionation of the high dose rate synchrotron-generated x-ray beam into an array of microbeams. As an important step towards the development of a dosimetry protocol for MRT, we have applied the International Atomic Energy Agency's TRS 398 absorbed dose-to-water protocol to the synchrotron x-ray beam in the case of the broad beam irradiation geometry (i.e. prior to spatial fractionation into microbeams). The very high dose rates observed here mean the ion recombination correction factor, k s , is the most challenging to quantify of all the necessary corrections to apply for ionization chamber based absolute dosimetry. In the course of this study, we have developed a new method, the so called 'current ramping' method, to determine k s for the specific irradiation and filtering conditions typically utilized throughout the development of MRT. Using the new approach we deduced an ion recombination correction factor of 1.047 for the maximum ESRF storage ring current (200 mA) under typical beam spectral filtering conditions in MRT. MRT trials are currently underway with veterinary patients at the ESRF that require additional filtering, and we have estimated a correction factor of 1.025 for these filtration conditions for the same ESRF storage ring current. The protocol described herein provides reference dosimetry data for the associated Treatment Planning System utilized in the current veterinary trials and anticipated future human clinical trials.

Multi-strip silicon sensors for beam array monitoring in micro-beam radiation therapy.

We present here the latest results from tests performed at the ESRF ID17 and ID21 beamlines for the characterization of novel beam monitors for Microbeam Radiation Therapy (MRT), which is currently being implemented at ID17. MRT aims at treating solid tumors by exploiting an array of evenly spaced microbeams, having an energy spectrum distributed between 27 and 600keV and peaking at 100keV. Given the high instantaneous dose delivered (up to 20kGy/s), the position and the intensity of the microbeams has to be precisely and instantly monitored. For this purpose, we developed dedicated silicon microstrip beam monitors. We have successfully characterized them, both with a microbeam array at ID17, and a submicron scanning beam at ID21. We present here the latest results obtained in recent tests along with an outlook on future developments.

D-IMRT verification with a 2D pixel ionization chamber: dosimetric and clinical results in head and neck cancer.

Dynamic intensity-modulated radiotherapy (D-IMRT) using the sliding-window technique is currently applied for selected treatments of head and neck cancer at Institute for Cancer Research and Treatment of Candiolo (Turin, Italy). In the present work, a PiXel-segmented ionization Chamber (PXC) has been used for the verification of 19 fields used for four different head and neck cancers. The device consists of a 32x32 matrix of 1024 parallel-plate ionization chambers arranged in a square of 24x24 cm2 area. Each chamber has 0.4 cm diameter and 0.55 cm height; a distance of 0.75 cm separates the centre of adjacent chambers. The sensitive volume of each single ionization chamber is 0.07 cm3. Each of the 1024 independent ionization chambers is read out with a custom microelectronics chip.The output factors in water obtained with the PXC at a depth of 10 cm were compared to other detectors and the maximum difference was 1.9% for field sizes down to 3x3 cm2. Beam profiles for different field dimensions were measured with the PXC and two other types of ionization chambers; the maximum distance to agreement (DTA) in the 20-80% penumbra region of a 3x3 cm2 field was 0.09 cm. The leaf speed of the multileaf collimator was varied between 0.07 and 2 cm s-1 and the detector response was constant to better than 0.6%. The behaviour of the PXC was measured while varying the dose rate between 0.21 and 1.21 Gy min-1; the mean difference was 0.50% and the maximum difference was 0.96%. Using fields obtained with an enhanced dynamic wedge and a staircase-like (step) IMRT field, the PXC has been tested for simple 1D modulated beams; comparison with film gave a maximum DTA of 0.12 cm. The PXC was then used to check four different IMRT plans for head and neck cancer treatment: cervical chordoma, parotid, ethmoid and skull base. In the comparison of the PXC versus film and PXC versus treatment planning system, the number of pixels with gamma parameter

Tolerance data of Gd-DTPA: a review.

Gd-DTPA is the first paramagnetic contrast agent approved for clinical use in cranial and spinal MRI in the F.R.G., U.S.A., Japan and several other countries. After submission 13,439 patients were enrolled in standardized protocolled clinical trials. The observed adverse drug reactions (ADRs) after i.v. injection of Gd-DTPA were comparable to those after administration of iodinated non-ionic roentgen contrast media (CM). However, the overall incidence of ADRs after intravenous injection of 0.1 or 0.2 mmol/kg body weight Gd-DTPA was found to be even lower. Adverse events were observed in only 1.46% of the patients - or 1.14% if localized warmth is excluded. None of them was critical. There was no correlation between patient age and the incidence of ADRs. In patients with a known history of allergy the incidence of ADRs was increased by a factor 3-4, which is still lower than the incidence reported after intravenous administration of iodinated non-ionic roentgen CM to patients without known allergy. Good renal tolerance was seen in all patients, irrespective of pre-existing renal impairment. Fast bolus injections of Gd-DTPA were tolerated without added risk. The favorable safety profile is also reflected in the post marketing surveillance reports since Gd-DTPA became available as a commercial drug.

A grounded theory study of the experience of type 2 diabetes mellitus in First Nations adults in Canada.

Diabetes among First Nations peoples has reached epidemic proportions, and diabetes prevalence, complications, and mortality rates are higher than in Whites. The purpose of this grounded theory study was to investigate the experience of Type 2 diabetes in First Nations adults. Ten individuals living in one reserve community, in southwestern Ontario, participated in this research. Participants were interviewed on two occasions by a First Nations nurse. All interviews were audiotaped and transcribed verbatim. A three-phase process of integration emerged, similar to the process of integration discovered in prior research with Type 1 diabetic Whites. However, there were some important differences in the characteristics of these three phases. In addition, there were surprising findings related to beliefs about the type of diabetes educator desired by these First Nations clients.

Solid state microdosimetry in hadron therapy.

A report of recent developments in silicon microdosimetry is presented. SOI based microdosemeters have shown promise as a viable alternative to traditional tissue-equivalent proportional counters. The application of these silicon microdosemeters to such radiation therapy modalities as boron neutron capture therapy (BNCT), boron neutron capture synovectomy (BNCS), proton therapy (PT), and fast neutron therapy (FNT) has been performed. Several shortcomings of the current silicon microdosemeter were identified and will be taken into account in the design of a second-generation device.

Simulations of silicon microdosimetry measurements in fast neutron therapy.

Experimental silicon microdosimetry measurements were performed at a Fast Neutron Therapy facility. Monte Carlo based calculations of these measurements were made using the GEANT4 toolkit. Reasonable agreement between theoretical and experimental results was obtained and the contribution of elastic and inelastic reaction products to the final microdosimetric spectrum was determined.

Geant4 simulation of the CERN-EU high-energy reference field (CERF) facility.

The CERN-EU high-energy reference field facility is used for testing and calibrating both active and passive radiation dosemeters for radiation protection applications in space and aviation. Through a combination of a primary particle beam, target and a suitable designed shielding configuration, the facility is able to reproduce the neutron component of the high altitude radiation field relevant to the jet aviation industry. Simulations of the facility using the GEANT4 (GEometry ANd Tracking) toolkit provide an improved understanding of the neutron particle fluence as well as the particle fluence of other radiation components present. The secondary particle fluence as a function of the primary particle fluence incident on the target and the associated dose equivalent rates were determined at the 20 designated irradiation positions available at the facility. Comparisons of the simulated results with previously published simulations obtained using the FLUKA Monte Carlo code, as well as with experimental results of the neutron fluence obtained with a Bonner sphere spectrometer, are made.

[Effect of certain causes of death on life expectancy in the Federal Republic of Germany]. / Auswirkuingen ausgewählter Todesursachen auf die Lebenserwartung in der Bundesrepublik Deutschland.

PIP: The authors present an analysis of the 10 major causes of death in the Federal Republic of Germany in 1970 and 1976 with regard to their impact on life expectancy. The relative impact of eliminating each of the 10 causes of death on life expectancy by sex is considered. (summary in ENG)^ieng

Safety of gadolinium-DTPA: extended clinical experience.

This review reports data on the general and renal tolerance of the paramagnetic contrast agent Gd-DTPA after intravenous administration. Gd-DTPA was administered usually at a dose level of 0.1-0.2 mmol/kg body wt (range: 0.005-0.25 mmol/kg body wt) in cranial, spinal and body MR indications. In phase I-IIIa studies a total of 2154 healthy volunteers and patients were investigated, usually at a dose of 0.1 mmol/kg body wt. From the obtained results it was concluded that adverse events (AEs) may be expected in the order of magnitude of 1%. In phase IIIb-IV studies 13,439 patients were investigated at 0.1 or 0.2 mmol/kg body wt. Tolerance data were collected according to a standardized protocol and metaanalysis of obtained data was performed. AEs, irrespective of their drug relationship, were observed in 1.15% of the patients. The observed AEs were comparable to those after intravenous administration of iodinated nonionic X-ray contrast media. There was no correlation between patient age and the incidence of AEs. In patients with a known history of allergy the incidence of AEs increased to 2.6%. In pediatric use no added risk was observed in a total of 826 neonates, children, and adolescents up to 18 years of age. Gd-DTPA showed good renal tolerance in patients with and without preexisting impairment of renal function. A prospective open safety and pharmacokinetic study was conducted in patients with hemodialysis. Gd-DTPA was shown to be eliminated completely by hemodialysis. Fast bolus injections were tolerated without added risk. Presented data from postmarketing surveillance (up to March 31, 1991) cover an estimated total of more than 2,000,000 applications.(ABSTRACT TRUNCATED AT 250 WORDS)