Early postnatal high-dose fat-soluble enteral vitamin A supplementation for moderate or severe bronchopulmonary dysplasia or death in extremely low birthweight infants (NeoVitaA): a multicentre, randomised, parallel-group, double-blind, placebo-controlled, investigator-initiated phase 3 trial

BACKGROUND

Vitamin A plays a key role in lung development, but there is no consensus regarding the optimal vitamin A dose and administration route in extremely low birthweight (ELBW) infants. We aimed to assess whether early postnatal additional high-dose fat-soluble enteral vitamin A supplementation versus placebo would lower the rate of moderate or severe bronchopulmonary dysplasia or death in ELBW infants receiving recommended basic enteral vitamin A supplementation.

METHODS

This prospective, multicentre, randomised, parallel-group, double-blind, placebo-controlled, investigator-initiated phase 3 trial conducted at 29 neonatal intensive care units in Austria and Germany assessed early high-dose enteral vitamin A supplementation (5000 international units [IU]/kg per day) or placebo (peanut oil) for 28 days in ELBW infants. Eligible infants had a birthweight of more than 400 g and less than 1000 g; gestational age at birth of 32+0 weeks postmenstrual age or younger; and the need for mechanical ventilation, non-invasive respiratory support, or supplemental oxygen within the first 72 h of postnatal age after admission to the neonatal intensive care unit. Participants were randomly assigned by block randomisation with variable block sizes (two and four). All participants received basic vitamin A supplementation (1000 IU/kg per day). The composite primary endpoint was moderate or severe bronchopulmonary dysplasia or death at 36 weeks postmenstrual age, analysed in the intention-to-treat population. This trial was registered with EudraCT, 2013-001998-24.

FINDINGS

Between March 2, 2015, and Feb 27, 2022, 3066 infants were screened for eligibility at the participating centres. 915 infants were included and randomly assigned to the high-dose vitamin A group (n=449) or the control group (n=466). Mean gestational age was 26·5 weeks (SD 2·0) and mean birthweight was 765 g (162). Moderate or severe bronchopulmonary dysplasia or death occurred in 171 (38%) of 449 infants in the high-dose vitamin A group versus 178 (38%) of 466 infants in the control group (adjusted odds ratio 0·99, 95% CI 0·73-1·55). The number of participants with at least one adverse event was similar between groups (256 [57%] of 449 in the high-dose vitamin A group and 281 [60%] of 466 in the control group). Serum retinol concentrations at baseline, at the end of intervention, and at 36 weeks postmenstrual age were similar in the two groups.

INTERPRETATION

Early postnatal high-dose fat-soluble enteral vitamin A supplementation in ELBW infants was safe, but did not change the rate of moderate or severe bronchopulmonary dysplasia or death and did not substantially increase serum retinol concentrations.

FUNDING

Deutsche Forschungsgemeinschaft and European Clinical Research Infrastructures Network (ECRIN).

Similar adverse outcome rates with high or low oxygen saturation targets in an area with low background mortality

Background

Randomized controlled trials have indicated reduced mortality rates in very preterm infants assigned to high compared to low oxygen saturation (SpO2) target levels, accompanied by higher rates of retinopathy of prematurity and bronchopulmonary dysplasia. However, the benefit-to-harm ratio may depend on the local background mortality risk. We therefore aimed to quantify the risk-benefit ratios of different SpO2 target ranges in 10 tertiary newborn intensive care units (NICUs) in East Germany.

Methods

In a retrospective multicenter study, 1,399 infants born between 2008 and 2012 at a gestational age between 24 0/7 and 27 6/7 weeks and with a birthweight below 1,250 g were grouped according to the hospital's target SpO2 range [high oxygen saturation group (HOSG) above 90%], low oxygen saturation group (LOSG) below 90%] and the compliance of units with their target SpO2 range. The association between neonatal morbidities, neurodevelopmental outcomes, selected treatment strategies, and target SpO2 ranges was calculated using chi-squared and Mann Whitney U tests.

Results

Nine of the ten participating NICUs met their SpO2 target ranges. Five units were considered as HOSG, and five units were considered as LOSG. Necrotizing enterocolitis and intraventricular hemorrhage grade ≥ 2 occurred significantly more frequently in the HOSG than in the LOSG (8.4% vs. 5.1%, p = 0.02; and 26.6% vs. 17.7%, p < 0.001). No significant differences in the mortality rate and the rate of retinopathy of prematurity were found.

Conclusion

In our patient population, a lower SpO2 target range was not associated with increased safety risks in extremely preterm infants. We cannot be sure that our outcome differences are associated with differences in oxygen saturations due to the retrospective study design and the differences in site practices.

Umbilical venous catheter- and peripherally inserted central catheter-associated complications in preterm infants with birth weight < 1250 g : Results from a survey in Austria and Germany

BACKGROUND AND OBJECTIVE

Umbilical venous catheters (UVC) and peripherally inserted central catheters (PICC) are commonly used in preterm infants but have been associated with a number of serious complications. We performed a survey in Austria and Germany to assess the use of UVCs and PICCs in preterm infants with a birth weight < 1250 g and associated rates of catheter-related adverse events.

METHODS

Electronic survey of participating centers of the NeoVitaA trial. Main outcome parameter was the reported rates of UVC- and PICC-associated complications (infection, thrombosis, emboli, organ injury, arrhythmia, dislocation, miscellaneous).

RESULTS

In total, 20 neonatal intensive care units (NICU) providing maximal intensive care in Austria and Germany (level I) were contacted, with a senior neonatologist response rate of 12/20 (60%). The reported rates for UVC with a dwell time of 1-10 days were bacterial infection: 4.2 ± 3.4% (range 0-10%); thrombosis: 7.3 ± 7.1% (0-20%); emboli: 0.9 ± 2.0% (0-5%); organ injury: 1.1 ± 1.9% (0-5%); cardiac arrhythmia: 2.2 ± 2.5% (0-5%); and dislocation: 5.4 ± 8.7% (0-30%); and for PICCs with a dwell time of 1-14 days bacterial infection: 15.0 ± 3.4% (range 2.5-30%); thrombosis; 4.3 ± 3.5% (0-10%); emboli: 0.8 ± 1.6% (0-5%); organ injury: 1.5 ± 2.3% (0-5%); cardiac arrhythmia: 1.5 ± 2.3% (0-5%), and dislocation: 8.5 ± 4.6% (0-30%).

CONCLUSION

The catheter-related complication rates reported in this survey differed between UVCs and PICCs and were higher than those reported in the literature. To generate more reliable data on this clinically important issue, we plan to perform a large prospective multicenter randomized controlled trial investigating the non-inferiority of a prolonged UVC dwell time (up to 10 days) against the early change (up to 5 days) to a PICC.

Ranibizumab in retinopathy of prematurity - one-year follow-up of ophthalmic outcomes and two-year follow-up of neurodevelopmental outcomes from the CARE-ROP study

Purpose:

The primary endpoint results from the comparing alternative ranibizumab dosages for safety and effcacy in retinopathy of prematurity (CARE-ROP) core study identified ranibizumab as an effective treatment to control acute retinopathy of prematurity (ROP). This study reports the 1- and 2-year follow-up data focusing on long-term functional outcomes and safety.

Methods:

The CARE-ROP trial compared 0.12 mg versus 0.20 mg ranibizumab in 20 infants with ROP in a multicentric, prospective, randomized, double-blind, controlled study design. Sixteen patients entered the follow-up period. An ophthalmologic assessment at one year postbaseline was acquired from all 16 patients and a neurodevelopmental assessment at two years postbaseline was acquired from 15 patients.

Results:

Fifteen of 16 infants were able to fixate and follow moving objects at one year postbaseline treatment. One child progressed to stage 5 ROP bilaterally between the end of the core study and the 1-year follow-up (first seen at PMA 75 weeks). Mean spherical equivalents were −1.9 diopters (D) and −0.75 D in the 0.12 mg and the 0.20 mg treatment arms. Strabismus was present in seven and nystagmus in five out of 16 infants. Mental development scores were within normal limits in six out of ten patients with available data. No statistically significant difference was observed between the two treatment arms.

Conclusion:

Neurodevelopmental and functional ocular outcomes 1 and 2 years after treatment with ranibizumab are reassuring regarding long-term safety. Late reactivation of ROP, however, represents a challenge during the follow-up phase and it is of utmost importance that regular follow-ups are maintained.

Active perinatal care of preterm infants in the German Neonatal Network

OBJECTIVE

To determine if survival rates of preterm infants receiving active perinatal care improve over time.

DESIGN

The German Neonatal Network is a cohort study of preterm infants with birth weight <1500 g. All eligible infants receiving active perinatal care are registered. We analysed data of patients discharged between 2011 and 2016.

SETTING

43 German level III neonatal intensive care units (NICUs).

PATIENTS

8222 preterm infants with a gestational age between 22/0 and 28/6 weeks who received active perinatal care.

INTERVENTIONS

Participating NICUs were grouped according to their specific survival rate from 2011 to 2013 to high (percentile >P75), intermediate (P25-P75) and low (<P25) survival. We compared these survival rates with data in 2014-2016.

MAIN OUTCOME MEASURES

Death by any cause before discharge.

RESULTS

Total survival increased from 85.8% in 2011-2013 to 87.4% in 2014-2016. This increase was due to reduced mortality of NICUs with low survival rates in 2011-2013. Survival increased in these centres from 53% to 64% in the 22-24 weeks strata and from 73% to 84% in the 25-26 weeks strata.

CONCLUSIONS

Our data support previous reports that active perinatal care of very immature infants improves outcomes at the border of viability and survival rates at higher gestational ages. The high total number of surviving infants below 24 weeks of gestation challenges national recommendations exclusively referring to gestational age as the single criterion for providing active care. However, more data are needed before recommendations for parental counselling should be reconsidered.

TRIAL REGISTRATION

Approval by the local institutional review board for research in human subjects of the University of Lübeck (file number 08-022) and by the local ethic committees of all participating centres has been given.

On defects' role in enhanced perpendicular magnetic anisotropy in Pt/Co/Pt, induced by ion irradiation

Modifications of magnetic and magneto-optical properties of Pt/Co(d _Co )/Pt upon Ar⁺ irradiation (with energy 1.2, 5 and 30 keV) and fluence, F at the range from 2 · 10¹³-2 · 10¹⁶ Ar⁺ cm^-2) were studied. Two 'branches' of increased perpendicular magnetic anisotropy (PMA) and enhanced magneto-optical response are found on 2D (d _Co , F) diagrams. The difference in F between 'branches' is driven by ion energy. Structural features correlated with magnetic properties have been analysed thoroughly by x-ray diffraction, Rutherford backscattering spectrometry and positron annihilation spectroscopy. Experimental results are in agreement with TRIDYN numerical calculations of irradiation-induced layers intermixing. Our work discusses particularly structural factors related to crystal lattice defects and strain, created and modified by irradiation, co-responsible for the increase in the PMA.

Morphological and Functional Modifications of Optical Thin Films for Space Applications Irradiated with Low-Energy Helium Ions

Future space missions will operate in increasingly hostile environments, such as those in low-perihelion solar orbits and Jovian magnetosphere. This exploration involves the selection of optical materials and components resistant to the environmental agents. The conditions in space are reproduced on ground through the use of ion accelerators. The effects of He particles coming from the solar wind impinging on a gold thin film have been systematically investigated, considering absorbed doses compatible with the duration of the European Space Agency Solar Orbiter mission. Structural and morphological changes have been proved to be dependent not only on the dose but also on the irradiation flux. A predictive model of the variation of thin film reflectance has been developed for the case of lower flux irradiation. The results are discussed regarding reliability and limitations of laboratory testing. The outcomes are important to address the procedures for the space qualification tests of optical coatings.

Self-Diffusion in Amorphous Silicon by Local Bond Rearrangements

Experiments on self-diffusion in amorphous silicon (Si) were performed at temperatures between 460 to 600° C. The amorphous structure was prepared by Si ion implantation of single crystalline Si isotope multilayers epitaxially grown on a silicon-on-insulator wafer. The Si isotope profiles before and after annealing were determined by means of secondary ion mass spectrometry. Isothermal diffusion experiments reveal that structural relaxation does not cause any significant intermixing of the isotope interfaces whereas self-diffusion is significant before the structure recrystallizes. The temperature dependence of self-diffusion is described by an Arrhenius law with an activation enthalpy Q=(2.70±0.11)  eV and preexponential factor D_{0}=(5.5_{-3.7}^{+11.1})×10^{-2}  cm^{2} s^{-1}. Remarkably, Q equals the activation enthalpy of hydrogen diffusion in amorphous Si, the migration of bond defects determining boron diffusion, and the activation enthalpy of solid phase epitaxial recrystallization reported in the literature. This close agreement provides strong evidence that self-diffusion is mediated by local bond rearrangements rather than by the migration of extended defects as suggested by Strauß et al. (Phys. Rev. Lett. 116, 025901 (2016)PRLTAO0031-900710.1103/PhysRevLett.116.025901).

Plasmonic nanoparticles embedded in single crystals synthesized by gold ion implantation for enhanced optical nonlinearity and efficient Q-switched lasing

We report on the synthesis of embedded gold (Au) nanoparticles (NPs) in Nd:YAG single crystals using ion implantation and subsequent thermal annealing. Both linear and nonlinear absorption of the Nd:YAG crystals have been enhanced significantly due to the embedded Au NPs, which is induced by the surface plasmon resonance (SPR) effect in the visible light wavelength band. Particularly, through a typical Z-scan system excited by a femtosecond laser at 515 nm within the SPR band, the nonlinear absorption coefficients of crystals with Au NPs have been observed to be nearly 5 orders of magnitude larger than that without Au NPs. This giant enhancement of nonlinear absorption properties is correlated with the saturable absorption (SA) effect, which is the basis of passive Q-switching or mode-locking for pulsed laser generation. In addition, the linear and nonlinear absorption enhancement could be tailored by varying the fluence of implanted Au⁺ ions, corresponding to the NP size and concentration modulation. Finally, the Nd:YAG wafer with embedded Au NPs has been applied as a saturable absorber in a Pr:LuLiF₄ crystal laser cavity, and efficient pulsed laser generation at 639 nm has been realized, which presents superior performance to the MoS₂ saturable absorber based system. This work opens an avenue to enhance and modulate the nonlinearities of dielectrics by embedding plasmonic Au NPs for efficient pulsed laser operation.

Influence of PCO2 Control on Clinical and Neurodevelopmental Outcomes of Extremely Low Birth Weight Infants

BACKGROUND

Levels or fluctuations in the partial pressure of CO2 (PCO2) may affect outcomes for extremely low birth weight infants.

OBJECTIVES

In an exploratory analysis of a randomized trial, we hypothesized that the PCO2 values achieved could be related to significant outcomes.

METHODS

On each treatment day, infants were divided into 4 groups: relative hypocapnia, normocapnia, hypercapnia, or fluctuating PCO2. Ultimate assignment to a group for the purpose of this analysis was made according to the group in which an infant spent the most days. Statistical analyses were performed with analysis of variance (ANOVA), the Kruskal-Wallis test, the χ2 test, and the Fisher exact test as well as by multiple logistic regression.

RESULTS

Of the 359 infants, 57 were classified as hypocapnic, 230 as normocapnic, 70 as hypercapnic, and 2 as fluctuating PCO2. Hypercapnic infants had a higher average product of mean airway pressure and fraction of inspired oxygen (MAP × FiO2). For this group, mortality was higher, as was the likelihood of having moderate/severe bronchopulmonary dysplasia (BPD), necrotizing enterocolitis (NEC), and poorer neurodevelopment. Multiple logistic regression analyses showed an increased risk for BPD or death associated with birth weight (p < 0.001) and MAP × FiO2 (p < 0.01). The incidence of adverse neurodevelopment was associated with birth weight (p < 0.001) and intraventricular hemorrhage (IVH; p < 0.01).

CONCLUSIONS

Birth weight and respiratory morbidity, as measured by MAP × FiO2, were the most predictive of death or BPD and NEC, whereas poor neurodevelopmental outcome was associated with low birth weight and IVH. Univariate models also identified PCO2. Thus, hypercapnia seems to reflect greater disease severity, a likely contributor to differences in outcomes.

Polyatomic ions from a high current ion implanter driven by a liquid metal ion source

High current liquid metal ion sources are well known and found their first application as field emission electric propulsion thrusters in space technology. The aim of this work is the adaption of such kind of sources in broad ion beam technology. Surface patterning based on self-organized nano-structures on, e.g., semiconductor materials formed by heavy mono- or polyatomic ion irradiation from liquid metal (alloy) ion sources (LMAISs) is a very promising technique. LMAISs are nearly the only type of sources delivering polyatomic ions from about half of the periodic table elements. To overcome the lack of only very small treated areas by applying a focused ion beam equipped with such sources, the technology taken from space propulsion systems was transferred into a large single-end ion implanter. The main component is an ion beam injector based on high current LMAISs combined with suited ion optics allocating ion currents in the μA range in a nearly parallel beam of a few mm in diameter. Different types of LMAIS (needle, porous emitter, and capillary) are presented and characterized. The ion beam injector design is specified as well as the implementation of this module into a 200 kV high current ion implanter operating at the HZDR Ion Beam Center. Finally, the obtained results of large area surface modification of Ge using polyatomic Bi₂⁺ ions at room temperature from a GaBi capillary LMAIS will be presented and discussed.

Neurodevelopmental outcomes of extremely low birthweight infants randomised to different PCO2 targets: the PHELBI follow-up study

BACKGROUND

Tolerating higher partial pressures of carbon dioxide (PCO₂) in mechanically ventilated extremely low birthweight infants to reduce ventilator-induced lung injury may have long-term neurodevelopmental side effects. This study analyses the results of neurodevelopmental follow-up of infants enrolled in a randomised multicentre trial.

METHODS

Infants (n=359) between 400 and 1000 g birth weight and 23 0/7-28 6/7 weeks gestational age who required endotracheal intubation and mechanical ventilation within 24 hours of birth were randomly assigned to high PCO₂ or to a control group with mildly elevated PCO₂ targets. Neurodevelopmental follow-up examinations were available for 85% of enrolled infants using the Bayley Scales of Infant Development II, the Gross Motor Function Classification System (GMFCS) and the Child Development Inventory (CDI).

RESULTS

There were no differences in body weight, length and head circumference between the two PCO₂ target groups. Median Mental Developmental Index (MDI) values were 82 (60-96, high target) and 84 (58-96, p=0.79). Psychomotor Developmental Index (PDI) values were 84 (57-100) and 84 (65-96, p=0.73), respectively. Moreover, there was no difference in the number of infants with MDI or PDI <70 or <85 and the number of infants with a combined outcome of death or MDI<70 and death or PDI<70. No differences were found between results for GMFCS and CDI. The risk factors for MDI<70 or PDI<70 were intracranial haemorrhage, bronchopulmonary dysplasia, periventricular leukomalacia, necrotising enterocolitis and hydrocortisone treatment.

CONCLUSIONS

A higher PCO₂ target did not influence neurodevelopmental outcomes in mechanically ventilated extremely preterm infants. Adjusting PCO₂ targets to optimise short-term outcomes is a safe option.

TRIAL REGISTRATION NUMBER

ISRCTN56143743.

Permissive hypercapnia in extremely low birthweight infants (PHELBI): a randomised controlled multicentre trial

BACKGROUND

Tolerating higher partial pressure of carbon dioxide (pCO2) in mechanically ventilated, extremely low birthweight infants might reduce ventilator-induced lung injury and bronchopulmonary dysplasia. We aimed to test the hypothesis that higher target ranges for pCO2 decrease the rate of bronchopulmonary dysplasia or death.

METHODS

In this randomised multicentre trial, we recruited infants from 16 tertiary care perinatal centres in Germany with birthweight between 400 g and 1000 g and gestational age 23-28 weeks plus 6 days, who needed endotracheal intubation and mechanical ventilation within 24 h of birth. Infants were randomly assigned to either a high target or control group. The high target group aimed at pCO2 values of 55-65 mm Hg on postnatal days 1-3, 60-70 mm Hg on days 4-6, and 65-75 mm Hg on days 7-14, and the control target at pCO2 40-50 mmHg on days 1-3, 45-55 mm Hg on days 4-6, and 50-60 mm Hg on days 7-14. The primary outcome was death or moderate to severe bronchopulmonary dysplasia, defined as need for mechanical pressure support or supplemental oxygen at 36 weeks postmenstrual age. Cranial ultrasonograms were assessed centrally by a masked paediatric radiologist. This trial is registered with the ISRCTN registry, number ISRCTN56143743.

RESULTS

Between March 1, 2008, and July 31, 2012, we recruited 362 patients of whom three dropped out, leaving 179 patients in the high target and 180 in the control group. The trial was stopped after an interim analysis (n=359). The rate of bronchopulmonary dysplasia or death in the high target group (65/179 [36%]) did not differ significantly from the control group (54/180 [30%]; p=0·18). Mortality was 25 (14%) in the high target group and 19 (11%; p=0·32) in the control group, grade 3-4 intraventricular haemorrhage was 26 (15%) and 21 (12%; p=0·30), and the rate of severe retinopathy recorded was 20 (11%) and 26 (14%; p=0·36).

INTERPRETATION

Targeting a higher pCO2 did not decrease the rate of bronchopulmonary dysplasia or death in ventilated preterm infants. The rates of mortality, intraventricular haemorrhage, and retinopathy did not differ between groups. These results suggest that higher pCO2 targets than in the slightly hypercapnic control group do not confer increased benefits such as lung protection.

FUNDING

Deutsche Forschungsgemeinschaft.

Effects of low-dosed imidacloprid pulses on the functional role of the caged amphipod Gammarus roeseli in stream mesocosms

Effects of two series of imidacloprid pulses on caged amphipods (Gammarus roeseli) and their shredder efficiency for litter decomposition were studied for 70 days as part of a comprehensive stream mesocosm experiment. The duration of each imidacloprid pulse of 12µgL(-1) was 12h. About 250mL cages with an initial stock of 10 adult gammarids together with different conditioned litter substrates were used. Beside alder leaves (Alnus glutinosa), straw (× Triticosecale) was also used in different trials and tested for its suitability to serve as litter substrate. Results from tracer and microprobe measurements approved the suitability of the test system under low-flow condition of 10cms(-1) in the surrounding stream water. Population development followed a logistic growth function with a carrying capacity of 200 Ind cage(-1) for alder and 161 for straw. In the course of the study, the F1 generation reached sexual maturity and F2 offspring appeared. Increased nitrogen contents of gammarid-free trials compared to stocked ones after 70 days indicated that biofilm on both substrates was an important food source for G. roeseli. However, increased shredding activity by gammarids was only detected for alder during the second pulse series. During the remaining time and also for straw, losses of coarse particular organic matter were quite constant and slow indicating the dominance of transport limited decomposition processes on the litter surfaces. No effect of imidacloprid pulses on population levels and litter decomposition could be detected. However, the number of brood carrying females was reduced in the treatments compared to the control groups in the last 3 weeks of the study. In conclusion, repeated low-level and short-term exposition may have adverse long-term effects on G. roeseli in the field with regard to both the population size and the functional role as key shredder.

Closer to reality--the influence of toxicity test modifications on the sensitivity of Gammarus roeseli to the insecticide imidacloprid

Laboratory toxicity test designs are far from reality and therefore extrapolations to field situations may be more difficult. In laboratory experiments with the amphipod Gammarus roeseli exposed to the insecticide imidacloprid it was investigated if test conditions closer to reality influences its sensitivity and if it is possible to extrapolate results from these laboratory tests to results from a stream mesocosm study. Experiments were run by varying medium, temperature, size, and seasonal origin of gammarids. Age and seasonal aspects had strongest effects with juveniles and animals taken from a spring population being most sensitive with an EC₅₀ (96 h) of 14.2 μg L⁻¹ imidacloprid. The test designs closest to the conditions in the stream mesocosms reflected best the results in mesocosms study on basis of LOEC values. However, the EC(x) extrapolation failed to predict the effects of short term imidacloprid pulses in the field.

Set-up and calibration of a triple ionization chamber system for dosimetry in mixed neutron/photon fields

The aim of this study is to introduce a triple ionization chamber system to separate dose components of mixed neutron/photon fields. Fast and thermal neutron dose components have a different biological effectiveness than gamma dose components. If boron neutron capture is used to enhance the dose in certain areas of a patient, the precise knowledge of the thermal neutron flux is essential. A tissue equivalent and two magnesium ionization chambers have been prepared for use in a triple chamber system for this purpose. One of the magnesium chambers is coated with (10)B on the inside to enhance its response to thermal neutrons. All three chambers have been calibrated at a cobalt source, medical linear accelerators and several neutron sources. The chambers have been studied in Monte Carlo simulations and the results are compared with measurements.

Measurement of the fluence response of the GSI neutron ball dosemeter in the energy range from thermal to 19 MeV

At high-energy particle accelerators, area monitoring needs to be performed in a wide range of neutron energies. In principle, neutrons occur from thermal energies up to the energy of the accelerated ions, which is for the present GSI (Gesellschaft für Schwerionenforschung) accelerator facility approximately 1-2 GeV per nucleon. There are no passive dosemeters available, which are designed for the use at high-energy accelerators. At GSI, a neutron dosemeter was developed, which is suitable for the measurement of high-energy neutron radiation by the insertion of a lead layer around Thermoluminescence (TL) detection elements (pairs of TL 600/700) at the centre of the dosemeter. The design of the sphere was derived from the construction of the extended range rem-counters for the measurement of ambient dose equivalent H(10). In this work, the dosemeter fluence response was measured in the quasi-monoenergetic neutron fields of the accelerator facility of the PTB in Braunschweig and in the thermal neutron field of the GKSS research reactor FRG-1 in Geesthacht. For the accelerator measurements, the reactions (7)Li(p,n)(7)Be, (3)H(p,n)(3)He and (2)H(d,n)(3)He were used to produce neutron fields with energy peaks between 144 keV and 19 MeV. The measured fluence responses are 27% too low for thermal energies and show an agreement with approximately 14% for the accelerator produced neutron fields related to the computed fluence responses (MCNP, FLUKA calculations). The measured as well as the computed fluence responses of the dosemeter are compared with the corresponding conversion coefficients.

Application of different TL detectors for the photon dosimetry in mixed radiation fields used for BNCT

Different approaches for the measurement of a relatively small gamma dose in strong fields of thermal and epithermal neutrons as used for Boron Neutron Capture Therapy (BNCT) have been studied with various thermoluminescence detectors (TLDs). CaF(2):Tm detectors are insensitive to thermal neutrons but not tissue-equivalent. A disadvantage of applying tissue-equivalent (7)LiF detectors is a strong neutron signal resulting from the unavoidable presence of (6)Li traces. To overcome this problem it is usual to apply pairs of LiF detectors with different (6)Li content. The experimental determination of the thermal neutron response ratio of such a pair at the Geesthacht Neutron Facility (GeNF) operated by PTB enables measurement of the photon dose. In the experimental mixed field of thermal neutrons and photons of the TRIGA reactor at Mainz the photon dose measured with different types of (7)LiF/(nat)LiF TLD pairs agree within a standard uncertainty of 6% whereas the CaF(2):Tm detectors exhibit a photon dose by more than a factor of 2 higher. It is proposed to determine suitable photon energy correction factors for CaF(2):Tm detectors with the help of the (7)LiF/(nat)LiF TLD pairs in the radiation field of interest.

Quasi-monoenergetic neutron reference fields in the energy range from thermal to 200 MeV

Well-characterised neutron fields are a prerequisite for the investigation of neutron detectors. Partly in collaboration with external partners, the PTB neutron metrology group makes available for other users neutron reference fields covering the full energy range from thermal to 200 MeV. The specification of the neutron fluence in these beams is traceable to primary standard cross sections.