Neutron Generator Output Monitoring for Normalization of Gamma-Ray Spectra

Neutron generators (NG) being devices where neutron outputs are accomplished electrically, suffer from fluctuations in their outputs. Of particular importance are the short term variations that may affect individual data acquisition runs. Thus when using NGs for quantitative neutron-induced gamma-ray spectroscopy, the neutron output must be continuously monitored in real time, and normalization procedures subsequently applied to properly evaluate the gamma-ray spectra. Using a plastic scintillator, we developed a scheme for detecting fast neutrons that relies firstly, on recording a spectrum and, secondly, on establishing a region-of-interest (ROI) that may effectively discriminate against gamma rays that are always present in a neutron field. We discuss the optimization of these procedures for a field system to measure carbon in soil

Monitoring Neutron Generator Output in a Mixed Neutron-Gamma Field Using a Plastic Scintillator.

Quantitative neutron-induced gamma-ray spectroscopy employing neutron generators (NGs) entails monitoring them for possible fluctuations in their neutron output. We accomplished this using a plastic scintillator and recording a spectrum from which we selected a neutron region-of-interest (nROI) to discriminate between neutrons and the accompanying high-energy gamma-rays. We show that the selected nROI is insensitive to changes in the gamma-ray background, thus allowing satisfactory normalization of the gamma-ray spectra of an in-situ system for analyzing soil carbon

The use of chest magnetic resonance imaging in interstitial lung disease: A systematic review

Thin-slices multi-detector computed tomography (MDCT) plays a key role in the differential diagnosis of interstitial lung disease (ILD). However, thin-slices MDCT has a limited ability to detect active inflammation, which is an important target of newly developed ILD drug therapy. Magnetic resonance imaging (MRI), thanks to its multi-parameter capability, provides better tissue characterisation than thin-slices MDCT. Our aim was to summarise the current status of MRI applications in ILD and to propose an ILD-MRI protocol. A systematic literature search was conducted for relevant studies on chest MRI in patients with ILD. We retrieved 1246 papers of which 55 original papers were selected for the review. We identified 24 studies comparing image quality of thin-slices MDCT and MRI using several MRI sequences. These studies described new MRI sequences to assess ILD parenchymal abnormalities, such as honeycombing, reticulation and ground-glass opacity. Thin-slices MDCT remains superior to MRI for morphological imaging. However, recent studies with ultra-short echo-time MRI showed image quality comparable to thin-slices MDCT. Several studies demonstrated the added value of chest MRI by using functional imaging, especially to detect and quantify inflammatory changes. We concluded that chest MRI could play a role in ILD patients to differentiate inflammatory and fibrotic changes and to assess efficacy of new ILD drugs

Considerations for patient positioning in static beams for BNCT

The objective of this short communication is to provide a guideline for patient positioning, verification, and immobilization for boron neutron capture therapy

Basic considerations for Monte Carlo calculations in soil

Abstract Monte Carlo codes are extensively used for probabilistic simulations of various physical systems. These codes are widely used in calculations of neutron and gamma ray transport in soil for radiation shielding, soil activation by neutrons, well logging industry, and in simulations of complex nuclear gauges for in soil measurements. However, these calculations are complicated by the diversity of soils in which the proportions of solid, liquid and gas vary considerably together with extensive variations in soil elemental composition, morphology, and density. Nevertheless use of these codes requires knowledge of the elemental composition and density of the soil and its physical characteristics as input information for performing these calculations. It is shown that not always all of the soil parameters are critical but depend on the objectives of the calculations. An approach for identifying soil elemental composition and some simplifying assumptions for implementing the transport codes are presented.

Dose measurements and calculations in the epithermal neutron beam at the Brookhaven Medical Research Reactor (BMRR)

The characteristics of the epithermal neutron beam at BMRR were measured, calculated, and reported. This beam has already been used for animal irradiations. We anticipate that it will be used for clinical trials. Thermal and epithermal neutron flux densities distributions, and dose rate distributions, as a function of depth were measured in a lucite dog-head phantom. Monte Carlo calculations were performed and compared with the measured values. 2 refs., 4 figs., 1 tab

Structure and Function of the Vocal Cords after Airway Reconstruction on Magnetic Resonance Imaging

Objectives/Hypothesis: Dysphonia is a common problem at long-term follow-up after airway surgery for laryngotracheal stenosis (LTS) with major impact on quality of life. Dysphonia after LTS can be caused by scar tissue from initial stenosis along with anatomical alterations after surgery. There is need for a modality to noninvasively image structure and function of the reconstructed upper airways including the vocal cords to assess voice outcom

MR imaging for the quantitative assessment of brain iron in aceruloplasminemia: a postmortem validation study

Aims: Non-invasive measures of brain iron content would be of great benefit in neurodegeneration with brain iron accumulation (NBIA) to serve as a biomarker for disease progression and evaluation of iron chelation therapy. Although magnetic resonance imaging (MRI) provides several quantitative measures of brain iron content, none of these have been validated for patients with a severely increased cerebral iron burden. We aimed to validate R 2 * as a quantitative measure of brain iron content in aceruloplasminemia, the most severely iron-loaded NBIA phenotype. Methods: Tissue samples from 50 gray-and white matter regions of a postmortem aceruloplasminemia brain and control subject were scanned at 1.5 T to obtain R 2 * , and biochemically analyzed with inductively coupled plasma mass spectrometry. For gray matter samples of the aceruloplasminemia brain, sample R 2 * values were compared with postmortem in situ MRI data that had been obtained from the same subject at 3 T - in situ R 2 * . Relationships between R 2 * and tissue iron concentration were determined by linear regression analyses. Results: Median iron concentrations throughout the whole aceruloplasminemia brain were 10 to 15 times higher than in the control subject, and R 2 * was linearly associated with iron concentration. For gray matter samples of the aceruloplasminemia subject with an iron concentration up to 1000 mg/kg, 91% of variation in R 2 * could be explained by iron, and in situ R 2 * at 3 T and sample R 2 * at 1.5 T were highly correlated. For white matter regions of the aceruloplasminemia brain, 85% of variation in R 2 * could be explained by iron. Conclusions: R 2 * is highly sensitive to variations in iron concentration in the severely iron-loaded brain, and might be used as a non-invasive measure of brain iron content in aceruloplasminemia and potentially other NBIA disorders.Metals in Catalysis, Biomimetics & Inorganic Material

Boron neutron capture therapy of glioblastoma multiforme using the p- boronophenylalanine-fructose complex and epithermal neutrons

The amino acid analogue p-boronophenylalanine (BPA) is under investigation as a neutron capture agent for BNCT of glioblastoma multiforme. A series of patients undergoing surgical removal of tumor received BPA orally as the free amino acid. Favorable tumor/blood boron concentration ratios were obtained but the absolute amount of boron in the tumor would have been insufficient for BNCT. BPA can be solubilized at neutral pH by complexation with fructose (BPA-F). Studies with rats suggest that intraperitoneal injection of BPA-F complex produces a much higher tumor boron concentration to rat intracerebral 9L gliosarcoma that were possible with oral BPA. Higher boron concentrations have allowed higher tumor radiation doses to be delivered while maintaining the dose to the normal brain vascular endothelium below the threshold of tolerance. The experience to date of the administration of BPA-F to one patient is provided in this report