TL-SDA: A designed toolkit for the deconvolution analysis of thermoluminescence glow curves.

In the present study, a graphical user interface (GUI) toolkit has been developed to analyze the thermoluminescence (TL) glow-curve and evaluate the trapping parameters using TL expression based on the one-trap one-recombination model. The basic idea of the deconvolution analysis in the developed toolkit is based on performing a sequence of successful fits, where the information provided by each fit is used by the next fit until the deconvolution of the entire glow curve approaches an optimum solution. The starting values and ranges of the fitting parameters can be controlled and adjusted to improve the deconvolution analysis of complex structure glow curves. The designed toolkit is also supported by the background-subtraction option to improve the analysis at low irradiation dose levels. The expanded uncertainty at the 95 % confidence level of the fitted trapping parameters is also provided. All the evaluations performed using the designed toolkit are allowed to be extracted into an Excel spreadsheet. The TL-SDA toolkit can be freely downloaded from: TLSDA_v1 - File Exchange - MATLAB Central (https://www.mathworks.com/matlabcentral/fileexchange/154136-tlsda_v1-1).

Uncertainty of LiF thermoluminescence at low dose levels: Experimental results.

The LiF:Mg,Ti (TLD-100) thermoluminescence (TL) detectors are widely used in many dosimetric applications, particularly in personal dosimetry area. In the present study, the uncertainty of TLD-100 measurements at the low dose levels has been assessed for different TL readout analysis methods. The criteria used to evaluate the minimum measurable dose (MMD) have been also investigated. It has been found that between-sample variations and the precision of the TL measurements were the significant uncertainty components. However, the precision of the measurement is critically dependent on the TL readout analysis and background (BG) subtraction methods. The estimation of the MMD based on the 3σBG approach may lead to inaccurate measurements. On the other hand, a new criterion for evaluating the MMD based on the signal-to-noise ratio and can be evaluated from the glow-curve deconvolution analysis has been established. It has been shown that the implementation of this criterion ensures acceptable levels for both the precision and trueness of TL measurements.

Influence of scatter data and temperature lag on the analysis of thermoluminescence glow peak: A Monte Carlo simulation study.

The effects of the scattering data that might appear at the low radiation doses and the temperature lag that might occur between the heater pan and the detector on the thermoluminescence (TL) glow-curve have been addressed. The scattering data were mathematically induced in the TL glow curve using the Monte Carlo (MC) algorithm. While the phenomenon of the temperature lag has been simulated, assuming an exponential function. The deconvolution analysis has been carried out by TL expressions based on a presumed kinetics order value in comparison with the general-order kinetics equation. It has been found that even though the glow peak is known to obey the first- or second-order kinetics model, using the general-order kinetics equation in the deconvolution analysis is better than using the corresponding model equation.

UNCERTAINTY OF THERMOLUMINESCENCE AT LOW DOSE LEVELS: A MONTE-CARLO SIMULATION STUDY.

The purpose of the current work is to investigate the effect of the scatter data and the background noise level on the uncertainty of the thermoluminescence (TL) measurements. The Monte-Carlo (MC) algorithm has been used to simulate the scattering data and the background noise signal in TL glow-curve. Under the simulation and experimental parameters used in the present study, a new general criterion for the minimum measurable dose has been established. It has been found from the results that the TL measurements, using either the peak maximum or the peak integral, can be conducted with an uncertainty level $<\pm 10\%[2\sigma ]$ when the TL signal is at least 10 times greater than the background noise signal. It has also been found that the same criterion can be used for the evaluation of the kinetics parameters of the TL glow-peak using either the peak fitting or the peak shape methods.

A new approach to the analysis of thermoluminescence glow-curve of TLD-600 dosimeters following Am-241 alpha particles irradiation.

A new approach to the analysis of thermoluminescence (TL) glow-curves of LiF:Mg, Ti (TLD-600) following alpha particles irradiation has been presented using general expressions derived from the one-trap-one recombination (OTOR)-level model. It has been found that the results of the deconvolution in the case of using these expressions are different from the case of using the other TL expressions, especially for the high-temperature region. The advantage of using the OTOR expressions is that, unlike the usual analysis, a good fit and reasonable kinetic parameter values could be obtained with a lower number of deconvoluted peaks. The kinetic parameters and the dosimetric properties of each peak have been investigated over different absorbed doses and new findings have been found. Improvement of the accuracy and the precision of the dose measurements at low-dose levels has been achieved using the glow-curve deconvolution algorithm. In addition, theoretical interpretations of some observed behaviors have been presented using the interactive multiple trap system model.

Thermally enhanced TLD output: Impacts on the response curve.

Pre-irradiation background reading of thermoluminescent LiF dosimeters results in severe changes in the glow curve qualitatively and quantitatively. Current work focuses on the possible changes in the response of TLD-700 dosimeters after this effect. This work examines changes in the level of the glow curve as a whole and on the level of individual peaks as well. It was found that the response of TLD-700 dosimeters has increased by factors ranging from 20% to 44% in terms of area under the glow curve. Changes in individual peaks were examined by performing deconvolution for the glow curves. Results confirmed that the response due to such effect is not uniform over the studied temperature range and each individual peak has its own behavior either in terms of peak area or peak intensity. It was observed that the third peak (P3) leads these changes as the change in its area after being exposed to this thermally enhanced thermoluminescence output (TETO) effect was in the range from 4.1 to 3.0 folds compared to the corresponding values obtained without reading the background prior to irradiation. Peak intensity possesses similar behavior where peaks P2 and P4 are following to P3 in their response, the rest of peaks are either neutral or have negative response to TETO. Response curves of each deconvoluted peak in terms of peak area and maximum intensity are analyzed over the range (0.05-30) Gy and discussed in details.

The deconvolution of thermoluminescence glow-curves using general expressions derived from the one trap-one recombination (OTOR) level model.

The new developed thermoluminescence (TL) glow-peak expressions derived from the one trap-one recombination (OTOR) level model were used to analyze the TL glow-curves recorded with linear and exponential heating function profiles under various experimental conditions. The results showed that these expressions can, accurately, analyze the TL glow-curves even with the overlapped glow-peaks. Low values of R=An/Am were reported for glow-peaks in different TL materials. A glow-peak with the possibility of An>Am was also pointed out.

Development of a model using the MATLAB System identification toolbox to estimate (222)Rn equilibrium factor from CR-39 based passive measurements.

Can and Bare method is a widely used passive method for measuring the equilibrium factor F through the determination of the track density ratio between bare (D) and filtered (Do) detectors. The dimensions of the used diffusion chamber are altering the deposition ratios of Po-isotopes on the chamber walls as well as the ratios of the existing alpha emitters in air. Then the measured filtered track density and therefore the resultant equilibrium factor is changed according to the diffusion chamber dimensions. For this reason, high uncertainty was expected in the measured F using different diffusion chambers. In the present work, F is derived as a function of both track density ratio (D/Do) and the dimensions of the used diffusion chambers (its volume to the total internal surface area; V/A). The accuracy of the derived formula was verified using the black-box modeling technique via the MATLAB System identification toolbox. The results show that the uncertainty of the calculated F by using the derived formula of F (D/Do, V/A) is only 5%. The obtained uncertainty ensures the quality of the derived function to calculate F using diffusion chambers with wide range of dimensions.

Effects of aging on the cerebral distribution of technetium-99m hexamethylpropylene amine oxime in healthy humans.

Some brain functions decline at a linear rate throughout adulthood. Others remain relatively stable until very late in the life cycle. This study characterized the effects of aging on the regional cerebral distribution of hexamethylpropylene amine oxime (HMPAO) in healthy human volunteers. The sample consisted of 26 men and 18 women with a mean age of 41.6+/-14.9 years (range: 19-73). Their past medical histories, physical examinations, and laboratory screening tests were normal. Single-photon emission tomography (SPET) scans of the brain were performed with a standardized acquisition and processing protocol on a triple-headed camera equipped with fan beam collimators. A 3-D restorative filter and a correction for uniform attenuation were applied before the images were reinterpolated in planes parallel to the line connecting the frontal and occipital poles. Mean counts per pixel were measured in multiple regions of interest (ROIs) within each hemisphere by custom fitting a set of templates to the images. The mean activity in each ROI was compared with the mean activity per pixel in the whole brain. Regression analyses were used to relate the activity ratios to age with both linear and nonlinear models. The relative concentration of radioactivity decreased significantly with age in most, but not all, gray matter structures. It increased in the white matter regions. The nonlinear model of aging fit the data significantly better than a straight line did. Most of the changes with age occurred during young adulthood. No further changes were detectable after the onset of middle age. The median breakpoint age at which the rate of change became negligible was 36.6 years. Aging significantly affects the relative uptake of HMPAO in healthy humans. It decreases in many gray matter regions and increases in most white matter regions. However, the changes do not appear to be linear. Most seem to occur during young adulthood before people reach their late thirties. The distribution then appears to remain relatively stable throughout middle age.

Study of chemical constituents of thoracic duct lymph in schistosomal hepatic fibrosis.

Concentrations of serum and thoracic duct proteins, immunoglobulins, lipids, enzymes and electrolytes were estimated in 15 patients with schistosomal hepatic fibrosis and presinusoidal obstruction and in 12 controls. There was a significant decrease of thoracic duct total proteins, albumin and triglycerides, with marked and significant increase in IgG and IgM in SHF, compared to the controls. The levels of transaminases, alkaline phosphatases and inorganic phosphorus were significantly higher in the lymph of SHF patients compared with healthy controls. It is presumed that these changes represent the pattern of lymph constituents in presinusoidal obstruction.

Percutaneous trans hepatic lymphography: evaluation in schistosomal hepatic fibrosis.

The increased interest in lymph and lymphatics has cast its mantle over the portal circulation. Lymphography has contributed greately to our knowledge. In the present study percutaneous transhepatic lymphography showed some of the factors sharing in the production of portal hypertension in schistosomal hepatic fibrosis, and gave a further evidence that the liver is not a source of excess lymph production in hepatic lesions associated with presinusoidal block to portal blood flow. Hepatic lymphatics were opacified in cases with mixed cirrhosis and schistosomal hepatic fibrosis as the sinusoidal pressure is elevated with subsequent cases increase in hepatic lymph production.

Beta-adrenergic receptors and the effect of beta-adrenergic blocking agent propranolol on histamine and reserpine stimulated gastric acid secretion in man: normals and duodenal ulcer cases.

The effects of the beta adrenergic stimulant drug, "Nylidrin", and the beta adrenergic blocking agent, "Propranolol", on human basal gastric acid secretion were studied in 20 healthy volunteer subjects and 10 chronic D.U. cases. Nylidrin increased gastric acid secretion and volume. All effects of nylidrin were blocked by prior administration of beta adrenergic inhibitor propranolol. Propranolol diminished both acid secretion and volume in both normal and D.U. cases. The presence of beta adrenergic receptors in the human stomach was suggested. The effects of beta adrenergic blocking agent propranolol on gastric secretion, stimulated with histamine, were studied in 10 normal subjects and 10 cases of chronic duodenal ulcer patients. Pretreatment with propranolol produced a signigicant depression of the 90 minute acid response to histamine in both volume and acidity in normals and duodenal ulcer cases. It is concluded that propranolol has an antisecretory effect, not only on basal gastric secretion but also on histamine stimulated secretion in man. Reserpine stimulated gastric acid secretion and volume in normals but showed no similar effect in D.U. cases. After pretreatment with propranolol it reduces the gastric acid secretion and volume in normals and D.U. cases.

Thoracic duct changes in schistosomal hepatic fibrosis.

The changes in the thoracic duct were studied in schistosomatic hepatic fibrosis, particularly in cases with ascites. The postmortem findings, lymphangiography, and clinical thoracic duct cannulation showed that, particularly in cases with ascites, the thoracic duct is dilated, pressure within is raised, and the lymph flow is increased. The significance of these findings is discussed in relation to the site and the treatment of ascites.