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Spyrou NM, Awotwi-Pratt JB, Williams AM. Monte Carlo calculations and neutron spectrometry in quantitative prompt gamma neutron activation analysis (PGNAA) of bulk samples using an isotopic neutron source. J Radioanal Nucl Chem 2004. [DOI: 10.1023/b:jrnc.0000017304.36246.f9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Brushwood JM, Gow JPD, Beeley PA, Spyrou NM. Development and testing of an active area neutron dosemeter. RADIATION PROTECTION DOSIMETRY 2004; 110:263-266. [PMID: 15353656 DOI: 10.1093/rpd/nch157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
This paper describes the design, development and testing of an active area neutron dosemeter (AAND). The classic moderator and central detector is retained but in AAND this arrangement is augmented by small thermal neutron detectors positioned within the moderating body. The outputs from these detectors are combined using an appropriately weighted linear superposition to fit both the ambient dose equivalent and the radiation weighting factor. Experimental verifications of both the modelled detector energy reponses and the overall AAND response are given. In the relatively soft D2O moderated 252Cf spectra, the AAND determined both the H*(10) and mean radiation weighting factor to better than +10%.
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Akanle OA, Ho J, Muhiddin K, Admans L, Croft NM, Spyrou NM. Elemental composition of hair and bone density measurements at diagnosis in paediatric inflammatory bowel disease. J Radioanal Nucl Chem 2004. [DOI: 10.1023/b:jrnc.0000017318.63963.fe] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Cutts DA, Maguire RP, Leenders KL, Spyrou NM. Hemispherical dominance of glucose metabolic rate in the brain of the 'normal' ageing population. J Radioanal Nucl Chem 2004. [DOI: 10.1023/b:jrnc.0000017302.40092.db] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Altaf WJ, Akanle OA, Admans LL, Beasley D, Butler C, Spyrou NM. The University of Surrey database of elemental composition of human hair. J Radioanal Nucl Chem 2004. [DOI: 10.1023/b:jrnc.0000020925.61388.d8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Abstract
A simple pharmacokinetic model to explain the time course of [O-15] water in human whole blood after bolus injection is described. The model has been derived from measurements in twelve healthy volunteers who were measured repeatedly, resulting in 67 datasets, made in the context of PET blood flow studies. In contrast to traditional volume of distribution estimates of total body water (TBW) which rely on measurements after many hours, the model and data provide insights into the fast uptake components in the distribution of water in the body. Data fitting shows that the volume of distribution of fast exchanging tissues is 21 l. TBW was calculated to be 37 l. Monte Carlo simulation showed that the expected inaccuracy of determination of parameters due to unsystematic sources in the measurement data was around 5% for most parameters. Our data show that water extraction to tissue is somewhat higher than would be predicted from the tabulated values, probably because skeletal blood flow is sensitive to physiological status and environmental conditions. The study provides valuable reference data on the distribution and kinetics of water in man. Using the parameters and model from this study, reference input time-activity curves can be calculated, e.g. for the Monte Carlo study of error propagation in PET studies.
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Giouvanoudi A, Amaee WB, Sutton JA, Horton P, Morton R, Hall W, Morgan L, Freedman MR, Spyrou NM. Physiological interpretation of electrical impedance epigastrography measurements. Physiol Meas 2003; 24:45-55. [PMID: 12636186 DOI: 10.1088/0967-3334/24/1/304] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Measurement of the electrical impedance of the gastric region is carried out with the epigastrograph. This generates and applies alternating current around the abdominal area and measures the potential difference in order to determine the impedance externally, via electrodes. The change of epigastric impedance for a subject, given a meal after fasting, depends on the conductivity of the meal compared to the stomach and surrounding tissues. Typically a conductive meal has conductivity >7 mS cm(-1), non-conductive <2 mS cm(-1) and neutral about 4.5 mS cm(-1). Half-emptying times (T50s) from gastric emptying studies in volunteers using three test meals of 450 ml volume were obtained and found to be shorter than expected from the literature. The meals were a 10% glucose solution and two milk shakes of energy 1,300 kJ and 2,850 kJ, respectively. These electrical impedance epigastrography (EIE) measurements were carried out with scintigraphy. The T50 values of the latter were significantly longer. The direct comparison of the normalized experimental data obtained by both methods led to the concept that EIE measurements are mainly influenced by gastric secretion. Thus the EIE trace of a 'neutral' meal suggests the hypothesis that the volume of the meal is not the significant factor but is influenced by gastric acid secretions. Physiology of the gastric mucosa during the digestion of a meal and intragastric pH values also suggests this. Gastric function studies using EIE measurements may therefore reflect gastric ionic concentration rather than the volume of the contents of the stomach. In turn this could lead to the development of a non-invasive method for the continuous recording of gastric acid secretions.
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Panayi AE, Spyrou NM, Iversen BS, White MA, Part P. Determination of cadmium and zinc in Alzheimer's brain tissue using inductively coupled plasma mass spectrometry. J Neurol Sci 2002; 195:1-10. [PMID: 11867068 DOI: 10.1016/s0022-510x(01)00672-4] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In this work, brain tissue was taken from Alzheimer's Disease (AD) subjects (n=11), 'normal' subjects (n=10) and from subjects with senile involutive cortical changes (SICC) (n=6). Concentrations of Cd and Zn were determined in all samples, using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The brain tissue was selected and obtained from the Netherlands Brain Bank. Samples were taken in each case, from both hemispheres of the superior frontal gyrus, the superior parietal gyrus, the medial temporal gyrus, the hippocampus and the thalamus of the same brain.Cd which is known to have no essential role in the brain was found to follow, as expected, a lognormal distribution of concentrations in 'normal' subjects (Shapiro-Wilk's test (0.98) (p<0.18)). For the Alzheimer's Disease subjects and SICC subjects, the data tends to follow a lognormal distribution, rather than a normal distribution, but is still significantly different from it (Shapiro-Wilk's test (0.97) (p<0.03); (0.93) (p<0.0067), respectively)). In the case of Zn concentrations, the data tends to follow a normal distribution for the 'normal' subject group, even though the data is significantly different from it (Shapiro-Wilk's test (0.95) (p<0.001)). Whereas in the Alzheimer's Disease and SICC subject groups, the data follows a normal distribution (Shapiro-Wilk's test (0.98) (p<0.21); (0.97) (p<0.2002), respectively)). When comparing age-matched groups, for all regions and both hemispheres, no significant differences (p>0.1) for Cd were found between 'normals' and Alzheimer's Disease subjects and Alzheimer's Disease subjects and SICC but at a low level of significance, lower concentrations of Cd were found in the SICC group compared to the 'normals'. For all regions and both hemispheres, Zn was found to be significantly decreased in the Alzheimer's Disease group, compared to the 'normal' and SICC groups. Zn concentrations were also found to be significantly decreased in the 'normals' compared to the SICC group. It is also of interest that Cd negatively correlates with the scale of tangles in both 'normals' (p<0.001) and Alzheimer's Disease subjects (p<0.01). In the SICC subjects Cd correlates negatively with the tangles but not significantly so (p>0.1).
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Grant JP, Clarke RN, Symm GT, Spyrou NM. A critical study of the open-ended coaxial line sensor technique for RF and microwave complex permittivity measurements. ACTA ACUST UNITED AC 2000. [DOI: 10.1088/0022-3735/22/9/015] [Citation(s) in RCA: 131] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Maguire RP, Spyrou NM, Leenders KL. Variance in parametric images: direct estimation from parametric projections. Phys Med Biol 2000; 45:91-102. [PMID: 10661585 DOI: 10.1088/0031-9155/45/1/307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Recent work has shown that it is possible to apply linear kinetic models to dynamic projection data in PET in order to calculate parameter projections. These can subsequently be back-projected to form parametric images--maps of parameters of physiological interest. Critical to the application of these maps, to test for significant changes between normal and pathophysiology, is an assessment of the statistical uncertainty. In this context, parametric images also include simple integral images from, e.g., [O-15]-water used to calculate statistical parametric maps (SPMs). This paper revisits the concept of parameter projections and presents a more general formulation of the parameter projection derivation as well as a method to estimate parameter variance in projection space, showing which analysis methods (models) can be used. Using simulated pharmacokinetic image data we show that a method based on an analysis in projection space inherently calculates the mathematically rigorous pixel variance. This results in an estimation which is as accurate as either estimating variance in image space during model fitting, or estimation by comparison across sets of parametric images--as might be done between individuals in a group pharmacokinetic PET study. The method based on projections has, however, a higher computational efficiency, and is also shown to be more precise, as reflected in smooth variance distribution images when compared to the other methods.
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Long SJ, Sutton JA, Amaee WB, Giouvanoudi A, Spyrou NM, Rogers PJ, Morgan LM. No effect of glucagon-like peptide-1 on short-term satiety and energy intake in man. Br J Nutr 1999; 81:273-9. [PMID: 10999014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Centrally administered glucagon-like peptide-1 (GLP-1) inhibits feeding in fasted rats, but its role in human satiety has been largely unexplored. The present study investigated the effect of peripheral GLP-1 infusion on gastric emptying and satiety in man. Ten non-obese male subjects were infused in a randomized single-blind within-subject crossover study using saline infusion as control. They received either a GLP-1 infusion (1.2 pmol/kg per min) or a saline infusion for 1 h, at 18.00 hours. At 20 min after starting the infusion the gastric emptying of a 400 ml water load was measured. Subjects completed behavioural self-rating scales to assess hunger and satiety. After 40 min subjects were given a buffet meal ad libitum and their food intake was recorded. GLP-1 infusion raised circulating GLP-1 concentrations to approximately twice those seen following a meal. It did not affect circulating insulin levels but caused a small fall in glucose levels. Gastric emptying of the water load was significantly delayed by the GLP-1 infusion. Energy intake from the buffet was unaffected by GLP-1 infusion. Self-assessment of hunger and satiety was similarly unaffected by the infusion before the buffet meal, although subjects tended to be less hungry after the buffet meal following GLP-1 infusion (P < 0.09). GLP-1 infusion delayed gastric emptying but had a minimal effect on food intake and satiety. This study casts doubts on whether GLP-1 is a major satiety factor in man, although a raised circulating plasma glucose level, as would normally occur postprandially, might be necessary for GLP-1 to increase satiety.
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Bauk S, Farquharson MJ, Highgate DJ, Spyrou NM. Hydrophilic crosslinked copolymers as tissue-equivalent materials for breast cancer detection. Biol Trace Elem Res 1999; 71-72:603-9. [PMID: 10676537 DOI: 10.1007/bf02784249] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Crosslinked hydrophilic copolymers have the potential to be used as breast phantom materials because they can be made to have similar elemental composition to that of body soft tissues. The copolymer, which consists of a combination of hydrophobic monomers (methyl methacrylate [MMA]) and hydrophilic monomers (vinylpyrolidone [VP]), have all the required major elements, such as hydrogen, carbon, nitrogen, and oxygen, found in tissues. Photon attenuation measurements were performed on the crosslinked hydrophilic copolymers in order to ascertain whether they are good representatives of breast tissues in the photon energy range of interest. The results of the measurements of transmission of photons by the hydrophilic copolymers at different discrete energies between 10 and 60 keV are presented.
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Cutts DA, Maguire RP, Stedman JD, Leenders KL, Spyrou NM. A comparative study in Alzheimer's and normal brains of trace element distribution using PIXE and INA analyses and glucose metabolism by positron emission tomography. Biol Trace Elem Res 1999; 71-72:541-9. [PMID: 10676530 DOI: 10.1007/bf02784242] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The onset of Alzheimer's disease has been shown to affect trace element concentrations in the brain when compared to "normal" subjects in ex vivo samples. The techniques used to determine trace element concentrations were proton-induced X-ray emission and instrumental neutron activation analysis. With these methods, significant differences are seen between lobes within a hemisphere and between the same lobes of opposing hemispheres for "normal" brains. The change observed in trace element concentrations may indicate a possible alteration in the function of the blood-brain barrier, the effect of which can be investigated in vivo using the imaging technique of positron emission tomography (PET). A PET study was performed on nine female and nine male subjects to determine whether the regional metabolic rate of glucose (rCMRGlu) varied between hemispheres and sex in the Alzheimer diseased brain as was seen in the trace element study. Glucose metabolism was measured using [F-18]-fluorodeoxyglucose (18F-FDG). Hemispherical differences were observed for the frontal, occipital, parietal lobes, and the temporolateral region in both males and females for rCMRGlu. Variation was also seen between sexes, where the frontal lobe had a lower rCMRGlu in females compared to that of males.
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Spyrou NM, Mesbahi ME. Improvements in the determination of radionuclide distribution in the analysis of irradiated samples using double-differentiation method. Biol Trace Elem Res 1999; 71-72:83-90. [PMID: 10676482 DOI: 10.1007/bf02784194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The spatial response of an 8 x 4 block detector made up of 5.6-mm-wide, 12.9-mm-high, 30-mm-thick individual detector crystals to a collimated line source of 511 keV annihilation photons was examined. The response of each crystal showed a spread around the average positioning values and distributions from adjacent crystals overlapped as the collimated source scanned the individual detectors. This leads to possible errors in the event assignment. The implementation of double differentiation or the second derivative method was proposed for the removal of scattered photons so as to reduce the overlap and, hence, avoid mis-positioning. This method is a mathematical solution implemented when analysing the results. A curve in a spatial spectrum could be considered to be a function f(x), where x is the position. When double differentiation of f(x) is carried out, then the normalized curve d2f(x) appears with some reduction in the wings. It was shown that a reduction of the scattering contribution in the tails without overestimating the contribution of scattered events could be achieved by implementing a double-differentiation process.
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Panayi AE, Spyrou NM, Ubertalli LC, White MA, Part P. Determination of trace elements in porcine brain by inductively coupled plasma-mass spectrometry, electrothermal atomic absorption spectrometry, and instrumental neutron activation analysis. Biol Trace Elem Res 1999; 71-72:529-40. [PMID: 10676529 DOI: 10.1007/bf02784241] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Methods have been developed for the analyses of trace metals in various areas of porcine brains, (temporal, parietal, frontal cortex, both right and left hemispheres). Determinations were carried out using inductively coupled plasma-mass spectrometry (ICP-MS) and electrothermal atomic absorption spectrometry (ETAAS). The elements investigated were Li, Mn, Cu, Zn, Cd, Hg, and Pb by ICP-MS and Cu, Cd, and Mn by ETAAS. For determination by ICP-MS, a method of standard additions calibration coupled with internal standards was used, and for ETAAS, standard additions calibrations were prepared. The accuracy of all methods was determined using NIST and IAEA certified reference material. A small number of pig brains were analyzed by instrumental neutron activation analysis for Cr, Co, Cs, Fe, Rb, Se, Sc, Sb, and Zn using the comparator method of analysis. Four separate NIST standard reference materials have been used to examine the validity of the comparator method.
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Hollands R, Spyrou NM. Elemental composition changes between breast tissue with and without silicone gel sheeting and hypertrophic scar tissue. Biol Trace Elem Res 1999; 71-72:575-83. [PMID: 10676534 DOI: 10.1007/bf02784246] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Hypertrophic scars occur after dermal trauma and are characterized by being elevated above normal skin level as a result of an abundance of collagen. The application of silicone gel sheeting (SGS) has been found to be an effective method of treatment, causing them to regress much quicker than they would do naturally. Normal skin and hypertrophic scar tissue were characterized using proton-induced X-ray emission (PIXE). Skin tissue that had been covered in SGS was also analyzed. For each element and sample type, the concentrations in the epidermis were plotted against the dermis. By considering the concentrations of breast tissue with and without SGS, it could be seen if the SGS changed the compositional structure of the skin. It was found that for the elements P, S, Cl, and K the SGS has no effect on the structure of the skin, as both breast types (with and without SGS) have regression lines that overlap. However, this work shows that there are significant differences for P in the dermis and Cl in the epidermis between the breast tissue with SGS and its control. Therefore, this work shows that the effect the SGS has on concentration occurs similarly for both the epidermis and dermis.
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Akanle OA, Akintanmide A, Durosinmi MA, Oluwole AF, Spyrou NM. Elemental analysis of blood of Nigerian hypertensive subjects. Biol Trace Elem Res 1999; 71-72:611-6. [PMID: 10676538 DOI: 10.1007/bf02784250] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Proton-induced X-ray emission (PIXE) has been used to obtain the concentrations of 11 elements (P, S, Cl, K, Ca, Fe, Cu, Zn, Br, Rb, and Cd) in whole-blood samples of 16 hypertensive subjects (mean age: 52.5 +/- 0.5 yr) and 18 age-matched controls (mean age: 51.5 +/- 0.5 yr) in a Nigerian population. The results of the study indicate that the hypertensive subjects have significantly higher mean concentration of Cl, Cd, Cu, and Zn when compared with the controls, and the mean concentration of P, K, and Ca was found to be significantly lower in the hypertensive group in comparison to the controls. Furthermore, the Zn:Cd ratio was found to be significantly higher in the controls than in the hypertensives, and the Cu:Zn ratio was significantly higher in the hypertensives.
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al-Bahri JS, Spyrou NM. Electron density of normal and pathological breast tissues using a Compton scattering technique. Appl Radiat Isot 1998; 49:1677-84. [PMID: 9745699 DOI: 10.1016/s0969-8043(97)10106-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Compton (incoherently) scattered photons which are directly proportional to the electron density of the scatterer, have been employed in characterising human breast tissues. Gamma ray photons scattered incoherently from normal and pathological breast tissue samples of nine breast cancer patients were measured using a high purity germanium detector and an americium (Am-241) source. The breast tissue samples were obtained from female patients undergoing mastectomy. The samples were examined in freeze dried form and the results were corrected for the reduction in the water content of each tissue type by use of the Mixture Rule. This study is aimed at providing electron density information in support of the introduction of new tissue substitute materials for mammography phantoms.
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