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PubMed2004

A history of radiation detection instrumentation.

A review is presented of the history of radiation detection instrumentation. Specific radiation detection systems that are discussed include the human senses, photography, calorimetry, color dosimetry, ion chambers, electrometers, electroscopes, proportional counters, Geiger Mueller counters, scalers and rate meters, barium platinocyanide, scintillation counters, semiconductor detectors, radiophotoluminescent dosimeters, thermoluminescent dosimeters, optically stimulated luminescent dosimeters, direct ion storage, electrets, cloud chambers, bubble chambers, and bubble dosimeters. Given the broad scope of this review, the coverage is limited to a few key events in the development of a given detection system and some relevant operating principles. The occasional anecdote is included for interest.

Equipment Design↗
PubMed2005

A history of radiation detection instrumentation.

A review is presented of the history of radiation detection instrumentation. Specific radiation detection systems that are discussed include the human senses, photography, calorimetry, color dosimetry, ion chambers, electrometers, electroscopes, proportional counters, Geiger Mueller counters, scalers and rate meters, barium platinocyanide, scintillation counters, semiconductor detectors, radiophotoluminescent dosimeters, thermoluminescent dosimeters, optically stimulated luminescent dosimeters, direct ion storage, electrets, cloud chambers, bubble chambers, and bubble dosimeters. Given the broad scope of this review, the coverage is limited to a few key events in the development of a given detection system and some relevant operating principles. The occasional anecdote is included for interest.

Equipment Design↗
PubMed2001

Imaging and quantitative analysis of tritium-labelled cells in lymphocyte proliferation assays using microchannel plate detectors originally developed for X-ray astronomy.

Microchannel plate detectors have been used in many astronomical X-ray telescopes. Recently we have begun to use similar detectors to image electron emission from radiolabelled biological assays. Here we show how a microchannel plate (MCP) detector can be used to image tritium uptake in T lymphocyte proliferation assays. Quantitative analysis using the MCP detector has the same sensitivity and speed as conventional liquid scintillation counter (LSC) analysis whilst obviating the need for scintillation fluid. In addition the system permits the imaging of whole plate harvests from a range of plate sizes. Here we present data obtained with 96-well plates and Terasaki plates.

Cell Division↗
PubMed1998

Zinc metabolism in patients with exocrine pancreatic insufficiency.

OBJECTIVE: Metabolism of zinc was studied by administering radioactive zinc (Zn65), and by performing metabolic balance studies in eight patients with exocrine pancreatic insufficiency and eighteen control subjects. METHODS: Retention of radioactive zinc was measured by total body counter, and its urinary and fecal excretion by gamma scintillation counter. Metabolic balance studies were carried out by measuring dietary zinc intake as well as fecal and urinary excretion of zinc by atomic absorption spectrophotometry in this group of patients. RESULTS: These studies revealed a 50% reduction in intestinal absorption of Zn65 in patients with exocrine pancreatic insufficiency as compared to alcoholic and non-alcoholic control subjects. In addition, there was a 2 to 4 fold increase (p<0.05) in urinary excretion of zinc in subjects with pancreatic disease. In pancreatic insufficiency, reduced zinc absorption and increased urinary zinc excretion were balanced by lower (p<0.05) endogenous excretion of zinc as evidenced by reduced excretion of Zn65 in feces during the second 4-day period. The mean biological half-life of Zn65 tended to be lower in patients with pancreatic insufficiency as compared to alcoholic control subjects, however the difference did not reach statistical significance. CONCLUSION: These observations indicate marked alterations in zinc metabolism in patients with advanced chronic pancreatic disease and provide greater insight into development of zinc deficiency in this group of patients.

Adult↗
PubMed2003

Effect of lipid excipients on in vitro pancreatic lipase activity.

PURPOSE: To study the effects of two lipid excipients, Peceol and Gelucire 44/14 on the in vitro pancreatic lipase activity. METHODS: A 50 microL reaction mixture, consisting of 45 microL (3H) triolein as the radiolabeled substrate, 2.5 microL Peceol or Gelucire 44/14 (0.05-0.5%), either alone or in combination, 2.5 microL colipase (100 microg/mL), and 2.5 microL pancreatic lipase (1 mg/mL), was incubated for 10 min at room temperature. At the end of incubation, the reaction was stopped by the addition of an extraction solvent containing chloroform, methanol, and n-heptane (12.5:14:10), and the mixture vortexed briefly. Subsequently, 250 microL of 50 mM sodium carbonate was added and the aqueous and organic phase separated by centrifugation for 5 min at 1000 g. One hundred microliters of the supernatant was transferred to a scintillation counter and then radioactivity measured after the addition of 3.6 mL of scintillation fluid. Pancreatic lipase activity was determined by measuring the amount of free fatty acid released into the incubation medium and expressed as micromol free fatty acid released/min. RESULTS: When used alone, Peceol inhibited the pancreatic lipase activity significantly in a concentration-dependent manner, with a maximum inhibition of 57% at 0.4% of the excipient [p < 0.05, one-way analysis of variance (ANOVA)]. Similarly, Gelucire 44/14 alone caused inhibition of lipase activity in a concentration-dependent manner. However, the maximum inhibition (30%) was smaller in magnitude compared with the former agent. When the two excipients were used in combination, the inhibitory effects on the enzyme activity were similar to those observed with the individual agents (p < 0.05, one-way ANOVA). However, the maximum inhibition of 30% was lower than that observed with Peceol alone. CONCLUSIONS: The results from this study suggest that these lipid excipients inhibit in vitro pancreatic lipase activity and should be taken into consideration when developing oral formulations using these agents.

Excipients↗
PubMed2007

Improved iron bioavailability in an oat-based beverage: the combined effect of citric acid addition, dephytinization and iron supplementation.

BACKGROUND: Iron deficiency in children is a major worldwide nutritional problem. An oat beverage was developed for 1- to 3-year-old children and different treatments were used to improve the iron bioavailability. AIM OF THE STUDY: To investigate the effects of citric acid addition, phytase treatment and supplementation with different iron compounds on non-heme iron absorption in human from a mineral-supplemented oat-based beverage. METHODS: A 240 g portion of a 55Fe-labeled test product (T) or a 59Fe-labeled reference dose (R) was served as breakfast after overnight fasting on four consecutive days in the order of TRRT. On day 18 the retention of 59Fe was measured by a whole-body counter and the erythrocytes uptake of 55Fe and 59Fe by a liquid-scintillation counter. Forty-two healthy subjects (men and women) were randomized into four study groups, members of each being given one of the studied four products (A, B, C, and D) supplemented with Fe (1.3 mg/portion), Zn, Ca, Se and P. Ferric ammonium citrate (FeAC) was added to products A, B, and C and ferric pyrophosphate (FePP) to product D. Citric acid (60 mg/portion) was added to products B, C, and D and phytase treatment applied to products C and D. RESULTS: Citric acid improved iron absorption by 54% from 3.9% in product A to 6.0% in product B (p = 0.051). Phytase treatment increased iron absorption by 78% (from 6.0 to 10.7%, p = 0.003) by reducing the phytate-phosphorus content per portion from 16.3 mg in product B to 2.8 mg in product C. The two compounds gave similar iron absorption rates (p = 0.916). CONCLUSIONS: A combination of citric acid addition, dephytinization and iron supplementation significantly increased the iron absorption in an oat-based beverage. Such a beverage can be useful in the prevention of iron deficiency in 1- to 3-year-old children.

6-Phytase↗
PubMed2004

Real-time analysis of endosomal lipid transport by live cell scintillation proximity assay.

A scintillation proximity assay has been developed to study the endosomal trafficking of radiolabeled cholesterol in living cells. Mouse macrophages were cultured in the presence of tritiated cholesterol and scintillant microspheres. Microspheres were taken up by phagocytosis and stored in phagolysosomes. Absorption of tritium beta particles by the scintillant produces light signals that can be measured in standard scintillation counters. Because of the short range of tritium beta particles and for geometric reasons, scintillant microspheres detect only that fraction of tritiated cholesterol localized inside phagolysosomes or within a distance of approximately 600 nm. By incubating cultures in a temperature-controlled microplate reader, the kinetics of phagocytosis and cholesterol transport could be analyzed in near-real time. Scintillation signals were significantly increased in response to inhibitors of lysosomal cholesterol export. This method should prove a useful new tool for the study of endosomal trafficking of lipids and other molecules.

Animals↗
PubMed2003

A new, practical, low-dose 14C-urea breath test for the diagnosis of Helicobacter pylori infection: clinical validation and comparison with the standard method.

The carbon-14 urea breath test (UBT) is a reliable and non-invasive technique for the diagnosis of Helicobacter pylori (HP) infection. In this study we evaluated the diagnostic performance of a new, practical and low-dose (14)C-UBT system for the diagnosis of HP and compared the results with those obtained using the standard method. Seventy-five patients (56 female, 19 male) with dyspepsia underwent (14)C-UBT and endoscopy with antral biopsies for histological analysis. The rapid urease test (CLO test) was applied to 50 of these patients. After a 6-h fasting period, a 37-kBq (14)C-urea capsule was swallowed for UBT. Breath samples were collected and counted using two different methods, the Heliprobe method and the standard method. In the Heliprobe method, patients exhaled into a special dry cartridge system (Heliprobe BreathCard) at 10 min. The activities of the cartridges were counted using a designated small GM counter system (Heliprobe analyser). Results were expressed both as counts per minute (HCPM) and as grade (0, not infected; 1, equivocal; 2, infected) according to the counts. In the standard method, breath samples were collected by trapping in a liquid CO(2) absorber. Radioactivity was counted as disintegrations per minute (SDPM) using a liquid scintillation counter after addition of a liquid scintillation cocktail. Histological examination was used as a gold standard. Two patients were excluded from the study because of inadequate biopsy sampling. Forty-eight patients (65%) were found to be HP positive on histology. The Heliprobe method correctly classified 48 of 48 HP-positive patients and 19 of 25 HP-negative patients (sensitivity 100%, specificity 76%, PPV 88%, NPV 100%, accuracy 91%). The standard method correctly classified 48 of 48 HP-positive patients and 20 of 25 HP-negative patients (sensitivity 100%, specificity 80%, PPV 90%, NPV 100%, accuracy 93%). On the other hand, the CLO test identified 26 of 32 HP-positive and 12 of 16 HP-negative patients (sensitivity 81%, specificity 75%, PPV 86%, NPV 66%, accuracy 79%). With the Heliprobe method, all of the positive results were grade 2, and all of the negative results were grade 0. No patients were defined as having grade 1 results. Counts allowed clear discrimination of HP-positive and -negative patients with both methods, the difference being statistically significant in each case ( P<0.001). A significant correlation was found between HCPM and SDPM ( r 0.863, P<0.001). According to the ROC analysis, the area under the curve was nearly the same with HCPM (AUC, 0.888; 95% CI, 0.785-0.992) and SDPM (AUC, 0.898; 95% CI, 0.802-0.994). In conclusion, the new (14)C-UBT system is a highly accurate method for the diagnosis of HP infection. It is rapid and practical, and therefore suitable for clinical and office practice.

Adult↗
PubMed2003

The evolution of medical imaging: from Geiger counters to MRI--a personal saga.

This article traces the evolution of medical imaging, from the crude images of the thyroid gland obtained using Geiger and scintillation counters, to the automatic scanners built to image brain tumors and organs, to gamma cameras, to digital imaging. A computed tomography scanner built in Aberdeen in the late 1960s led to the present-day gamma-camera tomographs, the main workhorse of nuclear medicine. The gradual evolution of the steps needed for clinical magnetic resonance imaging (MRI) are described, along with the rapid development of this novel form of body imaging. A brief account is also given of the present-day use of MRI in clinical medicine worldwide, with some modern cutting-edge applications, and its possible future.

Diagnostic Imaging↗
PubMed1985

Scintillation proximity radioimmunoassay utilizing 125I-labeled ligands.

A unique type of radioimmunoassay is described that does not require centrifugation or separation. Microbeads containing a fluorophor are covalently linked to antibody. When an 125I-labeled antigen is added it binds to the beads and, by its proximity, the emitted short-range electrons of the 125I excite the fluorophor in the beads. The light emitted can be measured in a standard scintillation counter. Addition of unlabeled antigen from tissue extracts displaces the labeled ligand and diminishes the fluorescent signal. Application of scintillation proximity immunoassay to tissue enkephalins, serum thyroxin, and urinary morphine is described. Applications of the principle to study the kinetics of interaction between receptors and ligands are discussed.

Chorionic Gonadotropin↗
PubMed1979

[Model for the study of influences on fracture healing. Animal experiments].

Primary and secondary bone healing were studied for 30 and 60 days, respectively, by means of X rays, scintigraphy, determination of callus thickness, scintillation counter, and determination of bone mineral content. Primary bone healing was terminated after 30 days, secondary healing after 60 days. Scintillation counting proved to be a quantitative method, the other methods serving as controls. The different influences on bone healing can be quantitatively studied by means of this model.

Animals↗
PubMed1987

Beta spectroscopy with liquid scintillation systems: applications in dosimetry of 90Sr and 90Y.

We have demonstrated that commercially available liquid scintillation counters are adequate for obtaining useful information about the variation of beta spectral shapes as a function of attenuation. A gel scintillation system that permitted the approximation of point source geometry worked well. The spectral shapes predicted by the Fermi equations were reasonably matched with experimental spectra of sources with geometry close to a point source. For energies in the range of 50-2300 keV, we found sufficient linearity of the energy scale and uniformity of detection limits for the direct output of the instrument to be experimentally useful. The gel scintillation system has been used to directly measure the energy distribution of the beta flux coming out of bone samples and incident on the soft tissue of dogs fed 90Sr-90Y from in utero to 540 days of age.

Animals↗
PubMed1999

Tissue distribution of polaprezinc in rats determined by the double tracer method.

The tissue distribution of polaprezinc (an insoluble zinc complex of L-carnosine) in rats was studied by the double tracer method using [U-14C-histidine]-, 65Zn-polaprezinc. The 65Zn-radioactivity was measured with an auto-gamma counter, and the 14C containing 65Zn was converted to an absolute count according to the calibration curve for quenching with a liquid scintillation counter with the spill-over method. After the administration of 14C-, 65Zn-polaprezinc to rats, the excretion ratio and time courses in the tissues of the 14C-and 65Zn-radioactivity were different each other. We found that polaprezinc was metabolized as endogenous amino acid or zinc after dissociation in the body. The zinc concentration in plasma reached its maximum at 1 h and decreased slowly, returning to the endogenous level at 11 h after the administration of non-labeled polaprezinc. The concentrations of zinc in liver, kidney, testis, prostate, and cerebrum remained rather constant. The replacement ratios of 65Zn to zinc in the tissues at its maximum percentage were 40% in plasma, 16-20% in liver, kidney, blood, and prostate. The low replacement ratios in testis and cerebrum (2-3%) suggested that zinc uptakes in testis and brain were regulated by the blood-testis-barrier and blood-brain-barrier, respectively.

Administration, Oral↗
PubMed1986

[Effect of spinal CSF dynamics on the subarachnoid diffusion of a substance applied close to the spinal cord].

In order to better understand the effects and side effects of intraspinal administration of morphine we studied the rostral spread of a comparable substance within the cerebrospinal fluid (CSF). This study was performed in connection with nuclear medical diagnostics ruling out possible rhinorrhoea or disturbances of CSF-circulation in 14 patients: Following lumbar intrathecal injection of the tracer 111-Indium-DTPA, the radioactivity over the medulla oblongata was measured continuously for 2 1/2 hours with a single probe scintillation counter; thereafter the distribution of activity over the total spinal canal was determined; finally the spread of activity was registered with the gamma scintillation camera in the 3rd, 24th and 48th hour. The diffusion of the tracer was followed in a model of the subarachnoid space. A few minutes after injection, activity over the medulla oblongata could be detected; initially it increased markedly, later less so; at the end of the 2 1/2 h observation time, approximately 8% of the total activity had reached this level. The timing of activity increase and the peak activity over the medulla oblongata varied between the individuals. Up to 48 hours the activity continued to shift from the spinal canal to the endocranium. Diffusion played a secondary role. These results are further evidence that morphine is transported cephalad within the CSF rather quickly and may act on cervical spinal cord and brainstem.

Anesthesia, Spinal↗
PubMed2006

Radiocarbon dating of archaeological samples (sambaqui) using CO(2) absorption and liquid scintillation spectrometry of low background radiation.

Sambaqui means, in the Tupi language, a hill of shells. The sambaquis are archaeological sites with remains of pre-historical Brazilian occupation. Since the sambaqui sites in the Rio de Janeiro state region are older than 10,000 years, the applicability of CO(2) absorption on Carbo-sorb and (14)C determination by counting on a low background liquid scintillation counter was tested. In the present work, sambaqui shells were treated with H(3)PO(4) in a closed vessel in order to generate CO(2). The produced CO(2) was absorbed on Carbo-sorb. On saturation about 0.6g of carbon, as CO(2), was mixed with commercial liquid scintillation cocktail (Permafluor), and the (14)C activity determined by counting on a low background counter, Packard Tricarb 3170 TR/SL, for a period of 1000 mins to enable detection of a radiocarbon age of 22,400 BP. But only samples with ages up to 3500 BP were submitted to the method because the samples had been collected in the municipality of Guapimirim, in archaeological sambaqui-type sites belonging to this age range. The same samples were sent to the (14)C Laboratory of the Centro de Energia Nuclear na Agricultura (CENA/USP) where similar results were obtained.

Absorption↗
PubMed2005

Neutron spectra and dosimetric features around an 18 mv linac accelerator.

Using the difference between responses to neutrons of TLD-600 and TLD-700, three experimental devices were constructed and arranged to measure thermal neutron fluences, neutron spectra, and neutron doses inside the treatment room of a radiotherapy 18 MV Linear electron accelerator (Linac). Thermal neutron fluences were measured with TLD-600/TLD-700 pairs arranged in both a bare and a cadmium (Cd) foil covered methacrylate box. Neutron spectra were measured in 26 energy bins by introducing pairs of TLD-600/TLD-700 in air and into the middle of five polyethylene spheres with diameters of 3, 5, 8, 10, and 12 inches. A PC version of the BUNKI code was used to unfold the six measurements in each sphere to obtain the 26 energy bins. Neutron and photon doses were measured by introducing pairs of TLD-600/TLD-700 into the middle of a single 25-cm-diameter paraffin sphere. The three required neutron calibrations were carried out at the Nuclear Technology Laboratory of the Polytechnique University of Madrid (UPM), using an 241Am-Be neutron source with an alpha activity of 111 GBq and a yield of 6.6 x 10(6) neutrons s(-1). Three devices were needed for the necessary calibrations: a BF3 counter for the thermal neutron fluence calibration, a LUDLUM 42-5 Bonner spectrometer with five 0.95 g cm(-3) polyethylene spheres with a LiI(Eu) 4 x 4 mm2 scintillation counter for the neutron spectrometer calibration and a NEMO 9140 remmeter for the paraffin remmeter calibration. The Monte Carlo code MCNP 4C has been used in two ways: to calculate the neutron kerma contribution to two TLDs (type 600 and 700) both in air and inside the paraffin sphere, and to determine the neutron spectra at those Linac room zones where the neutron spectra were measured. Thermal neutron fluences of 2.9 x 10(4) +/- 8.6 x 10(3) cm(-2) s(-1), measured around the Linac head plane, and 2.3 x 10(4) +/- 2.3 x 10(3) cm(-2) s(-1), measured at the patient couch plane, are in agreement with previous independent measurements from other authors. The calculated and measured neutron spectra obtained in the treatment room showed three distinct regions: a peak around 0.1 MeV, a flat epithermal region and a thermal region with values similar to those mentioned above. Patient dose equivalents of 0.5 mSv and 5 mSv from neutrons and photons, respectively, were obtained per treatment Gray.

Monte Carlo Method↗