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Biokinetics and radiation dosimetry for [4-14C] cholesterol in humans

Marcato L. A., Hamada M. M., de Mesquita C. H.

Nukleonika

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2012

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Vol. 57, No. 4

607-613

EN

This study proposes a biokinetic model for using in the assessment of the internal dose received by human subjects administered intravenously or orally with [4-14C]-cholesterol. The proposed model includes three systemic pools representing the short-term (T1/2 = 1 d), intermediate-term (T1/2 = 16 d) and long-term (T1/2 = 78 d) physiological exchanges and two excretion pathways: urine and feces. To validate the model, the predicted excretion and absorption of cholesterol was compared with that described in the literature. The radiometric doses were calculated in function of the phantom body mass (M) applying MIRD (medical internal radiation dose) protocol with ANACOMP software. The effective dose coefficients for oral administration were: 2.93×10–10 Sv.Bq–1 (73.3 kg); 3.84×10–10 Sv.Bq–1 (56.8 kg); 6.74 × 10–10 Sv.Bq–1 (33.2 kg) and 7.72 × 10–10 Sv.Bq–1 (19.8 kg). To determinate the dose for intermediate body mass M the polynomial interpolation can be used: Sv.Bq–1 (kg) = 6 × 10–15M3 – 8 × 10–13M2 + 2 × 10–11M + 6 × 10–10 (R2 ≅ 1). In the same way, for intravenous administration were: 3.72 × 10–10 Sv.Bq–1 (73.3 kg); 4.87 × 10–10 Sv.Bq–1 (56.8 kg); 8.49 × 10–10 Sv.Bq–1 (33.2 kg); 1.26 × 10–9 Sv.Bq–1 (19.8 kg). Similarly, for any M body mass: Sv.Bq–1 (kg) = –4 × 10–15M3 + 9 × 10–13M2 – 7 × 10–11M + 2 × 10–9 can be used.

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A comparative study on the performance of radiation detectors from the HgI2 crystals grown by different techniques

Martins J. F. T., Costa F. E., dos Santos R. A., de Mesquita C. H., Hamada M. M.

Nukleonika

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2012

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Vol. 57, No. 4

555-562

EN

In this work, the establishment of a technology for HgI2 purification and crystal growth is described, aiming at a future application of this crystal as a room temperature radiation semiconductor detector. Two methods of crystal growth were studied in the development of this work: (1) physical vapor transport (PVT) and (2) saturated solution from dimethylsulphoxide (DMSO) complexes. In order to evaluate the crystals obtained using each of these methods, systematic measurements were carried out for determining the stoichiometry, structure, orientation, surface morphology and impurity of the crystal. The influence of these physicochemical properties of the crystals developed was evaluated in terms of their performance as a radiation detector. The best response to radiation was found for the crystals grown by the PVT technique. Significant improvement in the performance of HgI2 radiation detector was found, purifying the crystal by means of two successive growths by the PVT technique.

3

Gamma-ray computed tomography SCANNERS for applications in multiphase system COLUMNs

Calvo W. A. P., Hamada M. M., Sprenger F. E., Vasquez P. A. S., Rela P. R., Martins J. F. T., de Matos Pereira J. C. S., Omi N., de Mesquita C. H.

Nukleonika

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2009

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Vol. 54, No. 2

129-133

EN

Gamma-ray tomography experiments have been carried out to detect spatial patterns in the porosity, in a 0.27 m diameter packed steel column using a first generation computed tomography (CT) system. The CT scanner consists of a NaI(Tl) detector 5.08 cm in diameter, and an encapsulated 137Cs (3.7 GBq) radioactive source, located opposite to the center of the detector. The detector and the source, mounted on a fixed support and the column, can rotated and dislocate by two stepping motors controlled through a microprocessor. Different sizes of stainless steel Raschig rings (12.6, 37.9 and 76 mm) have been examined. The primary objective of this work is to detect spatial patterns and statistical information on porosity variation in packed distillation columns. Horizontal scans, at different vertical positions of the packed bed were made for each size of Raschig rings. Radial porosity variation within the packed bed has been determined. This study has demonstrated that the porosity and its spatial distribution in a metallic packed column can be measured with adequate spatial resolution using the gamma-ray tomography technique. After validation of this first generation CT, the turntable design to rotate and dislocate the 60Co or 137Cs sealed gamma-ray sources and multidetector array for the third generation industrial computed tomography was also developed.

4

Development of crystals based on cesium iodide for measurements of gamma radiation and alpha particles

Pereira M. C. C., Filho T. M., Hamada M. M.

Nukleonika

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2009

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Vol. 54, No. 3

151-155

EN

During the past 50 years, scintillators have been among the most important nuclear radiation detectors. Inorganic scintillators are widely used in experimental nuclear physics, high energy physics, nuclear medicine, nuclear tomography, environmental studies and many other fields of use. Scintillation crystals based on cesium iodide (CsI) are matters of relatively low hygroscopy, high atomic number, easy handling and low cost, characteristics that favor their use as radiation detectors. In this work, the growth of pure CsI crystals, CsI:Br and CsI:Pb, using the Bridgman technique, is described. Ions of divalent lead (Pb2+) doped in the crystal structures are efficient emission centers and their application as scintillators is still the reason for intensive studies. Recently, promising results have been found for crystals of CsI doped by bromine (Br) for their use as radiation detectors. The concentration of the bromine doping element (Br) was studied in the range from 1.5 × 10–1 M to 10–2 M and the lead (Pb) in the range from 10–2 M to 5 × 10–4 M. To evaluate the scintillators developed, systematic measurements were carried out for luminescence emission and luminescence decay time for gamma radiation, Vickers microhardness assays, and analysis of crystals response to the gamma radiation, in the energy range from 350 keV to 1330 keV, and alpha particles from a 241Am source, with energy of 5.54 MeV. The obtained values for luminescence decay time for CsI:Br and CsI:Pb crystals, were from 13 to 19 ns.