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

100%

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

tom Vol. 57, No. 4

607-613

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.

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

88%

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

tom Vol. 57, No. 4

555-562

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.