Vol.18,

Radiotherapy for the treatment of prostate cancer has been extensively explored in the past. Along with the comprehensive understanding of the biology of prostate cancer and rapid advances in terms of technology, the outcome of treatment for the patients with prostate cancer has improved. The authors review radiotherapy as the primary treatment for the disease, with particular emphasis on the technological advances from both the radiobiological and radiophysics aspects. Nonconventional fractionated irradiation like hyper- or hypo-fractionation has been implemented in the clinic, the final results still need to be confirmed in the future. Technological advances like IMRT, IGRT, in the last two decades have significantly improved the delivery of external radiotherapy to the prostate. This has resulted in an overall increase in the total dose that can be safely delivered to the prostate, which has led to modest improvements in the biochemical outcome. However, establishing the standard therapy for prostate cancer remains controversial. It is hoped that the next decades will bring continued advances in the development of biologicals that will further improve current clinical outcomes.

325

The measurement of void fraction is of importance to the oil industry and chemical industry. In this article, the principle and mathematical method of determining the void fraction of horizontal gas–liquid flow by using a single-energy γ-ray system is described. The γ-ray source is the radioactive isotope of ²⁴¹Am with γ-ray energy of 59.5 keV. The time-averaged value of the void fraction in a 50.0-mm i.d. transparent horizontal pipeline is measured under various combinations of the liquid flow and gas flow. It is found that increasing the gas flow rate at a fixed liquid flow rate would increase the void fraction. Test data are compared with the predictions of the correlations and a good agreement is found. The result shows that the designed γ-ray system can be used for measuring the void fraction in a horizontal gas–liquid two-phase flow with high accuracy.

325

In the procedure of neutron fluence measurement in the whole energy range (10^-4 eV~18 MeV), in the irradiation chamber of a UZrH reactor, the neutron energy spectra are unfolded using the method of minimizing directed divergence and SAND-II, which are used broadly at home and abroad. These methods belong to the iterative methods. In this article, the procedure of the spectra unfolding using the two methods is described in detail. The neutron spectrum distribution unfolded by the two methods agree well with each other. In the end, the major differences of the two iterative methods are compared with each other, and the main factors affecting the accuracy of the spectra unfolding with the iterative method are discussed.

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The pH-sensitive polyacrylic acid (PAA) hydrogels were synthesized by gamma-ray irradiation at an ambient temperature. The influences of dose, monomer concentration, cross-linking agent content, pH, and ionic strength on the swelling ratio (SR) of the PAA hydrogels were investigated in detail. The results show that the SR of the hydrogel decreases with an increase in the dose, monomer concentration, and cross-linking agent content. In alkaline solution, the SR of the hydrogels is much higher than that in acid solution. Also, the ionic strength can influence the SR of the hydrogels. The more the concentration, the lower the SR.

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Small peptide-based compounds have attracted an enormous interest as carrier molecules to selectively deliver radionuclides to target tissues, sparing critical normal organs. When looking for "matched pairs" of radionuclides, suitable for radiolabeling of peptides for diagnosis and therapy, technetium and rhenium represent an almost ideal constellation. The important role of technetium-99m and Re-186/188 is based on the decay characteristics, suitable for tumor diagnosis and therapy. Tc-99m and Re-188 are readily available by either a ⁹⁹Mo/^99mTc or the ¹⁸⁸W/¹⁸⁸Re radionuclide generator system. Furthermore, technetium and rhenium are chemically related and share structural as well as reactive similarities, which prompt an attractive "matched-pair" situation. This article shows an overview of ^99mTc- and ^186/188Re-radiolabeled peptides that have been tested for their potential use as imaging and therapeutic agents in oncological diseases.

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To explore the preparation method of liposome-coated ^99mTc-labeled antisense oligonucleotide (ASON), targeteing the proliferating cell nuclear antigen (PCNA), and to explore the biological characteristics and the uptake kinetics of a radiolabeled probe in vascular smooth muscle cells, an 18-base single-stranded antisense oligonucleotide targeting PCNA mRNA and the complementary strand (sense oligonucleotide, SON) were synthesized. The ASON (SON) was labeled with ^99mTc, by conjugating the bifunctional chelator (hydrazino nicotinamide, HYNIC), and purified through a gel filtration column of Sephadex G-25. The product was then encapsulated in cationic liposome (oligofectamineTM). The radiolabeling efficiency, radiochemical purity, stability of the liposome-coated ^99mTc-HYNIC- ASON in a phosphate buffered solution (PBS), and fresh human serum and its uptake rate were studied. There was no significant difference between the ^99mTc radiolabeling efficiencies of HYNIC-ASON and HYNIC-SON, which were 60.04% ± 1.92% and 59.60% ± 2.53%, respectively (P > 0.05, n = 5). The radiochemical purity of the liposome-coated ^99mTc-HYNIC-ASON was 94.70% ± 1.90% (n = 5). And after incubation with PBS and fresh human serum at a concentration of 1.2 µg·mL^-1 for 120 min, the radiochemical purities were 92.27% and 91.55% respectively. At 90 min after transfection, the uptake rate of the liposome-coated ^99mTc-HYNIC-ASON reached its peak of 83.8% ± 5.92% in vascular smooth muscle cells (VSMCs) and was much higher than that of the nonliposome-coated ^99mTc- HYNIC-ASON, which was 11.16% ± 0.54% (P < 0.01, n = 4). The labeling method of PCNA ASON (SON) conjugated by HYNIC has been proved successful. The liposome was able to enhance the ASON (SON) uptake in VSMCs, and could be widely used as a safe, convenient, effective gene transfer carrier.

470

A test device for isotopic γ-ray imaging, which consists of an isotope γ-ray source, a CdZnTe γ-ray spectrometer and other auxiliary equipment, is studied here. Compared with the conventional X-ray, the isotope γ-ray, which is utilized in this project, has its own advantages in imaging. Furthermore, with a room-temperature high-energy-resolution CdZnTe detector and a modern imaging processing technique, this device is capable of effectively suppressing the background and gaining more information, thus it can obtain a better image than conventional X-ray devices. In the experiment of PCB imaging, all soldered points and chip components are sharply demonstrated.

359

The spatial resolution of a position sensitive gamma-ray detector configuration based on plastic scintillation fiber array was measured using a Monte Carlo simulation method. Both point spread function and modulation transfer function (MTF) were presented. The factors that influence the spatial resolution were also discussed. The results of the simulation showed that the intrinsic spatial resolution was consistent with the size of the physical pixels and a few centimeters spatial resolution could be obtained under certain circumstances.

384

To estimate the internal dose of a Chinese visiting scholar internally contaminated because of the Chernobyl Accident, the contents of ¹³⁴Cs and ¹³⁷Cs in urine were measured using a Ge(Li) γ-spectrometer. The internal doses were calculated based on data from the ICRP Publications. The effective doses from ¹³⁴Cs and ¹³⁷Cs were estimated to be 61μSv and 98μSv, respectively. The sum of 159μSv was lower than the total effective dose (310μSv), from the inhalation and ingestion of natural radionuclides. The dose of ¹³¹I was also reviewed referring to the UNSCEAR 2000 Report. The equivalent effective dose of ¹³¹I was estimated to be 2.9mSv, 18 times more than the amount of ¹³⁴Cs and ¹³⁷Cs. Therefore, it is considered that the earlier estimation of internal doses of ¹³¹I is important in evaluating radiation injuries from a nuclear reactor accident.

472

Distributions of natural gamma-emitting radionuclides were determined in 93 oil samples collected from some petroleum fields in the western desert of Egypt. The radioisotope activities in the area under investigation lay in the range of (21 ± 4) to (38 ± 13) Bq•L^-1 for ²²⁶Ra, (9 ± 2) to (15 ± 5) Bq•L^-1 for ²³²Th, and (154 ± 28) to (303 ± 54) Bq•L^-1 for ⁴⁰K. The mean values were 27, 12, and 201 Bq•L^-1, respectively. Among oils, variations in radionuclide activities could be on account of differences in TDS, HCo_3, and Ba, with high or low pH. In this environment, oil properties differently affected the mobilization of natural radionuclides. The range of ²²⁶Ra variation had been compared with available data from other countries. The calculated absorbed dose rate ranged from 22.33 to 32.66 nGy•h^-1 in location (B) and (E) respectively, which was less than the accepted value.

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Under severe accidents, natural circulation flows are important to influence the accident progression and result in a pressurized water reactor (PWR). In a station blackout accident with no recovery of steam generator (SG) auxiliary feedwater (TMLB' severe accident scenario), the hot leg countercurrent natural circulation flow is analyzed by using a severe-accident code, to better understand its potential impacts on the creep-rupture timing among the surge line, the hot leg, and SG tubes. The results show that the natural circulation may delay the failure time of the hot leg. The recirculation ratio and the hot mixing factor are also calculated and discussed.

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