1983年 · 第03卷第02期

The main points of ICRP publication 26 and the system of dose limitation of ICRP were presented in this paper. The following topics were discussed in detail: the gestation of ICRP-26; the objectives of radiation protection; the estimates of risk; the system of dose limitation: dose-equivalent limits for workers and dose limits for members of the public. (X. A. Chen)

It is a invited lecture given in Beijing to explain the basic concepts and the general applications of the optimization in radiation protection recommended by ICRP. Following the general introduction on methodology of the optimization, major emphasis is laid on the cost-benefit analysis, particularly on thevaluation of cost for protection and detriment. For implement of the optimization, the practical analysis of protection level charace terized by a suitable protection parameter is described. As to the fields in which the optimization of radiation protection can be applied, the design of radiation facilities, external and internal radiation, release of radioactive material into environment, transportation of radioactive material and medical exposure are discussed. At the last, some examples are presented to demonstrate some practical applications of the optimization. (X. Shen)

The exposure of population to the ionizing radiation from natural sources varies significently from place to place in the world, with a mean value of 2 mSv, 3/4 of which are from internal irradiation, especially from Rn and its daughters. The value are enhanced by human activities.

The application of a system of dose limitation recommended by ICRP are complicated by the various factors, such as the susceptibility to control, distribution of dose, voluntariness of exposure, human modification of natural environment, etc.

For purpose of evaluating radiation, a modified system of dose limitation was recommended. It has three stages: 1) categorization of exposures; 2) selection of exposure; and 3) evaluation and limitation of exposure.

There are two categories of exposure. If the practice is established, and the source exists, the practice is conveniently assigned to category 1. If the practice is established, but the sourse does not yet exist, the exposure may be assigned to category 2. The methods of limitation of these two categories are different. (C. S. Zhu)

Using EDTA-glucose, EDTA-dextran, ACD-A and ECD-B as anticoagulant solutions, the effect of concentrated platelet suspensions to haemorrhagic syndrome in irradiated dogs was investigated. The platelet count in peripheral blood, the red cell concentration in thoracic duct lymph and the severeness of haemorrhage in dogs after death were chosen as the end points to estimate the effectiveness of such platelet preparations.

The haemostatic activity of platelets separated from EDTA-blood was lower than those from ACD-blood. Although the platelets obtained from EDTA-dextran blood reduced the red cell number in thoracic duct lymph markedly, they did not modify the condition of haemorrhage in dogs which had been transfused repeatedly. The plateletst from ACD-B blood displayed the highes recovery rate and haemostatic activity, but platelet aggregation often took place when the platelet rich plasma was concentrated. Therefore, it is reasonable to chose ACD-A for preparing concentrated platelets and ACD-B for platelet rich plasma.

In the present experiments, the platelet level in peripheral blood after transfusion usually did not exceed 5×10⁴/mm³, but the haemostatic effect was significant. It seems that the endothelium supporting effect of platelets may play a major role in the haemostasis of this condition.

249 Wistar rats, 4~6 weeks old, 119 males and 130 females, were divided into four groups. They were fed with diet pellets containing 0.1% (W/W) DMAB for 104 days and/or irradiated with 300 rads of γ ray on whole-body on 7 th and 14th day after starting the experiment. In the first two months, one rat in each group was killed every week. The experiment lasted for 13.5~14.0 months.

The following results were obtained:

Morphological alterations ruring liver carcinogenic process mainly included 3 stages: 1. Degeneration and necrosis of liver cells; 2. Regeneration and repair of liver cells, including postnecrotic cirrhosis of liver, acidophilic hepatic cell focus, basophilic hepatic cell focus and clear hepatic cell focus; 3. Malignant transformation of the regenerative hepatic cells, forming early hepatocellular carcinoma (less than 3 mm in diameter) or microcarcinoma.

Incidence of tumour: Tumour incidence rate in the first 2 groups was about 90%. Latent period of tumour was 5~6 months in average. Almost all of the tumours were liver carcinomas (49/50), except 1 case was trichoepithelioma of skin. There were 2 cases of liver carcinomas accompanied with mammary tumour in females. All of the tumours in group 2 were liver carcinomas (47 cases).

Macropathologically, the liver carcinomas can be divided into three types, namely, nodular, huge and diffuse, which incidence rate were 62.5% (60/96), 32.3% (31/96) and 5.2% (5/96) respectively.

Generally, there was no synergetic effect of γ rays and DMAB on the induction of liver carcinomas.

Female Wistar rats were sensitive to γ rays in induction of mammary tumours.

The authors present 4 cases of chronic dermatitis caused by occupational radiation. Three of the patients were roentgenologists and the other an orthopedist. Of the two cases with radiodermatitis on hands, one received irradiation dose of 719 rad and the other 11470 rad. The clinical manifestations of affected parts were principally dystrophic changes, including verruciform lesions, atrophy, rhagades, erosion, telangiectasis, nail thickening and destruction. Microscopically, there were epithelial proliferation or atrophy, swollen and degenerated collagen fibers in the corium, trauma of sweat glands, sebaceous glands and hair follicles.

In the other two cases, the skin lesions were on the face, the upper part of thorax and the forearms. The local exposure dose was about 119~490 rad and the clinical manifestations were similar to those of Riehl's melanosis.

In connection with occupational history, clinical manifestations and histopathologic findings, the diagnosis and differential diagnosis are discussed in this paper.

It is observed that water, ethyl alcohol and acetone in environment seriously affect background counting rate of Au-Si surface barrier detector. This phenomenon was discussed in this paper. In order to increase accuracy of measurement, a suggestion was given that samples should be dried before measuring.

The protective effect of SOD on hematopoietic cells in mice irradiated with 700 rads was studied. The survival percentage of animals in the SOD-pretreated group was 72%, while that in the control group was 38%; and the number of bone marrow nucleated cells in the former was much higher than in the latter. On the basis of the dynamic study on the effect of SOD on bone marrow nucleated cells, it is demonstrated that SOD can accelerate the recovery of bone marrow cells in SOD-pretreated mice, which multiplied exponentially during 4~10 days after irradiation.

We have synthesized eight substituted phenol polyamino-polycarboxylic acid chelating agents. There is one or two iminodiacetic acids which can chelate radionuclides in their molecular. Since these chelating agents are generally considered as the very antidote for the removal of internally deposited radionuclides, we have used them for removing incorporated ¹⁴⁴Ce, ²³⁴Th and ¹⁴⁷Pm from rats. It came out that some of the chelating agents are markedly effective, for example, the clearance of ¹⁴⁴Ce from urine was increased 5~10 times.