Transmissions of 14 MeV neutrons for the samples were determined from radioactivities of Dy2O3targets. Semi-log plots of transmissions against the concentrations fell on straight lines, respectively. From the slope of lines, detection limits and standard deviations were calculated and found to be 5×10-3, 2×10-3, 6×10-4M and 5.2, 5.2, 4.5%. A plot of the slope against absorption cross sections of the isotopes for thermal neutron also fell on a straight line. The neutron transmission for aqueous solution samples was formulated as T=I/I0=exp (-1.01×10-21×σabs×C), where C is the concentration of isotope. From the results of interference by other elements for the analysis, the permitted concentrations in systems of10B-Cl and113Cd-Hg, were 1.5 M of Cl and 0.04 M of Hg, respectively. In systems of6Li-Na and113Cd-Zn, the interference was not observed.
The concentrations of226Ra and210Pb in field soil at various distinct in Japan were determined, and it was found that the mean value of the concentrations of210Pb was two times higher than that of226Ra, namely the mean values of the concentration of210Pb and226Ra in soil were 1.56 pCi/g and 0.79 pCi/g respectively. As it was considered that one of the sources of210Pb in the soil was based on210Pb in rain water, the correlation of the annual rain volume and the concentration of210Pb in the soil at the various district was studied under the assumption that210Pb in rain water should be absorbed to the soil. From the study, it was clearly presumed that a part of210Pb, generated from the disintegration of222Rn which was exhaled from the Chinese continent, was deposited on the soil through the rain water.
A dyed polymethyl methacrylate (PMMA) called ‘Sumipex 400’, which is commerci ally available, has been irradiated by60Co γ rays and 35 MeV pulsed electron beams from a linear accelerator and the radiation-induced optical absorption has been investigated. In the irradiated dyed PMMA, increased absorption was observed in the region of 600 nm to 1000 nm. The difference between an absorption curve of normal PMMA and that of irradiated PMMA has two peaks at 609 nm and 653 nm. However absorption curves obtained by both60Co γ rays and electron beams exhibit the similar shape. The change in optical density at 653 nm is a linear function of the dose, up to about 1 Mrads. The linearity of change in optical density for the dose is lost when the dose exceeds about 1 Mrads. But if the calibration curve is available, this technique is useful for measuring irradiation doses between 105and4×106rads within 2% fading during less than 24 hours after irradiation. This method has been also applied for measuring spatial distributions of electron beams from the linac, and reasonable results have been obtained. As a conclusion, it was experimentally shown that the radiation-induced optical absorption in the dyed PMMA had been found to be a convenient and inexpensive method of radiation dosimetry.
We have studied the development of C-peptide radioimmunoassay kit which is usable in the pancreatic function test with satisfactory results. The C-peptide antiserum was prapared by immunizing rabbits with synthetic human connecting peptide. The antiserum revealed no cross reaction to any other C-peptides except human C-peptide, porcine insulin and gastrointestinal hormon, and showed high specificity to human C-peptide. We adopted double antibody method in B, F separation, and chose 4°C, 48 hes. for 1st. incubation and 4°C, 24 hrs. for 2nd. incubation. On this kit, the assay range was 0.5 ng/ml-30ng/ml, the recovery rate was 98.4%-107.8% in the recovery test, the coefficient of variance was 6.2% on the intra assay and was 7.6% on the inter assay. We think this kit is sufficiently usable to assay the C-peptide in blood.
Carcinoembryonic antigen (CEA) radioimmunoassay with sandwich method was performed in addition to both α1fetoprotein (AFP) radioimmunoassay and liver scintigraphy to elevate the diagnostic accuracy of hepatic tumor in nuclear medicine. All of ten cases with healthy control and 47 out of 52 cases with benign disease showed a CEA titer less than 2.5 ng/ml. On the contrary, 78 out of 188 cases (41%) with malignant disease showed a titer over 2.5 ng/ml, and however most positive cases were metastatic, especially to liver. In metastatic liver cancer, thirty-three out of 46 cases (72%) showed a strongly positive CEA titer over 5 ng/ml taken as the lower limit predicting the metastasis to liver. On the other hand, in primary liver cancer thirty-two out of 35 cases (91%) showed a strongly positive AFP titer over 200 ng/ml, although only one case showed a CEA titer over 5 ng/ml. Seven cases (15%) with metastatic liver cancer also showed a strongly positive AFP titer, and however six of these positive cases showed a CEA titer over 5 ng/ml. Furthermore, in metastatic liver cancer, eleven out of 46 cases (24%) showed no clearcut focal defects on liver scintigram. In nine of these negative cases showed a CEA titer over 5 ng/ml, and at subsequent operation metastatic liver lesions were found. The overall diagnostic accuracy for detecting metastatic liver cancer with a combination of both method was 95%. From present study, CEA radioimmunoassay was useful for the elucidation of the nature of focal hepatic lesions in addition to AFP radioimmunoassay, and moreover could be used as an adjunct to liver scintigraphy for the detection of metastatic lesions in liver.
Bone scintigraphy with99mTc-EHDP (ethane-1-hydroxy-1, 1-diphosphonate) was performed in 22 cases of primary bone tumors, metastatic bone tumors and other diseases, using a scintillation camera and mini-computer system. Excellent skeletal images were obtained in 19 cases (86.4%) while other 3 were not so excellent, but all of them were helpful for clinical diagnosis. In the cases of primary bone tumors with high malignancy, the uptake of99mTc-EHDP in the lesions was observed about twice or higher than of healthy opposite side. And in other cases including metastatic bone tumors, the uptake was observed not more than 1.5 times. In all 4 cases of metastatic bone tumors showed positive scintigrams, although in 2 of them, their plain X-ray photographs showed no abnormality. It was observed that scintigraphy with this agent was useful for differential diagnosis of the lesions and the demonstration of early metastasis in bone. None of the patients showed any adverse reaction of99mTc-EHDP in administration.
203Hg-chlormerodrin has been widely used for renal scintigraphy in Japan but it is not the best scintigraphic agent because of large exposure dose to the kidneys. Renal scintigraphy with99mTc-DMS (dimercaptosuccinate) was performed on 36 patients suspected of having various renal disorders. The scintigraphic images with99mTc-DMS were similar to those with203Hg-chlormerodrin. Urinary excretion and kidney accumulation of99mTc-DMS were measured and the renal images were obtained at various times ranging from 5 min to 24 hr after injection in 6 normal subjects. Approximately 30% of the administered activity was excreted in the urine within 24 hr of injection. Kidney-to-background ratios rose sequentially with time, and renal image quality was better on scintiphotos obtained 2 hr or more after injection. No side effects were observed in this study. In conclusion, 99mTc-DMS was proved to be useful for renal static imaging and also for vascular dynamic studies.