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Methods and results are given to enable the computation of radiation dose as a function of depth in the wall of a suprasellar cyst containing radioactivity. Both beta- and gamma-emitting nuclides are considered. The methodology considers distribution of the radioactivity on the cyst wall (spherical shell geometry) and distribution uniformly in the fluid (volume geometry).
AIM: The number of therapies with radiopharmaceuticals labelled with (188)Re is increasing requiring the documentation of the beta radiation exposure Hp(0.07) of the staff at all working and production sites and during the application and follow-up of the patient according to the new German Radiation Protection Law (StrlSchV). However, data for beta-radiation exposure are rare. Therefore, we determined the personal dose Hp(0.07) of the skin of the hands handling (188)Re radiopharmaceuticals to identify steps of high radiation exposure and to optimize working conditions. METHOD: Thermoluminescence dosimeters (TLD 100) were fixed to the fingertips of the radiochemist, the physician and the nurse and compared to official ring dosimeters. In addition, to monitor radiation exposure continuously readable electronic beta- and gamma dosimeters EPD (Siemens) were used. At eight days in which therapies were performed these readings were evaluated. RESULTS: Considering one therapy with a (188)Re-labelled radiopharmaceutical the middle finger of the radiochemist (production) and the physician (application) showed a radiation burden of 894 and 664 muSv/GBq, respectively. The cumulative dose of the fingertips after eight days of therapy was 249 and 110 mSv for the radiochemist and physician, respectively. A cumulative finger dose after eight days of therapy of 17 and 38 muSv/GBq was found for physician and nurse leading to a Hp(0.07) of 3 and 6 mSv, respectively. Preparing the radiopharmaceutical labelled with 20GBq of (188)Re the reading of the personal electronic dosimeter of the radiochemist showed a gamma-dose rate Hp(10) of 55 muSv/h and a beta-dose rate Hp(0.07) of 663 muSv/h which are obviously not representative for the true radiation dose to the skin of the fingertips. CONCLUSION: During therapy with (188)Re-labelled radiopharmaceuticals the true radiation dose to the skin of the finger tips exceeds by far the readings of the official ring dosimeters as well as the continuously readable beta- and gamma dosimeters. This means a risk in exceeding the radiation limit of 500 mSv/a given in the German Radiation Protection Law ( section sign55 StrSchV) primarily in the working field of the radiochemist and the administering physician.
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Cultured mouse (C3H 10T1/2) cells in contact-inhibited state were subjected to protracted exposure at 4 degrees C or 37 degrees C to either beta-rays from HTO or 60Co gamma-rays. The duration of exposure was 20 h and the total dose was varied by changing the dose-rate. The dose-survival and dose-transformation curves for gamma-irradiation at 4 degrees C were close to those obtained after a single acute X-ray dose (0.5 Gy/min). When gamma-irradiation was administered at 37 degrees C, both the lethality and transformation induction were lower than those after the corresponding doses at 4 degrees C, presumably owing to repair of lethal and transformational damage during gamma-irradiation at 37 degrees C. The same effect of temperature was observed in the case of HTO exposure, indicating again the existence of repair of damage during beta-irradiation at 37 degrees C but not at 4 degrees C. These facts strongly suggest that when irradiated at a low temperature such as 4 degrees C, both the dose-lethality and dose-transformation induction relationships were independent of the dose-rate for either gamma- or beta-exposure, at least the dose-rates used in this experiment. Thus, the comparison of radiation effectiveness between beta- and gamma-exposures at 4 degrees C gave reliable values of relative biological effectiveness (RBE) of tritium beta-rays which were ca. 1.4 at the D0 for lethality and 1.6 for cell transformation within the dose range examined (1 to 6 Gy of beta-rays). The comparison between exposures at 37 degrees C resulted in RBE values (1.4 and 1.7, respectively) very close to those at 4 degrees C.
One of the critical factors for dosimetry of beta-rays from tritiated water is the water content within the cell. We estimated the cellular water concentration in cultured mammalian cells by measuring accurately the fraction of the extracellular water in the cell sample with [14C]inulin. The net water content (ml.g-1) after correcting for the extra-cellular water fraction was 0.858 for HeLa (human), 0.833 for JTC12P3 (monkey), 0.829 for NRK (rat), 0.843 for C3H10T1/2 (mouse) and 0.846 for L5178Y (mouse) cells. The mean water content (+/- S.E.M.) in these 5 lines of cultured mammalian cells was 0.842 +/- 0.005.
Radioresistant E. coli TGl harboring pUC 18 plasmid which was Ampicillin-resistant was exposed to 60Co gamma-rays or 3H beta-rays in saline to determine whether the relative biological effectiveness of 3H beta-rays is higher than one. After exposure to 60Co gamma-rays at a dose rate of 0.465 Gy/min, the D0 by colony formation was 145 Gy in the presence of Ampicillin in or absence from the agar medium; whereas, the D0 was calculated as 118 Gy with and without Ampicillin after exposure to 3H beta-rays at a dose rate of 0.431 Gy/min. The relative biological effectiveness established for 3H beta-rays to 60Co gamma-rays was 1.23. The reason for the higher effectiveness of 3H beta-rays as compared to the reference 60Co gamma-rays is discussed in terms of nascent 0 production.
Experiments on the dose-response of tumor development induced by repeated local beta irradiation of the back of mice are summarized. Results indicated a 100% tumor incidence on irradiation at 2.5-11.8 Gy per exposure (dose-saturation effect) and the threshold-like dose response at lower doses. The mechanism underlying these phenomena is discussed on the basis of the tissue-misrepair model, that is misrepair caused by repeated stimulation of cell growth after repeated tissue injury.
Pregnant adult C57BL/6J mice, randomly assigned to 1 of 4 groups, 3 of them were irradiated with beta-rays from tritiated water (HTO) by a single intraperitoneal injection on the 12.5th day of gestation. Their offspring received cumulative doses of 0, 5, 10 or 30 cGy in utero. Male pups were trained and examined using a set of behavioral tests that included avoidance acquisition and avoidance maintenance, open field test, hole-board dipping, a water maze, and a food labyrinth. Results were found for most parameters in the 10 and 30 cGy groups that differed significantly from results for the controls, indicating that the behavioral teratogenic effect of prenatal exposure to chronic beta-ray radiation from HTO may be greater than the same dose of acute X- or gamma-irradiation and that 10 cGy may be the lowest detectable dose level at which behavioral changes is detactable under the conditions used in this experiment.
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Mutagenesis assays using transgenic mice have been recently developed and applied to the studies on the mutagenesis. The present study was undertaken to clarify whether the mutagenesis assay with transgenic mice could detect the mutations induced by the internal beta-ray irradiation from 89Sr or the external gamma-ray irradiation. The transgenic mice used were Muta mouse strain, which carries 80 copies of the bacterial lacZ gene per cell as a target of mutagenesis. Female animals were given intraperitoneal injections of ethylnitrosourea (50 mg/kg per day) for five days, a single intravenous injection of 89Sr (7.4 and 74 MBq/kg), or daily irradiation with 1.5 Gy gamma-rays for five days. The liver, spleen, and bone marrow were collected 15 days after the treatment with each agent. After the genomic DNA was extracted from each tissue, mutation analysis at lacZ locus was carried out. The spontaneous lacZ mutant frequencies were 2-4 x 10(-5). The frequencies of mutants induced by ethylnitrosourea in the liver, spleen and bone marrow were 68, 55, and 11 x 10(-5), respectively. In contrast, the mutant frequencies detected after the treatment with gamma-rays were not so high in all three tissues as those treated with ethylnitrosourea. The injection of 89Sr at a dose of 74 MBq/kg induced mutation at significantly higher frequencies in the bone marrow, but not in the liver and spleen. The results clearly showed that the mutation assay system used here could detect mutagenic effects of the local irradiation from 89Sr, but was relatively insensitive to the beta- and gamma-ray irradiation compared with the chemical mutagens such as ethylnitrosourea.
The measurement of beta-emitters in biological samples (hair, urine and bone) from three patients in the JCO criticality accident was performed to assess the neutron dose to individuals. The result of the measurements of 32P in hair and urine collected immediately after the accident showed that sufficient 32P activities had been induced in the hair by fast neutrons and in the urine by thermal neutrons to know the severity of the exposure to the individuals and to the position. From the measurement of 32P and 45Ca in bone from various anatomical parts of two patients who died 82 and 210 days after the accident, it was suggested that the distribution of the induced beta-emitters activities could prove the position and posture of the patients at the moment of exposure.
The beta-ray induced scission of puC18 plasmid DNA from E. coli in tritiated water was examined in the presence or absence of a green tea percolate (TP) and the main constituent, (-)-epigallocatechin gallate (EGCg). An analysis of the ratio of the original closed-circular to the open-circular form of DNA, which was formed by the strand scission of DNA, revealed that TP and EGCg showed a protective effect on DNA scission depending on their concentrations. A new technique, named solid state spin trapping, was applied to examine this scavenging ability toward the hydroxyl (OH) radical generated in tritiated water. The result was kinetically analyzed to reveal that TP and EGCg showed the scavenging effect, suggesting that the protective effect on DNA scission was attributable to the scavenging effect on the OH radical.
The most serious damage to cells exposed to radiation is attributed mostly to effects on the structure of cellular DNA. We found that trehalose protects DNA from irradiation. In the presence of 10 mM trehalose, DNA can be protected from about 4 times higher doses of beta- and gamma-ray irradiation. The protective effect increases with the amount of the sugar. Other disaccharides, sucrose, and maltose had similar effects.
The bidirectionality of the upward radiance field in oceanic case 1 waters has been reinvestigated by incorporation of revised parameterizations of inherent optical properties as a function of the chlorophyll concentration (Chl), considering Raman scattering and making the particle phase function shape (beta(rho)) continuously varying along with the Chl. Internal consistency is thus reached, as the decrease in backscattering probability (for increasing Chl) translates into a correlative change in beta(rho). The single particle phase function (previously used) precluded a realistic assessment of bidirectionality for waters with Chl > 1 mg m(-3). This limitation is now removed. For low Chl, Raman emissions significantly affect the radiance field. For moderate Chl (0.1-1 mg m(-3)), new and previous bidirectional parameters remain close. The ocean reflectance anisotropy has implications in ocean color remote-sensing problems, in derivation of coherent water-leaving radiances, in associated calibration-validation activities, and in the merging of data obtained under various geometrical configurations.
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STUDY OBJECTIVE: To assess the feasibility and short-term outcome of intracoronary irradiation after pure balloon angioplasty (POBA) of de novo and post-POBA restenotic lesions with a liquid beta-emitter (188)Re-filled balloon. DESIGN AND SETTING: Nonrandomized prospective study with contemporaneous control group in a single medical center. PATIENTS AND METHODS: In the Taiwan Radiation in Prevention of Post-Pure Balloon Angioplasty Restenosis study, 40 patients underwent 14-Gy irradiation and 15 patients underwent 20-Gy irradiation at a tissue depth of 0.5 mm after POBA. Thirty control patients received a 5-min inflation with a perfusion balloon catheter after POBA. RESULTS: No procedural or in-hospital complications, or 30-day major adverse cardiac events were noted. Six-month angiographic restenosis rates were 49% in the 14-Gy group, 20% in the 20-Gy group, and 57% in the control group (p = 0.05, 20-Gy group vs control group). In the lesions with an arc of calcification of < 180 degrees, restenosis occurred in 15 of the 34 lesions (44%) in the 14-Gy group and in none of the 11 lesions (0%) in the 20-Gy group (p = 0.007). In a vessel with a reference diameter < 3.0 mm, restenosis occurred in 1 of the 8 lesions (13%) in the 20-Gy group, and in 8 of the 11 lesions (73%) in the control group (p = 0.02). In the post-POBA restenotic lesions, restenosis occurred in none of the six lesions (0%) in the 20-Gy group, and in five of the six lesions (83%) in the control group (p = 0.008). CONCLUSIONS: Post-POBA, catheter-based brachytherapy in nonstented native coronary artery with a (188)Re-filled balloon can effectively reduce target lesion restenosis with 20-Gy irradiation at a tissue depth of 0.5 mm and seems to be more effective in the treatment of lesions with an arc of calcification < 180 degrees, in a vessel with a reference diameter of < 3.0 mm, and in post-POBA restenotic lesions.
Neuroendocrine tumours (NET) have a particular tendency to express functional receptors and/or uptake mechanisms. Radionuclides, such as (111)In-pentetreotide, a somatostatin analogue, which bind to somatostatin receptors, present an imaging modality that has been used for both the diagnosis and staging of NET. Scintigraphy with (111)In-pentetreotide can identify lesions beyond the diagnostic sensitivity of conventional imaging modalities. In addition, NET that demonstrate positive uptake to a diagnostic (111)In-pentetreotide can, in theory, be treated with these radionuclides, thus presenting a novel and evolving therapeutic modality in addition to other traditional therapeutic approaches. Although experience with (90)Y-DOTA-D-Phe(1)-Tyr(3)-octreotide therapy is still limited, preliminary studies have demonstrated useful activity in a variety of NET with limited side-effects. Large phase II clinical trials using (90)Y-DOTA-D-Phe(1)-Tyr(3)-octreotide therapy are still on-going and the results are expected to be presented soon. In order to improve the response rates obtained, newer somatostatin analogues are being developed and the combination with other beta-emitting particles in addition to (90)Y is being considered.