Quantitative analysis of planar technetium-99m-sestamibi myocardial perfusion images using modified background subtraction.
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Standard interpolative background subtraction, as used for thallium-201 (201Tl), may create artifacts when applied to planar technetium-99m-Sestamibi (99mTc-Sestamibi) images, apparently because of the oversubtraction of relatively high extra-cardiac activity. A modified background subtraction algorithm was developed and compared to standard background subtraction in 16 patients who had both exercise-delayed 201Tl and exercise-rest 99mTc-Sestamibi imaging. Furthermore, a new normal data base was generated. Normal 99mTc-Sestamibi distribution was slightly different compared to 201Tl. Using standard background subtraction, mean defect reversibility was significantly underestimated by 99mTc-Sestamibi compared to 201Tl (2.8 +/- 4.9 versus -1.8 +/- 8.4, p less than 0.05). Using the modified background subtraction, mean defect reversibility on 201Tl and 99mTc-Sestamibi images was comparable (2.8 +/- 4.9 versus 1.7 +/- 5.2, p = NS). We conclude, that for quantification of 99mTc-Sestamibi images a new normal data base, as well as a modification of the interpolative background subtraction method should be employed to obtain quantitative results comparable to those with 201Tl. (+info)
Evaluation of genetic alterations in inhabitants of a naturally high level background radiation and Kudankulam nuclear power project site in India.
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Evaluation of genetic alterations in inhabitants of an area of Tamil Nadu, India, chronically exposed to high background radiation (HBRA), was the major purpose of the present study. A total of 216 samples (exposed inhabitants, 108; control subjects, 108) were selected based on the confirmation of radiation dose level using thermoluminescence dosimetry (TLD). After signing a consent form, volunteers provided blood samples (5 ml each) to establish cell cultures at 52 h. One hundred complete metaphase cells from each subject were evaluated for karyotyping. The frequencies of chromosomal alterations (CA) were found to be higher in the exposed groups and the aberrations predominately observed were of chromatid-type. Smoking was found to have considerable effect on the frequency of CA in exposed subjects. With the comet assay for DNA damage, a significant increase in comet tail frequency was also observed in exposed subjects compared to controls. At present there are no radioepidemiological data regarding the cytogenetic studies in these areas. Furthermore, the Kudankulam nuclear power plant nuclear power plant is being constructed in the same area. The study gives potentially important information on the general health effects due to radiation exposure and increases people's understanding of the hazardous nature of chronic low level natural radiation exposure. However, we may conclude that the HBRA by itself does not pose any significant risk of genetic damage as measured by conventional cytogenetic analysis. (+info)
Growth retardation of Paramecium and mouse cells by shielding them from background radiation.
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In the 1970s and 1980s, Planel et al. reported that the growth of paramecia was decreased by shielding them from background radiation. In the 1990s, Takizawa et al. found that mouse cells displayed a decreased growth rate under shielded conditions. The purpose of the present study was to confirm that growth is impaired in organisms that have been shielded from background radiation. Radioprotection was produced with a shielding chamber surrounded by a 15 cm thick iron wall and a 10 cm thick paraffin wall that reduced the gamma ray and neutron levels in the chamber to 2% and 25% of the background levels, respectively. Although the growth of Paramecium tetraurelia was not impaired by short-term radioprotection (around 10 days), which disagreed with the findings of Planel et al., decreased growth was observed after long-term (40-50 days) radiation shielding. When mouse lymphoma L5178Y cells were incubated inside or outside of the shielding chamber for 7 days, the number of cells present on the 6th and 7th days under the shielding conditions was significantly lower than that present under the non-shielding conditions. These inhibitory effects on cell growth were abrogated by the addition of a (1)(3)(7)Cs gamma-ray source disk to the chamber. Furthermore, no growth retardation was observed in XRCC4-deficient mouse M10 cells, which display impaired DNA double strand break repair. (+info)
A study on natural radioactivity in Khewra Salt Mines, Pakistan.
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The Khewra Salt Mines, the second largest salt mines in the world, are located 160 km south of Islamabad, the capital of Pakistan. Around 1000 workers are involved in the removal of salt from these mines. More than 40,000 visitors come annually to see the mines. The visitors and workers are directly exposed to the internal and external radiological hazards of radon and gamma rays in these mines. The general public is affected by the intake of the salt containing the naturally occurring radionuclides. Therefore the concentration of radon ((2)(2)(2)Rn) in the Khewra Salt Mines and activity concentrations of the naturally occurring radionuclides in the salt samples from these mines were measured. Both active and passive techniques were employed for the measurement of radon with Radon Alpha Detector (RAD-7) and SSNTD respectively. The concentration of (2)(2)(2)Rn was 26 +/- 4 Bq m(-)(3) measured by the active method while 43 +/- 8 Bq m(-)(3) was measured by the passive method. The activity concentration of the radionuclides was measured using gamma ray spectrometry with HPGe detector. The mean activity of (4)(0)K in salt samples was found to be 36 +/- 20 Bq kg(-)(1) and the concentration of (2)(2)(6)Ra and (2)(3)(2)Th in the salt samples was below the detection limits. Gamma radiation hazard was assessed in terms of the external gamma dose from salt slabs and the rooms made of salt and the annual effective dose due to gamma radiation. The exposure to radon daughters, annual effective dose and excessive lifetime cancer risk due to radon in the mines were estimated. The mean annual effective dose due to an intake of (4)(0)K from the salt was calculated as 20.0 +/- 11.1 microSv, which is lower than the average annual effective dose rate of 0.29 mSv, received by the ingestion of natural radionuclides. Due to the low concentration values of primordial radionuclides in the salt and radon (2)(2)(2)Rn) in the mines, a 'low level activity measurement laboratory' is suggested to be established in these mines. (+info)
A record-based case-control study of natural background radiation and the incidence of childhood leukaemia and other cancers in Great Britain during 1980-2006.
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