| 1. |
- Ahmed, Furman, et al.
(författare)
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Risk Assessment of Outdoor Background Gamma Radiation at Duhok City, in Kurdistan Region, Iraq
- 2022
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Ingår i: Polish Journal of Environmental Studies. - : HARD Publishing Company. - 1230-1485 .- 2083-5906. ; 31:6, s. 4989-4995
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a model „ADM606M Portable Multifunction Ratemeter /Scalar“ (Gamma GP110 Detector) was used to estimate the effective dose rate in (µSv.h-1). The data were analyzed for three specified hours per day (9:00 a.m., 11:00 a.m., and 1:00 p.m.) from January 2009 to June 2016. In July 2019, the gamma scout radiation meter (dosimeter) was used to measure the outdoor gamma effective dose rate (µSv.h-1) for the same building every minute for three hours, from 10 a.m. to 1 p.m., at 1m above the second floor of the building. The average effective dose rate and average Annual Effective Dose Rate were 0.158±0.013 µSv.h-1 and 0.2614145 mSv.y-1, respectively, within acceptable limits. The excess lifetime cancer risk (ELCR) value was also assessed to be (0.91495×10–³), which was found to be greater than the UNSCEAR, 2000 stated world average (0.29×10–³). The risks of cancer morbidity and mortality for specific organs and tissues from external sources of low linear energy transfer (LET) radiation were also assessed. They showed biological effects associated with the potential long-term exposure of Dohuk city residents to natural background radiation.
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| 2. |
- Larsson, Erik, et al.
(författare)
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A Small-Scale Anatomic Model for Testicular Radiation Dosimetry for Radionuclides Localized in the Human Testes.
- 2012
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Ingår i: Journal of Nuclear Medicine. - : Society of Nuclear Medicine. - 0161-5505 .- 2159-662X. ; 53, s. 72-81
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Tidskriftsartikel (refereegranskat)abstract
- The testis is a radiosensitive tissue. It contains a large number of lobules, which in turn are composed of convoluted seminiferous tubules. The epithelium inside each tubule consists of a complex mosaic of supporting cells and germ cells of different sizes and degrees of maturation. These cells are known to have diverse sensitivity to radiation, those with the highest sensitivity being the spermatogonia, which form part of the basal cell layer, and those with the lowest sensitivity being the mature sperm cells closest to the lumen of the tubule. For many years, the internal dosimetry community has discussed the need for improvements to bring about more detailed, cell-level testicular dosimetry. This paper presents a small-scale dosimetry model for calculation of S factors for several different source-target configurations within the testicular tissue. METHODS: A model of the testis was designed in which the lobules were approximated by a cross-section of seminiferous tubules arranged in a hexagonal pattern, with interstitial tissue between them. The seminiferous tubules were divided into concentric layers representing spermatogenic development in the seminiferous epithelium. S factors were calculated for electrons, photons, α-particles, and for (18)F, (90)Y, (99m)Tc, (111)In, (125)I, (131)I, (177)Lu, and (211)At using Monte Carlo simulations. RESULTS: For electrons with low energies the range was small, compared with the diameter of the seminiferous tubules, resulting in high energy deposition close to the source, whereas for higher electron energies more uniform energy deposition was seen, as expected. The same trend was seen for low-energy photons, whose mean free paths are small, compared with the diameter of the seminiferous tubules, resulting in high energy deposition close to the source, whereas for higher photon energies the location of the activity in the testis is less important. CONCLUSION: The model presented in this paper is a simplification of the organized chaos that constitutes the structure of the actual testis. However, it provides a relevant, small-scale anatomic model to help us understand the significance of the heterogeneity of radioactivity in this important radiosensitive tissue.
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| 3. |
- Meerkhan, Suaad
(författare)
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Small-Scale Dosimetry for the Testis: Applications in Nuclear Medicine Diagnostics and Therapy
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- It is well known that the testicles are among the most radiosensitive tissue, and constitute an important critical target for both external and internal radiation during diagnostic and therapeutic use of radionuclides. In systemic radionuclide therapy where very high activities are administered, the testis may become a dose-limiting organ; often with a complex, non-uniform activity distribution and a resulting non-uniform absorbed-dose distribution. A fundamental question in dosimetry research is then how the quantity absorbed dose links to certain biological effects in the volume of energy deposition. The main objective of the research presented in this thesis was to improve the commonly used MIRD dosimetry formalism for the testis, by the development of new methodology based on pre-clinical experiments and clinical patient data. In addition, the use of autoradiography for radioactivity distribution studies in mice, and immunohistochemistry for the detection of double-strand breaks in radiosensitive germ cells in the testis were studied. The work focused on the development of a geometrically realistic small-scale anatomical model of the human testicular tissue and by Monte Carlo modeling to determine S values for different source–target combinations. The model was applied on, and combined with pharmacokinetic modeling on individual patients that underwent pre-therapy imaging with 111-In-Zevalin®. By different autoradiography techniques the biokinetics and heterogeneity of activity distribution in the mouse testis was studied for 111-InCl3 and 111-In-Rituximab. Finally, a method using in vitro γH2AX immunofluorescence microscopy and confocal laser scanning microscope, for the determination of DNA double-strand breaks in spermatogonia and primary spermatocytes after 111-InCl3 uptake in the testis, was established. The results clearly show the importance of considering the heterogeneous distribution of radionuclides in the testis and possible hot spots of radioactivity. Autoradiography and small-scale dosimetry combined with compartment modeling may serve as a bridge between organ and tissue dosimetry. Finally, the thesis presents an efficient wide field γH2AX fluorescence quantifications method, side by side with a high specific intra-cellular confocal laser scanning microscope method to study cellular and intra-cellular radiation induced effects in the testis and might serve as powerful tool to study irradiation toxicity in the human testis.
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| 4. |
- Meerkhan, Suaad, et al.
(författare)
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Testis dosimetry in individual patients by combining a small-scale dosimetry model and pharmacokinetic modeling-application of (111)In-Ibritumomab Tiuxetan (Zevalin(®)).
- 2014
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 59:24, s. 7889-7904
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Tidskriftsartikel (refereegranskat)abstract
- A heterogeneous distribution of radionuclides emitting low-energy electrons in the testicles may result in a significant difference between an absorbed dose to the radiosensitive spermatogonia and the mean absorbed dose to the whole testis. This study focused on absorbed dose distribution in patients at a finer scale than normally available in clinical dosimetry, which was accomplished by combining a small-scale dosimetry model with patient pharmacokinetic data. The activity in the testes was measured and blood sampling was performed for patients that underwent pre-therapy imaging with (111)In-Zevalin(®). Using compartment modeling, testicular activity was separated into two components: vascular and extravascular. The uncertainty of absorbed dose due to geometry variations between testicles was explored by an assumed activity micro-distribution and by varying the radius of the interstitial tubule. Results showed that the absorbed dose to germ cells might be strongly dependent on the location of the radioactive source, and may exceed the absorbed dose to the whole testis by as much as a factor of two. Small-scale dosimetry combined with compartmental analysis of clinical data proved useful for gauging tissue dosimetry and interpreting how intrinsic geometric variation influences the absorbed dose.
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