| 1. |
- Ceberg, Crister, et al.
(författare)
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Photon activation therapy of RG2 glioma carrying Fischer rats using stable thallium and monochromatic synchrotron radiation.
- 2012
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 57:24, s. 8377-8391
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Tidskriftsartikel (refereegranskat)abstract
- 75 RG2 glioma-carrying Fischer rats were treated by photon activation therapy (PAT) with monochromatic synchrotron radiation and stable thallium. Three groups were treated with thallium in combination with radiation at different energy; immediately below and above the thallium K-edge, and at 50 keV. Three control groups were given irradiation only, thallium only, or no treatment at all. For animals receiving thallium in combination with radiation to 15 Gy at 50 keV, the median survival time was 30 days, which was 67% longer than for the untreated controls (p = 0.0020) and 36% longer than for the group treated with radiation alone (not significant). Treatment with thallium and radiation at the higher energy levels were not effective at the given absorbed dose and thallium concentration. In the groups treated at 50 keV and above the K-edge, several animals exhibited extensive and sometimes contra-lateral edema, neuronal death and frank tissue necrosis. No such marked changes were seen in the other groups. The results were discussed with reference to Monte Carlo calculated electron energy spectra and dose enhancement factors.
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| 2. |
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| 3. |
- Ljungberg, Michael, et al.
(författare)
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Comparison of Dual-Window and Convolution Scatter Correction Techniques using the Monte Carlo Method
- 1990
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 35:8, s. 1099-1110
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Tidskriftsartikel (refereegranskat)abstract
- In order to improve the accuracy of SPECT measurements, correction methods have to be used. Two different scatter correction techniques-the dual-window (DW) technique and the convolution (CV) technique-were compared using projection data, simulated by the Monte Carlo method. Comparison with measured data was also made to validate the accuracy of the Monte Carlo code. The main goal was to investigate how well the estimated scatter distributions, using these two scatter correction techniques, fit the simulated, true scatter distribution of the projection data obtained in the photo-peak window. The scatter distributions predicted by the CV technique were found to be consistently lower than those simulated by the Monte Carlo method in the part of the scatter distribution corresponding to the locations of the sources. The DW technique gives lower estimates of the scatter distribution. However, the scatter distribution estimated by the DW technique and the simulated scatter distribution bear a close resemblance to each other.
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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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| 5. |
- Stenvall, Anna, et al.
(författare)
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A small-scale anatomical dosimetry model of the liver.
- 2014
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 59:13, s. 3353-3371
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Tidskriftsartikel (refereegranskat)abstract
- Radionuclide therapy is a growing and promising approach for treating and prolonging the lives of patients with cancer. For therapies where high activities are administered, the liver can become a dose-limiting organ; often with a complex, non-uniform activity distribution and resulting non-uniform absorbed-dose distribution. This paper therefore presents a small-scale dosimetry model for various source-target combinations within the human liver microarchitecture. Using Monte Carlo simulations, Medical Internal Radiation Dose formalism-compatible specific absorbed fractions were calculated for monoenergetic electrons; photons; alpha particles; and (125)I, (90)Y, (211)At, (99m)Tc, (111)In, (177)Lu, (131)I and (18)F. S values and the ratio of local absorbed dose to the whole-organ average absorbed dose was calculated, enabling a transformation of dosimetry calculations from macro- to microstructure level. For heterogeneous activity distributions, for example uptake in Kupffer cells of radionuclides emitting low-energy electrons ((125)I) or high-LET alpha particles ((211)At) the target absorbed dose for the part of the space of Disse, closest to the source, was more than eight- and five-fold the average absorbed dose to the liver, respectively. With the increasing interest in radionuclide therapy of the liver, the presented model is an applicable tool for small-scale liver dosimetry in order to study detailed dose-effect relationships in the liver.
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