| 1. |
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| 2. |
- Forrer, Flavio, et al.
(författare)
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Treatment with 177Lu-DOTATOC of patients with relapse of neuroendocrine tumors after treatment with 90Y-DOTATOC.
- 2005
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Ingår i: Journal of nuclear medicine : official publication, Society of Nuclear Medicine. - 0161-5505. ; 46:8, s. 1310-6
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Tidskriftsartikel (refereegranskat)abstract
- Therapy with [(90)Y-DOTA(0), Tyr(3)]-octreotide (DOTATOC, where DOTA = tetraazacyclododecane tetraacetic acid and TOC = D-Phe-c(Cys-Tyr-D-Trp-Lys-Thr-Cys)-Thr(ol)) is established for the treatment of metastatic neuroendocrine tumors. Nevertheless, many patients experience disease relapse, and further treatment may cause renal failure. Trials with (177)Lu-labeled somatostatin analogs showed less nephrotoxicity. We initiated a prospective study with (177)Lu-DOTATOC in patients with relapsed neuroendocrine tumors after (90)Y-DOTATOC treatment. METHODS: Twenty-seven patients, pretreated with (90)Y-DOTATOC, were included. The mean time between the last treatment with (90)Y-DOTATOC and (177)Lu-DOTATOC was 15.4 +/- 7.8 mo (SD). All patients were injected with 7,400 MBq of (177)Lu-DOTATOC. Restaging was performed after 8-12 wk. Hematotoxicity or renal toxicity of World Health Organization grade 1 or 2 was not an exclusion criterion. RESULTS: Creatinine levels increased significantly, from 66 +/- 14 micromol/L to 100 +/- 44 micromol/L (P < 0.0001), after (90)Y-DOTATOC therapy. The mean hemoglobin level dropped from 131 +/- 14 to 117 +/- 13 g/L (P < 0.0001) after (90)Y-DOTATOC therapy. (177)Lu-DOTATOC therapy was well tolerated. No serious adverse events occurred. The mean absorbed doses were 413 +/- 159 mGy for the whole body, 3.1 +/- 1.5 Gy for the kidneys, and 61 +/- 5 mGy for the red marrow. After restaging, we found a partial remission in 2 patients, a minor response in 5 patients, stable disease in 12 patients, and progressive disease in 8 patients. Mean hemoglobin and creatinine levels did not change significantly. CONCLUSION: (177)Lu-DOTATOC therapy in patients with relapse after (90)Y-DOTATOC treatment is feasible, safe, and efficacious. No serious adverse events occurred.
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| 3. |
- Giussani, Augusto, et al.
(författare)
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A Compartmental Model for Biokinetics and Dosimetry of 18F-Choline in Prostate Cancer Patients
- 2012
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Ingår i: Journal of Nuclear Medicine. - : Society of Nuclear Medicine. - 0161-5505 .- 2159-662X. ; 53:6, s. 985-993
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Tidskriftsartikel (refereegranskat)abstract
- PET with F-18-choline (F-18-FCH) is used in the diagnosis of prostate cancer and its recurrences. In this work, biodistribution data from a recent study conducted at Skane University Hospital Malmo were used for the development of a biokinetic and dosimetric model. Methods: The biodistribution of F-18-FCH was followed for 10 patients using PET up to 4 h after administration. Activity concentrations in blood and urine samples were also determined. A compartmental model structure was developed, and values of the model parameters were obtained for each single patient and for a reference patient using a population kinetic approach. Radiation doses to the organs were determined using computational (voxel) phantoms for the determination of the S factors. Results: The model structure consists of a central exchange compartment (blood), 2 compartments each for the liver and kidneys, 1 for spleen, 1 for urinary bladder, and 1 generic compartment accounting for the remaining material. The model can successfully describe the individual patients' data. The parameters showing the greatest interindividual variations are the blood volume (the clearance process is rapid, and early blood data are not available for several patients) and the transfer out from liver (the physical half-life of F-18 is too short to follow this long-term process with the necessary accuracy). The organs receiving the highest doses are the kidneys (reference patient, 0.079 mGy/MBq; individual values, 0.033-0.105 mGy/MBq) and the liver (reference patient, 0.062 mGy/MBq; individual values, 0.036-0.082 mGy/MBq). The dose to the urinary bladder wall of the reference patient varies between 0.017 and 0.030 mGy/MBq, depending on the assumptions on bladder voiding. Conclusion: The model gives a satisfactory description of the biodistribution of F-18-FCH and realistic estimates of the radiation dose received by the patients.
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| 4. |
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| 5. |
- Kneifel, Stefan, et al.
(författare)
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Individual voxelwise dosimetry of targeted (90)Y-labelled substance P radiotherapy for malignant gliomas.
- 2007
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Ingår i: European journal of nuclear medicine and molecular imaging. - : Springer Science and Business Media LLC. - 1619-7070 .- 1619-7089. ; 34:9, s. 1388-95
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Substance P is the main ligand of neurokinin type 1 (NK-1) receptors, which are consistently overexpressed in malignant gliomas. The peptidic vector (111)In/(90)Y-DOTAGA-substance P binds to these receptors and can be used for local treatment of brain tumours. Dosimetry for this interstitial brachytherapy has mainly been done using geometrical models; however, they often do not faithfully reproduce the in vivo biodistribution of radiopharmaceuticals, which is indispensable to correlate the deposited energy with clinical response. The aim of this study was to establish a reproducible dosimetry protocol for intratumoural radiopeptide therapy. METHODS: For test and therapeutic injections, 2 MBq of (111)In-substance P and 370-3,330 MBq of (90)Y-substance P, respectively, were applied in 12 patients with malignant gliomas. Over a period of 24 h, serial SPECT scans were performed on a dual-head SPECT camera. The scans were acquired in a double-energy window technique together with (99m)Tc-ECD in order to co-register the dose distributions with a separately acquired, contrast-enhanced CT scan. Quantitative voxelwise dose distribution maps (in Gy/GBq) were computed from these data using a mono-exponential decay approach. Pre- and post-therapeutic values were compared. RESULTS: Agreement between pre- and post-therapeutic dosimetry was very good and delivered absolute dose values in Gy per injected GBq. In all patients, the pretherapeutic test injection together with the CT overlay technique could predict the precise localisation of dose deposition in an anatomical context. CONCLUSION: This protocol allows a precise pretherapeutic computation of the expected three-dimensional dose distribution and is clearly superior to the previously used dosimetry based on planar scintigraphic images. It has become an indispensable tool for planning intratumoural radiopeptide therapy in glioma patients.
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| 6. |
- Sydoff, Marie, et al.
(författare)
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ABSOLUTE QUANTIFICATION OF ACTIVITY CONTENT FROM PET IMAGES USING THE PHILIPS GEMINI TF PET/CT SYSTEM.
- 2010
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; Apr 7, s. 236-239
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Tidskriftsartikel (refereegranskat)abstract
- Positron emission tomography combined with computed tomography (PET/CT) is a quantitative technique suitable for diagnostics and uptake measurements. The quantitative results can be used for the purpose of the calculating absorbed dose to patients undergoing nuclear medicine investigations. Hence, the accuracy of the quantification of the activity content in organs or tissues is of great importance. When using a planar gamma camera and single photon emission computed tomography (SPECT) images, the activity content in organs and tumours has to be determined by the user, using the number of counts in the organs and the efficiency of the camera. However, when using a Philips Gemini TF PET/CT system, the activity concentration in a region of interest (ROI) is given by the system. The reliability of activity concentration values given by the Philips Gemini TF PET/CT system was studied using a Jaszczak phantom containing hot spheres of different sizes; the influence of the ROI size and the impact of organ size, that is the partial volume effect, was investigated with three different lesion-to-background ratios in the phantom. The use of a small ROI size (40 % of the large ROI size, which covered the entire sphere) showed a 15 % improvement in the recovery of the true activity. Small lesion sizes result in large underestimations of the activity concentration values.
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| 7. |
- Söderberg, Marcus, et al.
(författare)
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Evaluation of image reconstruction methods for 123I-MIBG-SPECT: a rank-order study.
- 2012
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Ingår i: Acta Radiologica. - : SAGE Publications. - 1600-0455 .- 0284-1851. ; 53:7, s. 778-784
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Tidskriftsartikel (refereegranskat)abstract
- Background: There is an opportunity to improve the image quality and lesion detectability in single photon emission computed tomography (SPECT) by choosing an appropriate reconstruction method and optimal parameters for the reconstruction. Purpose: To optimize the use of the Flash 3D reconstruction algorithm in terms of equivalent iteration (EI) number (number of subsets times the number of iterations) and to compare with two recently developed reconstruction algorithms ReSPECT and orthogonal polynomial expansion on disc (OPED) for application on (123)I-metaiodobenzylguanidine (MIBG)-SPECT. Material and Methods: Eleven adult patients underwent SPECT 4 h and 14 patients 24 h after injection of approximately 200 MBq (123)I-MIBG using a Siemens Symbia T6 SPECT/CT. Images were reconstructed from raw data using the Flash 3D algorithm at eight different EI numbers. The images were ranked by three experienced nuclear medicine physicians according to their overall impression of the image quality. The obtained optimal images were then compared in one further visual comparison with images reconstructed using the ReSPECT and OPED algorithms.ResultsThe optimal EI number for Flash 3D was determined to be 32 for acquisition 4 h and 24 h after injection. The average rank order (best first) for the different reconstructions for acquisition after 4 h was: Flash 3D(32) > ReSPECT > Flash 3D(64) > OPED, and after 24 h: Flash 3D(16) > ReSPECT > Flash 3D(32) > OPED. A fair level of inter-observer agreement concerning optimal EI number and reconstruction algorithm was obtained, which may be explained by the different individual preferences of what is appropriate image quality. Conclusion: Using Siemens Symbia T6 SPECT/CT and specified acquisition parameters, Flash 3D(32) (4 h) and Flash 3D(16) (24 h), followed by ReSPECT, were assessed to be the preferable reconstruction algorithms in visual assessment of (123)I-MIBG images.
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| 8. |
- Tavola, Federico, et al.
(författare)
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Nonlinear compartmental model of F-18-choline
- 2012
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Ingår i: Nuclear Medicine and Biology. - : Elsevier BV. - 1872-9614 .- 0969-8051. ; 39:2, s. 261-268
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: This work develops a compartmental model of F-18-choline in order to evaluate its biokinetics and so to describe the temporal variation of the radiopharmaceuticals' uptake in and clearance from organs and tissues. Methods: Ten patients were considered in this study. A commercially available tool for compartmental analysis (SAAM II) was used to model the values of activity concentrations in organs and tissues obtained from PET images or from measurements of collected blood and urine samples. Results: A linear compartmental model of the biokinetics of the radiopharmaceutical was initially developed. It features a central compartment (blood) exchanging with organs. The structure describes explicitly liver, kidneys, spleen, blood and urinary excretion. The linear model tended to overestimate systematically the activity in the liver and in the kidney compartments in the first 20 min post-administration. A nonlinear process of kinetic saturation was considered, according to the typical Michaelis-Menten kinetics. Therefore nonlinear equations were added to describe the flux of 18F-choline from blood to liver and from blood to kidneys. The nonlinear model showed a tendency for improvement in the description of the activity in liver and kidneys, but not for the urine. Conclusions: The simple linear model presented is not able to properly describe the biokinetics of 18F-choline as measured in prostatic cancer patients. The introduction of nonlinear kinetics, although based on physiologically plausible assumptions, resulted in nonsignificant improvements of the model predictive power. (C) 2012 Elsevier Inc. All rights reserved.
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| 9. |
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| 10. |
- Uusijärvi, Helena, et al.
(författare)
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Biokinetics Of 18F-Choline Studied In Four Prostate Cancer Patients
- 2010
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 139:1-3, s. 240-244
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Tidskriftsartikel (refereegranskat)abstract
- Biokinetic data are important when calculating the absorbed dose to the patients and can also be used to find the optimal time between injection and imaging. To the authors' knowledge, there are no published biokinetic data in humans for (18)F-choline, except some distribution data at single time points. Four patients with suspicion of metastases due to biochemical recurrence (measurable prostate-specific antigen in plasma) after radical prostatectomy were injected with (18)F-choline. Four whole-body PET/CT images were taken with 1 h interval, starting immediately after injection. Blood samples were taken and all urine was collected for 3.5 h. The corrected decay activity content in the kidneys was 22-37 % higher immediately after injection when compared with the later time points. The highest activity concentration was found in kidneys (43 kBq ml(-1)). The organ with highest activity content was the liver (11 % of injected activity, % IA). Thirty minutes after the injection 4-16 % IA was left in the blood. Less than 9 % IA was excreted with the urine during the first 3.5 h after injection.
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| 11. |
- Uusijärvi, Helena, 1979, et al.
(författare)
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Comparison of electron dose-point kernels in water generated by the Monte Carlo codes, PENELOPE, GEANT4, MCNPX, and ETRAN.
- 2009
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Ingår i: Cancer biotherapy & radiopharmaceuticals. - : Mary Ann Liebert Inc. - 1557-8852 .- 1084-9785. ; 24:4, s. 461-7
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Tidskriftsartikel (refereegranskat)abstract
- Point kernels describe the energy deposited at a certain distance from an isotropic point source and are useful for nuclear medicine dosimetry. They can be used for absorbed-dose calculations for sources of various shapes and are also a useful tool when comparing different Monte Carlo (MC) codes. The aim of this study was to compare point kernels calculated by using the mixed MC code, PENELOPE (v. 2006), with point kernels calculated by using the condensed-history MC codes, ETRAN, GEANT4 (v. 8.2), and MCNPX (v. 2.5.0). Point kernels for electrons with initial energies of 10, 100, 500, and 1 MeV were simulated with PENELOPE. Spherical shells were placed around an isotropic point source at distances from 0 to 1.2 times the continuous-slowing-down-approximation range (R(CSDA)). Detailed (event-by-event) simulations were performed for electrons with initial energies of less than 1 MeV. For 1-MeV electrons, multiple scattering was included for energy losses less than 10 keV. Energy losses greater than 10 keV were simulated in a detailed way. The point kernels generated were used to calculate cellular S-values for monoenergetic electron sources. The point kernels obtained by using PENELOPE and ETRAN were also used to calculate cellular S-values for the high-energy beta-emitter, 90Y, the medium-energy beta-emitter, 177Lu, and the low-energy electron emitter, 103mRh. These S-values were also compared with the Medical Internal Radiation Dose (MIRD) cellular S-values. The greatest differences between the point kernels (mean difference calculated for distances, <0.9 r/R(CSDA)), using PENELOPE and those from ETRAN, GEANT4, and MCNPX, were 3.6%, 6.2%, and 14%, respectively. The greatest difference between the cellular S-values for monoenergetic electrons was 1.4%, 2.5%, and 6.9% for ETRAN, GEANT4, and MCNPX, respectively, compared to PENELOPE, if omitting the S-values when the activity was distributed on the cell surface for 10-keV electrons. The largest difference between the cellular S-values for the radionuclides, between PENELOPE and ETRAN, was seen for 177Lu (1.2%). There were large differences between the MIRD cellular S-values and those obtained from PENELOPE: up to 420% for monoenergetic electrons and <22% for the radionuclides, with the largest difference for 103mRh. In conclusion, differences were found between the point kernels generated by different MC codes, but these differences decreased when cellular S-values were calculated, and decreased even further when the energy spectra of the radionuclides were taken into consideration.
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| 12. |
- Uusijärvi, Helena, 1979, et al.
(författare)
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Dosimetric characterization of radionuclides for systemic tumor therapy: influence of particle range, photon emission, and subcellular distribution.
- 2006
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Ingår i: Medical physics. - : Wiley. - 0094-2405 .- 2473-4209. ; 33:9, s. 3260-9
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Tidskriftsartikel (refereegranskat)abstract
- Various radionuclides have been proposed for systemic tumor therapy. However, in most dosimetric analysis of proposed radionuclides the charged particles are taken into consideration while the potential photons are ignored. The photons will cause undesirable irradiation of normal tissue, and increase the probability of toxicity in, e.g., the bone marrow. The aim of this study was to investigate the dosimetric properties according to particle range, photon emission, and subcellular radionuclide distribution, of a selection of radionuclides used or proposed for radionuclide therapy, and to investigate the possibility of dividing radionuclides into groups according to their dosimetric properties. The absorbed dose rate to the tumors divided by the absorbed dose rate to the normal tissue (TND) was estimated for different tumor sizes in a mathematical model of the human body. The body was simulated as a 70-kg ellipsoid and the tumors as spheres of different sizes (1 ng-100 g). The radionuclides were either assumed to be uniformly distributed throughout the entire tumor and normal tissue, or located in the nucleus or the cytoplasm of the tumor cells and on the cell membrane of the normal cells. Fifty-nine radionuclides were studied together with monoenergetic electrons, positrons, and alpha particles. The tumor and normal tissue were assumed to be of water density. The activity concentration ratio between the tumor and normal tissue was assumed to be 25. The radionuclides emitting low-energy electrons combined with a low photon contribution, and the alpha emitters showed high TND values for most tumor sizes. Electrons with higher energy gave reduced TND values for small tumors, while a higher photon contribution reduced the TND values for large tumors. Radionuclides with high photon contributions showed low TND value for all tumor sizes studied. The radionuclides studied could be divided into four main groups according to their TND values: beta emitters, Auger electron emitters, photon emitters, and alpha emitters. The TND values of the beta emitters were not affected by the subcellular distribution of the radionuclide. The TND values of the Auger electron emitters were affected by the subcellular radionuclide distribution. The photon emitters showed low TND values that were only slightly affected by the subcellular radionuclide distribution. The alpha emitters showed high TND values that were only slightly affected by the subcellular radionuclide distribution. This dosimetric characterization of radionuclides may be valuable in choosing the appropriate radionuclides for specific therapeutic applications.
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| 13. |
- Uusijärvi, Helena, 1979, et al.
(författare)
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Electron- and positron-emitting radiolanthanides for therapy: aspects of dosimetry and production.
- 2006
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Ingår i: Journal of nuclear medicine : official publication, Society of Nuclear Medicine. - 0161-5505. ; 47:5, s. 807-14
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Tidskriftsartikel (refereegranskat)abstract
- All lanthanides have similar chemical properties regarding labeling. Therefore, radiolanthanides that have been used for therapy, such as (153)Sm and (177)Lu, might easily be replaced with other radiolanthanides. The aim of this work was to investigate the suitability of electron- and positron-emitting radiolanthanides for radionuclide therapy with reference to dosimetry and production possibilities. METHODS: Radiolanthanides with half-lives of 1 h to 15 d, stable or long-lived daughters, and limited photon emission were selected. The ratio of the absorbed dose rate to the tumors and the normal tissue (TND) was calculated for different tumor sizes and compared with the TND values for (90)Y and (131)I. The normal tissue and tumors were simulated as an ellipsoid and spheres, respectively. The TND values depend on the physical parameters of the radionuclides, the tumor size, and the ratio between the activity concentrations in the tumor and normal tissue (TNC). RESULTS: (153)Sm, (161)Tb, (169)Er, (175)Yb, and (177)Lu had the highest TND values for most of the tumor sizes studied. Among these radiolanthanides, (161)Tb and (177)Lu are the only ones that can be produced no-carrier-added (nca) and with high specific activities. The Auger-electron emitters (161)Ho and (167)Tm had high TND values for tumors weighing less than 1 mg and can be produced nca and with high specific activities. (142)Pr, (145)Pr, and (166)Ho showed TND values similar to those of (90)Y. (166)Ho is generator produced and can be obtained nca and at high specific activities. (143)Pr, (149)Pm, (150)Eu, (159)Gd, (165)Dy, (176m)Lu, and (179)Lu had higher TND values than did (90)Y for all tumor sizes studied, but only (149)Pm can be produced nca and at high specific activities. The other electron-emitting radiolanthanides and the positron-emitting radiolanthanides showed low TND values for all tumor sizes because of the high photon contribution. CONCLUSION: The low-energy electron emitters (161)Tb, (177)Lu, and (167)Tm might be suitable for radionuclide therapy. The Auger-electron emitter (161)Ho might not be suitable for systemic radionuclide therapy (intravenous injection) because of its short half-life but might be suitable for local therapy (e.g., in body cavities). If higher electron energy is needed, (149)Pm or (166)Ho might be suitable for radionuclide therapy.
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| 14. |
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| 15. |
- Uusijärvi, Helena, 1979, et al.
(författare)
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Translation of dosimetric results of preclinical radionuclide therapy to clinical situations: influence of photon irradiation.
- 2007
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Ingår i: Cancer biotherapy & radiopharmaceuticals. - : Mary Ann Liebert Inc. - 1084-9785 .- 1557-8852. ; 22:2, s. 268-74
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Tidskriftsartikel (refereegranskat)abstract
- The radionuclide evaluation for therapy starts with preclinical studies in, for example, mice and rats, and various radionuclides have shown promising results. However, many radionuclides emit photons that will irradiate normal tissues. The risk of normal tissue toxicity in patients (e.g., bone marrow suppression) may be underestimated when relying on preclinical results. To illustrate the influence of photons in preclinical and clinical trials, the ratio between the tumor-to-normal tissue absorbed-dose rate ratio (TND) was calculated for humans, rats, and mice for 111In, 125I, 67Ga, 90Y, 131I, and 177Lu. The normal tissues were simulated by 70-kg, 300-g, and 20-g ellipsoids for humans, rats, and mice, respectively. It was assumed that the radionuclides were uniformly distributed, and that the activity concentration was 25 times higher in the tumor than in the normal tissue. There were only small differences between the TND values for the different species for 90Y and 177Lu. 131I showed similar TND values for rats and mice, whereas they were lower for humans. For 111In, 125I, and 67Ga, however, there were large differences between the different species. The influence of photons may thus be much lower in preclinical studies than in clinical situations. Therefore, translations of absorbed doses from animals to humans must be performed with caution.
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| 16. |
- Uusijärvi, Helena, 1979, et al.
(författare)
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Tumour control probability (TCP) for non-uniform activity distribution in radionuclide therapy.
- 2008
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Ingår i: Physics in medicine and biology. - : IOP Publishing. - 0031-9155 .- 1361-6560. ; 53:16, s. 4369-81
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Tidskriftsartikel (refereegranskat)abstract
- Non-uniform radionuclide distribution in tumours will lead to a non-uniform absorbed dose. The aim of this study was to investigate how tumour control probability (TCP) depends on the radionuclide distribution in the tumour, both macroscopically and at the subcellular level. The absorbed dose in the cell nuclei of tumours was calculated for (90)Y, (177)Lu, (103m)Rh and (211)At. The radionuclides were uniformly distributed within the subcellular compartment and they were uniformly, normally or log-normally distributed among the cells in the tumour. When all cells contain the same amount of activity, the cumulated activities required for TCP = 0.99 ((approximate)A(TCP=0.99)) were 1.5-2 and 2-3 times higher when the activity was distributed on the cell membrane compared to in the cell nucleus for (103m)Rh and (211)At, respectively. TCP for (90)Y was not affected by different radionuclide distributions, whereas for (177)Lu, it was slightly affected when the radionuclide was in the nucleus. TCP for (103m)Rh and (211)At were affected by different radionuclide distributions to a great extent when the radionuclides were in the cell nucleus and to lesser extents when the radionuclides were distributed on the cell membrane or in the cytoplasm. When the activity was distributed in the nucleus, (approximate)A(TCP=0.99) increased when the activity distribution became more heterogeneous for (103m)Rh and (211)At, and the increase was large when the activity was normally distributed compared to log-normally distributed. When the activity was distributed on the cell membrane, (approximate)A(TCP=0.99) was not affected for (103m)Rh and (211)At when the activity distribution became more heterogeneous. (approximate)A(TCP=0.99) for (90)Y and (177)Lu were not affected by different activity distributions, neither macroscopic nor subcellular.
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| 17. |
- Zankl, M., et al.
(författare)
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New calculations for internal dosimetry of beta-emitting radiopharmaceuticals
- 2010
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 139:1-3, s. 245-249
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Tidskriftsartikel (refereegranskat)abstract
- The calculation of absorbed dose from internally incorporated radionuclides is based on the so-called specific absorbed fractions (SAFs) which represent the fraction of energy emitted in a given source region that is absorbed per unit mass in a specific target organ. Until recently, photon SAFs were calculated using MIRD-type mathematical phantoms. For electrons, the energy released was assumed to be absorbed locally ('ICRP 30 approach'). For this work, photon and electron SAFs were derived with Monte Carlo simulations in the new male voxel-based reference computational phantom adopted by the ICRP and ICRU. The present results show that the assumption of electrons being locally absorbed is not always true at energies above 300-500 keV. For source/target organ pairs in close vicinity, high-energy electrons escaping from the source organ may result in cross-fire electron SAFs in the same order of magnitude as those from photons. Examples of organ absorbed doses per unit activity are given for F-18-choline and I-123-iodide. The impact of the new electron SAFs used for absorbed dose calculations compared with the previously used assumptions was found to be small. The organ dose coefficients for the two approaches differ by not more than 6 % for most organs. Only for irradiation of the urinary bladder wall by activity in the contents, the ICRP 30 approach presents an overestimation of approximately 40-50%.
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