Microdosimetric cellular-dose calculations for beta emitters /
Beta-particle emitters are a popular radiation source in the radioimmunotherapy of tumor metastases. Treatment planning in radiation therapy requires accurate predictions of therapeutic effect. Cells (or subcellular organelles) are critical targets responsible for biological responses, and therefo...
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| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1995.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742164101&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Beta-particle emitters are a popular radiation source in the radioimmunotherapy of tumor metastases. Treatment planning in radiation therapy requires accurate predictions of therapeutic effect. Cells (or subcellular organelles) are critical targets responsible for biological responses, and therefore accurate estimates of cellular dose can help improve the predictions. In this study, a microdosimetric algorithm has been developed to provide, for the first time, cellular-dose estimates in the form of probability density functions (pdf s) of a random quantity specific energy z. Electron transport is simulated using the electron Monte Carlo code OREC (Oak Ridge Electron-transport Code). The simulation parameters are the initial electron energy E and source-to-target distance r. The single group-event density gl(z;r,E) and the groupevent probability o)g(r,E) are defined as fundamental quantities for generating specific energy distributions. Specific energy distributions [ ](E)l and f([ ]) are, enerated as probabilistic point kernels for monoenergetic electron and beta-emitting sources, respectively: N(E) is the number of electron emissions, and A is the cumulated activity. . The mean specific energies, 'i from the pdfs show good agreement with the absorbed doses, D, from earlier macrodosimetric results. The n-microdosimetric approach has been applied to estimate cellular doses from beta emitters 131I and 90Y, using spherical models of tumor and normal tissue. The results show that the extent of randomness in cellular dose can be predicted by its corresponding mean dose. The randomness is negligible at high mean doses, but it becomes significant at low mean doses. For a mean dose of 24 Gy, the actual dose at a target site can be different from the mean value by up to 200% at the 99% confidence level. Considering that the average dose delivered to tumors in the current experimental studies of radioimmunotherapy ranges from 0.1 Gy to 100 Gy, this study suggests that dose estimation should be performed by a microdosimetric approach so as to improve the predictions of therapeutic effect, thereby improving treatment plans. |
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| Item Description: | Vita. "Major subject: Nuclear Engineering". |
| Physical Description: | xv, 158 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |