Specification of absorbed dose to water using model-based dose calculation algorithms for treatment planning in brachytherapy
| Autor: | Gudrun Alm Carlsson, Åsa Carlsson Tedgren |
|---|---|
| Rok vydání: | 2013 |
| Předmět: |
medicine.medical_specialty
Radiological and Ultrasound Technology Dose calculation Computer science business.industry Radiotherapy Planning Computer-Assisted medicine.medical_treatment Brachytherapy Water Radiotherapy Dosage Models Theoretical Radiation Dosage Percentage depth dose curve Absorbed dose medicine Humans Radiology Nuclear Medicine and imaging Medical physics Radiation treatment planning Nuclear medicine business Monte Carlo Method Algorithm Algorithms |
| Zdroj: | Physics in Medicine and Biology. 58:2561-2579 |
| ISSN: | 1361-6560 0031-9155 |
| Popis: | Model-based dose calculation algorithms (MBDCAs), recently introduced in treatment planning systems (TPS) for brachytherapy, calculate tissue absorbed doses. In the TPS framework, doses have hereto been reported as dose to water and water may still be preferred as a dose specification medium. Dose to tissue medium Dmed then needs to be converted into dose to water in tissue Dw,med. Methods to calculate absorbed dose to differently sized water compartments/cavities inside tissue, infinitesimal (used for definition of absorbed dose), small, large or intermediate, are reviewed. Burlin theory is applied to estimate photon energies at which cavity sizes in the range 1 nm-10 mm can be considered small or large. Photon and electron energy spectra are calculated at 1 cm distance from the central axis in cylindrical phantoms of bone, muscle and adipose tissue for 20, 50, 300 keV photons and photons from (125)I, (169)Yb and (192)Ir sources; ratios of mass-collision-stopping powers and mass energy absorption coefficients are calculated as applicable to convert Dmed into Dw,med for small and large cavities. Results show that 1-10 nm sized cavities are small at all investigated photon energies; 100 µm cavities are large only at photon energies20 keV. A choice of an appropriate conversion coefficient Dw, med/Dmed is discussed in terms of the cavity size in relation to the size of important cellular targets. Free radicals from DNA bound water of nanometre dimensions contribute to DNA damage and cell killing and may be the most important water compartment in cells implying use of ratios of mass-collision-stopping powers for converting Dmed into Dw,med. |
| Databáze: | OpenAIRE |
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