Radiotherapy is an established treatment modality of cancer. Radiation is delivered to the patients from internal or external sources. This thesis explores and introduces improvements to computational methods that are used in the application of internal and external radiotherapy. The aims of the work were to develop a general methodology for 3D treatment planning of internal radionuclide therapy, to apply 3D treatment planning to analyze radionuclide therapy cases, and to develop a pencil-beam dose kernel based calculation method for external photon therapy that also accounts for local variations in tissue material densities in 3D space. The variability of biological uptake and clearance of the therapy agent were analyzed in various patients undergoing radionuclide therapy by serial single-photon emission computed tomography (SPECT), and estimates of absorbed doses were calculated. Patient-specific dose calculation with the dose kernel method was compared with the widely used MIRD S-factor model. Large inter-patient variation of biological clearance and localized differences for individual patients were observed. The dose estimates from the S-factor model and point dose kernel approach agreed on average, but at an individual patient level there were large variations between the methods.For external photon therapy, an advanced pencil beam dose calculation method was developed. The resulting Analytical Anisotropic Algorithm (AAA) includes a density-scaling method of both lateral and depth-dependent components of the model. The results indicate generally good agreement between the calculations utilizing the presented method and Monte Carlo simulations in various heterogeneous geometries. Most of the observed discrepancies were within 2% (or 2 mm). The method is computationally very efficient and suitable for routine use in clinical setting.
|Translated title of the contribution||Konvoluutio- sekä mallipohjaiset annoslaskentamenetelmät isotooppi- ja ulkoisessa sädehoidossa|
|Publication status||Published - 2016|
|MoE publication type||G5 Doctoral dissertation (article)|
- pencil beam
- point kernel
- treatment planning