title: Feasibility of TCP-based dose painting by numbers applied to a prostate case with (18)F-choline PET imaging.
abstract: BACKGROUND
  A biologically adaptive radiation treatment method to maximize the TCP is shown. Functional imaging is used to acquire a heterogeneous dose prescription in terms of Dose Painting by Numbers and to create a patient-specific IMRT plan.
  
  
  METHODS
  Adapted from a method for selective dose escalation under the guidance of spatial biology distribution, a model, which translates heterogeneously distributed radiobiological parameters into voxelwise dose prescriptions, was developed. At the example of a prostate case with (18)F-choline PET imaging, different sets of reported values for the parameters were examined concerning their resulting range of dose values. Furthermore, the influence of each parameter of the linear-quadratic model was investigated. A correlation between PET signal and proliferation as well as cell density was assumed. Using our in-house treatment planning software Direct Monte Carlo Optimization (DMCO), a treatment plan based on the obtained dose prescription was generated. Gafchromic EBT films were irradiated for evaluation.
  
  
  RESULTS
  When a TCP of 95% was aimed at, the maximal dose in a voxel of the prescription exceeded 100Gy for most considered parameter sets. One of the parameter sets resulted in a dose range of 87.1Gy to 99.3Gy, yielding a TCP of 94.7%, and was investigated more closely. The TCP of the plan decreased to 73.5% after optimization based on that prescription. The dose difference histogram of optimized and prescribed dose revealed a mean of -1.64Gy and a standard deviation of 4.02Gy. Film verification showed a reasonable agreement of planned and delivered dose.
  
  
  CONCLUSIONS
  If the distribution of radiobiological parameters within a tumor is known, this model can be used to create a dose-painting by numbers plan which maximizes the TCP. It could be shown, that such a heterogeneous dose distribution is technically feasible.
authors: Universitätsklinikum Regensburg, Klinik und Poliklinik für Strahlentherapie, Regensburg, Germany. thomas.dirscherl@klinik.uni-regensburg.de
authors: Thomas
authors: T
authors: Dirscherl
authors: Mark
authors: M
authors: Rickhey
authors: Ludwig
authors: L
authors: Bogner
mesh_terms: D000465:Algorithms; D016477:Artifacts; D002794:Choline / Q000031:analogs & derivatives*; D005240:Feasibility Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D064847:Multimodal Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D011856:Radiographic Image Enhancement / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D012984:Software; D014057:Tomography, X-Ray Computed
chemical_list: C514960:fluorocholine; D002794:Choline