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Clinical Practice and Optimization of Radiation Therapy

#2746


System for Optimization of Radiation Therapy by Photon and Electron Beams on the Basis of a Pencil Beam Algorithm. Phase 2: Introducing into a Clinical Practice and Improving

Tech Area / Field

  • MED-RAD/Radiomedicine/Medicine
  • PHY-PFA/Particles, Fields and Accelerator Physics/Physics

Status
3 Approved without Funding

Registration date
31.03.2003

Leading Institute
MIFI, Russia, Moscow

Supporting institutes

  • VNIIEF, Russia, N. Novgorod reg., Sarov\nCancer Research Center, Russia, Moscow

Collaborators

  • Baylor College of Medicine, USA, TX, Houston\nUniversité Libre de Bruxelles / Centre des Tumeurs, Belgium, Brussels\nKrolinska Institute / Department of Medical Radiation Physics, Sweden, Stockholm\nSt. Jude Children's Research Hospital, USA, TN, Memphis

Project summary

The optimization of radiation therapy (RT) is being at present one of most actively studied problems. There are several systems for dosimetry planning optimization which are described in the literature up to now and the first steps on their introducing have been made. However it is rather difficult to forecast the wide introducing of optimization systems into routine clinical practice. The information of treatment efficiency on the basis of the optimized irradiation plans is insufficient so the accurate comparison with conventional treatment results is rather problematic. Moreover, it should be noted, considering RT optimization, that many aspects of this problem are still poorly developed. It concerns first of all to the problems of radiobiological optimization that could take into account the inpidual features of each patient, express selecting of optimum directions for irradiation, inhomogeneity corrections etc.

The authors of this project have suggested within the framework of previous ISTC project #1079/99 the comprehensive program for development of 3-D optimization system for distant therapy and its introducing into clinical practice. However by virtue of financing decreasing (more than twice) only the first part of the program was implemented.

The system for RT optimization (ORT) was created on the basis of a multi-criterion formulation, usage of large-scale element method, a pencil beam algorithm and other modern techniques. The rather impressive results were obtained also under development of the fast program for dose distribution calculating by a Monte-Carlo method.

It is suggested in this project to introduce created system into the clinical practice and to improve both system and its components. It includes both improvement of algorithms and performance of present modules of a system and development of new modules, which will expand functional capability of ORT system, taking into account the inpidual features of each patient. The tasks, that should be solved under this project, can be put together into the following main directions:


- Practical introducing of ORT system into treatment process;
- Creation of a technique and including into ORT system of a new module for radiobiological optimization that enables to determine the optimum fractionation scheme and irradiation dose, and also most preferable time for irradiation per each patient;
- Improving of present ORT modules to increase the calculation efficiency and using of more accurate algorithms for problem solving;
- Development and introducing into ORT system of a module that provides fast calculation of dose distributions and accurate inhomogeneity corrections by a Monte-Carlo method.

The following tasks will be solved under first direction:


- The installation of ORT system on dose delivery systems in leading Moscow oncology clinic and training of staff for system employing;
- Creation and introducing of a quality assurance (QA) program for optimized irradiation;
- Studying of the optimization approach efficiency in comparison with the conventional irradiation schemes.

The algorithm of a new module for radiobiological optimization will be based on combining of a cellular kinetics model and phenomenological one, and it takes also into account specific requirements for a particular case (curative, trial, symptomatic or preventive courses). The usage of this module for particular patient treatment is very sophisticated procedure. It involves the biopsy testing and DNA - flowing cytofluorometry (DNA-FC) to obtain the data on ploidy of a tumor cells and cells distribution over different phases of cellular cycle. There are basis to suppose, that the studying of the contents and DNA distribution in a tumor cells by DNA-FC method before and after RT stages will enable selecting well-grounded tactics for treatment of some cancer types.

The determination of phenomenological models parameters will be based on the retrospective analysis of the clinical data obtained by Cancer Research Center (CRC). For the first time it is taken into account the distribution of the survived cells over a tumor volume and organ volume under improving of phenomenological models ТСР and NTCP and optimization objective functions.

The calculation efficiency of ORT system, created within the framework of the project #1079/99, is quite reasonable under usage of physical objective functions. However under usage of radiobiological objective functions the time consumption increase essentially, as the convergence rate for the iteration procedure of a gradient projections (used in this case) is being very slow frequently. It is planned for the purpose of speed increasing to develop new algorithm for selecting of optimum step length along a gradient. For reduction of calculation amount under gradients calculation the technique similar to those used under training of neural networks, in particular similar to well-known algorithm "Back Propagation", will be developed.

The purpose of creation of fast Monte Carlo module is to make dose distribution calculating by most accurate way, in particular, to ensure accurate taking into account inhomogeneities and beam modifiers during a final stage of planning. The prototype of such a module was developed within the framework of the project #1079/99. It is planned in this project to increase the speed of calculation up to clinically acceptable level. Another feature of a module is that its adjustment to particular dose delivery system is carried out on the basis of conventional measured depth doses and dose distribution profiles.

The implementation of the project will allow improving essentially the immediate and remote results of radiation treatment and the quality of the patient’s life after treatment.


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