An iterative filtered backprojection inverse treatment planning algorithm for tomotherapy.

PURPOSE An inverse treatment planning algorithm for tomotherapy is described. METHODS AND MATERIALS The algorithm iteratively computes a set of nonnegative beam intensity profiles that minimizes the least-square residual dose defined in the target and selected normal tissue regions of interest. At each iteration the residual dose distribution is transformed into a set of residual beam profiles using an inversion method derived from filtered backprojection image reconstruction theory. These "residual" profiles are used to correct the current beam profile estimates resulting in new profile estimates. Adaptive filtering is incorporated into the inversion model so that the gross structure of the dose distribution is optimized during initial iterations of the algorithm, and the fine structure corresponding to edges is obtained at later iterations. A three dimensional, kernel based, convolutions/superposition dose model is used to compute dose during each iteration. RESULTS Two clinically relevant treatment planning examples are presented illustrating the use of the algorithm for planning conformal radiotherapy of the breast and the prostate. Solutions are generally achieved in 10-20 iterations requiring about 20 h of CPU time using a midrange workstation. The majority of the calculation time is spent on the three-dimensional dose calculation. CONCLUSIONS The inverse treatment planning algorithm is a useful research tool for exploring the potential of tomotherapy for conformal radiotherapy. Further work is needed to (a) achieve clinically acceptable computation times; (b) verify the algorithm using multileaf collimator technology; and (c) extend the method to biological objectives.

[1]  T. Bortfeld,et al.  Methods of image reconstruction from projections applied to conformation radiotherapy. , 1990, Physics in medicine and biology.

[2]  A T Redpath,et al.  A new technique for radiotherapy planning using quadratic programming. , 1976, Physics in medicine and biology.

[3]  David Sonderman,et al.  Radiotherapy Treatment Design Using Mathematical Programming Models , 1985, Oper. Res..

[4]  B. Lind Properties of an algorithm for solving the inverse problem in radiation therapy , 1990 .

[5]  R. Hamming Digital filters (3rd ed.) , 1989 .

[6]  Grant T. Gullberg,et al.  Users Manual: Donner Algorithms for Reconstruction Tomography , 1977 .

[7]  R Mohan,et al.  A model for computer-controlled delivery of 3-D conformal treatments. , 1992, Medical physics.

[8]  T. Holmes,et al.  A comparison of three inverse treatment planning algorithms. , 1994, Physics in medicine and biology.

[9]  T. J. Davy Physical Aspects of Conformation Therapy Using Computer-Controlled Tracking Units , 1985 .

[10]  A. Brahme,et al.  Optimization of stationary and moving beam radiation therapy techniques. , 1988, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[11]  C. K. Yuen,et al.  Digital Filters , 1979, IEEE Transactions on Systems, Man, and Cybernetics.

[12]  C S Hope,et al.  Computer Optimization of 4 MeV Treatment Planning , 1965 .

[13]  S Takahashi,et al.  Conformation radiotherapy. Rotation techniques as applied to radiography and radiotherapy of cancer. , 1965, Acta radiologica: diagnosis.

[14]  P Reckwerdt,et al.  A unified approach to the optimization of brachytherapy and external beam dosimetry. , 1991, International journal of radiation oncology, biology, physics.

[15]  J O Deasy,et al.  Tomotherapy: a new concept for the delivery of dynamic conformal radiotherapy. , 1993, Medical physics.

[16]  J J Weinkam,et al.  Automatic variation of field size and dose rate in rotation therapy. , 1977, International journal of radiation oncology, biology, physics.

[17]  T. Holmes,et al.  A filtered backprojection dose calculation method for inverse treatment planning. , 1994, Medical physics.

[18]  T. Bortfeld,et al.  Decomposition of pencil beam kernels for fast dose calculations in three-dimensional treatment planning. , 1993, Medical physics.

[19]  J A Purdy,et al.  Use of transputers for real time dose calculation and presentation for three-dimensional radiation treatment planning. , 1993, International journal of radiation oncology, biology, physics.

[20]  A Brahme,et al.  An algorithm for maximizing the probability of complication-free tumour control in radiation therapy , 1992, Physics in medicine and biology.

[21]  M. Langer,et al.  Optimization of beam weights under dose-volume restrictions. , 1987, International journal of radiation oncology, biology, physics.

[22]  D. Convery,et al.  The generation of intensity-modulated fields for conformal radiotherapy by dynamic collimation , 1992 .

[23]  Isaac I. Rosen,et al.  Custom beam profiles in computer-controlled radiation therapy. , 1992 .

[24]  S. Webb Optimization by simulated annealing of three-dimensional, conformal treatment planning for radiation fields defined by a multileaf collimator: II. Inclusion of two-dimensional modulation of the x-ray intensity. , 1992, Physics in medicine and biology.

[25]  C. Orton Progress in medical radiation physics , 1982 .

[26]  J. Kereiakes,et al.  The method of linear programming applied to radiation treatment planning. , 1968, Radiology.

[27]  S. Webb Optimisation of conformal radiotherapy dose distributions by simulated annealing. , 1989, Physics in medicine and biology.

[28]  S. McDonald,et al.  Optimization of external beam radiation therapy. , 1977, International journal of radiation oncology, biology, physics.

[29]  G Starkschall,et al.  A constrained least-squares optimization method for external beam radiation therapy treatment planning. , 1984, Medical physics.

[30]  M. Goitein,et al.  Tolerance of normal tissue to therapeutic irradiation. , 1991, International journal of radiation oncology, biology, physics.

[31]  I. Rosen,et al.  Assessment of a linear accelerator for segmented conformal radiation therapy. , 1993, Medical physics.

[32]  I. Rosen,et al.  Treatment plan optimization using linear programming. , 1991, Medical physics.

[33]  K E Halnan,et al.  Optimization of X-ray Treatment Planning by Computer Judgement , 1967, Physics in medicine and biology.