Method for decomposing particle beam fluence into pencil beams based on optimization algorithm

Abstract

The invention discloses a method for decomposing particle beam fluence into pencil beams based on an optimization algorithm. Particle beams are decomposed into small pencil beams based on the radiotherapy dose calculation demand of a pencil beam algorithm. The pencil beams are generally distributed in a Gaussian type. The total dose distribution is the summation of the dose distribution of each pencil beam. The method is the method by which the particle beam fluence decomposing problem in radiotherapy dose calculation of charged particles (such as proton and heavy ions) is solved, and the problem is solved by using the optimization algorithm. According to the method, the fluence distribution of the particle beams is obtained through measurement of a detector, then the particle beams are decomposed into a plurality of pencil beams based on the optimization algorithm, and the center position, size and weight of each pencil beam are obtained. The method is wide in applicability. Compared with the original distribution, the total fluence distribution after decomposition is higher in fitness; or under the same error condition, the number of the decomposed pencil beams is lower; and the radiotherapy dose calculation speed or precision of the particle beams can be greatly improved.

Description

technical field [0001] The invention relates to the field of particle beam radiotherapy dose calculation, in particular to a method for decomposing particle fluence into pencil beams when using a pencil beam dose algorithm. Background technique [0002] The use of particle beam radiotherapy is the basic means of radiotherapy, which includes traditional photon and electron beam radiotherapy, as well as emerging proton and ion beam radiotherapy. The dose deposition of the latter two particle beams in the medium has a "Bragg peak", that is, the particles lose energy rapidly at the end of the path, resulting in a high local dose deposition, while the dose is low before the dose peak and completely at a distance after the peak. No dose deposition. The Bragg peak position depends on particle energy and medium density. This feature of proton and ion beams is very suitable for tumor treatment. Through appropriate field shape design and dynamic adjustment of proton beam energy, it ...

AI Technical Summary

Problems solved by technology

The accuracy and speed of dose calculation are directly related to the pencil beam decomposition method. The use of a finer pencil beam can better deal with lateral non-uniformity, thereby improving the calculation accuracy. However, finer pencil beam decomposition can improve accuracy and also will increase calculation time

[0003] There are three current methods for pencil beam decomposition. One is to use a rectangular grid to decompose each scanning beam with the same energy as a whole. The disadvantage of this method is that it is impossible to obtain the respective dose distribution of each scanning beam.

The second method is also a rectangular decomposition, but it decomposes each scanning beam independently, and its disadvantage is that generally a scanning beam needs to be decomposed into many pencil beams, and the efficiency is low

This method is more efficient than the second method, but the maximum difference between the original beam intensity and the sum of the decomposed pencil beam intensities can reach 9%, and this error leads to some jagged dose distributions in dose calculations

Moreover, this method has a lot of experience, such as the size of the two rings and the weight of each pencil beam

In addition, this method is only applicable to the case where the original scanning beam is circular (ie, symmetrical Gaussian distribution), and it can only be decomposed into a circular pencil beam

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