Pencil beam dose algorithm based on self consistency

Abstract

The invention discloses a pencil beam dose algorithm based on self consistency. An original three dimensional pencil beam dose distribution is decomposed into a product of two functions, wherein the two functions respectively represent two dimensional dose distributions of a beam with finite width and infinite length. The algorithm uses two dimensional data to obtain a three dimensional dose distribution of a pencil core, which means a dose distribution of a rectangular pencil beam is processed to be a product of a depth dose distribution and two transverse distributions, wherein the depth dose distribution represents a dose value along the center axis of the pencil beam (denoted as a Z direction) and is a one dimensional distribution, and the transverse distributions represent the relative dose distributions in XZ and YZ planes and are two dimensional distributions. The algorithm reduces storage requirements, and the form of the algorithm is simple which facilitates the calculation and improves the calculation speed. Meanwhile, the decomposition form can satisfy requirements of symmetry and self consistency, which means uniform dose distributions can be produced under uniform field intensity.

Description

technical field [0001] The invention relates to the field of dose calculation in tumor radiotherapy, in particular to a pencil beam dose algorithm based on self-consistency. Background technique [0002] Radiation therapy is one of the main ways to treat cancer. It uses radioactive rays to kill tumor cells. Radiation therapy requires the calculation of the dose distribution of radiation beams in the body, known as dose calculation. A commonly used method for clinical dose calculation is called the pencil beam algorithm. This algorithm decomposes the radiotherapy beam into multiple small pencil beams, calculates the dose distribution of each pencil beam separately, and then superimposes to obtain the total dose distribution. [0003] [0004] in, Indicates the intensity of the radiotherapy beam at that point, It is the pen core. [0005] Therefore, the key point in the pencil beam dose algorithm is to calculate the dose distribution of a single pencil beam vertically...

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Problems solved by technology

But because the dose distribution of a pen kernel is in three-dimensional space, discretizing the dose distribution in three-dimensional space into a numerical table requires a large storage space, such as a typical three-dimensional Monte Carlo pen kernel, in order to ensure the accuracy of the data under interpolation, the depth At least about 200 grids are required, and at least 100 grids are required in the X and Y directions in the horizontal direction, so the pen core data is at least on the order of millions. Excessively large data not only increases the storage cost, but also reduces the speed

[0006] If the 3D pen nucleus is not used, but the 2D pen nucleus is directly used, then the pen nucleus distribution will only include two variables: depth d and lateral distance r, but because the transverse dose distribution of the pen nucleus does not only depend on r, so this Processing will result in lower doses at intersection points of individual pencil beams, since these calculated points are farther away from the pencil beams, the dose contribution of individual pencil beams is underestimated, so the calculated dose results will have large oscillations unless very small Pen core, but this will greatly increase the amount of calculations for dose calculations

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