Method for Optimization Radiotherapy Particle Beams

• US 20110291028A1
• Filed: 05/27/2010
• Published: 12/01/2011
• Est. Priority Date: 05/27/2010
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Research Laboratories, Inc. (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Electric Research Laboratories, Inc. (Mitsubishi Electric Corporation)
• Inventors: Brand, Matthew
• Granted Patent: US 8,492,735 B2
• Time in Patent Office: Days
• US Class Current: 250/492.1
• CPC Class Codes: A61N 2005/1087 Ions; Protons
• CPC Class Codes: A61N 5/103 Treatment planning systems
• CPC Class Codes: A61N 5/1031 using a specific method of dose optimization

Abstract

Radiation doses are optimized by providing a model of the set of beams and a target dose in normalized forms. A Gram matrix is determined from the model. The target dose is subsampled to determine initial intensity values for the set of beams. Then, the following steps are iterated until convergence. A very small positive value, 0<ε<<1, is added to each intensity value to ensure the intensity value is greater than zero. Each intensity value is multiplied by the Gram matrix to determine a product, which is divided element-wise into the normalized target dose to determine corresponding ratios. If the ratios are all close to 1, within a numerical error tolerance, the intensity values of the set of beam are output. Otherwise, the intensity values are multiplied by the ratios before a next iteration.

Claims

1. A method for optimizing radiation doses delivered by a set of beams, wherein each beam is a radiotherapy particle beam, comprising the steps of:

providing a model of the set of beams, and a target dose;

determining a model and a target dose in normal form, including a Gram matrix from the model;

subsampling the target dose to determine initial intensity values for the set of beams, and iterating over the following steps until convergence;

adding a very small positive value, 0<

ε

<

<

1, to each intensity value to ensure the intensity values are greater than zero;

multiplying a vector of intensity values by the Gram matrix to determine a product;

dividing, element-wise, the product into the form target dose to determine corresponding ratios; and

determining whether the ratios are all close to 1, within a numerical error tolerance, and if true, outputting the intensity values of the set of beam, and otherwise if false, multiplying the intensity values by the ratios before a next iteration.

2. The method of claim 1, wherein each elements of the Gram matrix represents, for each pair of beams, an inner product of the radiation doses delivered by the pair of beams.

3. The method of claim 1, further comprising:

decomposing the Gram matrix, whenever possible, into outer products and applying factors of the outer products directly to the intensity values of the set of beams.

4. The method of claim 1, further comprising:

reducing an error in the radiation doses to rectangular subregions of the target dose by adding auxiliary matrix-vector products, representing extra penalties for missing dose values within the subregions, to the denominators of the ratios.

5. The method of claim 1, further comprising:

imposing hard radiation limits on arbitrary subregions of the radiation doses by adding auxiliary matrix-vector products, representing shadow prices of assuring hard radiation limits, to the numerators of the ratios.

6. The method of claim 1, further comprising:

putting the model into a dual form and applying subsampling step to the dual model to calculate a shadow price for every constraint that is prescribed for the target dose.