Charged Particle Therapy Planning Using Hydrogen Density
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Solution Overview
Problem
Current radiation treatment planning for charged particle beams, such as protons and Carbon ions, faces uncertainties in the position of the distal dose gradient of the Bragg peak due to variations in particle absorption and stopping power among tissues, leading to reduced clinical effectiveness and increased exposure to healthy tissues.
Innovation Solution
The method involves determining hydrogen density along the beam track using medical image data from MRI or CT scans, calculating the stopping power ratio, and adjusting the beam track or energy to optimize the treatment plan, thereby improving the precision of the Bragg peak placement and reducing range uncertainties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard proton treatment techniques use large treatment volume expansions to ensure target coverage, then the reliability of tumor coverage is improved, but the manufacturing precision of dose delivery to the distal edge of the Bragg peak deteriorates
Solution Approach 1:
The patent replaces the mechanical/geometric approach of expanding treatment volumes with a physics-based approach using dual-energy CT imaging to measure electron density and calculate stopping power ratios. This substitution allows precise prediction of proton range and Bragg peak position without requiring conservative volume expansions, thereby maintaining tumor coverage reliability while improving dosimetric precision.
Solution Approach 2:
The patent uses dual-energy CT imaging to create a detailed map of electron density distribution (a copy of the physical tissue properties) along the proton beam path. This electron density map serves as a surrogate for directly measuring stopping power, enabling accurate prediction of proton range and Bragg peak position without physical trial-and-error adjustments.
2Ease of operation
If empirically derived HU-to-SPR calibration curves are used to determine stopping power ratio, then the ease of operation is improved, but the measurement precision of SPR deteriorates
Solution Approach 1:
The patent substitutes the empirical HU-to-SPR calibration approach with a physics-based calculation method using dual-energy CT imaging. Instead of relying on population-averaged empirical relationships, the system directly measures electron density at each voxel and calculates SPR using fundamental physics relationships, thereby improving measurement precision while maintaining ease of operation through automated processing.
Solution Approach 2:
The patent applies local quality by calculating stopping power ratios individually for each voxel along the proton beam path based on local electron density measurements from dual-energy CT. This voxel-by-voxel approach captures local variations in tissue composition that empirical calibration curves average out, thereby improving SPR measurement precision while maintaining ease of operation through automated voxel-wise processing.
3Measurement precision
If Dual Energy CT is used to enhance soft tissue contrast, then the measurement precision of tissue characterization is improved, but the device complexity increases
Solution Approach 1:
The patent applies universality by using dual-energy CT imaging to achieve multiple objectives simultaneously: (1) generating anatomical images for treatment planning, (2) measuring electron density distribution for stopping power calculation, and (3) characterizing tissue composition for range prediction. This multi-functionality justifies the increased device complexity by eliminating the need for separate measurement systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces range uncertainties from 2.7% to 3.5% to less than 2%, enhancing the accuracy of dose distribution and treatment planning for charged particle therapy, potentially improving patient outcomes by minimizing exposure to healthy tissues.
Implementation Method 1
the deposited dose rises, as the average particle speed in the beam slows, to a sharp maximum deposited dose, known as the Bragg peak, near the end of the beam's range in the patient
Implementation Method 2
When high-energy radiation is delivered to a subject, it kills cells in the body. A charge particle beam initially deposits a relatively low dose upon entering the patient, and the deposited dose rises, as the average particle speed in the beam slows
Data Source
AI summary
Techniques are presented for optimizing a treatment plan for charged particle therapy. The method includes obtaining medical image data voxels inside a subject in a reference frame of a radiation source that emits a beam of charged particles at multiple tracks with a controlled emitted energy at each track. Hydrogen density (HD) is determined based on the medical image data. Stopping power ratio (SPR) along a first beam having a first track and first emitted energy is calculated based on HD. A range to a Bragg peak is calculated along the first beam based on the SPR and the first emitted energy. The first beam track or the first emitted energy, or both, is modified based at least in part on the beam range to determine a second track and second emitted energy. Output data that indicates the second track and second emitted energy are sent.