Plan Dose Perturbation for Radiation Therapy QA
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Solution Overview
Problem
Current radiation therapy dose delivery quality assurance methods are limited in accurately assessing dose delivery to patients due to complex human anatomy and reliance on sub-system validation, which may not guarantee accurate dose delivery or quantify errors effectively.
Innovation Solution
The Plan Dose Perturbation (PDP) method uses a QA phantom with radiation detectors to create a dose map for comparison with TPS calculations, generating a 3D dose error grid for beam segments, allowing for dose corrections in the patient anatomy without independent dose calculation algorithms, thereby providing a 'virtual measurement' of the corrected dose distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sub-system validation methods are used to verify dose delivery, then the complexity of validating the entire system is reduced, but the accuracy and reliability of dose delivery assessment deteriorates
Solution Approach 1:
The patent divides the complex dose validation problem into manageable segments by using detector arrays that measure dose at specific locations within a phantom. Each detector provides localized measurement data, and these segments are then integrated through interpolation algorithms to reconstruct the complete 3D dose distribution, thereby maintaining reliability while managing complexity.
Solution Approach 2:
The patent introduces a phantom as an intermediary object between the radiation delivery system and the detectors. The phantom serves as a mediator that translates complex internal dose distributions into measurable signals at detector locations, enabling indirect but accurate assessment of dose delivery without requiring direct measurement within the patient's anatomy.
2Measurement precision
If direct measurement of dose in patient anatomy is performed, then the accuracy of dose delivery assessment is improved, but the complexity and invasiveness of the measurement process increases
Solution Approach 1:
The patent creates a physical copy (phantom) that replicates the geometric and material properties of patient anatomy. By performing measurements in this copy rather than the original patient anatomy, the system achieves accurate dose assessment while avoiding the complexities and ethical issues of direct patient measurement. The phantom serves as a surrogate model that preserves the essential dosimetric characteristics.
Solution Approach 2:
The phantom acts as an intermediary that enables indirect measurement of dose distribution. Instead of placing detectors directly in patient anatomy, the phantom provides a safe and practical medium through which dose can be measured and then transferred to patient anatomy through geometric transformation and interpolation algorithms.
3Measurement precision
If high spatial density dose maps are generated for comparison with TPS calculations, then the precision of dose error localization is improved, but the quantity of measurement data and processing requirements increases
Solution Approach 1:
The patent uses a limited number of detectors positioned at specific strategic locations within the phantom rather than attempting to measure dose at every possible point. The measurement data from these partial sampling points is then sufficient to reconstruct the complete 3D dose distribution through interpolation, avoiding the need for excessive measurement data while maintaining high precision in dose error localization.
Solution Approach 2:
The patent transitions from 2D detector plane measurements to 3D dose distribution reconstruction by adding the depth dimension through interpolation algorithms. This dimensional transformation allows the system to generate comprehensive 3D dose maps with high spatial density from relatively sparse 2D measurement data, thereby achieving high precision without proportionally increasing measurement data volume.
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 method effectively corrects dose errors in the patient anatomy by generating a 3D dose error grid, ensuring accurate dose delivery and reducing uncertainty in treatment plans, with simulated results showing maximum percentage differences of less than 1% compared to actual measurements.
Implementation Method 1
measuring a dose distribution from a patient plan as delivered in a QA phantom
Data Source
Figure 1~1A
Figure 2
Figure 3
AI summary
A method of determining a patient dose during or prior to therapy from an external radiation beam includes determining a dose distribution from a patient plan as delivered in a QA phantom at each appropriate beam angle and comparing the dose distribution determined from measurements or calculations to a corresponding treatment planning system (TPS) dose modeled distribution in the QA phantom and providing a correction distribution when applied to the TPS dose modeled distribution results in the dose distribution determined. The correction distribution may optionally be interpolated to non-measured points for each beam angle and geometrically projected toward the source of radiation through a volume that equals a dose volume of the TPS for a patient beam for each beam angle. The correction distribution is applied to the TPS patient dose volume for each beam angle for providing a corrected dose distribution in the patient.