Iterative Proton CT Reconstruction Algorithm for Range Uncertainty
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Solution Overview
Problem
Current proton CT image reconstruction algorithms suffer from uncertainties in proton range prediction due to inaccurate conversion of x-ray Hounsfield units to proton relative stopping power, leading to potential tissue damage from overshooting or undershooting the desired stopping depth in proton therapy.
Innovation Solution
An iterative 3D proton imaging algorithm that directly measures relative stopping power without image artifacts, optimizing spatial and RSP resolution, and minimizing iterations, with the ability to define optimal step sizes and noise direction, and efficient computing resource utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current algorithms for proton CT image reconstruction are used, then the reconstruction process can be completed, but range uncertainties of 3-4% remain due to inaccurate conversion of x-ray Hounsfield units to proton relative stopping power
Solution Approach 1:
The patent replaces the indirect mechanical conversion process (x-ray Hounsfield units → proton RSP) with a direct measurement approach using proton radiography. Proton beams are used to directly measure the water equivalent path length and relative stopping power of tissues along the beam path, eliminating the need for inaccurate conversion algorithms and achieving superior range prediction accuracy.
Solution Approach 2:
The patent introduces an intermediary measurement layer using proton radiography images as a mediator between the proton therapy treatment planning and the actual tissue properties. These intermediate images provide direct information about water equivalent path lengths and relative stopping power, serving as a bridge to improve the accuracy of proton range prediction without relying on flawed conversion factors.
2Manufacturing precision
If proton beam-based image guidance is used to achieve conformal dose distributions, then treatment precision improves, but additional imaging procedures increase patient dose and complexity
Solution Approach 1:
The patent makes the proton radiography system multi-functional by using the same proton beam imaging capability for both treatment verification and relative stopping power measurement. The system serves dual purposes: guiding proton therapy delivery and providing accurate RSP data for treatment planning, thereby reducing overall system complexity compared to having separate imaging and treatment systems.
Solution Approach 2:
The patent merges the functions of proton therapy delivery and relative stopping power measurement into a single integrated process. By combining the proton beam therapy with the imaging measurement capability, the system eliminates the need for separate imaging procedures, reducing patient dose and system complexity while maintaining high dose delivery precision.
3Measurement precision
If iterative algorithms with multiple iterations are used for image reconstruction, then image quality improves, but computation time and processing complexity increase
Solution Approach 1:
The patent performs preliminary actions by pre-calculating and storing lookup tables that map proton energy loss to water equivalent path lengths and relative stopping power values. These pre-computed tables are then used during the actual image reconstruction process, eliminating the need for time-consuming iterative calculations and significantly reducing computation time while maintaining high reconstruction accuracy.
Solution Approach 2:
The patent creates a simplified copy of the complex iterative reconstruction process by using pre-computed lookup tables that replicate the results of multiple iterations in a single lookup operation. This copying approach preserves the accuracy of iterative algorithms but reduces the computational time requirement from multiple iterations to a single table lookup, making the process much faster and more efficient.
Data Source
AI summary
Described herein is a system for 3D proton imaging encompassing both proton radiography (pRad) and proton CT (pCT). The disclosed system can reduce range uncertainties, while providing a fast and efficient check of patient set up and integrated range along a beam's eye view just before treatment. The disclosed system provides a complete solution to the range inaccuracy problem in proton therapy, substantially reducing the uncertainties of treatment planning by directly measuring relative stopping power without being affected by image artifacts and with much lower dose to the patient than comparable x-ray images. Also described herein is a proton imaging algorithm for prompt iterative 3D pCT image reconstruction, where each iteration is fast and efficient, and the number of iterations is minimized. The method offers a unique solution that optimally fits different protons and does not depend on the starting point for the first iteration.