CT-Based Patient Positioning System for Radiation Therapy
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Solution Overview
Problem
Conventional radiation therapy positioning methods are time-consuming and prone to human error, relying on tattoo marks and laser alignment, which can lead to inaccuracies in delivering therapeutic radiation doses to tumors while minimizing exposure to healthy tissue.
Innovation Solution
A system that acquires three-dimensional computed tomography images of the patient volume and determines a transformation between the CT image coordinate system and the linear accelerator's coordinate system using projection images, allowing precise alignment of the treatment isocenter with the linac isocenter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If tattoo marks and laser alignment are used for patient positioning, then the positioning process can be performed with simple equipment, but the positioning accuracy deteriorates due to human error and time-consuming procedures
Solution Approach 1:
The patent replaces the mechanical/manual positioning system (tattoo marks and laser alignment requiring human operators) with an automated image-based system. The system automatically acquires CT images, extracts fiducial marker positions, computes transformations between coordinate systems, and determines patient positioning without manual intervention, thereby eliminating human error while maintaining simplicity.
Solution Approach 2:
The patent uses digital copies of the patient's anatomical structure from CT images as fiducial markers instead of physical tattoo marks. These virtual fiducials are extracted from the CT data and used for registration, providing more precise and repeatable positioning references that are not subject to human error in placement or alignment.
2Device complexity
If manual alignment of seeds with lasers is performed, then the equipment required is simple, but the time required for positioning increases significantly
Solution Approach 1:
The patent performs preliminary extraction of fiducial marker positions from CT images and computation of transformation matrices before the actual treatment session. The system pre-processes the imaging data to establish the relationship between the CT coordinate system and the treatment room coordinate system, so that during treatment only simple image acquisition and automated registration are needed, dramatically reducing positioning time.
Solution Approach 2:
The patent replaces the manual mechanical alignment process (physically placing and aligning seeds with laser guides) with an automated computational process that uses image data to calculate and apply positioning transformations, eliminating the time-consuming manual steps while requiring minimal equipment.
3Ease of operation
If tattoo marks and laser alignment are used, then the process is straightforward to implement, but the reliability of radiation dose delivery deteriorates due to positioning errors
Solution Approach 1:
The patent creates digital copies of fiducial markers from CT images that serve as precise, error-free reference points. These virtual fiducials are extracted with sub-pixel accuracy and used to compute transformation matrices, providing reliable and repeatable positioning references that ensure accurate radiation dose delivery without the variability introduced by manual tattoo placement and laser alignment.
Solution Approach 2:
The patent replaces the manual mechanical positioning system with an automated image-based registration system that computationally determines the relationship between coordinate systems. This substitution eliminates human error in alignment while maintaining operational simplicity through automated image acquisition and processing, thereby improving the reliability of radiation dose delivery.
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 improves patient positioning accuracy, reducing the risk of under- or over-dosing tumors and healthy tissue, thereby enhancing the effectiveness and safety of radiation therapy.
Implementation Method 1
acquire a three-dimensional computed tomography image of a patient volume
Implementation Method 2
a beam of radiation is directed toward a target volume... by a linear accelerator (linac)
Data Source
AI summary
A system includes acquisition of a three-dimensional computed tomography image of a patient volume at a computed tomography scanner, acquisition of projection images of the patient volume located at an isocenter of a linear accelerator, and determination of a transformation between a coordinate system of the linear accelerator and a coordinate system of the three-dimensional computed tomography image based on the projection images.