Radiotherapy Apparatus X-Ray Calibration for Beam Alignment
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Solution Overview
Problem
In radiotherapy, precise alignment of the therapeutic beam with the lesion is challenging due to changes in the X-ray imaging structure over time, leading to potential misalignment between the aiming point and the actual lesion position, which can result in unnecessary irradiation of normal tissues.
Innovation Solution
A radiotherapy apparatus that calculates transformation parameters based on X-ray imaging of a calibration object and patient volume data to generate transformed projection images, ensuring accurate alignment between the X-ray projection images and reconstructed images, thereby ensuring precise targeting of the therapeutic beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an X-ray imaging unit permanently mounted on a radiotherapy apparatus is used for imaging, then the imaging structure is stable and integrated, but the imaging conditions (position, angle) change with time leading to mismatch between projected images
Solution Approach 1:
The patent applies preliminary action by performing calibration imaging with a calibration object before actual patient treatment. Transformation parameters are calculated in advance by comparing the calibration object's projected image with its reconstructed image from volume data. These pre-calculated parameters are then used to correct subsequent patient images, compensating for temporal changes in imaging conditions without requiring recalibration during each treatment session.
2Ease of operation
If visual inspection by an engineer is used for confirmation, then the system is simple and easy to operate, but the alignment accuracy between aiming point and lesion position is insufficient
Solution Approach 1:
The patent replaces the manual visual inspection method with an automated image processing system. The system automatically calculates transformation parameters by comparing imaging data, generates corrected projected images, and performs alignment verification without requiring engineer intervention. This substitution maintains operational simplicity while dramatically improving alignment accuracy through computational precision.
Solution Approach 2:
The patent introduces an intermediary computational process that acts as a mediator between the raw imaging data and the final alignment confirmation. Transformation parameters serve as an intermediary element that bridges the gap between changing imaging conditions and the reference volume data, enabling automated and precise alignment verification without direct human visual inspection.
3Reliability
If multiple irradiation sessions are performed over plural days, then the treatment is thorough and effective, but the accumulation of imaging condition changes leads to increasing misalignment
Solution Approach 1:
The calibration and transformation parameter calculation are performed in advance before the series of irradiation sessions. These pre-established parameters remain valid across multiple treatment days, allowing consistent image correction and beam positioning accuracy to be maintained throughout the treatment course without degradation from accumulated imaging condition changes.
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 enhances the accuracy of the therapeutic beam's alignment with the lesion, minimizing exposure to normal tissues and improving the overall precision of radiotherapy treatments.
Implementation Method 1
an X-ray projection image obtained by imaging the patient lying on a bed with the use of an X-ray imaging unit permanently mounted on a radiotherapy apparatus
Data Source
AI summary
A radiotherapy apparatus includes an receiver receiving a first projection image of a calibration object under X-ray imaging; a storing portion storing an ideal projection image of the calibration object, the ideal projection image generated based on design information of an X-ray imaging structure, positional information of the calibration object, and volume data of the calibration object; a calculator calculating a transformation parameter for transforming the first projection image into an ideal projection image; a transformed image generator generating a transformed projection image of the patient by transforming a second projection image of a patient obtained under X-ray imaging with the transformation parameter; a reconstructed image generator generating a reconstructed projection image based on volume data of the patient, positional information of the patient, and the design information; and a matching image generator generating a matching reference image used for matching between the transformed projection image and the reconstructed projection image.