Radiotherapy System Target-Guided Cone Beam CT Reconstruction
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Solution Overview
Problem
Current radiotherapy systems using cone beam CT imaging struggle to accurately capture the positional relationship of a target, radiation passing area, and critical organs due to imaging cycles longer than respiration cycles, leading to blurred images and inadequate patient positioning for precise radiation treatment.
Innovation Solution
A radiotherapy system with a rotatable support device, X-ray imaging, and a target recognizing device that selects and reconstructs cone beam CT images only when the target position satisfies specific treatment radiation conditions, enabling precise three-dimensional imaging and positioning of patients during radiation treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cone beam CT imaging is performed by rotating the support device at one rotation per minute, then the imaging can be completed with standard equipment, but the imaging cycle becomes longer than the respiration cycle causing blurred images and loss of treatment-state accuracy
Solution Approach 1:
The system performs preliminary actions by acquiring multiple projection images during rotation and identifies images where the target is present before reconstruction. This preliminary identification ensures that only treatment-state images are used, resolving the contradiction between standard imaging speed and positioning accuracy by pre-filtering images based on target detection.
Solution Approach 2:
The system uses feedback from target recognition results to control the image selection and reconstruction process. By detecting whether the target is present in each projection image and using this feedback to select only appropriate images for reconstruction, the system ensures accurate treatment-state positioning while maintaining efficient use of imaging resources.
2Productivity
If all projection images are used for CT reconstruction, then the imaging process is simple and fast, but the resulting CT image is blurred due to including images from various respiration states
Solution Approach 1:
The system extracts only the necessary component from the full set of projection images by identifying and selecting only those images where the target is present. This extraction process removes images from non-treatment states, producing a sharp, accurate CT image while maintaining imaging efficiency by avoiding reconstruction of unnecessary images.
Solution Approach 2:
The system applies local quality control by selecting images based on local target detection results. Each projection image is evaluated individually for target presence, and only images meeting the quality criterion (target present) are included in reconstruction, ensuring high image quality in the critical treatment region.
3Manufacturing precision
If respiration-correlated imaging is used to reduce motion blur, then image quality improves, but the breathing phase state does not necessarily coincide with the treatment radiation state
Solution Approach 1:
The system replaces mechanical respiration-gating mechanisms with a target-based selection approach. Instead of gating images by respiration phase, the system uses target recognition to identify treatment-state images directly, substituting the mechanical breathing-synchronization system with an intelligent target-detection-based selection process that directly ensures treatment-state accuracy.
4Area of stationary object
If imaging is performed continuously during rotation, then complete coverage is achieved, but radiation exposure to the patient increases
Solution Approach 1:
The system applies partial action by reconstructing CT images from only the subset of projection images where the target is present, rather than using all acquired images. This partial use of data maintains complete anatomical coverage in the reconstructed image while reducing the number of X-ray exposures, thereby lowering patient radiation exposure.
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 allows for precise patient positioning and motion tracking treatment by generating clear, treatment-state-specific images, improving the accuracy of radiation delivery and reducing radiation exposure.
Implementation Method 1
an X-ray imaging device attached to the rotatable support device and configured to apply X-rays to the subject from a plurality of directions while rotating around the subject to perform X-ray imaging
Implementation Method 2
a target recognizing device that recognizes a three-dimensional position of the target in the subject from X-ray images acquired by the X-ray imaging device
Implementation Method 3
a first CT image generating apparatus configured to select the images in which the position of the target recognized by the target recognizing device satisfies the treatment radiation irradiation condition for the motion tracking treatment, out of the X-ray images to perform image reconstruction and generates a first cone beam CT image
Data Source
AI summary
A radiotherapy system is provided that permit acquiring of an image which is necessary for positioning of a patient (1) for radiation treatment and enables grasping of a positional relationship of a target (2) in a treatment radiation irradiated state, a radiation passing area and a critical organ. The radiotherapy system includes: an X-ray imaging device 45 attached to the rotatable support device (7) and configured to apply X-rays to the subject (1) from plural directions while rotating around the subject (1) to perform X-ray imaging; a target recognizing device 9 that recognizes a three-dimensional position of the target 2 in the subject 1 from X-ray images acquired by the X-ray imaging device 45; and CT image generating devices 10, 11, 12 configured to select, from the X-ray images acquired by the X-ray imaging device 45, the images in which the position of the target 2 recognized by the recognizing device 9 satisfies the treatment radiation irradiation condition for the motion tracking treatment to perform image reconstruction and generate a cone beam CT image.