Radiotherapy Gantry Synchronization for Image-Guided Targeting
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Solution Overview
Problem
Current radiotherapy techniques face challenges in accurately delivering targeted radiation due to tumor movement and patient positioning issues, leading to suboptimal dose distribution and increased exposure to healthy tissues, as existing imaging methods provide poor contrast and accuracy.
Innovation Solution
A radiotherapy apparatus with a rotatable gantry supporting both therapeutic and diagnostic radiation sources, using a control system to acquire and retain images, adjust collimators, and control the beam based on diagnostic image data to ensure precise targeting, even with tumor movement, by employing a multi-leaf collimator and cone-beam CT reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-energy therapeutic radiation beam is used for treatment, then the therapeutic effect on the tumour is improved, but the image quality for positioning and monitoring deteriorates due to poor contrast between human tissue types
Solution Approach 1:
The system separates the therapeutic and diagnostic functions into distinct radiation sources. The therapeutic source produces high-energy radiation for treatment, while the diagnostic source produces low-energy radiation for high-quality imaging. This segmentation allows each source to be optimized for its specific function without compromise.
Solution Approach 2:
A diagnostic radiation source acts as an intermediary between the therapeutic beam and the imaging system. This intermediary source provides the necessary imaging information with high contrast, enabling accurate positioning and monitoring without requiring the therapeutic high-energy beam to be used for imaging purposes.
2Measurement precision
If the tumour position changes between treatment fractions due to organ movement or patient positioning, then the treatment plan becomes less effective, but taking diagnostic images immediately prior to treatment adds time to the treatment process
Solution Approach 1:
The system performs diagnostic imaging immediately before treatment delivery, ensuring the most recent and accurate information about tumour position is available. This preliminary action captures any inter-fraction motion or intra-fraction changes that occurred during patient setup, allowing for real-time plan adaptation.
Solution Approach 2:
The system uses real-time feedback from diagnostic images taken during treatment to monitor tumour position and organ movement. This feedback loop enables dynamic adjustment of the treatment plan during the fraction, maintaining accuracy despite patient or organ motion.
3Ease of operation
If the diagnostic source is located on the gantry 90 degrees from the therapeutic source to maximize access, then the spatial arrangement is optimized, but the image acquisition timing must be coordinated with gantry rotation adding complexity
Solution Approach 1:
The system dynamically coordinates the gantry rotation to bring the diagnostic source into the correct rotational position for image acquisition. The treatment delivery is paused or synchronized with the gantry rotation, allowing the diagnostic source to occupy the appropriate angular position relative to the patient before imaging, then returning to the therapeutic position for treatment.
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 treatment accuracy by continuously monitoring and adjusting for patient and tumor position changes, reducing dosimetric errors and minimizing exposure to healthy tissues, particularly effective for intracranial, extracranial, and spine treatments.
Implementation Method 1
a source of diagnostic radiation, the two sources being rotationally (or angularly) spaced apart around a rotation axis of the gantry
Implementation Method 2
directing a beam of harmful radiation, usually ionising radiation, such as an x-ray or electron beam, towards the lesion
Implementation Method 3
at least one collimator associated with the source of therapeutic radiation and arranged to limit the cross-sectional area of a beam produced by that source
Implementation Method 4
a reconstruction means arranged to i. obtain two-dimensional images of a patient using the source of diagnostic radiation, ii. retain those images at least temporarily, iii. apply a recency threshold to the retained images thereby to exclude images less recent than the threshold, iv. select at least three such retained images meeting the recency threshold and reconstruct a CT volume using the selected images
Data Source
AI summary
A radiotherapy apparatus comprises a rotatable gantry, supporting a source of therapeutic radiation and a source of diagnostic radiation, the two sources being rotationally (or angularly) spaced apart around a rotation axis of the gantry, with at least one collimator associated with the source of therapeutic radiation and arranged to limit the cross-sectional area of a beam produced by that source, a control means arranged to conduct a treatment fraction using the apparatus by causing the apparatus to i. acquire images of a patient using the source of diagnostic radiation, ii. retain those images at least temporarily, iii. subsequently, after further rotation of the gantry, select a retained image acquired when the source of diagnostic radiation was at a rotational position corresponding to the instantaneous rotational position of the source of therapeutic radiation, and iv. control the beam relative to the patient using information derived from the selected image. The corresponding rotational position is ideally one in which the source of therapeutic radiation is at the same or substantially the same rotational position as was the source of diagnostic radiation at the point in time when the image was acquired. An alternative a radiotherapy apparatus comprises a rotatable gantry supporting a source of therapeutic radiation and a source of diagnostic radiation, at least one collimator associated with the source of therapeutic radiation and arranged to limit the cross-sectional area of a beam produced by that source, a reconstruction means arranged to i. obtain two-dimensional images of a patient using the source of diagnostic radiation, ii. retain those images at least temporarily, iii. apply a recency threshold to the retained images thereby to exclude images less recent than the threshold, iv. select at least three such retained images meeting the recency threshold and reconstruct a CT volume or tomographic image using the selected images, and a control means arranged to conduct a treatment fraction or treatment session using the apparatus, controlling the collimator using information derived from the CT volume.