Depth Camera Positioning via Plane Association for Radiation Therapy
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Solution Overview
Problem
In radiation therapy, the complexity of rotating gantries and patient support movements increases the likelihood of collisions between medical devices and patients, necessitating accurate determination of depth camera position and orientation to prevent such incidents.
Innovation Solution
A system that includes an input for receiving depth images, a plane determination module to identify planes, a plane-association module to associate these planes with tool-planes of known positional relationships, and a positional determination unit to calculate the camera's positional information, using techniques like principal component analysis and direct linear transform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a depth camera is used to detect patient surface and monitor proximity, then collision avoidance capability is improved, but the complexity of determining camera position and orientation increases
Solution Approach 1:
The system performs preliminary calibration by capturing depth images of a calibration object with known geometric features before actual use. The plane determination module pre-identifies planes in the depth image and associates them with tool-planes having known positional relationships, establishing a reference coordinate system in advance. This preliminary action simplifies subsequent real-time collision monitoring operations.
Solution Approach 2:
The patent introduces a calibration object as an intermediary element between the depth camera and the patient. This calibration object contains planar structures with known geometric relationships that serve as a mediator to establish the camera's position and orientation relative to the treatment coordinate system, thereby simplifying the determination process.
2Measurement precision
If multiple planes are detected and associated with tool-planes for accurate camera positioning, then measurement precision is improved, but the processing time and computational complexity increase
Solution Approach 1:
The system performs plane detection and association operations during a preliminary calibration phase rather than in real-time during treatment. Depth images of the calibration object are captured and processed beforehand to establish the camera's coordinate transformation parameters, which are then stored for rapid retrieval during actual radiation therapy operations.
Solution Approach 2:
The patent detects and processes multiple planes (first plane, second plane, third plane) from the calibration object, using more geometric features than the minimum required. This excessive action of processing additional planes provides redundant information that improves measurement precision through statistical averaging and error reduction, while the computations are performed offline to minimize time loss.
Data Source
AI summary
A system for determining positional information of a camera, includes: a plane determination module configured to determine a first plane and a second plane based on a depth image; a plane-association module configured to associate the first plane determined by the plane determination module with a first tool-plane, and to associate the second plane determined by the plane determination module with a second tool-plane, the first and second tool-planes having known positional relationship with respect to each other; and a positional determination unit configured to determine the positional information of the camera based on an output from the plane-association module.