Calibration Phantom Inclined Surface for Radiotherapy Isocenter
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Solution Overview
Problem
Existing methods for calibrating patient monitoring systems for radiotherapy are not sufficiently accurate, particularly in determining the relative locations of image detectors and the treatment room isocenter.
Innovation Solution
A method involving a calibration phantom with its center located at the treatment room isocenter and its surface inclined approximately 45° relative to the camera plane of the image capture devices, allowing for improved accuracy in generating a model of the calibration phantom and determining the relative locations of the cameras and the isocenter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a calibration phantom with surface inclined at approximately 45° relative to the camera plane is used, then the accuracy of determining relative locations of image detectors and isocenter is improved, but the complexity of the calibration setup increases
Solution Approach 1:
The calibration phantom incorporates a surface inclined at approximately 45° relative to the camera plane, changing the geometric parameter of the calibration object. This angular parameter optimization enables the image capture devices to accurately determine the relative locations of cameras and isocenter by providing optimal viewing angles and minimizing perspective distortion, thereby resolving the measurement accuracy issue.
Solution Approach 2:
The calibration phantom serves as an intermediary object between the image capture devices and the treatment room isocenter. By positioning the phantom's center at the isocenter and inclining its surface at 45°, it mediates the calibration process, enabling indirect but accurate determination of relative camera positions without requiring direct measurement at the isocenter point.
2Measurement precision
If the center of the calibration phantom is located at the treatment room isocenter, then the accuracy of patient positioning is improved, but the difficulty of detecting and measuring the isocenter location increases
Solution Approach 1:
The calibration phantom acts as a mediator that transfers the isocenter location information to a measurable form. By placing the phantom's center at the isocenter and using its inclined surface features, the system can detect and measure the isocenter location indirectly through image processing of the phantom's known geometry, rather than requiring direct measurement at the isocenter point itself.
Solution Approach 2:
The calibration phantom utilizes specific geometric parameters including a 45° inclined surface and known dimensions, which transform the abstract concept of isocenter location into measurable image features. These parameter changes enable accurate detection and measurement of the isocenter position through standard imaging and processing techniques.
Data Source
AI summary
A method of calibrating a monitoring system (10,14) is described in which a calibration phantom (70) is located with its center located approximately at the isocenter of a treatment room through which a treatment apparatus (16) is arranged to direct radiation, wherein the surface of the calibration phantom (70) closest to an image capture device (72) of the monitoring system (10,14) is inclined approximately 45° relative to the camera plane of an image capture device of the monitoring system. Images of the calibration phantom (70) are then captured using the image capture device (72) and the images are processed to generate a model of the imaged surface of the calibration phantom. The generated model of the imaged surface of the calibration phantom (70) is then utilized to identify the relative location of the center of the calibration phantom (70) and the camera plane of the image capture device (72) which is then utilized to determine the relative location of the camera plane of the image capture device and the isocenter of a treatment room.