dorsal/arxiv
View SchemaThe geometric calibration of cone-beam imaging and delivery systems in radiation therapy
| Authors | Evangelos Matsinos, Wolfgang Kaissl |
|---|---|
| Categories | |
| ArXiv ID | physics/0607018 |
| URL | https://arxiv.org/abs/physics/0607018 |
Abstract
We propose a method to achieve the geometric calibration of cone-beam imaging and delivery systems in radiation therapy; our approach applies to devices where an X-ray source and a flat-panel detector, facing each other, move in circular orbits around the irradiated object. In order to extract the parameters of the geometry from the data, we use a light needle phantom which is easy to manufacture. A model with ten free parameters (spatial lengths and distortion angles) has been put forth to describe the geometry and the mechanical imperfections of the units being calibrated; a few additional parameters are introduced to account for residual effects (small effects which lie beyond our model). The values of the model parameters are determined from one complete scan of the needle phantom via a robust optimisation scheme. The application of this method to two sets of five counterclockwise (ccw) and five clockwise (cw) scans yielded consistent and reproducible results. A number of differences have been observed between the ccw and cw scans, suggesting a dissimilar behaviour of the devices calibrated in the two rotation modes. The description of the geometry of the devices was achieved at the sub-pixel level.
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"abstract": "We propose a method to achieve the geometric calibration of cone-beam imaging\nand delivery systems in radiation therapy; our approach applies to devices\nwhere an X-ray source and a flat-panel detector, facing each other, move in\ncircular orbits around the irradiated object. In order to extract the\nparameters of the geometry from the data, we use a light needle phantom which\nis easy to manufacture. A model with ten free parameters (spatial lengths and\ndistortion angles) has been put forth to describe the geometry and the\nmechanical imperfections of the units being calibrated; a few additional\nparameters are introduced to account for residual effects (small effects which\nlie beyond our model). The values of the model parameters are determined from\none complete scan of the needle phantom via a robust optimisation scheme. The\napplication of this method to two sets of five counterclockwise (ccw) and five\nclockwise (cw) scans yielded consistent and reproducible results. A number of\ndifferences have been observed between the ccw and cw scans, suggesting a\ndissimilar behaviour of the devices calibrated in the two rotation modes. The\ndescription of the geometry of the devices was achieved at the sub-pixel level.",
"arxiv_id": "physics/0607018",
"authors": [
"Evangelos Matsinos",
"Wolfgang Kaissl"
],
"categories": [
"physics.med-ph"
],
"title": "The geometric calibration of cone-beam imaging and delivery systems in radiation therapy",
"url": "https://arxiv.org/abs/physics/0607018"
},
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