| 摘要 |
A method of establishing coincidence between a field size of a light field used in a setup mode of a radiation system and a field size of a radiation field used in an operation mode of the system includes providing automatic adjustment of field-defining structure to compensate for differences in optical properties of the light and the radiation. A light beam passing through the field-defining structure typically exhibits greater scattering than an X-ray beam passing through the structure. For each of a number of different settings of the field-defining structure, the difference between the field sizesof the light and the radiation are determined and recorded. Then, for a particular desired field size, the field-defining structure can be automaticallyadjusted to provide compensation. In the preferred embodiment, the field-defining structure includes jaws of a collimator of a radiation system and the determination of field size differences of the light and the radiation occurs for each of various energy level settings of the radiation system.
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