A vision system for patient positioning in radiation therapy
Date
2003
Authors
Shukla, Salil
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Abstract
This thesis outlines a new approach to position a patient on the treatment table for all the radiotherapy treatment sessions. Positioning is done by comparing the patient's contour from the diagnostic CT data to that from the Vision system. This vision system is accurate, rel iable and easy to use.
The presence of cancerous cells is detected in the CT scan. Treatment planning is done based on the CT files. The patient undergoes several radiotherapy sessions that irradiate the cancerous tissues. The exact location of the patient during the diagnostic CT scan is known and used for dose calculations as well as positioning.
To ensure that the patient orientation is the same during each radiotherapy session, compensators or portal images are used. These procedures either expose the patient to more radiation or are tedious.
In this approach, the patient is positioned on the treatment table by a vision system. The vision system comprises a multiple line laser that projects equally spaced laser lines on the patient. A 20 image captured by the CCD camera is interpreted to generate the 30 contour of the patient. Various issues with processing the CT files and the 20 images are discussed. Comparison between the CT and the Vision contour is done in 30 by the Iterative Closest Point (ICP) algorithm. The iterative process calculates the overall positioning error that is used to reorient the treatment table.