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A matrix ionisation chamber imaging device for on-line patient setup verification during radiotherapy
1Radiotherapy Department, The Netherlands Cancer Institute (Antoni van Leeuwenhoekhuis), Amsterdam.
Summary
A new on-line imaging device for radiotherapy provides daily patient setup verification. This system uses liquid-filled ionisation chambers to deliver high-quality portal images in seconds, enabling rapid treatment decisions and motion monitoring.
Area of Science:
- Medical Physics
- Radiotherapy Technology
- Diagnostic Imaging
Background:
- Accurate patient setup is crucial for effective radiotherapy.
- Daily verification is essential to ensure precise radiation delivery.
- Existing imaging methods can be time-consuming or lack real-time feedback.
Purpose of the Study:
- To develop and evaluate an on-line imaging device for high-energy photons.
- To enable rapid verification of patient setup during radiotherapy treatments.
- To assess the image quality and speed of the new imaging system.
Main Methods:
- Development of a 128x128 liquid-filled ionisation chamber matrix with a 320x320 mm field of view.
- Utilisation of a dedicated microcomputer for high-speed current measurement, image restoration, and processing.
- Testing with high and low contrast phantoms and patient imaging.
Main Results:
- The device achieved an imaging time of 3.1 seconds.
- Image quality comparable to film was obtained.
- High-quality portal images were available within seconds of treatment initiation.
Conclusions:
- The developed on-line imaging device facilitates near-instantaneous decisions on patient setup approval.
- It allows for real-time observation of organ or patient motion during treatment.
- High-speed analysis of these portal images presents a promising new research avenue.