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An electronic portal imaging device for transit dosimetry
J R Symonds-Tayler1, M Partridge, P M Evans
1Joint Department of Physics, Institute of Cancer Research, Sutton, Surrey, UK.
Physics in Medicine and Biology
|December 12, 1997
Summary
A new electronic portal imaging device using 128 CsI crystals offers high contrast and spatial resolution for medical imaging. This system shows potential for transit dosimetry and compensator design in radiation therapy.
Area of Science:
- Medical Physics
- Radiological Imaging
- Radiation Oncology
Background:
- Accurate imaging is crucial for effective radiation therapy planning and delivery.
- Existing portal imaging devices have limitations in resolution and accuracy.
- Transit dosimetry requires precise measurement of dose distribution during treatment.
Purpose of the Study:
- To design and construct a novel electronic portal imaging device (EPID).
- To evaluate the imaging performance, including contrast and spatial resolution.
- To assess the system's capability for transit dosimetry applications.
Main Methods:
- Developed an EPID with 128 CsI scintillation crystals coupled to photodiodes.
- Scanned the detector array across the field in 4 seconds at a linac dose rate of 400 cGy/min.
- Acquired images using approximately 27 cGy dose and analyzed phantom and clinical images.
Main Results:
- Achieved a contrast resolution of 0.3% (at 15 mm diameter) and spatial resolution of 2.5-3.2 mm.
- Demonstrated accurate measurement of radiological thickness to within 2-3 mm of water.
- Presented sample images including humanoid phantom and clinical breast cancer patient data.
Conclusions:
- The designed EPID exhibits excellent contrast and spatial resolution.
- The system is capable of accurate radiological thickness measurements.
- The detector is suitable for transit dosimetry and compensator design in radiation therapy.