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Portal imaging

Medical Physics Department, Lincoln County Hospital, Greetwell Road, Lincoln, UK

View larger version (41K): [in a new window]   Figure 1. Cross-sectional representation of the Kodak portal imaging device.

View larger version (103K): [in a new window]   Figure 2. Examples of commercially available electronic portal imaging devices: (a) Electa iView system; (b) Varian PortalVision system; (c)Siemens BeamView system; and (d) Eliav PortPro, a portable system.

View larger version (8K): [in a new window]   Figure 3. Cross-sectional representation of a camera- based electronic portal imaging device. The X-ray-to-light converter is usually a metal plate with a phosphor screen, although scintillators have been used.

View larger version (22K): [in a new window]   Figure 4. Cross-sectional representation of a liquid ion chamber array.

View larger version (41K): [in a new window]   Figure 5. Cross-sectional representation of an amorphous silicon electronic portal imaging device. The illustration shows only one pixel.

View larger version (14K): [in a new window]   Figure 6. (a) The principle of thresholding. The background pixels have grey level values between 250 and 600, whilst the irradiated field pixel values fall between 1000 and 1400. If a threshold of 800 is set, then the irradiated field will be outlined. (b) Histogram of frequency against grey level for a typical image.