Radiotherapy: EPID position error tests of small multi-leaf X-ray fields

An electronic portal imaging device (EPID) is routinely fitted as a radiotherapy linear accelerator accessory. The EPID can be used to verify the multi-leaf collimator (MLC) leaf positions and other quality assurance (QA) type tasks. EPID-based MLC has been extensively studied for position error detection of large fields and using a variety of leaf verification algorithms [1–7]. But there are currently no widely accepted EPID methods that can accurately measure position errors for exceptionally small irregular-shaped MLC fields.

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