A feasibility study for megavoltage cone beam CT using a commercial EPID
Autor: | Stewart Michael Midgley, J Dudson, R M Millar |
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Rok vydání: | 1998 |
Předmět: |
Physics
Radiological and Ultrasound Technology Phantoms Imaging business.industry Detector Biophysics Streak Water Magnification Iterative reconstruction Biophysical Phenomena Linear particle accelerator Optics Ionization chamber Image Processing Computer-Assisted Humans Dosimetry Radiology Nuclear Medicine and imaging Tomography Particle Accelerators Radiometry Tomography X-Ray Computed business Algorithms |
Zdroj: | Physics in Medicine and Biology. 43:155-169 |
ISSN: | 1361-6560 0031-9155 |
DOI: | 10.1088/0031-9155/43/1/010 |
Popis: | This study used a standard commercial electronic portal imaging device (EPID) area detector attached to an isocentric linear accelerator and the Feldkamp algorithm to produce cone beam tomographic reconstructions. The EPID has a active area of 32.5 x 32.5 cm2, and can record 12-bit images using two monitor units (MU), with a resolution of 2.1 x 2.0 mm2 FWHM. Since the EPID was not large enough to record the full patient projection at about 1.5 geometric magnification, it was necessary to offset the detector to collect half-cone projections. Corrections are required to convert pixel values into units of exit dose and to realign the projections to overcome the +/- 4 mm support arm sag. With a geometric magnification of 1.5 the sensitive volume is a cylinder of radius 21 cm and length 17 cm. Unfortunately, the patient couch contains metal bed support rails that lie just outside this cylinder, and produce streak artefacts in the reconstruction. Using 90 views the system delivers a central dose of 90 cGy, and has a density resolution of 4%. |
Databáze: | OpenAIRE |
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