Developments in megavoltage cone beam CT with an amorphous silicon EPID: Reduction of exposure and synchronization with respiratory gating Journal Article

  

Authors:	Sillanpaa, J.; Chang, J.; Mageras, G.; Riem, H.; Ford, E.; Todor, D.; Ling, C. C.; Amols, H.
Article Title:	Developments in megavoltage cone beam CT with an amorphous silicon EPID: Reduction of exposure and synchronization with respiratory gating
Abstract:	We have studied the feasibility of a low-dose megavoltage cone beam computed tomography (MV CBCT) system for visualizing the gross tumor volume in respiratory gated radiation treatments of nonsmall-cell lung cancer. The system consists of a commercially available linear accelerator (LINAC), an amorphous silicon electronic portal imaging device, and a respiratory gating system. The gantry movement and beam delivery are controlled using dynamic beam delivery toolbox, a commercial software package for executing scripts to control the LINAC. A specially designed interface box synchronizes the LINAC, image acquisition electronics, and the respiratory gating system. Images are preprocessed to remove artifacts due to detector sag and LINAC output fluctuations. We report on the output, flatness, and symmetry of the images acquired using different imaging parameters. We also examine the quality of three-dimensional (3D) tomographic reconstruction with projection images of anthropomorphic thorax, contrast detail, and motion phantoms. The results show that, with the proper choice of imaging parameters, the flatness and symmetry are reasonably good with as low as three beam pulses per projection image. Resolution of 5% electron density differences is possible in a contrast detail phantom using 100 projections and 30 MU. Synchronization of image acquisition with simulated respiration also eliminated motion artifacts in a moving phantom, demonstrating the system's capability for imaging patients undergoing gated radiation therapy. The acquisition time is limited by the patient's respiration (only one image per breathing cycle) and is under 10 min for a scan of 100 projections. In conclusion, we have developed a MV CBCT system using commercially available components to produce 3D reconstructions, with sufficient contrast resolution for localizing a simulated lung tumor, using a dose comparable to portal imaging. © 2005 American Association of Physicists in Medicine.
Keywords:	computer assisted tomography; tumor volume; lung non small cell cancer; lung neoplasms; tomography, x-ray computed; simulation; feasibility studies; pilot projects; geometry; imaging, three-dimensional; device; artifact; equipment design; phantom; artifacts; linear accelerator; copper; radiographic image interpretation, computer-assisted; silicon; respiratory mechanics; electron; equipment failure analysis; radiographic image enhancement; exposure; cone beam ct; electronic portal imaging device; setup verfication
Journal Title:	Medical Physics
Volume:	32
Issue:	3
ISSN:	0094-2405
Publisher:	American Association of Physicists in Medicine
Date Published:	2005-03-01
Start Page:	819
End Page:	829
Language:	English
DOI:	10.1118/1.1861522
PUBMED:	15839355
PROVIDER:	scopus
DOI/URL:	http://www.scopus.com/inward/record.url?eid=2-s2.0-15744396320&partnerID=40&md5=1fbefa9963be64b252fe081f2d4144ff
Notes:	--- - "Cited By (since 1996): 42" - "Export Date: 24 October 2012" - "CODEN: MPHYA" - "Source: Scopus"

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