Abstract：
PURPOSE:Current on-board imaging systems commonly used by modern linear accelerators (LINACs) have a limited field of view (FOV) for a cone-beam CT (CBCT) scan, which is typically less than 50 cm. Consequently, truncation artifacts often occur for large patients. The goal of this work is to investigate a novel method to increase the FOV for current on-board CBCT systems. METHODS:When a large patient is scanned with CBCT, any region outside the FOV is only partially sampled within a short range of projection angles, and at other angles no x-ray beams may pass through that region. To increase the sampling rate for the region outside the FOV, we have designed a new source trajectory by shifting the center of rotation during a CBCT scan. This resulted in a reduced sampling rate at the central area and increased sampling rate at the edges. The tradeoff led to a more balanced sampling for an enlarged FOV. An iterative algorithm was also developed to reconstruct the CT image under the new sampling scheme using a compressed sensing technique. RESULTS:The method was validated by numerical simulations mimicking a Varian Trilogy CBCT system, and it was found that artifact-free images could be obtained with the FOV as large as 80 cm. CONCLUSIONS:The new CT scanning trajectory can be easily realized under current clinical setup with little modification of the control system, and this can be useful for treating obese patients.
journal_name
Med Physjournal_title
Medical physicsauthors
Li T,Li X,Yang Y,Heron DE,Huq MSdoi
10.1118/1.3514130subject
Has Abstractpub_date
2010-12-01 00:00:00pages
6233-9issue
12eissn
0094-2405issn
2473-4209journal_volume
37pub_type
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