In this paper, we report our investigation using a CsI(Tl) transparent scintillator x-ray detector together with the multi-level scheme algebraic reconstruction technique (MLS- ART) for megavoltage computed tomography (CT) reconstructions. The reconstructed CT images may be useful for positional verification in radiotherapy. The CsI(Tl) imaging system consists of a scintillator screen coupled to a liquid- nitrogen-cooled slow-scan CCD-TV camera. This system provides better contrast resolution than the standard electronic portal imaging system (EPID), which is especially useful given the low number of projections we are aiming at. The geometry of the imaging system has also been optimized to achieve high spatial resolution (1 lp/mm) in spite of the thickness of the screen. We present the images reconstructed using a pediatric head phantom using a total of 99 projections, and a combined phantom using 50 projections. Image reconstruction was carried out using the MLS-ART technique. We also present the CT images obtained using the back projection technique for comparison purposes.
We investigate the use of the kinestatic charge detector (KCD) together with the multi-level scheme algebraic reconstruction technique (MLS-ART) for computer tomography (CT) reconstruction, to be used in position verification in radiotherapy. The KCD offers very good contrast resolution, which is especially useful given the low number of projections we are aiming at. We present the images reconstructed using a head phantom (Rando-phantom) using a total of 95 projections, and a standard low contrast CT phantom using 63 projections. The reconstruction was carried out using MLS-ART technique, in this technique satisfactory images are generally obtained after one or two iteration, which in effect makes ART a noniterative algorithm. We also present the CT images obtained using the back projection technique for comparison purposes.
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