24 July 1998 Portal imaging with a CsI(Tl) transparent scintillator x-ray detector
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Abstract
In a previous paper, a portal imaging system was described that used a 101 mm diameter, 3 mm thick CsI (Tl) transparent scintillating screen coupled to a liquid-nitrogen-cooled slow- scan CCD-TV camera with a 40 mm f1.0 macro lens with a 5:1 demagnification. Meanwhile, improved images have been acquired using a 50 mm f1.1 macro lens with a 7:1 demagnification. These images were presented at an AAPM International Symposium on Electronic Portal Imaging in Detroit, MI, in May, 1997. Since the Detroit meeting, a 203 mm diameter, 13 mm thick CsI(Tl) crystal has been purchased from Bicron. This transparent screen has been used with a Nikkor 35 mm f1.4 lens to show the whole 203 mm circular field at 0.53 mm pixel size with the existing Astromed liquid nitrogen cooled CCD TV camera system. The geometry of the imaging system has been optimized to achieve high spatial resolution (1 lp/mm) in spite of the increased thickness of the screen. This increased thickness allows the high image quality achieved with the older screen at 72 MU to be maintained with the newer screen while reducing the dose to 1 MU. Images have been acquired with the new screen of lead bar patterns, low-contrast hole patterns in Lucite blocks, and anthropomorphic phantoms.
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Herbert D. Zeman, Sanjiv S. Samant, Gunnar Lovhoiden, Brent D. Weinberg, Amit R. Sawant, "Portal imaging with a CsI(Tl) transparent scintillator x-ray detector", Proc. SPIE 3336, Medical Imaging 1998: Physics of Medical Imaging, (24 July 1998); doi: 10.1117/12.317015; https://doi.org/10.1117/12.317015
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