Development of a novel optical CT employing a laser to create a collimated line-source with a flat-top intensity distribution

In order to improve the scanning efficiency of commercial optical computed tomography (OptCT) scanners which use a conventional scanning laser, a novel optical CT scanner is being developed which employs a laser-based line source for the gel-scanning process. This line-source laser system can generate a uniform and parallel illumination profile in a line pattern, and consists of a Gaussian spot laser, a beam shaping module to convert a Gaussian laser beam into a 90° fan-angle line pattern with flat-top profile, and a set of cylindrical lenses which converts the rays into parallel light. The optical CT scanner consists of a gel cylinder mounted inside the scanning tank, two scanning motors to operate the rotations and translations of the gel cylinder, and a CCD detector to record the image data. We present our analysis of the sources of uncertainty and evaluate the basic performance parameters of the optical CT scanner in conjunction with polymer gel dosimeters. To improve dose accuracy of this prototype, it may also be necessary to decrease the wall thicknesses of both the gel container and the matching liquid tank and more precisely to match the refractive indices of the whole system.