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1.S. J. Doran, “The history and principles of optical computed tomography for scanning 3-D radiation dosimeters: 2008 update,” J. Phys.: Conf. Ser. 164, 012020 (2009).
2.S. J. Doran, K. K. Koerkamp, M. A. Bero, P. Jenneson, E. J. Morton, and W. B. Gilboy, “A CCD-based optical CT scanner for high-resolution 3D imaging of radiation dose distributions: Equipment specifications, optical simulations and preliminary results,” Phys. Med. Biol. 46(12), 31913213 (2001).
3.J. C. Gore, M. Ranade, M. J. Maryanski, and R. J. Schulz, “Radiation dose distributions in three dimensions from tomographic optical density scanning of polymer gels: I. Development of an optical scanner,” Phys. Med. Biol. 41(12), 26952704 (1996).
4.S. J. Doran and D. N. Yatigammana, “Eliminating the need for refractive index matching in optical CT scanners for radiotherapy dosimetry: I. Concept and simulations,” Phys. Med. Biol. 57(3), 665683 (2012).
5.L. Rankine and M. Oldham, “On the feasibility of optical-CT imaging in media of different refractive index,” Med. Phys. 40(5), 051701 (8pp.) (2013).
6.A. Thomas, J. Newton, J. Adamovics, and M. Oldham, “Commissioning and benchmarking a 3D dosimetry system for clinical use,” Med. Phys. 38(8), 48464857 (2011).
7.M. Oldham, “3D dosimetry by optical-CT scanning,” J. Phys.: Conf. Ser. 56, 5871 (2006).
8.A. Thomas and M. Oldham, “Fast, large field-of-view, telecentric optical-CT scanning system for 3D radiochromic dosimetry,” J. Phys.: Conf. Ser. 250, 012007 (2010).
9.W. G. Campbell, D. A. Rudko, N. A. Braam, D. M. Wells, and A. Jirasek, “A prototype fan-beam optical CT Scanner for 3D dosimetry,” Med. Phys. 40, 061712 (12pp.) (2013).
10.C. Clift, A. Thomas, J. Adamovics, Z. Chang, I. Das, and M. Oldham, “Toward acquiring comprehensive radiosurgery field commissioning data using the PRESAGE/optical-CT 3D dosimetry system,” Phys. Med. Biol. 55, 12791293 (2010).
11.N. Krstajic and S. J. Doran, “Characterization of a parallel-beam CCD optical-CT apparatus for 3D radiation dosimetry,” Phys. Med. Biol. 52, 36933713 (2007).
12.H. S. Sakhalkar and M. Oldham, “Fast, high-resolution 3D dosimetry utilizing a novel optical-CT scanner incorporating tertiary telecentric collimation,” Med. Phys. 35(1), 101111 (2008).
13.M. J. Maryanski and M. K. Ranade, “Laser microbeam CT scanning of dosimetry gels,” SPIE Proc. 4320, 764774 (2001).
14.M. Oldham, “ScanSim: A tool for simulating optical-CT imaging,” J. Phys.: Conf. Ser. 250, 012064 (2010).
15.D. Ramm, T. P. Rutten, J. Shepherd, and E. Bezak, “Optical CT scanner for in-air readout of gels for external radiation beam 3D dosimetry,” Phys. Med. Biol. 57(12), 38533868 (2012).
16.A. E. Papadakis, G. Zacharakis, T. G. Maris, J. Ripoll, and J. Damilakis, “A new optical-CT apparatus for 3-D radiotherapy dosimetry: Is free space scanning feasible?,” IEEE Trans. Med. Imaging 29(5), 12041212 (2010).
17.D. Ramm, “Laser beam optical CT scanner for in-air gel readout: Imaging artefacts,” J. Phys.: Conf. Ser. 444, 012078 (2013).
18.P. Y. Guo, J. A. Adamovics, and M. Oldham, “Characterization of a new radiochromic three-dimensional dosimeter,” Med. Phys. 33(5), 13381345 (2006).
19.T. Juang, J. Newton, M. Niebank, R. Benning, J. Adamovics, and M. Oldham, “Customizing PRESAGE(TM) for diverse applications,” J. Phys.: Conf. Ser. 444, 012029 (2013).
20.H. S. Sakhalkar, J. Adamovics, G. Ibbott, and M. Oldham, “A comprehensive evaluation of the PRESAGE/optical-CT 3D dosimetry system,” Med. Phys. 36(1), 7182 (2009).
21.J. Adamovics and M. J. Maryanski, “Characterisation of PRESAGE: A new 3-D radiochromic solid polymer dosemeter for ionising radiation,” Radiat. Prot. Dosim. 120, 107112 (2006).
22.S. Bache, J. Malcom, J. Adamovics, and M. Oldham, “SU-E-J-164: An investigation of a low-cost ‘dry’ optical-CT scanning system for 3D dosimetry,” Med. Phys. 41(6), 194 (2014).
23.A. Thomas, M. Pierquet, K. Jordan, and M. Oldham, “A method to correct for spectral artifacts in optical-CT dosimetry,” Phys. Med. Biol. 56, 34033416 (2011).
24.Y. Xua, C. S. Wuu, and M. J. Maryanski, “Determining optimal gel sensitivity in optical CT scanning of gel dosimeters,” Med. Phys. 30(8), 22572263 (2003).
25.See supplementary material at for additional figures and results regarding gap size analysis and ray-tracing diagrams.[Supplementary Material]

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In optical-CT, the use of a refractively matched polyurethane solid-tank in place of a fluid bath has the potential to greatly increase practical convenience, reduce cost, and possibly improve the efficacy of flood corrections. This work investigates the feasibility of solid-tank optical-CT imaging for 3D dosimetry through computer simulation.

A ray-tracing simulation platform, ScanSim, was used to model a parallel-source telecentric optical-CT imaging system through a polyurethane solid-tank containing a central cylindrical hollow into which radiochromic dosimeters can be placed. A small amount of fluid fills the 1–5 mm gap between the dosimeter and the walls of the tank. The use of the solid-tank reduces the required amount of fluid by approximately 97%. To characterize the efficacy of solid-tank, optical-CT scanning simulations investigated sensitivity to refractive index (RI) mismatches between dosimeter, solid-tank, and fluid, for a variety of dosimeter (RI = 1.5–1.47) and fluid (RI = 1.55–1.0) combinations. Efficacy was evaluated through the usable radius () metric, defined as the fraction of the radius of the dosimeter where measured dose is predicted to be within 2% of the ground truth entered into the simulation. Additional simulations examined the effect of increasing gap size (1–5 mm) between the dosimeter and solid-tank well. The effects of changing the lens tolerance (0.5°–5.0°) were also investigated.

As the RI mismatch between the dosimeter and solid-tank increased from 0 to 0.02, the usable radius decreased from 97.6% to 50.2%. The optimal fluid RI decreased nonlinearly from 1.5 to 1.34 as the mismatch increased and was up to 9% lower than the tank. Media mismatches between the dosimeter and solid-tank also exacerbate the effects of changing the gap size, with no easily quantifiable relationship with usable radius. Generally, the optimal fluid RI value increases as gap size increases and is closely matched to the dosimeter at large gap sizes (>3 mm). Increasing the telecentric lens tolerance increases the usable radius for all refractive media combinations and improves the maximum usable radius of mismatched media to that of perfectly matched media for tolerances >5.0°. The maximum usable radius can be improved up to a factor of 2 when lens tolerances are small (<1.0°).

Dry solid-tank optical-CT imaging in a telecentric system is feasible if the dosimeter RI is a close match with the solid-tank (<0.01 difference), providing accurate dose measurements within ±2% of true dose to over 80% of the dosimeter volume. In order to achieve accurate measurements over 96% of the dosimeter volume (representing out to 2 mm from the dosimeter edge), the dosimeter-tank RI mismatch must be less than 0.005. Optimal results occur when the RI of the dosimeter and tank is the same, in which case the fluid will have the same RI. If mismatches between the tank and dosimeter RI occur, the RI of the matching fluid needs to be fine tuned to achieve the highest usable radius.


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