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SU‐EE‐A4‐04: Monte Carlo Simulation and Design of a Carbon Nanotube Small‐Animal Micro‐RT System
Author(s) -
Schreiber E,
Chang S
Publication year - 2007
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2760355
Subject(s) - monte carlo method , pixel , image resolution , collimator , optics , materials science , isocenter , carbon nanotube , dosimetry , beam (structure) , physics , imaging phantom , nuclear medicine , nanotechnology , medicine , statistics , mathematics
Purpose: To use Monte Carlo simulations to characterize the design and performance of a nanotechnology‐based high spatial and temporal resolution small animal micro‐RT system. Method and Materials: The proposed micro‐RT system uses carbon nanotube field emission technology to produce arrays of individually and electronically controllable x‐ray pixels that can form spatially and temporally high resolution modulated irradiation. Combined with the existing carbon‐nanotube field emission micro‐CT, the future micro‐CT‐RT system promises a high spatial and temporal resolution image‐guided irradiation system ideal for small animal research. Prospective designs for the micro‐RT system were evaluated using EGSnrc‐based Monte Carlo simulations. Design aspects studied included: 1) x‐ray anode design, 2) collimator design, and 3) dosimetric considerations, including dose rate, inhomogeneity corrections, and the overlap effect of adjacent pixel beams. Results: Anode studies indicate that reflective and transmission target designs produce similar dosimetric properties, finding dose rates of 40 cGy/min/mA/pixel are achievable at isocenter (10 cm SAD) for 2 mm × 2 mm pixels in a 3 cm diameter mouse model. For beam energies of 80–100 kV, photons below 20 keV must be filtered out to eliminate excessive surface dose for the mouse model. This filtration can be achieved using a tungsten transmission target 26 μm thick or a 2.5 mm Al filter with the reflective target. Dose overlap between adjacent x‐ray pixels produces high or low dose spots for a single beam array direction. When opposing beam pair configurations are used, the dose inhomogeneity is reduced to negligible levels near isocenter and 20% near the surface. Conclusion: Monte Carlo simulation studies are instrumental to the development of a novel micro‐RT system. They are used to evaluate performance on different system designs without the cost of prototype fabrication. The Monte Carlo study verified basic dosimetric features of the intended micro‐RT design.