Preliminary commissioning investigations with the DMOS-RPC optical-CT scanner

A midsized broad beam Optical-CT scanner is being developed for collaborative research between Duke and the Radiological Physics Center (RPC). The Duke Midsized Optical-CT Scanner (DMOS-RPC) is designed to be compatible with several of the RPC phantoms, including the head and neck, stereotactic SRS, and lung phantoms. Preliminary data investigating the basic performance of the scanner is described. Two 10 cm PRESAGE cylinders were irradiated with simple test plans. Projections of ∼80 μm resolution of each dosimeter were collected at 1 degree intervals over a full 360 degrees both before and after irradiation. 3 dimensional reconstructions of attenuation coefficients throughout the dosimeter were computed with 1 mm³ resolution. Scans were normalized to the calculated dose distribution and a 3D comparison was made with a commissioned treatment planning system. Initial results indicate DMOS-RPC can produce accurate relative dose distributions with high spatial resolution (up to 1 mm³ in 3D) in less than 30 minutes (acquisition and reconstruction). A maximum dose of ∼3.6Gy was delivered in these tests, and observed noise was ∼2% for 1 mm³ reconstructions. Good agreement is observed with the planning system in these simple distributions, indicating promising potential for this scanner.