Room: Exhibit Hall | Forum 9
Purpose: To study the imaging characteristics of a prototype prompt gamma camera consisting of two orthogonally oriented Compton imagers.
Methods: The prototype dual head Compton camera is composed of two orthogonal imagers placed 9 cm from the isocenter along the x and y axes with each detector containing two 25x25x10 mm CZT crystals arranged horizontally. This system was used to image both Co-60 and Cs-137 sources while the detectors were used either together or individually. The collected Compton scatter data was reconstructed using either back projection, the CORE reconstruction algorithm or the MLEM reconstruction algorithm. The resulting images were used to study the ability to accurately locate the source position and to determine the spatial resolution for the dual head Compton camera setup in combination with the image reconstruction techniques.
Results: In the dual head configuration, all of the reconstruction algorithms were able to reconstruct both single and multiple point sources. Using a single detector, the algorithms effectively reconstructed the single point source, but they all failed to reconstruct the multiple point sources data. For a single detector, the three reconstruction algorithms were able to locate the single source point within 16.5 mm for backprojection, 19.5 mm for CORE and 21.0 mm for MLEM. For the orthogonal setup, the location of the single point improved to 2.6 mm for backprojection, 3.6 mm for CORE and 3.8 for MLEM. For the dual head setup, all three algorithms distinguished between two Co-60 sources located 3.0 cm apart, but could not resolve identical sources closer together.
Conclusion: This work has shown that the dual head, orthogonal Compton camera configuration greatly improves 3D imaging over a single planer detector. The three reconstruction algorithms exhibited similar spatial resolution capability and, surprisingly, the backprojection algorithm most closely identified the actual point source location.
Treatment Verification, Maximum Likelihood Estimation, Radiation Detectors
TH- External Beam- Particle therapy: Proton therapy - Development (new technology and techniques)