Experimental results from the C-SPRINT prototype Compton camera

A Compton camera is being tested for nuclear medicine applications. Our design uses a single 3 cm by 3 cm silicon pad detector, and an array of position-sensitive NaI modules. Experimental results with a ^99mTc point source show coincidence energy spectra agreeing with theoretical predictions. The coincidence energy spectra for both silicon and SPRINT detectors correspond to the geometry-determined scattering angle range. Recorded energy falls outside of strict geometric limits because of Doppler broadening and detector energy resolution. The summed energy peak in the initial data run for a ^99mTc source has a FWHM energy resolution of 33 keV, primarily due to energy uncertainty in the SPRINT modules. A second data run showed an improvement to 25 keV in summed energy resolution due to careful calibration of, and correction for, significant first and second detector gain non-uniformities. Images generated from the second acquired data set result in a backprojection image resolution of 1.5 cm at a source distance of 10 cm. Analytical and Monte Carlo calculations show a very close agreement of 1.6 cm. Using a list-mode likelihood EM reconstruction algorithm, the image resolution is improved to 7 mm, although the resolution recovery is at the expense of increased noise in the image