Computed Tomography Using a Cs137 Source

The purpose of this work was to explore the use of a monenergetic gamma ray source and pulse counting techniques for use In a CT device. The ideal source for CT scanning is one with a 100-keV gamma ray, long lifetime and low-cost availabiltly in high specific activity. However, since the attenuation coefficient of tissue-like materials varies slowly with energy a Cs-137 source was used without significant disadvantage. Phantoms consisting of brass, aluminum and low-Z, organic polymers were scanned with 2.0 mm ray spacing and up to 60 angular orientations. The results from 0.1% statistical accuracy data obtained with the prototype scanner have demonstrated that a 2.5% density gradient can be detected. One of the advantages of a Cs-137 source is that the calculated attenuation coefficients are directly proportional to physical densities of the materials scanned.