Imaging of breast phantoms using a high-resolution position sensitive photomultiplier tube

The results of studies conducted with a small field of view gamma camera based on a Position Sensitive Photomultiplier Tube (PSPMT) and a pixelized scintillator crystal, made of CsI(Tl), are reported. Using a computer-controlled step motor allowing object rotation, projection data from several angles are acquired. Images of slices of the object are obtained and compared with the use of a Filtered Backprojection and a Maximum Likelihood algorithm. Phantom studies have shown a spatial resolution of 2–3 mm in both two and three dimensions, and mice experiments have shown successful SPECT imaging of small organs. 3D images obtained from a paraffin cylinder phantom and from a 99mTc water solution phantom showed that a “hot” spot with a size down to 0.2 ml can be detected with a resolution of about 2 mm if the tumor to background activity ratio is 6:1.