Preliminary evaluations of high resolution positron emission tomography for breast imaging

A program of work has been undertaken using Monte Carlo simulations and experimental measurements with the RPET scanner to evaluate the role of a dedicated high resolution positron camera for breast imaging. The simulated detector consists of 20 mm long crystals arranged in a ring of diameter 220 mm by 52 mm long. The sides of the crystal faces were varied from 1 mm to 4.5 mm. The breast was simulated by a cylinder 69 mm in diameter by 65 mm long containing a lesion varying from 2 mm to 10 mm in diameter with an SUV in the range 2-8. The number of simulated counts varied from 1-10 million. Preliminary measurements with the RPET camera have also been made using the same size phantom/lesion combination. After these measurements are completed it is hoped to evaluate a hybrid photo diode detector for its usefulness as a dedicated PET breast scanner. The simulations show that a 4 mm diameter lesion with an SUV of 6 (typical of measured values) can be detected with 1 million acquired counts using 2.5 mm crystals. The detection of smaller lesions is severely limited by sensitivity. Using smaller crystals does not help detect smaller lesions but increasing acquired counts does. Experimental measurements show the importance of minimising the background from the heart.