Bipolar analog signal multiplexing for position-sensitive PET block detectors

This paper describes a block detector multiplexing technique that simplifies the extension of axial length or ring radius without employing extra data acquisition channels. The proposed multiplexing circuit (bipolar multiplexing) multiplexes block detectors by encoding the position-related signal outputs with different combinations of polarity. Accordingly, it is possible to distinguish the detectors using a shared readout channel. This method was evaluated by assessing one to 16 block detectors using four data acquisition channels and one trigger input at different count rates. The experimental results showed that the multiplexing of block detectors did not significantly degrade timing, energy or spatial performance at low count rates, while reducing the required number of data acquisition channels and wire routing density. On the other hand, the degradation was seen as total count rates of all blocks increased.