A compact PET detector array using wavelength shifting fibres

The basis for a design of a high-resolution PET imaging system, utilising a wavelength-shifting (WLS) fibre readout technique is presented here. Scintillation light is transported from the individual LSO pixels in the detector array through the WLS fibres to a multi-pixel hybrid photodiode (M-HPD). Each detector array consists of a number of 2×2×10 mm LSO crystals viewed by two orthogonal ribbons of WLS fibres. An array of as many as 30×31 crystals can thus be read-out by a single, small 61-pixel M-HPD tube. The design is both compact, inexpensive and suitable for application not only in the field of small-animal PET or in a dedicated PEM system, but could also operate in a combined PET/MRI system. Initial tests have shown that the signal level generated at the detector by a single 511 keV energy-deposit, is 20-25 photoelectrons. Separate tests have indicated that, at this signal-level, a resolving time of ~25 ns could be achievable