Sajedi, S., Zeraatkar, N., Taheri, M., Kaviani, S, Khanmohammadi, H., Sarkar, S., Sabet, H., Ay, M.R.
In this work we present a Positron Emission Tomography (PET) detector block, which can be used in different scanner geometries. The block uses 12×12 Silicon Photomultiplier (SiPM) pixels with the overall dimension of 50×50 mm 2 . The SiPM technology has widely used in PET detectors, particularly in the presence of magnetic field. The large number of SiPM pixels per unit area, requires channel reduction technique to avoid readout complexity and cost. The presented detector block consists of the detector head and the digital front-end (DFE) board. The read-out dimension is so that the blocks can be arranged in the arbitrary numbers in a ring, or in the axial extension. In the DFE board the basic information required for a PET scanner (i.e. position, energy, and time of photon incidence), are measured. We used Scrambled Crosswire Readout (SCR) method by exploiting the third output of SiPM, which has faster rise time instead of cathode. This method reduces 144 fast outputs to 9 tile signals and 144 standard outputs to 16 energy channels. The multiplexed fast signals are also used to generate time pickoff information for timing measurement. To calculate the position of the photon, 16 energy signals locate the position inside the tile, and the tile signals locate the tile in the array. The position calculation uses threshold and centroid method which is described in detail in the tile edges, when two or four tiles are fired by a single event. The basic design uses a 24×24 LYSO:Ce array with 2×2×10 mm 3 pixel size to be used in the small animal PET project. In the 2D flood image, all the pixels are clearly resolved in the room temperature. The energy resolution of the detector block is measured ~12.5% by calibrating energy values for all crystal pixels.