Performance of a 0.4 mm Pixelated Ce:GAGG Block Detector With Digital Silicon Photomultiplier

The intrinsic spatial resolution of the detector is an important aspect to reconstruct high quality nuclear medicine images. In order to realize a high spatial resolution, small pixelated Cerium doped Gd3Al2Ga3O12 (Ce:GAGG) scintillators–known for their high light output, high density and relatively fast decay time, were coupled to a digital silicon photomultiplier (dSiPM) for read out. This detector module consists of a $ {24 \times 24}$ Ce:GAGG scintillator block of 0.4 mm $ {\times }0.4$ mm $ {\times }5$ mm crystal elements and a 2 mm thick light guide made of acrylic resin. The digital silicon photomultiplier (dSiPM), DPC-3200-22-44, was used to acquire 2-D position histogram, energy resolution and coincidence timing resolution. The 2-dimensional position histogram of the Ce:GAGG block detector irradiated with 22Na gamma photons showed that most pixels were clearly resolved with an average peak-to-valley (P/V) ratio of ~3.4. The average energy resolution of the Ce:GAGG block detector was 17.8%. At trigger scheme 1 ( $ {1}^{\mathrm {st}}$ photon trigger), the coincidence timing resolution was 342 ± 7 ps FHWM when acquired in coincidence with a 2 mm $ {\times }2$ mm $ {\times }6$ mm LSO crystal (after skew correction). This study demonstrates that a pixelated Ce:GAGG block coupled with dSiPM provides good position performance and time resolution. We conclude that the highly pixelated Ce:GAGG detector module may be a good candidate for implementing ultrahigh resolution nuclear medicine systems and applications requiring good timing resolution.