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 Gd<sub>3</sub>Al<sub>2</sub>Ga<sub>3</sub>O<sub>12</sub> (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 <inline-formula> <tex-math notation="LaTeX">$ {24 \times 24}$ </tex-math></inline-formula> Ce:GAGG scintillator block of 0.4 mm <inline-formula> <tex-math notation="LaTeX">$ {\times }0.4$ </tex-math></inline-formula> mm <inline-formula> <tex-math notation="LaTeX">$ {\times }5$ </tex-math></inline-formula> 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 <sup>22</sup>Na 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 (<inline-formula> <tex-math notation="LaTeX">$ {1}^{\mathrm {st}}$ </tex-math></inline-formula> photon trigger), the coincidence timing resolution was 342 ± 7 ps FHWM when acquired in coincidence with a 2 mm <inline-formula> <tex-math notation="LaTeX">$ {\times }2$ </tex-math></inline-formula> mm <inline-formula> <tex-math notation="LaTeX">$ {\times }6$ </tex-math></inline-formula> 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.