The effect of scintillator manipulation on a thick crystal gamma detector

When a NaI(Tl) based gamma camera is used for high energy single photon imaging or positron imaging, a relatively thick scintillation crystal is required to provide enough stopping power for impinging gamma rays. However, it causes worsening of the image quality due to the wider scintillated light spread and parallax error. To address the image quality degradation problem with a thick crystal, we investigated the effects of crystal manipulation on detector performance. The methods include drilling holes, cutting grooves and making pyramid shapes on the gamma ray entrance surface of the crystal. It has been proven throughout this investigation that the proposed method can improve intrinsic spatial/energy resolution, DOI (depth of interaction) decodeability and uniformity. This is done by proper controlling of the optical characteristics of scintillated light photons. Among the tested methods, entrance side groove cutting found to be the most promising method in terms of improving detector performance and providing cost effective manufacturability as well.