Crystal scintillation gamma camera plates are widely used in Nuclear Medicine to image tissues containing gamma-emitting tracer compounds introduced into the patient. A matrix of photomultiplier tubes or other light sensors optically coupled directly to the detector or a window detect the scintillation photons produced in the crystal. The camera system electronics compute the locations of the scintillation events in the crystal and evaluate the corresponding intake of the tracer in the tissue. This information is expressed in the image.
Large area flat NaI(Tl) plates are traditionally used for SPECT. In 1998, Saint-Gobain produced a curved camera plate for UGM Medical for a dedicated PET system. The curved design brought the field of view closer to the body. Also during this time, thicker crystals were being used to image in both SPECT and PET modes. Thicker crystals, while improving high energy efficiency, tended to degrade low energy performance. The solution was cutting slots into the NaI(Tl) crystal to direct light to the photomultiplier tubes. This allows for excellent SPECT performance while still maintaining the improved efficiency for PET.
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Traditional Gamma Camera Plates are flat rectangular or round NaI(Tl) crystals with a glass window (for light transmission) and an aluminum housing and is hermetically sealed.
The original gamma cameras incorporated a single NaI(Tl) flat crystal. To increase patient throughput and improve resolutions, systems were designed with larger and/or multiple crystals. By using two or more large area detectors and by rotating them around the patient, a three-dimensional image of the radioactivity distribution can be obtained. This technique is called SPECT.
Rectangular or Circular configurations
Sizes up to a 60cm by 45 cm field of view are typical with alternate sizes available by request
Pixellated Array crystals result in improved spatial resolution due to decreased light spread. Saint-Gobain’s proprietary manufacturing process ensures superior light output and improved pixel-to-pixel uniformity. These are typically used with position-sensitive photomultiplier tubes (PSPMT) or silicon photomultipliers (SiPM).
Most PET systems use denser materials such as BGO or LYSO. LYSO combines a short decay time, high light output and good energy resolution. LaBr3 crystals are also of interest to achieve ultra-low Coincidence Resolving Times (CRT’s).
For arrays used for Positron Emission Tomography (PET) imaging click here
Minimal pixel separation
Reduced optical crosstalk
Minimal dead space at array edges
Can be used with position-sensitive PMT or SiPM to produce small field of view and organ-specific detectors
Crystal scintillator: LYSO is standard but other crystals are available
Design options including pixel size, the number of pixels, pixel separator reflective materials available, and crystal surface finish.
2D arrays are typically used with pixelated photodiodes, position-sensitive photomultiplier tubes (PSPMT) and silicon photomultipliers (SiPM) for more compact designs.