Scintillator Crystals For Medicine Imaging

The typical detector structure of nuclear medicine imaging equipment consists of a crystal at the front end, a photoelectric converter in the middle, and readout electronics at the back end. When gamma photons reach the detector, they first complete energy conversion in the crystal. The high-energy photons are converted into low-energy visible light. Then they pass through the photoelectric converter. The optical signal is converted into an electrical signal and then transmitted to the back-end electronic system for information detection. In this process, the performance of the crystal and photoelectric converter can be said to directly determine the performance of the detector. Let's learn about the crystal and how to evaluate the performance of the crystal.

Performance of Scintillator Crystals

Nuclear medicine usually uses inorganic scintillator. As the name implies, its main body is mainly some inorganic compounds, such as NaI, BGO, LSO, etc. The function of the crystal is to absorb gamma rays and produce visible light. The indicators generally used to evaluate the performance of the crystal include: atomic number and density, light yield, luminescence decay time, luminescence wavelength, absorption thickness, deliquescentness, etc.

1. The higher the atomic number and density, the better: the stronger the crystal’s ability to absorb gamma photons, the less likely it is for photons to penetrate the crystal. Therefore, the higher the detection efficiency of the detector will be;

2. The higher the light yield, the better: Light yield refers to the ability of the crystal to convert gamma photons into visible light. The higher the light yield, the energy resolution and spatial resolution of the detector can be improved accordingly;

3. The shorter the luminescence decay time, the better: that is, the time difference between when the scintillator is excited and produces scintillation light. The shorter this value, the better the time resolution of the crystal, and the detector can obtain higher detection at a high count rate. efficiency;

4. The emission spectrum should match the response spectrum of the photoelectric conversion device to obtain higher light output;

2. 5. The gamma photon absorption thickness refers to how long a crystal can be used to completely absorb gamma photons. The shorter the value, the better, which means that we can use shorter crystals to absorb gamma photons and obtain higher detection efficiency.

Performance Comparison of Scintillator Crystals

The typical detector structure of nuclear medicine imaging equipment consists of a crystal at the front end, a photoelectric converter in the middle, and readout electronics at the back end. When gamma photons reach the detector, they first complete energy conversion in the crystal. The high-energy photons are converted into low-energy visible light. Then they pass through the photoelectric converter. The optical signal is converted into an electrical signal and then transmitted to the back-end electronic system for information detection. In this process, the performance of the crystal and photoelectric converter can be said to directly determine the performance of the detector, so in this issue we will learn about crystals and how to evaluate the performance of crystals.