Study of electrode pattern design for a CZT-based PET detector.
We are developing a 1 mm resolution small animal positron emission tomography (PET) system using 3D positioning cadmium zinc telluride photon detectors comprising 40 mm × 40 mm × 5 mm crystals metalized with a cross-strip electrode pattern with a 1 mm anode strip pitch. We optimized the electrode pattern design for intrinsic sensitivity and spatial, energy and time resolution performance using a test detector comprising cathode and steering electrode strips of varying dimensions. The study found 3 and 5 mm width cathode strips locate charge-shared photon interactions near cathode strip boundaries with equal precision. 3 mm width cathode strips exhibited large time resolution variability as a function of photon interaction location between the anode and cathode planes (~26 to ~127.5 ns full width at half maximum (FWHM) for 0.5 mm and 4.2 mm depths, respectively). 5 mm width cathode strips by contrast exhibited more stable time resolution for the same interaction locations (~34 to ~83 ns FWHM), provided more linear spatial positioning in the direction orthogonal to the electrode planes, and as much as 68.4% improvement in photon sensitivity over the 3 mm wide cathode strips. The results were understood by analyzing the cathode strips' weighting functions, which indicated a stronger 'small pixel' effect in the 3 mm wide cathode strips. Photon sensitivity and anode energy resolution were seen to improve with decreasing steering electrode bias from 0 to -80 V w.r.t. the anode potential. A slight improvement in energy resolution was seen for wider steering electrode strips (400 versus 100 µm) for charge-shared photon interactions. Although this study successfully focused on electrode pattern features for PET performance, the results are generally applicable to semiconductor photon detectors employing cross-trip electrode patterns.
Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA. Molecular Imaging Instrumentation Laboratory, Department of Radiology, Stanford University, Stanford, CA 94305, USA.
Y
Y
Gu
C S
CS
Levin
D000818:Animals; D002104:Cadmium; D004566:Electrodes; D004867:Equipment Design; D016014:Linear Models; D017785:Photons; D049268:Positron-Emission Tomography / Q000295:instrumentation*; D013691:Tellurium; D013997:Time Factors; D015032:Zinc
C474490:CdZnTe; D002104:Cadmium; D015032:Zinc; D013691:Tellurium