Positron emission tomography detector performance with different crystal pitches

In this work, we evaluated the performance of three pitches positron emission tomography (PET) detectors for building a high-resolution small-animal PET imaging experimental platform. The evaluation of PET detectors includes two-dimensional crystal identification, energy resolution, and crystal look-up table. The nuclear instrumentation module and PXI data acquisition (DAQ) system were both used to obtain flood images. The energy spectrum of the Na-22 source was measured. PET detectors of 2.0 and 1.6 mm pitches used in our present experiment were composed of lutetium yttrium oxyorthosilicate (LYSO) crystals directly coupled to position-sensitive photomultiplier tubes (PSPMTs). The 1.3-mm pitch detector comprises a LYSO crystal, a tapered light-guide, and a PSPMT. The crystal sizes of the detectors were a $$10 \times 10$$ array of $$2.0 \times 2.0 \times 10\,\hbox {mm}^{3}$$ crystals, a $$10 \times 10$$ array of $$1.6 \times 1.6 \times 10\,\hbox {mm}^3$$ crystals, and an $$18 \times 18$$ array of $$1.3 \times 1.3 \times 10\,\hbox {mm}^3$$ crystals, respectively. Due to the lower sampling frequency of the DAQ system, a spline interpolation algorithm was introduced in the signal waveform to reconstruct the peak values. The experimental results indicated that all three PET detector crystals could be clearly identified. A detailed analysis demonstrated that the key characteristic full width at half maximum (FWHM) values of the crystals profile could reach $$0.46\pm 0.03$$ , $$0.32\pm 0.03$$ , and $$0.21\pm 0.02\,\hbox {mm}$$ , while the crystal average energy resolutions were $$16.8\%\pm 1.76\%$$ , $$20.1\%\pm 2.24\%$$ , and $$31.5\%\pm 3.76\%$$ , which correspond to pitches of 2.0-, 1.6-, and 1.3-mm, respectively. The PET detector modules of LYSO crystal arrays could be potentially used in the small-animal PET imaging applications and are promising to achieve sub-millimeter PET images.