Development of brain PET using GAPD arrays

Department of Electronic Engineering, Sogang University, Mapo-Gu, Seoul, Korea.
Medical Physics (Impact Factor: 2.64). 03/2012; 39(3):1227-33. DOI: 10.1118/1.3681012
Source: PubMed


In recent times, there has been great interest in the use of Geiger-mode avalanche photodiodes (GAPDs) as scintillator readout in positron emission tomography (PET) detectors because of their advantages, such as high gain, compact size, low power consumption, and magnetic field insensitivity. The purpose of this study was to develop a novel PET system based on GAPD arrays for brain imaging.
The PET consisted of 72 detector modules arranged in a ring of 330 mm diameter. Each PET module was composed of a 4 × 4 matrix of 3 × 3 × 20 mm(3) cerium-doped lutetium yttrium orthosilicate (LYSO) crystals coupled with a 4 × 4 array three-side tileable GAPD. The signals from each PET module were fed into preamplifiers using a 3 m long flat cable and then sent to a position decoder circuit (PDC), which output a digital address and an analog pulse of the interacted channel among 64 preamplifier signals transmitted from four PET detector modules. The PDC outputs were fed into field programmable gate array (FPGA)-embedded data acquisition (DAQ) boards. The analog signal was then digitized, and arrival time and energy of the signal were calculated and stored.
The energy and coincidence timing resolutions measured for 511 keV gamma rays were 18.4 ± 3.1% and 2.6 ns, respectively. The transaxial spatial resolution and sensitivity in the center of field of view (FOV) were 3.1 mm and 0.32% cps/Bq, respectively. The rods down to a diameter of 2.5 mm were resolved in a hot-rod phantom image, and activity distribution patterns between the white and gray matters in the Hoffman brain phantom were well imaged.
Experimental results indicate that a PET system can be developed using GAPD arrays and the GAPD-based PET system can provide high-quality PET imaging.

9 Reads
  • [Show abstract] [Hide abstract]
    ABSTRACT: There has been great interest in the development of combined PET/MR, a useful tool for both functional and anatomic imaging. We have developed a proof-of-principle MR compatible PET, employing a design concept that uses GAPD arrays as a PET photo-sensor and charge signal transmission method for human brain imaging. The purpose of this study was to design the 2nd version of brain PET with an extended axial field-of-view (FOV) and to evaluate its initial performance. The PET consisted of 18 detector blocks arranged in a ring of 390 mm diameter with 60 mm axial FOV. Each detector block was composed of a 4 × 4 matrix of detector module, each of which consisted of a 4 × 4 array L YSO coupled to a 4-side tileable 4 × 4 GAPD array. The PET gantry was shielded with gold-plated conductive fabric tapes with a thickness of 0.1 mm. PET signals were fed into the position decoder circuit (PDC) generating the digital address and analog pulse of the one interacted channel among the 256 output channels of the detector block, using a 4 m long flat cable. Commercial DAQ modules were used to digitize analog output signals of the PDCs and to store the data in list mode format. The flat cable was shielded with a mesh-type aluminum sheet, which had a thickness of 0.24 mm. All electronics were enclosed in an aluminum box, which had a thickness of 10 mm, located outside the MR bore. Average energy and timing resolutions of the developed PET measured outside the MR room were 18.1±3.2% (n=4,608) and 3.6 ns, respectively. The sensitivity and spatial resolution were 1.2% and 3.1 mm at the center of the field of view, respectively. No significant degradations of PET performance and the uniformity of MR image were observed. Simultaneous PET and MR images of hot-rod phantom and cat brain were successfully acquired. Experimental results indicate that the high performance compact and lightweight PET insert for hybrid PET-MRI can be developed using GAPD arrays and cha- ge signal transmission method.
    Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2012 IEEE; 01/2012
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Purpose: The aim of this study was to develop a prototype magnetic resonance (MR)-compatible positron emission tomography (PET) that can be inserted into a MR imager and that allows simultaneous PET and MR imaging of the human brain. This paper reports the initial results of the authors' prototype brain PET system operating within a 3-T magnetic resonance imaging (MRI) system using newly developed Geiger-mode avalanche photodiode (GAPD)-based PET detectors, long flexible flat cables, position decoder circuit with high multiplexing ratio, and digital signal processing with field programmable gate array-based analog to digital converter boards. Methods: A brain PET with 72 detector modules arranged in a ring was constructed and mounted in a 3-T MRI. Each PET module was composed of cerium-doped lutetium yttrium orthosilicate (LYSO) crystals coupled to a tileable GAPD. The GAPD output charge signals were transferred to preamplifiers using 3 m long flat cables. The LYSO and GAPD were located inside the MR bore and all electronics were positioned outside the MR bore. The PET detector performance was investigated both outside and inside the MRI, and MR image quality was evaluated with and without the PET system. Results: The performance of the PET detector when operated inside the MRI during MR image acquisition showed no significant change in energy resolution and count rates, except for a slight degradation in timing resolution with an increase from 4.2 to 4.6 ns. Simultaneous PET/MR images of a hot-rod and Hoffman brain phantom were acquired in a 3-T MRI. Rods down to a diameter of 3.5 mm were resolved in the hot-rod PET image. The activity distribution patterns between the white and gray matter in the Hoffman brain phantom were well imaged. The hot-rod and Hoffman brain phantoms on the simultaneously acquired MR images obtained with standard sequences were observed without any noticeable artifacts, although MR image quality requires some improvement. Conclusions: These results demonstrate that the simultaneous acquisition of PET and MR images is feasible using the MR insertable PET developed in this study.
    Medical Physics 04/2013; 40(4):042503. DOI:10.1118/1.4793754 · 2.64 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Adapting acquisition electronics to new detector designs has often led to complications and compromises. As we developed depth-of-interaction detector designs based on both discrete crystal arrays (dMiCE) and monolithic crystals (cMiCE) concepts, we found that our previous electronics design was inadequate to the task and launched a design effort we have termed our Phase II electronics. The system is based on a basic card design (the Phase II board) that has a large field programmable gate array (FPGA) with sufficient static RAM to support a variety of pulse processing algorithms our group has developed–including timing estimation, pulse integration with pileup correction, and statistical estimation of the event location in the detector. Here we report on the initial development and testing of the Phase II digital board as a basic building block for data acquisition systems.
    IEEE Transactions on Nuclear Science 02/2014; 61(1):79-87. DOI:10.1109/TNS.2013.2295037 · 1.28 Impact Factor
Show more

Similar Publications