-
Key Jo Hong,
Yong Choi,
Jin Ho Jung,
Jihoon Kang,
Wei Hu,
Hyun Keong Lim, Yoonsuk Huh,
Sangsu Kim,
Ji Woong Jung,
Kyu Bom Kim,
Myung Sung Song,
Hyun-Wook Park
[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. · 2.83 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: 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.
Medical Physics 03/2012; 39(3):1227-33. · 2.83 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Positron emission tomography (PET) employing Geiger-mode avalanche photodiodes (GAPDs) and charge signal transmission approach was developed for small animal imaging. Animal PET contained 16 LYSO and GAPD detector modules that were arranged in a 70 mm diameter ring with an axial field of view of 13 mm. The GAPDs charge output signals were transmitted to a preamplifier located remotely using 300 cm flexible flat cables. The position decoder circuits (PDCs) were used to multiplex the PET signals from 256 to 4 channels. The outputs of the PDCs were digitized and further-processed in the data acquisition unit. The cross-compatibilities of the PET detectors and MRI were assessed outside and inside the MRI. Experimental studies of the developed full ring PET were performed to examine the spatial resolution and sensitivity. Phantom and mouse images were acquired to examine the imaging performance. The mean energy and time resolution of the PET detector were 17.6% and 1.5 ns, respectively. No obvious degradation on PET and MRI was observed during simultaneous PET-MRI data acquisition. The measured spatial resolution and sensitivity at the CFOV were 2.8 mm and 0.7%, respectively. In addition, a 3 mm diameter line source was clearly resolved in the hot-sphere phantom images. The reconstructed transaxial PET images of the mouse brain and tumor displaying the glucose metabolism patterns were imaged well. These results demonstrate GAPD and the charge signal transmission approach can allow the development of high performance small animal PET with improved MR compatibility.
Journal of Instrumentation 08/2011; 6(08):P08012. · 1.87 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The use of a dual-ended readout PET detector module based on Geiger-mode avalanche photodiodes (GAPDs) with large-area microcells was proposed to obtain high photon detection efficiency (PDE) and overcome energy non-linearity problems. A simulation study was performed and experimental measurement were taken for the single- and dual-ended PET detector modules consisting of the two types of GAPDs with 50 × 50 μm2 and 100 × 100 μm2 microcells. A Monte Carlo simulation was conducted to predict the number of incident photons impinging on the GAPD entrance surface to estimate the light collection efficiency (LCE) and energy linearity performance. A depth of interaction (DOI) ratio histogram was also obtained. An experimental study was performed to acquire the spectra of different energy γ-rays, and the energy linearity was evaluated by analyzing the photo-peak channels. The simulation results showed that the LCE and energy linearity of the dual-ended PET detector modules were considerably improved compared to the single-ended one, with 100 × 100 μm2 microcell GAPDs. We also estimated that the proposed method can provide accurate (3–4 mm) and uniform DOI resolution. In the experimental measurement, the 511 keV photo-peak channels of the dual-ended PET detector modules were increased 26% and 71% compared to the single-ended one, with 50 × 50 μm2 and 100 × 100 μm2 microcell GAPDs, respectively. The coefficients of determination (R2) were increased from 0.97 to 0.99 and from 0.86 to 0.93 with 50 × 50 μm2 and 100 × 100 μm2 microcell GAPDs, respectively. The results of this study demonstrate that the dual-ended readout scheme using GAPDs with large-area microcells provides high LCE and DOI information with minimized energy non-linearity. This will enable investigators to configure PET detector modules with high sensitivity and resolution.
Journal of Instrumentation 07/2011; 6(07):P07003. · 1.87 Impact Factor
-
Jihoon Kang,
Yong Choi,
Key Jo Hong,
Wei Hu,
Hyun Keong Lim, Yoonsuk Huh,
Sangsu Kim,
Kyu Bom Kim,
Ji Woong Jung,
Byung-Tae Kim,
Ji Yeon Hwang,
Yong Hyun Chung
[show abstract]
[hide abstract]
ABSTRACT: Light sharing PET detector configuration coupled with thick light guide and Geiger-mode avalanche photodiode (GAPD) with large-area microcells was proposed to overcome the energy non-linearity problem and to obtain high light collection efficiency (LCE). Theoretical evaluations were performed for 90 types of PET detector modules. A Monte Carlo simulation was conducted for the three types of LSO block, 4×4 array of 3×3×20 mm<sup>3</sup>, 6×6 array of 2×2×20 mm<sup>3</sup>, and 12×12 array of 1×1×20 mm<sup>3</sup> discrete crystals, to investigate the scintillation light distribution after conversion of the γ-rays in LSO. The incident photons were read out by three types of 4×4 array photo-sensors, which were PSPMT of 25% quantum efficiency (QE), GAPD1 with 50×50 μm<sup>2</sup> microcells of 30% photon detection efficiency (PDE) and GAPD2 with 100×100 μm<sup>2</sup> of 45% PDE. The number of counted photons in each photo-sensor was analytically calculated. The LCE, linearity and flood histogram were examined for each PET detector module as a function of light guide thickness ranging from 1 to 10 mm. The performance of PET detector modules based on GAPDs was significantly improved by using the thick light guide. The LCE was increased from 24 to 30% and from 14 to 41%, and the linearity was also improved from 0.96 to 0.99, from 0.78 to 0.99, for GAPD1 and GAPD2, respectively. In the contrary, the performance was not changed for PSPMT based detector. The flood histogram of 12×12 array PET detector modules using 3 mm light guide coupled with GAPDs was obtained by simulation, and all crystals of 1×1×20 mm<sup>3</sup> size was clearly identified. PET detector module coupled with thick light guide and GAPD array with large-area microcells was proposed to obtain high QE and high spatial resolution, and its feasibility was verified. It-
-
demonstrates GAPDs could be a competitive and cost-effective photo-sensor respect to the high QE (~40%) PMT.
Nuclear Science Symposium Conference Record (NSS/MIC), 2010 IEEE; 12/2010
-
[show abstract]
[hide abstract]
ABSTRACT: A dual-ended readout PET detector module based on Geiger-mode avalanche photodiode (GAPD) with large-area microcells was proposed to obtain high photon detection efficiency (PDE) and to overcome the energy non-linearity problem. Theoretical analysis and experimental measurement were performed for the single- and dual-ended PET detector modules which were consisted of the two types of GAPDs with 50×50 μm<sup>2</sup> and 100×100 μm<sup>2</sup> microcell sizes. A Monte Carlo simulation was conducted to predict the number of incident photons impinging on the GAPD entrance surface to estimate the light collection efficiency (LCE) and linearity performance. Also, the depth of interaction (DOI) ratio histogram was obtained. Experimental study was performed to acquire the energy spectra of different γ-rays, and the linearity was evaluated by analyzing the photo-peak channels. The simulation results showed the LCE of dual-ended PET detector modules were improved 9% and 55% comparing to the single-ended one, with 50×50 μm<sup>2</sup> and 100×100 μm<sup>2</sup> microcells GAPDs, respectively. Also, it was estimated that the proposed method can provide excellent (3-4 mm) and uniform DOI resolution. In the experimental measurement, the 511 keV photo-peak channels of dual-ended PET detector modules was increased 26% and 71% comparing to the single-ended one, with 50×50 μm<sup>2</sup> and 100×100 μm<sup>2</sup> microcells GAPDs, respectively. The coefficient of determination (R<sup>2</sup>) was improved from 0.86 to 0.93 with 100×100 μm<sup>2</sup> microcells GAPD. The similar improvement in photo-peak channel and linearity was observed in the simulation results. It demonstrated that the dual-ended PET detector configuration could considerably improve the non-linearity properties of GAPD without modification of microcell size and, hence, such configuration could -
-
provide high LCE, as well as DOI capabilities, for high PET detector performance.
Nuclear Science Symposium Conference Record (NSS/MIC), 2010 IEEE; 12/2010
