The Korea Rare Isotope Accelerator, currently referred to as KoRIA, is briefly presented. The KoRIA facility is aimed to enable cutting-edge sciences in a wide range of fields. It consists of a 70 kW isotope separator on-line (ISOL) facility driven by a 70 MeV, 1 mA proton cyclotron and a 400 kW in-flight fragmentation (IFF) facility. The ISOL facility uses a superconducting (SC) linac for post-acceleration of rare isotopes up to about 18 MeV/u, while the SC linac of IFF facility is capable of accelerating uranium beams up to 200 MeV/u, 8 pμA and proton beams up to 600 MeV, 660 μA. Overall features of the KoRIA facility are presented with a focus on the accelerator design.

The aim of this study was to explore the spatial and energy resolutions of a PET scanner that we have recently developed. The scanner, which consists of six detector modules with 1-layer LGSO crystals, has a hexagonal configuration with a faceto-face distance of 86.4 mm between two opposite PET modules; such properties facilitate the imaging of small animals. A 22Na point source was employed to estimate horizontal and vertical spatial resolutions. To assess the energy resolution, a uniform 18F cylindrical phantom was scanned. A software-based spectrum analysis of list-mode data was used to assign a local energy window centered on the photopeak position for every single crystal. For the image reconstruction, an ML-EM algorithm was used. The spatial resolutions at the center of the scanner were 0.99 mm in the horizontal direction and 1.13 mm in the vertical direction. The energy resolution averaged over each PMT ranged from 13.3%-14.3%, which gave an average value of 13.8%. These results show that this simple system is promising for small animal imaging with excellent spatial and energy resolutions.

In this paper, we report on the development of a scintillation-fiber detection method for close verification in hadron therapy. In order to achieve the position sensitivity required for precision measurement of closes, a detector composed of 1-mm-thick scintillation fibers and a multi-channel photodiode was constructed and tested with 45-MeV proton beams provided by the MC50 proton cyclotron at the Korea Institute of Radiological and Medical Science (KIRAMS). The results of the beam test showed that the spatial resolution of the data determined by using the standard deviation sigma was similar to 1.0 mm, which is sufficiently accurate to verify beam-induced doses in hadron therapy. Furthermore, the quantitative accuracy appearing in the data is on the order of similar to 1%. We expect the detector composed of scintillation fibers and operating in the charge-integration mode to allow us to perform quality measurement of doses in various hadron therapies.

PET detectors with depth-of-interaction (DOI) encoding capability allow high spatial resolution and high sensitivity to be achieved simultaneously. To obtain DOI information from a mono-layer array of scintillation crystals using a single-ended readout, the authors devised a method based on light spreading within a crystal array and performed Monte Carlo simulations with individual scintillation photon tracking to prove the concept. A scintillation crystal array model was constructed using a grid method. Conventional grids are constructed using comb-shaped reflector strips with rectangular teeth to isolate scintillation crystals optically. However, the authors propose the use of triangularly shaped teeth, such that scintillation photons spread only in the x-direction in the upper halves of crystals and in the y-direction in lower halves. DOI positions can be estimated by considering the extent of two-dimensional light dispersion, which can be determined from the multiple anode outputs of a position-sensitive PMT placed under the crystal array. In the main simulation, a crystal block consisting of a 29 × 29 array of 1.5 mm × 1.5 mm × 20 mm crystals and a multi-anode PMT with 16 × 16 pixels were used. The effects of crystal size and non-uniform PMT output gain were also explored by simulation. The DOI resolution estimated for 1.5 × 1.5 × 20 mm3 crystals was 2.16 mm on average. Although the flood map was depth dependent, each crystal was well identified at all depths when a corner of the crystal array was irradiated with 511 keV gamma rays (peak-to-valley ratio ∼9:1). DOI resolution was better than 3 mm up to a crystal length of 28 mm with a 1.5 × 1.5 mm2 or 2.0 × 2.0 mm2 crystal surface area. The devised light-sharing method allowed excellent DOI resolutions to be obtained without the use of dual-ended readout or multiple crystal arrays.

In order to build an animal PET system with high sensitivity and resolution, we propose a four-layer PET system which provides the DOI (depth of interaction) information. Each crystal layer has a relative offset of half the crystal pitch with each other and uses an identical type of crystals simplifying readout electronics. The proposed system PET system consists of four LYSO (Lu18Y0.2SiO5:Ce) or L0.9GSO (Lu1.8Gd0.2 Si0.4:Ce) crystal layers with a crystal dimension of 1.5times1.5times5.0 mm3. The animal PET system has a diameter of 84 mm with one Hamamatsu H9500 flat panel PMT ring, and can be upgraded to two PMT ring configuration. An estimated efficiency using GATE simulation is ~15% at the center of one detector ring system. We present flood images obtained with a 22Na radiation source to verify the concepts of the proposed system, and obtained promising results.

353 Objectives PET detectors with DOI encoding capability allow the simultaneous achievement of high spatial resolution and sensitivity. To measure the DOI information in a monolayer of pixelated crystals with single-ended readout, we propose a new light-spreading method within the crystal block. Methods A crystal block is constructed using a grid method in which the crystals are placed within the grid. In the conventional grid method, the grid is made of comb-shaped reflector strips that have rectangular teeth to optically isolate the crystals. In this study, the shape of the teeth was changed into a triangle so that the scintillation photons would spread only in the x-direction in the upper-half of the crystal and in the y-direction in the lower-half. The DOI position was estimated by considering the degree of 2-dimensional light dispersion that was calculated from the multiple anode outputs of the position-sensitive PMT. Monte Carlo simulations with individual photon tracking were performed for the proof-of-concept. The crystal block consisted of a 29x29 array of crystals, 1.5x1.5x20mm3 in size, and a multi-anode PMT in which 16x16 or 8x8 pixels were assumed. Results The DOI resolutions estimated by the simulation were 1.5 and 2.0 mm for the PMTs with 16x16 and 8x8 anodes, respectively. Although the flood map was depth-dependent, each crystal was well-identified at all depths when the 511 keV gamma rays were irradiated at 5 positions with a 4 mm interval. Conclusions Using the newly developed light-sharing method, we obtained excellent DOI and spatial resolutions without any incorporation of dual-ended readout or multiple crystal layers.

Photon detecting Geiger-mode solid-state devices are being actively researched and developed because, unlike photo- multiplier tubes (PMT), they can be used in high-magnetic-field and radio-frequency environments, such as in magnetic resonance imaging (MRI) scanners. In addition, some Geiger-mode solid-state devices have higher photon detection efficiencies than PMTs and higher gains than avalanche photo-diodes (APD). We tested Geiger-mode solid-state photomultipliers (SSPM) inside a 3 T MRI to study the possibility of using them in combined PET/MRI scanners. Approximately 16% energy resolutions and ~1.3 ns coincidence time resolutions with 22 Na and lutetium yttrium oxyorthosilicate (LYSO) were obtained for full-width at half maximum (FWHM) for T1, T2, and gradient echo T2* MRI pulse sequences with little MR image degradation. The study shows that SSPMs have excellent potential for use in combined PET/MRI scanners.

In the management of colo-retal and anal cancer, accurate staging, treatment evaluation, early detection of recurrence are main clinical problems. F-18 FDG PET (PET/CT) has been reported as useful in the management of colo-rectal and anal cancer because that PET has high diagnostic performance comparing to conventional studies. In case of liver metastases, for confirmation of no extrahepatic metastases, in case of high risk of metastasis, for avoiding unnecessary operation, PET (PET/CT) is expected more useful. In anal cancer, PET is expected useful in lymph node staging. For the early prediction of chemotherapy or radiation therapy effect PET has been reported as useful, also. In early detection of recurrence by PET, cost-benefit advantages has been suggested, also. PET/CT is expected to have higher diagnostic performance than PET alone.

Improved spatial resolution without sacrificing sensitivity is one of the most challenging developmental goals for small animal PET scanners. The 3-layer configuration that we propose here utilizes relative offsets of half a crystal pitch in x- and y-directions, and pulse shape discrimination to obtain depth of interaction (DOI). Three layers of crystals with a dimension 1.5 x 1.5 x 7.0 mm(3) were composed of a L-0.2 GSO (Lu-0.4 Gd-1.6 SiO4: Ce) crystal layer and a L-0.9 GSO (Lu-1.8 Gd-0.2 SiO4: Ce) crystal layer aligned with each other, and a L-0.9 GSO crystal layer offset at half a crystal pitch in x- and y-directions. The L-0.9 GSO crystal layer was attached to a Hamamatsu H9500 flat-panel PMT. The devised small animal PET scanner has a diameter of 84 mm with one detector ring, and can be upgraded to two detector rings. GEANT4 Monte-Carlo simulation was used to estimate sensitivities of similar to 12 % and similar to 20 %, respectively, at the center of one and two PMT ring system with an energy window of 350 similar to 750 keV. We present flood images with peak-to-valley ratios of about 5-6 obtained using Na-22 and layer identification capability of similar to 99 % with pulse shape analysis, and verified the basic concepts of multi-layer small animal PET.

1824 Objectives: Improving the spatial resolution without sacrificing the sensitivity is one of the most challenging goals for small animal PET scanners. The 3-layer configuration that we propose consists of 7 mm long L0.2GSO and 7 mm long L0.9GSO crystals aligned with each other, and 7 mm long L0.9GSO crystals with an offset of a half crystal pitch. This presentation describes the design and the Monte-Carlo simulation, along with test results. Methods: The 3-layer configuration proposes to distinguish signals of outer L0.9GSO from those of L0.2GSO using the different timing characteristics and signals of inner L0.9GSO from those of outer L0.9GSO using the charge-division algorithm. The cross section area 1.5 × 1.5 mm2 of all the crystals is chosen to obtain a ~3 mm3 volume resolution at the center of the scanner. The proposed system consists of 6 Hamamatsu H9500 PMTs and about 16000 crystals. To estimate the improvement of the spatial resolution and the sensitivity, we used GEANT4 to compare the 3-layer configuration with the 2-layer configuration of L0.9GSO and L0.2GSO. Matrix structures made of 3M multilayer polymer were built to provide wrapping and support of crystals. We also built a charge-division circuit to be used with Hamamatsu H9500 PMTs. Results: The Monte-Carlo simulation showed a volume resolution to be ~3 mm3 at the center and ~5 mm3 at a 25 mm distance from the central axis with an average sensitivity of ~6 % within the axial direction of |z|

Solid-state devices to detect photons are under active research and development because they, unlike photomultiplier tubes (PMT), can be used under high-magnetic-field and radio-frequency environments, such as in magnetic resonance imaging (MRI) scanners. In addition, some of the solid-state devices have a higher particle detection efficiency and only a slightly less gain than PMTs, currently the first choice to detect photons in positron emission tomography (PET) scanners. We have tested solid-state photomultipliers (SSPM) among several different solid-state devices in the market. This paper describes the test methods and the characteristics of SSPMS with an emphasis on use in PET scanners. We obtained a 25 % energy resolution and a 4.5-ns time resolution with 22 Na and lutetium yttrium oxyorthosilicate (LYSO), both full-width at half maximum (FWHM). The number of fired mini-cells and the amplification factor were, respectively, estimated to be 154 +/- 37 for Na-22 and (3.8 +/- 0.9) x 10(5). Even though SSPM-LYSO couplings resulted in worse performances than PMT-LYSO couplings, the solid-state devices have good potential for use in the PET scanners, especially in combined PET/MRI scanners because the new solid-state devices appear to have better characteristics, such as a higher quantum efficiency and a larger number of mini-cells, than the tested SSPMs.