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Background Recently, there has been an increase in the number of reports of needle tract seeding (NTS) of tumor cells after a biopsy as one of the adverse events related to endoscopic ultrasonography-guided fine needle aspiration (EUS-FNA). In most of the previously reported cases of NTS in pancreatic cancer, distal pancreatectomy was performed as the initial surgery, following which metachronous metastasis was discovered in the gastric wall, whose localization matched the puncture route of the EUS-FNA. We report a case of early metastasis from pancreatic cancer in the gastric wall, which was postulated to be caused by NTS. Our patient underwent a total pancreatectomy (TP), and the NTS was resected synchronously. Case presentation A 70-year-old woman with a diagnosis of pancreatic head-body-tail cancer presented to our department for surgery. Transgastric EUS-FNA and biopsy established the histological diagnosis in her case. We administered neoadjuvant chemotherapy (NAC) to the patient and performed a TP. Histopathological and immunohistochemical examination subsequently confirmed the diagnosis of pT3N1aM1 pancreatic adenocarcinoma and its gastric metastasis, which was caused by NTS. It is postulated that the tumor cells of NTS had progressed to develop the metastatic lesion in the gastric wall during the NAC period. This was also resected during the initial surgery. The patient developed an early postoperative recurrence in the peritoneum 8 months after the surgery. Conclusion In pancreatic head cancer cases, the puncture route is often included in the resection area of radical surgery, and NTS is seldom considered as a potential clinical problem. However, NTS can progress rapidly and may be associated with early recurrence of malignancy. Therefore, when transgastrointestinal puncture is performed for the diagnosis of pancreatic cancer, the treatment strategy should be established considering the potential development of NTS.

Rice is susceptible to abiotic stresses such as drought stress. To enhance drought resistance, elucidating the mechanisms by which rice plants adapt to intermittent drought stress that may occur in the field is an important requirement. Roots are directly exposed to changes in the soil water condition, and their responses to these environmental changes are driven by photosynthates. To visualize the distribution of photosynthates in the root system of rice plants under drought stress and recovery from drought stress, we combined X-ray computed tomography (CT) with open type positron emission tomography (OpenPET) and positron-emitting tracer imaging system (PETIS) with 11C tracer. The short half-life of 11C (20.39 min) allowed us to perform multiple experiments using the same plant, and thus photosynthate translocation was visualized as the same plant was subjected to drought stress and then re-irrigation for recovery. The results revealed that when soil is drier, 11C-photosynthates mainly translocated to the seminal roots, likely to promote elongation of the root with the aim of accessing water stored in the lower soil layers. The photosynthates translocation to seminal roots immediately stopped after rewatering then increased significantly in crown roots. We suggest that when rice plant experiencing drought is re-irrigated from the bottom of pot, the destination of 11C-photosynthates translocation immediately switches from seminal root to crown roots. We reveal that rice roots are responsive to changes in soil water conditions and that rice plants differentially adapts the dynamics of photosynthates translocation to crown roots and seminal roots depending on soil conditions.

We developed a human-scale single-ring OpenPET (SROP) system, which had an open space allowing us access to the subject during measurement. The SROP system consisted of 160 4-layer depth-of-interaction detectors. The open space with the axial width of 430 mm was achieved with the ring axial width of 214 mm and the ring inner diameter of 660 mm. The detectors were axially shifted to each other so that the detector ring was aligned along a plane horizontally tilted by 45° against the axial direction. The system was developed as a mobile scanner to be used not only in clinical positron emission tomography (PET) rooms but also in charged-particle therapy treatment rooms as well as animal experiment rooms. Almost uniform spatial resolution better than 3 mm throughout the entire field of view (FOV) was realized with an iterative image reconstruction method. Peak absolute sensitivity was 3.1%, and there was a region with sensitivity better than 0.8% for a length of more than 700 mm. An in-beam imaging experiment conducted at the heavy ion medical accelerator in Chiba showed that the system was operable even at the highest beam intensity available for heavy-ion therapy. In addition, we conducted entire-body monkey dynamic imaging utilizing the long region inside the gantry by positioning a monkey along the direction having the longest FOV tilted by 45° against the axial direction. We concluded the developed system has a capability to realize versatile PET applications by utilizing its wide-open space and mobility in addition to high spatial resolution with sufficiently good sensitivity. -9mm]Please consider rephrasing the sentence “We concluded the developed system” for clarity.

Makoto Kobayashi, Eiji Yoshida, Takuro Kyuno, Ryoko Kawagishi, Kei Sato, Tsuyoshi Kono, Takehiro Chiba, Hitoshi Yonezawa, Osamu Funato, Akinori Takagane Department of Surgery, Hakodate Goryoukaku Hospital, Hakodate City, Hokkaido, 040-8611, JapanCorrespondence: Makoto KobayashiDepartment of Surgery, Hakodate Goryoukaku Hospital, 38-3 Goryoukaku-cho, Hakodate City, Hokkaido, 040-8611, JapanTel +81-138-51-2295Fax +81-138-56-2696Email koba86gg@gmail.comPurpose: Faster surgery has been associated with better outcomes. In the present study, we aimed to determine whether surgical duration affected overall survival (OS) in patients undergoing esophagectomy. Additionally, we assessed factors that influence surgical duration.Patients and Methods: This single-center retrospective cohort study included 128 patients who underwent Ivor-Lewis esophagectomy by a single surgeon between 2005 and 2019. The Cox proportional hazard model was used to evaluate the association of OS with the following variables: surgical duration, neo-adjuvant chemotherapy, pathological grade of depth of tumor invasion, lymph node (LN) metastasis, body mass index (BMI), and cervical LN dissection. Additionally, factors associated with prolonged surgical duration were examined by logistic regression analysis.Results: Based on the multivariate analysis, surgical duration was not associated with OS [hazard ratio (HR), 1.065; 95% confidence interval (CI), 0.586– 1.937; P = 0.837]. On the other hand, tumor invasion (HR, 2.901; 95% CI, 1.483– 5.674; P = 0.002) and LN metastasis (HR, 2.338 2.403; 95% CI, 1.237– 4.420 1.257– 4.593; P = 0.009 0.008) significantly influenced OS. The assessment of variables affecting surgical duration showed that BMI had a significant effect on surgical duration (odds ratio, 2.790; 95% CI, 1.254– 6.204, P = 0.012).Conclusion: According to the analysis of patients who underwent the same surgical approach by a single surgeon, surgical duration of esophagectomy for esophageal cancer was significantly influenced by BMI; however, surgical duration had no impact on patient survival.Keywords: esophagectomy, Ivor-Lewis approach, depth of tumor invasion, lymph node metastasis, body mass index, overall survival

Using time-of-flight (TOF) information in image reconstruction improves image signal-to-noise ratio and quantitative accuracy in positron emission tomography (PET). A new TOF-PET detector module with a 3.2 mm pitch lutetium fine silicate (LFS) scintillator array one-to-one coupled to a 16×16 (256-ch) silicon photomultiplier (SiPM) array was made commercially available (C13500 series, Hamamatsu Photonics K.K.). In this study, as a candidate detector module for the next generation brain-dedicated PET, we changed the scintillator length of 20 mm to 10 mm according to our helmet-type PET geometry and investigated the basic performance of the PET detector module, including its energy resolution, sensitivity, coincidence response function (CRF) and coincidence timing resolution (CTR). All performance values were compared with those of the 4.2 mm pitch 144-ch detector module which was selected for our current helmet-type PET prototype. The energy resolution was 12% at 511 keV. The sensitivity was about 10% lower compared with those of the 4.2 mm pitch module. The average full width at half maximum (FWHM) of the CRFs was 1.9 mm. The CTRs had values of 235–241 ps with various energy windows after applying timing calibration. The CTR was not significantly changed (

To improve positron emission tomography (PET) image quality, depth-of-interaction (DOI) information and time-of-flight (TOF) information are key technologies. In this work, we developed the DOI-TOF detector based on our original single-ended readout scheme with the continuous layered gadolinium fine aluminum garnet (GFAG) array. The size of each GFAG crystal is $1.45\times 1.45\times 20$ mm3. The multipixel photon counter (MPPC) used as a photo sensor has a surface area of $3.0\times 3.0$ mm2. One pair of crystals coupled with a partial optical window is arranged across two MPPCs. Boundaries without the partial optical window are covered with optical reflectors. Each pair is coupled with paired MPPCs of different patterns. Crystal identification is obtained from paired MPPCs of different patterns and output rates. By limiting the spread of scintillation light, the proposed DOI detector based on the local centroid calculation was expected to improve crystal response, including the edge. For performance comparison, we prepared three discrete layers of the GFAG array with the same total thickness. For the continuous layer, the DOI resolution, the energy resolution and the timing resolution of the pair of detectors are 4.7 mm, 14%, and 402 ps, respectively. Their respective values are 29%, 20%, and 33% better than those with the three discrete layers.

A synthetic route to ecteinascidin 743 has been established via an intramolecular cascade Heck reaction to construct the diazabicyclo[3.3.1]nonane skeleton while controlling the two contiguous stereogenic centers. The strategically formed five-membered ring was oxidatively cleaved to generate a dialdehyde intermediate, from which the B ring of ecteinascidin 743 was constructed.

Background In pancreatic cancer surgery, accurate identification and resection of intrapancreatic residual tumors are quite difficult. We have developed a novel open-typed PET system (called 'OpenPET'), which enables high-resolution PET-guided surgery in real time, and demonstrated that OpenPET-guided surgery with intraperitoneally administered 64Cu-labeled anti-epidermal growth factor receptor antibody cetuximab is useful to detect and resect primary pancreatic cancer. Here, we investigated applicability of OpenPET-guided surgery for unexpected residual intrapancreatic tumors and examined its survival benefit over conventional surgery. Methods A mouse model with large (>1 cm) resectable pancreatic cancer of xPA-1-DC cells expressing red fluorescent protein was used. OpenPET-guided surgery was conducted 24 h after intraperitoneal administration of 64Cu-labeled cetuximab (7.4 MBq/mouse). For comparison, similar surgical procedures were conducted, and conventional tumor resection was attempted using only the naked eye (control). Survival rate after OpenPET-guided surgery was compared to that after control operations. Results Intraoperative OpenPET guidance enabled detection and resection of small residual tumors. Ten residual tumor specimens (3-10 mm in diameter) were intraoperatively isolated with OpenPET guidance (n = 7 mice). All isolated specimens showed tumor RFP signals. No resection of tumor tissue was performed in control group because the tumor could not be clearly detected with the naked eye alone. Mice after OpenPET-guided surgery showed significantly longer survival rates than those in control group. Conclusions OpenPET-guided surgery with 64Cu-labeled-cetuximab enabled intraoperative identification and resection of intrapancreatic small residual tumors. This technology could be useful to prevent tumor residuals during surgery and improve pancreatic cancer survival.

In pancreatic cancer surgery, accurate identification and resection of intrapancreatic residual tumors are quite difficult. We have developed a novel open-typed PET system (called 'OpenPET'), which enables high-resolution PET-guided surgery in real time, and demonstrated that OpenPET-guided surgery with intraperitoneally administered 64Cu-labeled anti-epidermal growth factor receptor antibody cetuximab is useful to detect and resect primary pancreatic cancer. Here, we investigated applicability of OpenPET-guided surgery for unexpected residual intrapancreatic tumors and examined its survival benefit over conventional surgery.

多様な核医学用シンチレータについて、ごく簡単に概説した。

[Objectives] A PET system can be more efficient in terms of size and cost when it is designed as an organ-dedicated or application-specific system. Considering the potential need for brain PET, we proposed the concept of a hemispherical detector arrangement, which enables higher sensitivity with fewer number of detectors than a conventional cylindrical geometry has. A laboratory benchtop prototype has been evolved into a complete brain PET system, which has been commercialized in Japan under the product name of VrainTM. In this work, we characterize the system and carry out its first human imaging tests. [Methods] The VrainTM has 54 detectors. A hemispherical part is formed by 45 detectors and the other 9 detectors are located at the backside of the neck. Each detector is a one-to-one combination of lutetium-based scintillators (crystal element size: 4.1×4.1×10 mm3) and silicon photomultipliers (SiPMs) (active area size: 4×4 mm2). The inner diameter of the bottom detector ring is 279 mm. The crystal thickness is optimized by simulation to reduce the parallax error and to improve the TOF performance. The energy window is also optimized to 450–590 keV to get better image quality. We evaluated the physical performance of the VrainTM according to the NEMA NU 2-2018 standards. Some measurements were added and others were modified to suit the hemispherical detector arrangement. Finally, we carried out the first healthy volunteer imaging. 18F-FDG of 3.7 MBq/kg was intravenously injected to a male subject (42 years old). The PET measurement duration was 10 min starting at 45 min after injection. PET images were reconstructed using the OSEM with 4 iterations and 8 subsets. A Gaussian filter of 4 mm FWHM was applied to PET images. CT images, which were obtained by another PET/CT scanner, were used for attenuation and scatter corrections. [Results] The 2.2 mm rods of a small rod phantom were resolved. The TOF resolution at the peak noise-equivalent count ratio (NECR) (9.8 kBq/mL) was 256 ps and the TOF gain in sensitivity was calculated as 5.2 (20 cm diameter / 3.8 cm localization accuracy). The effective sensitivity was 21.8 kcps/MBq and the effective peak NECR was 129 kcps at 9.8 kBq/mL. The sensitivity was higher at the upper position in the axial direction. For the brain-sized image quality phantom evaluation, the percent contrast of the 10 mm sphere was 48% with the percent background variability of 8.6%. For the human FDG PET imaging, the whole brain was successfully imaged without any artifacts. Gray and white matters were clearly visualized with a high contrast. [Conclusion] The helmet-type brain PET system VrainTM showed 2.2 mm spatial resolution, 256 ps TOF resolution, and excellent image quality. The brain FDG PET images of the healthy volunteer were high contrast and low noise. Further studies are warranted to assess the potential clinical impact of PET imaging with the VrainTM., SNMMI 2022 Annual Meeting

Background To confirm the performance of the first hemispherical positron emission tomography (PET) for the brain (Vrain) that we developed to visualise the small nuclei in the deep brain area, we compared 18F-fluorodeoxyglucose (FDG) brain images with whole-body PET images. Methods Ten healthy male volunteers (aged 22–45 years) underwent a representative clinical whole-body PET, followed by Vrain each for 10 min. These two scans were initiated 30 min and 45 min after FDG injection (4.1 ± 0.5 MBq/kg), respectively. First, we visually identified the small nuclei and then compared their standardised uptake values (SUVs) with the participants’ age. Next, the SUVs of each brain region, which were determined by applying a volume-of-interest template for anatomically normalised PET images, were compared between the brain images with the Vrain and those with the whole-body PET images. Results Small nuclei, such as the inferior colliculus, red nucleus, and substantia nigra, were more clearly visualised in Vrain than in whole-body PET. The anterior nucleus and dorsomedial nucleus in the thalamus and raphe nucleus in the brainstem were identified in Vrain but not in whole-body PET. The SUVs of the inferior colliculus and dentate gyrus in the cerebellum positively correlated with age (Spearman’s correlation coefficient r = 0.811, p = 0.004; r = 0.738, p = 0.015, respectively). The SUVs of Vrain were slightly higher in the mesial temporal and medial parietal lobes than those in whole-body PET. Conclusions This was the first time that the raphe nuclei, anterior nuclei, and dorsomedial nuclei were successfully visualised using the first hemispherical brain PET. Trial registration Japan Registry of Clinical Trials, jRCTs032210086, Registered 13 May 2021, https://jrct.niph.go.jp/latest-detail/jRCTs032210086.

Objective. For PET imaging systems, a smaller detector ring enables less intrinsic spatial resolution loss due to the photon non-collinearity effect as well as better balance between production cost and sensitivity, and a hemispherical detector arrangement is more appropriate for brain imaging than a conventional cylindrical arrangement. Therefore, we have developed a brain-dedicated PET system with a hemispherical detector arrangement, which has been commercialized in Japan under the product name of VRAINTM. In this study, we evaluated imaging performance of VRAIN. Approach. The VRAIN used 54 detectors to form the main hemispherical unit and an additional half-ring behind the neck. Each detector was composed of a 12 × 12 array of lutetium fine silicate crystals (4.1 × 4.1 × 10 mm3) and a 12 × 12 array of silicon photomultipliers (4 × 4 mm2 active area) with the one-to-one coupling. We evaluated the physical performance of VRAIN according to the NEMA NU 2–2018 standards. Some measurements were modified so as to fit the hemispherical geometry. In addition, we performed 18F-FDG imaging in a healthy volunteer. Main results. In the phantom study, the VRAIN showed high resolution for separating 2.2 mm rods, 229 ps TOF resolution and 19% scatter fraction. With the TOF gain for a 20 cm diameter object (an assumed head diameter), the peak noise-equivalent count rate was 144 kcps at 9.8 kBq ml−1 and the sensitivity was 25 kcps MBq−1. Overall, the VRAIN provided excellent image quality in phantom and human studies. In the human FDG images, small brain nuclei and gray matter structures were clearly visualized with high contrast and low noise. Significance. We demonstrated the excellent imaging performance of VRAIN, which supported the advantages of the hemispherical detector arrangement.

To improve positron emission tomography (PET) image quality, depth-of-interaction (DOI) information and timeof-flight (TOF) information are key technologies. In this work, we developed the DOI-TOF detector based on our original singleended readout scheme with the continuous layered gadolinium fine aluminum garnet (GFAG) array. The size of each GFAG crystal is 1.45×1.45×20 mm3. The multi-pixel photon counter (MPPC) used as a photo-sensor has a surface area of 3.0×3.0 mm2. One pair of crystals coupled with a partial optical window is arranged across two MPPCs. Boundaries without the partial optical window are covered with optical reflectors. Each pair is coupled with paired MPPCs of different patterns. Crystal identification is obtained from paired MPPCs of different patterns and output rates. By limiting the spread of scintillation light, the proposed DOI detector based on the local centroid calculation was expected to improve crystal response including the edge. For performance comparison, we prepared three discrete layers of the GFAG array with the same total thickness. For the continuous layer, the DOI resolution, the energy resolution and the timing resolution of the pair of detectors are 4.7 mm, 14% and 402 ps, respectively. Their respective values are 29%, 20% and 33% better than those with the three discrete layers.

PETを用いた小動物イメージングは創薬や病態解明研究に活用されている。一方で、全ての研究者にPETが十分に行き届いているとは言い難い。例えば、特定エリアでの管理が必要な遺伝子操作マウスのPET撮像、粒子線照射直後のラットのPET撮像、マウスやラットの全身薬物動態の観察、微小腫瘍内の不均一薬剤集積の可視化、限られたスペースへの小動物用PET装置の導入、といった様々なアンメットニーズが存在する。このような多様な研究ニーズに応えるべく、サブミリ分解能を有する多目的用途のポータブル小型PET装置を開発した。 独自に開発した22 mm角のcrosshair light-sharing (CLS) 検出器（1.45×1.45×15 mm3のGFAGシンチレータ14×14アレイと3×3 mm2の半導体光センサSiPM 8×8アレイを接合）を使用した。相互作用を起こした深さによって光の分配パターンに差がでるように反射材が組んであり、深さ方向の検出位置（DOI）を5 mm単位で識別できる。128個の検出器を用いて体軸方向視野207 mmの8リング装置を製作し、CLS-PETと名付けた（下図a）。ガントリやデータ収集機器は台車上に配置し、1人で移動できるポータブル仕様とした（重量約100 kg）。撮像場所を選ばないよう、100V電源1つで動作する仕様とした。空間分解能評価として、22Na密封ロッドファントム（1 MBq）の30分撮像を行った。小動物全身撮像の実証として、健常ラットに18F-NaF（37 MBq）を投与し、60分後より60分撮像を行った。ファントムでは0.75 mmロッドが識別でき、サブミリ分解能を達成した（下図b）。ラットNaF PETでは、骨構造が明瞭に描出された全身画像を得た（下図c）。 サブミリ分解能を有する多目的ポータブル装置CLS-PETを開発した。PET室に縛られないポータブル装置のため様々なニーズに対応でき、新しいPET応用研究を開拓できる可能性がある。, 第16回日本分子イメージング学会総会・学術集会参加発表

[Purpose] We developed the world’s first helmet-type time-of-flight (TOF) PET, which had a hemispherical detector arrangement. The developed system is characterized as its high-performance and compactness as well as an unusual seat-type design which enables keeping the subject’s eye view wide. Here, we report the basic performance characteristics and the first FDG imaging results of healthy volunteers. [Methods] The helmet-type PET consisted of 54 detectors. The 45 detectors were arranged to form a hemisphere and the other 9 detectors were placed to form a half-ring behind the neck. The detector was composed of 12×12 lutetium fine silicate (LFS) scintillators (4×4×10 mm3) connected to a 12×12 silicon photomultiplier (SiPM) array with one-to-one coupling. The energy window was 450–590 keV and the coincidence time window was 3.6 ns. Image reconstruction was performed using 3D-OSEM with 4 iterations and 8 subsets. The performance was characterized based on the NEMA NU2 standards. The coincidence timing resolution was measured using a 22Na point source. 18F-FDG PET and MRI were performed for 11 normal control subjects. The PET data were measured for 10 minutes starting at 45 minutes after injection of 285±23 MBq. [Results] The coincidence timing resolution was 235 ps. With the sensitivity gain of 5.7 (= 20-cm-diameter object / 3.5 cm TOF localization), the effective sensitivity was 24 cps/kBq and the effective noise-equivalent count ratio was 120 kcps@9 kBq/mL. The spatial resolution of the FBP image was 2.9 mm at the central position (1 cm offset) of the field-of-view. For the human FDG PET images, the gray matter was clearly visualized with a high contrast to the white matter. Small brain nuclei such as the substantia nigra, the red nucleus, and the superior colliculus were able to be identified. [Conclusion] We have successfully demonstrated first human imaging on the helmet-type PET., 第78回日本放射線技術学会総会学術大会

Methicillin-resistant Staphylococcus aureus (MRSA) is the leading cause of infection in hospitalized patients and can be prevalent in humans and various animal species. In European countries, MRSA isolates belonging to clonal complex 398 have been detected at high rates in pigs. However, the prevalence of MRSA in pigs and farm environments in Japan remains unclear. MRSA isolates were obtained from pigs in slaughterhouses, diseased pigs on farms, imported breeding pigs, and farm dust. We conducted whole-genome sequencing (WGS) and analyzed the molecular epidemiological relationship between these MRSA isolates using core genome multilocus sequence typing (cgMLST). The prevalence rates of MRSA among pigs in slaughterhouses, diseased pigs on farms, imported breeding pigs, and farm dust were 5.2 %, 3.4 %, 28.8 %, and 0.06 %, respectively. ST 398 isolates that classified as ST398/t034 were isolated from pigs from all sources. The results of cgMLST showed that ST398/t034 isolates originating from domestic pigs clustered into the same cluster as the isolates from imported breeding pigs. However, some clusters only included isolates of domestic pig origin. Most MRSA isolates in this study carried resistance genes for aminoglycosides, β-lactams, macrolides, tetracyclines, and zinc. None of the MRSA isolates in this study harbored Panton-Valentine leukocidin toxin genes. Molecular epidemiological analysis suggested a relationship between isolates from slaughter pigs and imported breeding pigs and the presence of MRSA isolates of domestic origin. However, more data are needed for elucidation of the origin of these MRSA variants in the pig industry in Japan.

In this article, we developed the novel single-end readout depth-of-interaction (DOI) detector with quadrisected crystals comparable in size to a single photo sensor. The proposed DOI detector consists of 784 gadolinium aluminum gallium garnet (GAGG) crystals, which are arranged in four layers of $14\times14$ arrays coupled with an $8\times8$ multipixel photon counter (MPPC) array. The size of each GAGG crystal is $1.45\times 1.45\times4.5$ mm3. Also, each MPPC has a surface area of $3.0\times3.0$ mm2. One pair of four-layered crystals coupled with a partial optical window is arranged across two MPPCs. Boundaries without the partial optical window are covered with optical reflectors. Light sharing is done between a pair of four-layered crystals optically coupled at one end. Each pair is coupled with paired silicon photomultipliers of different patterns. Crystal identification from each pair is obtained from the output rate of two MPPCs. From 511-keV uniform irradiation, responses of all crystal elements in the four layers can be separated clearly on a 2-D position histogram after applying the Anger calculation. Also, DOI information can be mapped to each cluster on curved lines. The energy resolution for all crystals is 9.1% after event reduction of intercrystal scatter.

—In this article, we developed the novel single-end readout depth-of-interaction (DOI) detector with quadrisected crystals comparable in size to a single photo sensor. The proposed DOI detector consists of 784 gadolinium aluminum gallium garnet (GAGG) crystals, which are arranged in four layers of 14 × 14 arrays coupled with an 8 × 8 multipixel photon counter (MPPC) array. The size of each GAGG crystal is 1.45 × 1.45 × 4.5 mm3. Also, each MPPC has a surface area of 3.0 × 3.0 mm2. One pair of four-layered crystals coupled with a partial optical window is arranged across two MPPCs. Boundaries without the partial optical window are covered with optical reflectors. Light sharing is done between a pair of four-layered crystals optically coupled at one end. Each pair is coupled with paired silicon photomultipliers of different patterns. Crystal identification from each pair is obtained from the output rate of two MPPCs. From 511-keV uniform irradiation, responses of all crystal elements in the four layers can be separated clearly on a 2-D position histogram after applying the Anger calculation. Also, DOI information can be mapped to each cluster on curved lines. The energy resolution for all crystals is 9.1% after event reduction of intercrystal scatter.

Pancreatic cancer (PC) has a poor prognosis owing to difficulties in the diagnosis of resectable PC at early stages. Several clinical studies have indicated that the detection and surgery of small resectable PC (64Cu-labeled anti-epidermal growth factor receptor antibody cetuximab was intraperitoneally administered into mice. It clearly identified PC tumors ≥3 mm. In contrast, neither OpenPET with intravenous-administered 64Cu-cetuximab nor intraperitoneal/intravenous-administered 18F-FDG (a traditional PET probe) could detect PC in this model. Immuno-OpenPET-guided surgery accurately resected small PC in mice and achieved significantly prolonged survival. This technology could provide a novel diagnostic and therapeutic strategy for small resectable PC to improve patient survival.

High-performance computing (HPC) cluster systems sometimes adopt a two-layered file system composed of local and global file systems to achieve both capacity and performance in storage. In such a cluster system, the input data of an application needs to be staged from the global storage into the local storage, and the output data needs to be staged from the local storage out to the global storage. This staging operation must be efficiently and quickly performed to gain higher job throughput because an inefficient staging operation prevents waiting job requests from being executed. In particular, in the case of the cluster system with the oversubscribed interconnect shared by the storage and the computing nodes, the inter-node communication and this staging operation traffic collides, which may degrade the job throughput. In this research, we focus on the traffic collision of the inter-node communication and the staging traffic to improve job throughput, targeting the cluster system with the oversubscribed interconnect where these two types of traffic flow. In other words, whether the dynamic control of the traffic flow derived from the staging operation leads to the improvement in the job throughput or not is investigated. For the investigation, we present a traffic collision avoidance method to dynamically configure a set of data paths for each type of the traffic only while the staging operation is conducted. The evaluation in this article shows that the proposed method avoids a traffic collision and accelerates the staging operation by 22.0% on our cluster system. Also, this evaluation indicates the overhead of the application incurred by the proposed method is negligible. Furthermore, 8.7% of the job execution time is reduced by the proposed method.

Noninvasive quantification of myocardial blood flow with PET is a vital tool for detecting and monitoring of coronary artery disease. However, current standard cylindrical PET scanners are not optimized for cardiac imaging because they are designed mainly for whole-body imaging. In this study, we proposed two compact geometries, the elliptical geometry and the D-shape geometry, for cardiac-dedicated PET systems. We then evaluated their performance compared with a whole-body-size cylindrical geometry by using the Geant4 Monte Carlo simulation toolkit. In the simulation, an elliptical water phantom was scanned for 10-sec, and we calculated the sensitivity and the noise-equivalent count rate (NECR). Subsequently, a digital chest phantom was scanned for 30-sec and the coincidence data were reconstructed by in-house image reconstruction software. We evaluated the image noise in the liver region and the contrast recoveries in the heart region. Even with the limited number of detectors, the proposed compact geometries showed higher sensitivity than the whole-body geometry. The D-shape geometry achieved 47% higher NECR and 44% lower image noise compared with the whole-body cylindrical geometry. However, the contrasts in the hot area obtained by the proposed compact geometries were not as good as that obtained by the whole-body cylindrical geometry. There was no considerable difference in image quality between the elliptical geometry and the D-shape geometry. In conclusion, the compact geometries we have proposed are promising designs for a high-sensitivity and low-cost cardiac-dedicated PET system. A further study using a defect phantom model is required to evaluate the contrast of cold areas.

Silicon photomultiplier (SiPM) based scintillation detectors are widely used for positron emission tomography (PET), but their application to Compton cameras should be further explored. Whole gamma imaging (WGI) is a combination of PET and a Compton camera realized by inserting a scatter detector ring into a PET ring. In a previous study, we developed a WGI prototype in which the scatter detector consists of Gd3Al2Ga3O12:Ce (GAGG) scintillators coupled with SiPM for a proof-of-concept. However, its Compton imaging performance was not as good as its PET imaging performance. In this paper, we developed a two-layer staggered GAGG scatter detector which was optimized for WGI. GAGG crystals 1.45×1.45×4.5 mm3 in size were arranged into a 13×13 array for the 1st layer and a 14×14 array for the 2nd layer with a staggered arrangement. The two-layer crystal block was optically coupled to an 8×8 SiPM array (3 mm pixel). Using radioactive sources with different energies, we investigated the energy resolution performance experimentally. Almost all crystals were clearly separated in the flood histogram at multiple energies. The developed detector showed energy resolutions of 7.7% to 8.5% at 511 keV, which was better than that of the detector of the current WGI prototype. The next generation WGI system was modeled in simulations using the obtained energy resolution data. The simulation results showed that the WGI with the developed detector had 1.2 times better sensitivity and better angular resolution in the peripheral region than the current WGI prototype.

我々が開発を進めているWGI(Whole Gamma Imaging)は、散乱検出器リングを吸収検出器リングへ挿入することでPETとコンプトンイメージングを融合した構造となっており、様々なガンマ線の利用を目指している。また、これまでに開発したWGI試作機は、コンプトンイメージング装置としては世界初のフルリング型ジオメトリを実現したものであった。ここで、コンプトン画像再構成の条件に着目すると、理論的にはフルリング型である必要性はなく、検出器を削減できれば設計の柔軟性向上や、コスト削減が期待できる。しかしながら、実際には散乱角度の検出限界やブロック型検出器の配置方法などの影響で、再構成条件は保証されていない。そこで、本研究では、WGI試作機の89Zr円柱ファントム測定データに対し、後処理によって検出器を制限し、909keVのコンプトン画像のアーチファクトを評価することで3次元画像再構成に必要なジオメトリ条件の検討を行った。その結果、散乱検出器、吸収検出器共に、測定対象上のすべての領域を180°以上囲うことが必要であると示唆された。, 第61回日本核医学会学術総会

膵がんは生存率が低く、有効な診断・治療法の開発が望まれる。我々はこれまでに、1 cm未満の早期膵がん同所移植モデルにおいて、64Cu標識抗EGFR抗体（セツキシマブ）腹腔投与を用いた高分解能開放型PET（OpenPET）ガイド手術により、早期膵がんを的確に検出し切除できることを報告してきた。本発表では、より浸潤の進んだ>1cmの膵がん同所移植モデルを作成しOpenPETガイド手術を実施し、術中残存膵がん切除における本法の有用性を検討した。【方法・結果】ヒト膵がんxPA-1-RFP細胞液をマウス膵臓に移植しモデルを作成した。64Cu-セツキシマブ（7.4 MBq）を腹腔投与し24h後リアルタイムOpenPETガイド手術を行った。本法より肉眼では検出できない約3mmの膵臓内微小残存膵がんを術中で明瞭に検出し摘出できた。また、OpenPETガイド手術は従来の肉眼による手術に比べ、生存を有意に延長した。【結論】本法は、腫瘍の術中残存を防ぎ、膵がんの生存率改善に寄与すると期待される。, 第61回日本核医学会学術総会

Purpose Early management is crucial for acute intestinal blood flow disorders; however, no published study has identified criteria for the time limit for blood flow resumption. This study specifically examines the time factors for avoiding intestinal resection. Methods The subjects of this retrospective cohort study were 125 consecutive patients who underwent emergency surgery for a confirmed diagnosis of intestinal strangulation (n = 86), incarceration (n = 27), or volvulus (n = 12), between January 2015 and March 2021. Intestinal resection was performed when intestinal irreversible changes had occurred even after ischemia was relieved surgically. We analyzed the relationship between the time from computed tomography (CT) imaging to the start of surgery (C-S time) and intestinal resection using the Kaplan–Meier method and calculated the estimated intestinal rescue rate. Patient background factors affecting intestinal resection were also examined. Results The time limit for achieving 80% intestinal rescue rate was 200 min in C-S time, and when this exceeded 300 min, the intestinal rescue rate dropped to less than 50%. Multivariate analysis identified the APACHE II score as a significant influencing factor. Conclusion A rapid transition from early diagnosis to early surgery is critical for patients with acute abdomen originating from intestinal blood flow disorders. The times from presentation at the hospital to surgery should be reduced further, especially for severe cases.

Breast-dedicated PET systems are categorized into two geometries: a ring-shaped detector arrangement and a dual flat-panel (FP) detector arrangement. Although there are some advantages in the FP arrangement, PET images are blurred due to the limited angular coverage. To compensate for this issue, we have proposed a dual round-edge (RE) detector arrangement, in which detectors at both edge positions are tilted toward the center of the field-of-view. In this study, for a proof-of-concept of the RE arrangement, we developed the first bench-top prototype. Our original crosshair light-sharing (CLS) depth-of-interaction (DOI) detector was used; it consisted of a 14×14 array of 1.45×1.45×15 mm3 GFAG scintillator crystals coupled with an 8×8 array of silicon photomultipliers each with a photosensitive area of 3.0×3.0 mm2. The data acquisition system was the TOFPET2 ASIC (PETsys Electronics). We examined the conventional FP arrangement and the proposed RE arrangement using 32 CLS detectors. A 22Na point source and a multi-rod phantom (rod diameters: 1.6, 2.2, 3.0, 4.0, 5.0 and 6.0 mm) were used for spatial resolution measurements. The RE arrangement showed better spatial resolution compared with the FP arrangement (64% improvement in the vertical direction). For the multi-rod phantom, in the coronal plane (parallel to the detector surface), the 1.6 mm rods were clearly resolved in both arrangements. However, in the axial plane (perpendicular to the detector surface), the RE arrangement resolved the 2.2 mm rods that had not been resolved by the FP arrangement. We demonstrated that the proposed RE detector arrangement showed better spatial resolution than the conventional FP arrangement., 2021 IEEE NSS/MIC

Once a high-resolution PET detector with both depth-of-interaction and time-of-flight capabilities is established, it will be applied to various-type PET systems using a software-based coincidence method. Toward this goal, we have developed a crosshair light-sharing (CLS) detector. In this work, as the first development of a practical system based on the CLS detector, we realized a high-resolution portable small animal PET with a long axial field-of-view (FOV) of 20 cm. The system was composed of 128 CLS detectors. All devices were mounted on a pushcart, and the system was operated on a 100V power supply. The axial FOV was 207 mm, which covered the total-body of a rat. A 22Na ultra-micro hot phantom was used for spatial resolution measurement, and the NEMA NU4 image quality phantom was used for image quality test. The developed CLS-PET system successfully resolved 0.75 mm rods. Subsequently, normal mouse and rat imaging with 18F-NaF and 18F-FDG were demonstrated. For the NaF-PET, mouse and rat total-body images were obtained, and detailed bone structures were clearly imaged. For the mouse FDG-PET, cardiac FDG uptakes were clearly visualized by the CLS-PET system. In conclusion, the CLS-PET system achieved, 2021 IEEE NSS/MIC

We developed a whole gamma imaging (WGI) prototype composed of a scatterer ring insert and an absorber ring. It was the world’s first realization of a full-ring Compton camera geometry. In this study, we focused on the data sufficiency condition (DSC) for Compton image reconstruction. Contrary to PET which requires a full-ring geometry to satisfy the DSC, Compton imaging does not require a full ring theoretically. Reducing the detector-ring coverages can improve flexibility of the geometry design and reduce manufacturing costs although sensitivity is decreased. However, the DSC for reconstruction is not guaranteed in a practical situation due to actual absorber ring arrangement and detection limits in scattering angle. In this study, we experimentally assessed the DSC for the angular coverages. We evaluated image artifacts on reconstructed Compton images because, in general, images distort and exhibit artifacts when the DSC is not satisfied, degrading quantitative accuracy. We measured a cylindrical phantom filled with 89Zr solution of 10.2 MBq by the WGI prototype for 60 min and extracted 909-keV Compton events. We selected events related to the detector blocks marked as available to change detector angular coverages defined for the phantom bottom point. First, we changed the number of detectors in the scatterer ring, keeping the full-ring absorber. Next, we changed the absorber ring angular coverage by changing the number of detectors, keeping the scatterer ring at the number where the angular coverage just exceeded 180°. As a result, when the angular coverage of the scatterer detector was less than 180°, reconstructed images exhibited artifacts. The absorber ring detector with less than 180° coverage showed artifacts when used with the scatterer detector with more than 180° coverage. We concluded that angular coverages of more than 180° for both the scatterer and absorber detectors against any region on a subject are the DSC for Compton image reconstruction., IEEE NSS MIC 2021

昨年の発表では，我々が開発を進めているWGI(Whole Gamma Imaging) の小動物実証機におけるコンプトンイメージングによって，高精細なマウス画像が得られたことを報告した．高精細な画像が得られた要因の一つとして，WGI がフルリング型であることが考えられるが，実際にどの程度寄与しているのか明らかにはなっていない．そこで，本研究では，画像再構成に利用する測定データを限定し，フルリングの場合と比較することで，物体を囲むリングの範囲の変化が再構成画像へ与える影響を検討した．円筒型ファントムの測定データを用い，再構成画像を視覚的に評価した結果，散乱検出器に囲まれる範囲が180°未満の領域が物体にある場合，画像にアーチファクトが生じたが，物体全域が180°以上囲まれている場合には，フルリングと同様にアーチファクトのない画像が得られた．よって，WGI コンプトン画像再構成の完全性条件として，対象視野全域を180°以上囲む必要があることが示唆された．, 第40回日本医用画像工学会大会

Coincidence timing resolution (CTR) is an important parameter in clinical positron emission tomography (PET) scanners to increase the signal-to-noise ratio of PET images by using time-of-flight (TOF) information. Lutetium (Lu) based scintillators are often used for TOF-PET systems. However, the self-radiation of Lu-based scintillators may influence the image quality for ultra-low activity PET imaging. Recently, a gadolinium fine aluminum gallate (Ce:GFAG) scintillation crystal that features a fast decay time (∼55 ns) and no self-radiation was developed. The present study aimed at optimizing the GFAG crystal surface treatment to enhance both CTR and energy resolution (ER). The TOF-PET detector consisted of a GFAG crystal (3.0 × 3.0 × 20 mm3) and a SiPM with an effective area of 3.0 × 3.0 mm2. The timing and energy signals were extracted using a high-frequency SiPM readout circuit and then were digitized using a CAMAC DAQ system. The CTR and ER were evaluated with nine different crystal surface treatments such as partial saw-cut and chemical polishing and the 1-side saw-cut was the best choice among the treatments. The respective CTR and ER of 202 ± 2 ps and 9.5 ± 0.1% were obtained with the 1-side saw-cut; the other 5-side mechanically polished GFAG crystals had respective values which were 18 ps (9.0%) and 1.3% better than those of the all-side mechanically polished GFAG crystal. The chemically polished GFAG crystals also offered enhanced CTR and ER of about 17 ps (8.2%) and 2.1%, respectively, over the mechanically polished GFAG crystals.

[Objectives] 18F-FDG PET is useful for diagnosis of breast cancer. Compared to whole-body imaging, local breast imaging with a dedicated PET system can more clearly visualize the extent of the primary breast tumor and axillary lymph nodes metastasis. Breast-dedicated PET systems are categorized into two geometries: a ring-shaped detector arrangement and a dual flat-panel detector arrangement. Although the flat-panel system allows imaging axillary lymph nodes from a similar view as X-ray mammography, PET images are blurred (i.e. spatial resolution is degraded) in the direction perpendicular to the detectors due to the limited angular coverage. To compensate for this issue, we proposed a dual round-edge detector arrangement, in which the detector blocks at both edge positions were tilted toward the center of the field-of-view (FOV). The proposed detector arrangement is expected to reduce image blurring and improve spatial resolution while keeping the advantages of the dual panel arrangement. For a proof of concept, we developed a small prototype and evaluated the spatial resolution. [Methods] We used the crosshair light-sharing (CLS) detectors which had depth-of-interaction (DOI) and time-of-flight (TOF) measurement capabilities*. A 14×14 array of 1.45×1.45×15 mm3 GFAG scintillator was coupled with an 8×8 array of silicon photomultipliers (SiPMs) each with a photosensitive area of 3.0×3.0 mm2. DOI was digitalized into three bins. The data acquisition system was the TOFPET2 ASIC (PETsys Electronics), which was designed to digitize energy and time signals from photo sensors. The small prototype was composed of 32 detector blocks. We examined the conventional flat-panel arrangement and our proposed round-edge arrangement. A 22Na Derenzo-like multi-rod phantom (rod diameters: 1.6, 2.2, 3.0, 4.0, 5.0 and 6.0 mm) was used for spatial resolution measurement. The phantom was measured (90 min) in the two directions (coronal and axial planes) at the center of the FOV. [Results] In the coronal plane, the 1.6 mm rods were clearly resolved in both arrangements. In the axial plane, the round-edge arrangement significantly improved the spatial resolution compared with the flat-panel arrangement. While the conventional flat-panel arrangement could not resolve the 3.0 mm rods, the proposed round-edge arrangement resolved the 2.2 mm rods. [Conclusion] The proposed dual round-edge detector arrangement showed better spatial resolution than the conventional flat-panel arrangement while keeping the geometrical advantage for the breast PET imaging. (*Yoshida, et al. A crosshair light sharing PET detector with DOI and TOF capabilities using four-to-one coupling and single-ended readout. IEEE TRPMS 2020.), SNMMI 2021 Annual Meeting

The quality and uniformity of positron emission tomography (PET) images can be improved significantly using a PET scanner, which has both time-of-flight (TOF) and depth-of-interaction (DOI) capabilities. We have already developed a DOI dual-end detector using segmented crystal bars by applying a subsurface laser engraving (SSLE) technique, and the DOI was determined by the ratio of the detected light between two readouts using the Anger calculation. In this study, we investigated the influence of the number of DOI segments on the performance of DOI identification and the coincidence timing performance of the detector. The detector consisted of a single lutetium fine silicate (LFS) crystal bar (3 × 3 × 20 mm3) with various numbers of DOI segments that were made by applying the SSLE technique and Hamamatsu silicon photomultiplier (SiPM) modules. The maximum number of DOI segments was six, and the SiPM module included one hundred forty-four 4 mm × 4 mm SiPM readouts. The coincidence resolving time (CRT) of each DOI segment was obtained from the side irradiation of the dual-end detector. All DOI segments of the detector with 2, 3, 4, 5 or 6 DOI segments were clearly identified, and average energy resolutions of 9.8 ± 0.5% and 12.5 ± 1.4% were obtained at the 511 keV photo peak for the detectors with 2 DOI and 6 DOI segments, respectively. The minimum and maximum estimated CRT of 180 ± 6 ps and 236 ± 6 ps were obtained for the detectors with 2 DOI and 6 DOI segments, respectively. Insignificant differences were observed between the CRT values of different segments of one detector. Greater CRT values were obtained for detectors with larger DOIs. The results of this study prove that there is a high potential for segmented crystal bars using the SSLE technique as a good candidate for PET scanners with TOF and DOI capabilities, which can significantly improve the quality of PET images.

Previously, we had developed a four-layered depth-of-interaction (DOI) PET detector based on the light sharing method. Reflectors , which were inserted in every two lines of crystal segments and shifted differently for each layer, projected 3D crystal positions onto a 2D position histogram without any overlapping after applying the Anger-type calculation. The best crystal separation we ever obtained was for the four-layered 32 × 32 array of LYSO crystals sized at 1.45 × 1.45 × 5 mm3. However, assembling small crystals tended to cost a lot, and fine tuning of the front-end circuit was required to get fine crystal identification. In this paper, therefore, we proposed a more practical four-layered DOI detector. Its key concept was that the crystals in the top layer, which have the highest detection efficiency, are the biggest contributors to the PET spatial resolution. We applied two new ideas: (1) using quarter size crystals only for the first (top) layer and (2) inserting a thin light guide between the first and the second layers of the crystal array. In the developed prototype detector, we used 24 × 24 LYSO crystals of quarter size (1.4 × 1.4 × 5.0 mm3) in the first layer and the other layers were 12 × 12 arrays of crystals of 2.8 × 2.8 × 5.0 mm3. For better crystal identification of small crystals in the first layer, we optimized the optical condition between crystals by using an optical adhesive and air. Also, the thin light guide of 0.5 mm thickness was inserted between the first and the second layers for improvement of crystal identification of the first layer. With the appropriate insertion of the light guide, all crystals of the first layer were identified as well as the crystals in the other layers. Our developed four-layered DOI detector showed good potential for high spatial resolution without a large increase in the number of crystals.