Recovery after Prolonged Disturbance of Consciousness and Repeated Cerebral Perfusion Changes in Neuronal Intranuclear Inclusion Disease.

Encephalitic episodes are a clinical manifestation of neuronal intranuclear inclusion disease (NIID) and often show transient disturbance of consciousness. We herein report a genetically confirmed patient with NIID who initially presented progressive dementia and showed prolonged disturbance of consciousness preceded by an acute-onset headache. During that time, we performed N-isopropyl-p-[123I] iodoamphetamine single-photon-emission computed tomography twice and found that the blood flow increased in different regions. Prolonged disturbance of consciousness following an encephalitic episode may be associated with repeated hyperperfusion in various regions resulting from mitochondrial dysfunction. NIID patients presenting with encephalitic episodes can recover gradually and spontaneously even after prolonged disturbances of consciousness.

Case Report: Guanfacine and methylphenidate improved chronic lower back pain in autosomal dominant polycystic kidney disease with comorbid attention deficit hyperactivity disorder and autism spectrum disorder.

Autosomal dominant polycystic kidney disease (ADPKD) is an inherited renal disease characterized by the bilateral development of multiple cysts in the kidneys. Pain management is a clinically important issue, especially because approximately 60% of patients with ADPKD experience chronic pain related to hemorrhage from renal cysts, which significantly reduces their daily life. The cystic fibrosis transmembrane conductance regulator, the molecule responsible for cyst formation in ADPKD, is also the cause of cystic fibrosis. Since attention deficit hyperactivity disorder (ADHD) is known to occur frequently in conjunction with cystic fibrosis, ADPKD may be associated with ADHD. However, to our knowledge, no study has investigated 1) ADHD or autism spectrum disorder (ASD) as comorbidities with ADPKD, 2) the effects of ADHD medications on chronic pain in ADPKD, or 3) cerebral blood flow corresponding to guanfacine (GF) or methylphenidate (MP) treatment for chronic pain. We report the case of a 15-year-old girl with ADPKD, who had chronic back pain associated with ADPKD and had to withdraw from high school because the pain interfered with her daily life. Although she took antihypertensive medications to prevent bleeding, they did not provide adequate blood pressure control. The patient was referred to a child psychiatrist and diagnosed with ASD; however, the pain did not improve. Subsequently, she was referred to our pain center. The diagnosis of ADHD was confirmed and treatment with ADHD medications was initiated. Monotherapy with MP, atomoxetine, and GF resulted in hypertension and hypotension as side effects; however, a combination of MP 18 mg and GF 4 mg provided pain relief and moderate blood pressure control, and the patient was able to go on to college. During the course of treatment, there was an improvement in the distribution of cerebral blood flow in the prefrontal and insular cortices. Confirmation of an ADHD diagnosis comorbid with ASD enabled the use of ADHD medications. The combination of MP and GF improved chronic back pain and high blood pressure due to ADPKD and cerebral blood flow. Screening for ADHD is important in the treatment of ADPKD.

Pre-acquired CT-based attenuation correction with automated headrest removal for a brain-dedicated PET system.

Attenuation correction (AC) is essential for quantitative positron emission tomography (PET) images. Attenuation coefficient maps (µ-maps) are usually generated from computed tomography (CT) images when PET-CT combined systems are used. If CT has been performed prior to PET imaging, pre-acquired CT can be used for brain PET AC, because the human head is almost rigid. This pre-acquired CT-based AC approach is suitable for stand-alone brain-dedicated PET, such as VRAIN (ATOX Co. Ltd., Tokyo, Japan). However, the headrest of PET is different from the headrest in pre-acquired CT images, which may degrade the PET image quality. In this study, we prepared three different types of µ-maps: (1) based on the pre-acquired CT, where namely the headrest is different from the PET system (µ-map-diffHr); (2) manually removing the headrest from the pre-acquired CT (µ-map-noHr); and (3) artificially replacing the headrest region with the headrest of the PET system (µ-map-sameHr). Phantom images by VRAIN using each µ-map were investigated for uniformity, noise, and quantitative accuracy. Consequently, only the uniformity of the images using µ-map-diffHr was out of the acceptance criteria. We then proposed an automated method for removing the headrest from pre-acquired CT images. In comparisons of standardized uptake values in nine major brain regions from the 18F-fluoro-2-deoxy-D-glucose-PET of 10 healthy volunteers, no significant differences were found between the µ-map-noHr and the µ-map-sameHr. In conclusion, pre-acquired CT-based AC with automated headrest removal is useful for brain-dedicated PET such as VRAIN.

Current and Future PET Imaging for Multiple Myeloma.

Positron emission tomography (PET) is an imaging modality used for the noninvasive assessment of tumor staging and response to therapy. PET with 18F labeled fluorodeoxyglucose (18F-FDG PET) is widely used to assess the active and inactive lesions in patients with multiple myeloma (MM). Despite the availability of 18F-FDG PET for the management of MM, PET imaging is less sensitive than next-generation flow cytometry and sequencing. Therefore, the novel PET radiotracers 64Cu-LLP2A, 68Ga-pentixafor, and 89Zr-daratumumab have been developed to target the cell surface antigens of MM cells. Furthermore, recent studies attempted to visualize the tumor-infiltrating lymphocytes using PET imaging in patients with cancer to investigate their prognostic effect; however, these studies have not yet been performed in MM patients. This review summarizes the recent studies on PET with 18F-FDG and novel radiotracers for the detection of MM and the resulting preclinical research using MM mouse models and clinical studies. Novel PET technologies may be useful for developing therapeutic strategies for MM in the future.

Case report: Atomoxetine improves chronic pain with comorbid post-traumatic stress disorder and attention deficit hyperactivity disorder.

Background: It is known that patients reporting chronic pain often experience trauma or post-traumatic stress disorder (PTSD) and tend to be more difficult to treat. Attention deficit hyperactivity disorder (ADHD), a neurodevelopmental disorder, is frequently associated with chronic pain. Furthermore, patients diagnosed with ADHD are more likely to encounter trauma and develop PTSD because of their inattentive and impulsive tendencies. There are reports stating that atomoxetine (ATX), a selective noradrenaline reuptake inhibitor for ADHD, is effective in patients diagnosed with PTSD and ADHD. However, there have been no reports on cases of comorbid PTSD and ADHD with chronic pain, and ATX's potential in improving chronic pain coexisting PTSD. Furthermore, no reports have evaluated patient cerebral blood flow in conjunction with the course of treatment with ATX for chronic pain. Case report: In this study, we reported a case where ATX improved chronic pain with PTSD and improved cerebral blood flow. The patient was a 56-year-old woman exhibiting chronic pain with PTSD, resulting from 6 years of severe domestic violence from her common-law husband. She had no history of ADHD diagnosis, but through aggressive screening, comorbid ADHD was diagnosed. When treated with ATX, there were significant improvements in her pain, quality of life, anxiety, depression, catastrophic thoughts, and cerebral blood flow. As a result, she could resume work after 11 years. Conclusion: The study showed that chronic pain with PTSD may be comorbid with ADHD. Moreover, we found that ATX can improve chronic pain with PTSD and cerebral blood flow. Aggressive screening of ADHD is important because once the diagnosis of comorbidity is confirmed, an ideal ADHD treatment can be selected. Therefore, based on the results of this study, ATX may be a candidate for treatment for cases of chronic pain with PTSD and ADHD.

Case report: Remission of chronic low back pain and oral dysesthesia comorbid with attention deficit/hyperactivity disorder by treatment with atomoxetine and pramipexole.

Introduction: Oral dysesthesia is a disease characterized by pain and/or abnormal sensations in the oral region, without any organic abnormality. Its symptoms include pain, and it is considered to be a disorder associated with idiopathic oral-facial pain. It is also known that idiopathic oral-facial pain tends to coexist with chronic musculoskeletal pain, including low back pain, even before its onset. Such coexisting idiopathic pain conditions are also called chronic overlapping pain conditions (COPCs). In general, COPCs are often refractory to treatment. Recently, it has been reported that attention deficit hyperactivity disorder (ADHD) is associated with many COPCs, such as pain in the facial and lower back regions and so on. However, there are no reports of (1) ADHD as a comorbidity with oral dysesthesia (OD) or (2) of the therapeutic effects of ADHD medications or dopamine agonists on low back pain and OD or an (3) evaluation of cerebral blood flow over time after treatment with these medications for OD and low back pain. Case Presentation: In this study, we report the case of an 80-year-old man with OD and chronic low back pain that persisted for more than 25 years. His OD and chronic back pain were refractory to standard treatment, prevented him from continuing work, and tended to be exacerbated by conflicts in his relationship with his son. In recent years, ADHD has often been found to be comorbid with chronic pain, and ADHD medications have been reported to improve chronic pain as well. The patient was confirmed to have undiagnosed ADHD and was treated with the ADHD medication atomoxetine and dopamine agonist pramipexole, which dramatically improved his OD, chronic back pain, and cognitive function. Furthermore, along the course of treatment, there was improvement in cerebral blood flow in his prefrontal cortex, which was thought to reflect improved function in the region. Consequently, he was able to resume work and improve his family relationships. Conclusion: Therefore, in the cases of ODs and COPCs, screening for ADHD and, if ADHD is diagnosed, ADHD medications or dopamine agonists may be considered.

Submillimeter-Resolution PET for High-Sensitivity Mouse Brain Imaging.

PET is a powerful molecular imaging technique that can provide functional information on living objects. However, the spatial resolution of PET imaging has been limited to around 1 mm, which makes it difficult to visualize mouse brain function in detail. Here, we report an ultrahigh-resolution small-animal PET scanner we developed that can provide a resolution approaching 0.6 mm to visualize mouse brain function with unprecedented detail. Methods: The ultrahigh-resolution small-animal PET scanner has an inner diameter of 52.5 mm and axial coverage of 51.5 mm. The scanner consists of 4 rings, each of which has 16 depth-of-interaction detectors. Each depth-of-interaction detector consists of a 3-layer staggered lutetium yttrium orthosilicate crystal array with a pitch of 1 mm and a 4 × 4 silicon photomultiplier array. The physical performance was evaluated in accordance with the National Electrical Manufacturers Association NU4 protocol. Spatial resolution was evaluated with phantoms of various resolutions. In vivo glucose metabolism imaging of the mouse brain was performed. Results: Peak absolute sensitivity was 2.84% with an energy window of 400-600 keV. The 0.55-mm rod structure of a resolution phantom was resolved using an iterative algorithm. In vivo mouse brain imaging with 18F-FDG clearly identified the cortex, thalamus, and hypothalamus, which were barely distinguishable in a commercial preclinical PET scanner that we used for comparison. Conclusion: The ultrahigh-resolution small-animal PET scanner is a promising molecular imaging tool for neuroscience research using rodent models.

Rearrangement of hydrogen bonds in dehydrated raffinose tetrahydrate: a time-of-flight neutron diffraction study.

Structural changes of the raffinose crystal on dehydration from the pentahydrate to the tetrahydrate were investigated by single-crystal time-of-flight neutron diffraction. It was revealed that during the dehydration, rearrangement occurs in the hydrogen bonds related to the lost water molecule, while the symmetry of the crystal structure is retained. The hydrogen-bonding status of raffinose pentahydrate and tetrahydrate were discussed comprehensively according to Jeffrey's hydrogen-bonding classification. It was shown that the water molecules are hydrogen bonded to the surrounding molecules by moderate O-H...O hydrogen bonds and weak C-H...O hydrogen bonds, and the number of these two types of hydrogen bonds determines the water molecules that are removed by dehydration. The lattice constant c showed a significant decrease on dehydration and further dehydration leads to loss of crystallinity of the raffinose crystals.

Performance evaluation of VRAIN: a brain-dedicated PET with a hemispherical detector arrangement.

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 mm2active 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 performed18F-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-1and 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.

Small nuclei identification with a hemispherical brain PET.

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 .

Brain PET motion correction using 3D face-shape model: the first clinical study.

OBJECTIVE: Head motions during brain PET scan cause degradation of brain images, but head fixation or external-maker attachment become burdensome on patients. Therefore, we have developed a motion correction method that uses a 3D face-shape model generated by a range-sensing camera (Kinect) and by CT images. We have successfully corrected the PET images of a moving mannequin-head phantom containing radioactivity. Here, we conducted a volunteer study to verify the effectiveness of our method for clinical data. METHODS: Eight healthy men volunteers aged 22-45 years underwent a 10-min head-fixed PET scan as a standard of truth in this study, which was started 45 min after 18F-fluorodeoxyglucose (285 ± 23 MBq) injection, and followed by a 15-min head-moving PET scan with the developed Kinect based motion-tracking system. First, selecting a motion-less period of the head-moving PET scan provided a reference PET image. Second, CT images separately obtained on the same day were registered to the reference PET image, and create a 3D face-shape model, then, to which Kinect-based 3D face-shape model matched. This matching parameter was used for spatial calibration between the Kinect and the PET system. This calibration parameter and the motion-tracking of the 3D face shape by Kinect comprised our motion correction method. The head-moving PET with motion correction was compared with the head-fixed PET images visually and by standard uptake value ratios (SUVRs) in the seven volume-of-interest regions. To confirm the spatial calibration accuracy, a test-retest experiment was performed by repeating the head-moving PET with motion correction twice where the volunteer's pose and the sensor's position were different. RESULTS: No difference was identified visually and statistically in SUVRs between the head-moving PET images with motion correction and the head-fixed PET images. One of the small nuclei, the inferior colliculus, was identified in the head-fixed PET images and in the head-moving PET images with motion correction, but not in those without motion correction. In the test-retest experiment, the SUVRs were well correlated (determinant coefficient, r2 = 0.995). CONCLUSION: Our motion correction method provided good accuracy for the volunteer data which suggested it is useable in clinical settings.

Measurement of biological washout rates depending on tumor vascular status in15O in-beam rat-PET.

Objective.The biological washout of positron emitters should be modeled and corrected in order to achieve quantitative dose range verification in charged particle therapy based on positron emission tomography (PET). This biological washout effect is affected by physiological environmental conditions such as blood perfusion and metabolism, but the correlation to tumour pathology has not been studied yet.Approach.The aim of this study was to investigate the dependence of the biological washout rate on tumour vascular status in rat irradiation. Two types of tumour vascularity conditions, perfused and hypoxic, were modelled with nude rats. The rats were irradiated by a radioactive15O ion beam and time activity curves were acquired by dynamic in-beam PET measurement. Tumour tissue sections were obtained to observe the histology as well. The biological washout rate was derived using a single-compartment model with two decay components (medium decay,k2mand slow decay,k2s).Main results.Allk2mvalues in the vascular perfused tumour tissue were higher than the values of the normal tissue. Allk2mvalues in the hypoxic tumour tissue were much lower than the values of the vascular perfused tumour tissue and slightly lower than the values of the normal tissue.Significance.The dependency of the biological washout on the tumour vasculature conditions was experimentally shown.

Noninvasive monitoring of allograft rejection in a rat lung transplant model: Application of machine learning-based 18F-fluorodeoxyglucose positron emission tomography radiomics.

BACKGROUND: Standardized uptake values (SUVs) derived from 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) are valuable but insufficient for detecting lung allograft rejection (AR). Using a rat lung transplantation (LTx) model, we investigated correlations of AR with the SUVmax and PET-derived radiomics and further evaluated the performance of machine learning (ML)-based radiomics for monitoring AR. METHODS: LTx was performed on 4 groups of rats: isograft, allograft-cyclosporinecontinuous (CsAcont), allograft-CsAdelayed, and allograft-CsA1week. Each rat underwent 18F-FDG PET at week 3 or 6. The SUVmax and radiomic features were extracted from the PET images. Least absolute shrinkage and selection operator regression was used to construct a radiomics score (Rad-score). Ten modeling algorithms with 7 feature selection methods were performed to develop 70 radiomics models (49 ML models and 21 logistic regression models) for monitoring AR, validated using the bootstrap method. RESULTS: In total, 837 radiomic features were extracted from each PET image. The SUVmax and Rad-score showed significant positive correlations with histopathology (p < .05). The area under the curve (AUC) of SUVmax for detecting AR was 0.783. The median AUC of ML models was 0.921, which was superior to that of logistic regression models (median AUC, 0.721). The optimal ML model using a random forest modeling algorithm with random forest feature selection method exhibited the highest AUC of 0.982 (95% confidence interval, 0.875-1.000) in all models. CONCLUSIONS: SUVmax provided a good correlation with AR, but ML-based PET radiomics further strengthened the power of 18F-FDG PET functional imaging for monitoring AR in LTx.

Marker-less and calibration-less motion correction method for brain PET.

Marker-less head motion correction methods have been well-studied; however, no reports discussing potential issues in positional calibration between a PET system and an external sensor remain limited. In this study, we develop a method for positional calibration between the PET system and an external range sensor to achieve practical head motion correction. The basic concept of the developed method involves using the subject's face model as a marker not only for head motion detection but also for the system positional calibration. The face model of the subject, which can be obtained easily using the range sensor, can also be calculated from a computed tomography (CT) image of the same subject. The CT image, which is acquired separately for attenuation correction in PET, has the same coordinates as the PET image because of the appropriate matching algorithm between CT and PET images. The proposed method was implemented in the helmet-type PET and the motion correction accuracy was assessed quantitatively using a mannequin head. The phantom experiments demonstrated the performance of the developed motion correction method; high-resolution images with no trace of the applied motion were obtained as if no motion was provided. Statistical analysis supported the visual assessment results in terms of the spatial resolution, contrast recovery; uniformity, and the results implied that motion with correction slightly improved image quality compared with the motionless case. The tolerance of the developed method against potential tracking errors had a minimum 10% difference in the amplitude of the rotation angle.

Influence of antidepressant use on 123I-MIBG heart and lung uptakes in the diagnosis of Lewy body disease.

OBJECTIVE: The clinical significance of decreased physiological lung uptake of 123I-metaiodobenzylguanidine (MIBG) has not been well investigated. This study aimed to elucidate the association between a decrease in lung MIBG uptake with antidepressant intake and the myocardial MIBG uptake in patients who were clinically diagnosed with Lewy body disease (LBD) and patients who were diagnosed as not having LBD. METHODS: We retrospectively reviewed the heart and lung uptakes on 167 consecutive MIBG scans, antidepressant status, and clinical diagnosis of LBD. The images were visually classified into two groups: decreased lung uptake and preserved lung uptake. A semi-quantitative analysis was performed using the heart-to-mediastinum ratio (H/M), lung-to-mediastinum ratio (L/M), and myocardial washout rate (WR). RESULTS: All 17 patients with decreased lung uptake were on treated with antidepressants, while none of the 150 patients with preserved lung uptake were treated with any antidepressants. Of the 17 patients with decreased lung uptake, 6 patients were clinically diagnosed as LBD and other 11 were clinically diagnosed as non-LBD. There was not significant difference in early H/M, delayed H/M, and myocardial WR between the 11 non-LBD patients with decreased lung uptake and 83 non-LBD patients with preserved lung uptake (2.87 ± 0.69 vs. 2.89 ± 0.44, 3.09 ± 0.48 vs. 2.98 ± 0.59, and 21.8 ± 11.3% vs. 21.1 ± 12.5%, respectively). Moreover, in LBD patients, there were no significant differences in those values between six patients with decreased lung uptake and 67 patients with preserved lung uptake (1.68 ± 0.32 vs. 1.73 ± 0.42, 1.34 ± 0.21 vs. 1.54 ± 0.57, 46.2 ± 22.8% vs. 42.8 ± 21.3%, respectively). CONCLUSIONS: Antidepressants probably blocked MIBG uptake in the lungs, and a decreased lung uptake was not significantly associated with heart uptake. A remarkable decrease in lung uptake can be a signal to check a patient's medication status.

A design of forceps-type coincidence radiation detector for intraoperative LN diagnosis: clinical impact estimated from LNs data of 20 esophageal cancer patients.

PURPOSE: To reduce postoperative complications, intraoperative lymph node (LN) diagnosis with 18F-fluoro-2-deoxy-D-glucose (FDG) is expected to optimize the extent of LN dissection, leading to less invasive surgery. However, such a diagnostic device has not yet been realized. We proposed the concept of coincidence detection wherein a pair of scintillation crystals formed the head of the forceps. To estimate the clinical impact of this detector, we determined the cut-off value using FDG as a marker for intraoperative LN diagnosis in patients with esophageal cancer, the specifications needed for the detector, and its feasibility using numerical simulation. METHODS: We investigated the dataset including pathological diagnosis and radioactivity of 1073 LNs resected from 20 patients who underwent FDG-positron emission tomography followed by surgery for esophageal cancer on the same day. The specifications for the detector were determined assuming that it should measure 100 counts (less than 10% statistical error) or more within the intraoperative measurement time of 30 s. The detector sensitivity was estimated using GEANT4 simulation and the expected diagnostic ability was calculated. RESULTS: The cut-off value was 620 Bq for intraoperative LN diagnosis. The simulation study showed that the detector had a radiation detection sensitivity of 0.96%, which was better than the estimated specification needed for the detector. Among the 1035 non-metastatic LNs, 815 were below the cut-off value. CONCLUSION: The forceps-type coincidence detector can provide sufficient sensitivity for intraoperative LN diagnosis. Approximately 80% of the prophylactic LN dissections in esophageal cancer can be avoided using this detector.

Simultaneous in vivo imaging with PET and SPECT tracers using a Compton-PET hybrid camera.

Positron-emission tomography (PET) and single-photon-emission computed tomography (SPECT) are well-established nuclear-medicine imaging methods used in modern medical diagnoses. Combining PET with 18F-fluorodeoxyglucose (FDG) and SPECT with an 111In-labelled ligand provides clinicians with information about the aggressiveness and specific types of tumors. However, it is difficult to integrate a SPECT system with a PET system because SPECT requires a collimator. Herein, we describe a novel method that provides simultaneous imaging with PET and SPECT nuclides by combining PET imaging and Compton imaging. The latter is an imaging method that utilizes Compton scattering to visualize gamma rays over a wide range of energies without requiring a collimator. Using Compton imaging with SPECT nuclides, instead of the conventional SPECT imaging method, enables PET imaging and Compton imaging to be performed with one system. In this research, we have demonstrated simultaneous in vivo imaging of a tumor-bearing mouse injected with 18F-FDG and an 111In-antibody by using a prototype Compton-PET hybrid camera. We have succeeded in visualizing accumulations of 18F-FDG and 111In-antibody by performing PET imaging and Compton imaging simultaneously. As simultaneous imaging utilizes the same coordinate axes, it is expected to improve the accuracy of diagnoses.

Simultaneous measurements of single gamma ray of 131I and annihilation radiation of 18F with Compton PET hybrid camera.

In internal 131I therapy for thyroid cancer, a decision to continue treatment is made by comparing 131I scintigraphy and [18F]FDG-PET. However, with current SPECT and PET systems, simultaneous imaging of diagnostic PET nuclides and therapeutic 131I nuclides has not been achieved so far. Therefore, we demonstrated that the recently developed Compton PET hybrid camera with Ce:Gd3(Al,Ga)5O12 (GAGG)- Silicon Photomultiplier(SiPM) scintillation detectors can be used to simultaneously image 131I Compton image and 18F PET image.