Japan Radioisotope Association

Chest symptoms, such as angina and palpitation, are common complaints in patients with cardiovascular diseases, but few studies have addressed how cardiac afferent information is processed through the brain. We recruited 10 patients (mean age 74.7±1.9 years; 9 men) with cardiac pacemaker implantation. The patients underwent brain H215O positron emission tomography (PET) followed by blood sampling during right ventricular pacing of sham (1.5 V) and stimulation (7.5-8 V) conditions with a 10min interval. A voxel-wise analysis of the brain PET images identified the anterior cingulate cortex (ACC), posterior cingulate cortex, prefrontal cortex, thalamus, amygdala and midbrain as regions of increased regional cerebral blood flow (rCBF) under stimulation compared to sham conditions at a family-wise error-corrected cluster-extent threshold of P<0.05 with an underlying voxel level of P<0.001. The stimulation conditions increased rCBF in the ACC (59.8±4.4 vs. 49.2±3.5 mL/100 g/min, P<0.001) and plasma noradrenaline levels (332.3±139.0 vs. 312.0±139.8 pg/mL, P=0.004) compared to the sham stimulation. A linear mixed-effects model showed a significant positive correlation between the changes in rCBF in the ACC and those in plasma noradrenaline levels (P<0.001). Cardiac electrical stimulation increased both rCBF in the ACC and plasma noradrenaline levels, and the changes were correlated. The ACC may be the brain center that transfers cardiac afferent information into autonomic arousal during cardiac pacing.

Actinium-225 radiopharmaceuticals have drawn great interest in cancer therapy due to their tumor-specific delivery of cytotoxic alpha-particles. Quality control (QC) is critical for these potent agents and there is currently no consensus for best practice of actinium-225 QC. Detection of actinium-225 (T1/2 = 9.92days) is challenging; however, the francium-221 (T1/2 = 4.8min, 218keV) and bismuth-213 (T1/2 = 45min, 440keV) gamma-emitting progenies facilitate the quantification. Multiple analytical methods were investigated for limit of quantification (LOQ), radiochemical yield (RCY%), and radiochemical purity (RCP%). Those were evaluated at both francium-221 and bismuth-213 secular equilibria, and compared for accuracy and precision. While each secular equilibrium has been amply explored for actinium-225 quantification, a direct comparison between the two approaches has sparsely been examined. The RCY% was evaluated using two TLC plate readers: a gas-filled proportional counter and a plastic silicon photomultiplier detector. TLC strips were also analyzed using Liquid Scintillation Counting (LSC), High Purity Germanium (HPGe), and NaI(Tl) gamma well counting. In absence of detectable radio-impurity, HPLC RCP% were correlated to RCY%. Finally, free actinium-225 spiking recoveries were evaluated in 225Ac-radiopharmaceuticals. The plastic silicon scanner resulted in RCY% differences between 30min and > 5h evaluations, whereas the gas-filled proportional counter, when varying voltages, showed minor differences. Similarly, HPGe-TLC demonstrated equivalent RCY% between both equilibria. The NaI(Tl), LSC- TLC, and HPLC-gamma counting significantly underestimated RCY% or RCP% at 30min. Considering gamma well counting LOQ and 225Ac-radiopharmaceutical low radioactive concentration, as low as 1% of free actinium-225 may be accurately detected in HPLC fractions. For TLC, LOQs were reported lower than measured in solution, free actinium-225 radioimpurity may be precisely measured as low as 0.5% of total content, except for the silicon detector. Five instruments have been tested for their linearity, sensitivity, accuracy and specificity to actinium-225 quantification using francium-221 and bismuth-213 equilibria. Francium-221 equilibrium was deemed acceptable for TLC RCY% using HPGe and gas-filled proportional counter. Gamma well counting, LSC, and plastic silicon detector required bismuth-213 equilibrium for accurate RCY%. Low content free actinium-225 impurity was accurately reported for all methods except for the silicon detector. Overall, this investigation sheds light on the appropriate analytical methods for 225Ac-radiopharmaceutical QC considering secular equilibrium.

This study utilized the Particle and Heavy Ion Transport code System (PHITS) Monte Carlo code to develop a computer model of a Varian CLINAC (iX) linear accelerator (LINAC) operating at 6 MV and to design the shielding for its treatment bunker. The LINAC head, comprising the target, primary collimator, flattening filter, and secondary collimator, was accurately modeled based on manufacturer specifications. A water phantom was incorporated to calculate the Percentage Depth Dose (PDD) and beam profiles for a 10×10 cm² field at a Source-to-Surface Distance (SSD) of 100 cm. The success of the model was validated by visualizing particle tracks (photons, electrons, neutrons). The maximum dose was found at a depth of 1.5 cm in water for a 6 MV beam. Furthermore, a comprehensive 3D model of a radiotherapy bunker was constructed using PHITS, with shielding composed of concrete and lead. Simulations confirmed that the designed shielding effectively reduced photon and electron doses to acceptable safety limits outside the bunker. No neutron production was observed at 6 MV, as expected. This work shows how PHITS can be applied to LINAC modeling and shielding assessment under the stated assumptions. Ban. J. Med. Phys., Vol -16, Issue -1, 2025 : 1-6

The PET Imaging Site Qualification Program for amyloid positron emission tomography (PET) in Japan includes visual evaluation of the cylinder phantom. This visual evaluation requires observation of the entire image of the phantom and confirmation of the absence of apparent artifacts. Because the evaluation is visually performed, inter-observer differences might exist among evaluators for difficult cases. Therefore, the workload of the staff who perform approval tasks must be reduced, and objective evaluation methods are needed. Thus, we attempted to develop an artificial-intelligence-based objective method for anomaly detection. Three artificial intelligence methods for anomaly detection were developed, and their accuracy was evaluated using AutoEncoder, AnoGAN, and a method combining feature extraction using AlexNet and a one-class support vector machine. In total, 10,207 normal images from 128 facilities and 594 abnormal images from eight facilities, all of which were submitted as part of application for amyloid PET certification, were used. Group five-fold cross-validation was employed for artificial intelligence training and evaluation. In addition, the performance of each artificial intelligence method was assessed using receiver operating characteristic analysis. The areas under the curve for anomaly detection using AutoEncoder, AnoGAN, and the method combining feature extraction using AlexNet and a one-class support vector machine were 0.80 ± 0.04, 0.77 ± 0.03, and 0.99 ± 0.01, respectively. Artificial intelligence effectively distinguished between normal and abnormal images with high accuracy. In the future, its practical implementation is anticipated to reduce the workload in the approval work for the Japanese site qualification program for amyloid PET.

Positronium (Ps) imaging is getting attention for nuclear medicine applications, but appropriate radionuclides have not been evaluated systematically. This paper investigated the use of 124I, which is a positron emitter with 603 keV prompt gamma ray emission with a fraction of 11.7%. The accuracy of positron annihilation lifetime measurement with 124I was compared with 22Na, which is often used in positron annihilation lifetime measurement, for certified reference materials. Results obtained with TOF-PET detectors suggested that the accuracy of the lifetime value estimation was slightly worse than that for 22Na, while the positron annihilation lifetime measurement using 124I was a feasible choice.

Abstract The iron sand around Mt. Aburayama (Fukuoka, Japan), where various ancient iron‐making sites are located, was investigated to establish a research infrastructure for identification of the raw material used in the archeological iron artifacts excavated from this area. Iron sand samples were magnetically collected from the rivers flowing in this area and nearby outcrop soil. The samples were qualitatively analyzed using Mössbauer spectroscopy and x‐ray diffractometry to identify the minerals present inside them. Additionally, the elemental concentrations in these samples were determined using x‐ray fluorescence spectrometry. The iron sand samples were characterized by comparing them with those from other Japanese regions using scatter diagrams developed based on the elemental concentrations in the samples. The scatter diagrams showed clear distinctions between the iron sand samples from the Mt. Aburayama area and other Japanese regions. These diagrams may enable us to clarify the relationship between the iron sand and archeological iron artifacts found in the vicinity of Mt. Aburayama.

Internal radiation therapy using Iodine-131 metaiodobenzylguanidine (131I-MIBG) for neuroblastoma has been discussed whether a special application scheme for off-labeled drugs called "Kouchi-Shinsei" could be applied to neuroblastoma or not by the Evaluation Committee on Unapproved or Off-labeled Drug with High Medical Needs (the Committee); if the Committee determines that Kouchi-Shinsei is applicable, neuroblastoma indication is expected to be regulatory approved within a year. Since a NHI medical technical fee is not yet set for neuroblastoma, the Japanese Society of Nuclear Medicine surveyed health resource use via a questionnaire survey of medical institution that has conducted a Japanese Advanced Medical Care B clinical study in neuroblastoma. Results showed that the necessary total cost per patient is 1,847,451 JPY when calculated based on the Draft Proposal for Medical Examination Value (Ver. 7.3) of the Japanese Health Insurance Federation for Surgery. Because follow-up is necessary for 3 months after administration, it was considered that an appropriate fee per patient is 1,847,451 JPY and an appropriate NHI medical technical fee per patient is 46,186 points which can be claimed up to once a month for 4 times including the initial month of the treatment.

Clioquinol (Quinoform) was extensively administered to treat indigestion and diarrhea in the mid-1900s. However, it was withdrawn from the market in Japan because its use was epidemiologically linked to an increase in the incidence of subacute myelo-optic neuropathy (SMON). SMON is characterized by the subacute onset of sensory and motor disturbances in the lower extremities with occasional visual impairments, which are preceded by abdominal symptoms. The underlying mechanisms of clioquinol toxicity, however, have not been elucidated in detail. We previously reported that clioquinol induced oxidation of the copper chaperone ATOX1, leading to the impairment of the functional maturation of a copper-dependent enzyme dopamine-β-hydroxylase and the inhibition of noradrenaline biosynthesis. Effects of clioquinol on expression levels of other copper-related proteins were investigated. Quantitative PCR demonstrated that clioquinol decreased mRNA levels of SCO1 and SCO2, copper chaperones for mitochondrial respiratory chain complex IV (cytochrome c oxidase), and of COX18, a membrane insertase of a complex IV component. In clioquinol-treated cells, the assembly and activity of complex IV were suppressed. Thus, clioquinol was suggested to suppress ATP synthesis through this pathway, leading to neuronal cell death.