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Introduction: Brain positron emission tomography/computed tomography (PET/CT) scans are useful for identifying the cause of dementia by evaluating glucose metabolism in the brain with F-18-fluorodeoxyglucose or Aβ deposition with F-18-florbetaben. However, since imaging time ranges from 10 to 30 minutes, movements during the examination might result in image artifacts, which interfere with diagnosis. To solve this problem, data-driven brain motion correction (DDBMC) techniques are capable of performing motion corrected reconstruction using highly accurate motion estimates with high temporal resolution. In this study, we investigated the effectiveness of DDBMC techniques on PET/CT images using a Hoffman phantom, involving continuous rotational and tilting motion, each expanded up to approximately 20 degrees. Materials and methods: Listmode imaging was performed using a Hoffman phantom that reproduced rotational and tilting motions of the head. Brain motion correction processing was performed on the obtained data. Reconstructed images with and without brain motion correction processing were compared. Visual evaluations by a nuclear medicine specialist and quantitative parameters of images with correction and reference still images were compared. Results: Normalized Mean Squared Error (NMSE) results demonstrated the effectiveness of DDBMC in compensating for rotational and tilting motions during PET imaging. In Cases 1 and 2 involving rotational motion, NMSE decreased from 0.15–0.2 to approximately 0.01 with DDBMC, indicating a substantial reduction in differences from the reference image across various brain regions. In the Structural Similarity Index (SSIM), DDBMC improved it to above 0.96 Contrast assessment revealed notable improvements with DDBMC. In continuous rotational motion, % contrast increased from 42.4% to 73.5%, In tilting motion, % contrast increased from 52.3% to 64.5%, eliminating significant differences from the static reference image. These findings underscore the efficacy of DDBMC in enhancing image contrast and minimizing motion induced variations across different motion scenarios. Conclusions: DDBMC processing can effectively compensate for continuous rotational and tilting motion of the head during PET, with motion angles of approximately 20 degrees. However, a significant limitation of this study is the exclusive validation of the proposed method using a Hoffman phantom; its applicability to the human brain has not been investigated. Further research involving human subjects is necessary to assess the generalizability and reliability of the presented motion correction technique in real clinical scenarios. [ABSTRACT FROM AUTHOR]

Simulations and numerical analysis of physical problems are important steps toward understanding underlying mechanisms of the processes. Important examples would be medical physics and medical imaging. Compartmental modeling has been found useful for estimating the transport and temporal variations of drugs/contaminants (commonly used in medical physics and medical imaging) in different organs, given that different organs would be modeled as compartments. Recycling among these modeled compartments (i.e., organs) was allowed through defining sets of constant transfer rates. In order to mathematically define these systems, one needs to use sets of differential equations (depending on the number of compartments) which would in fact be time-consuming and prone to mathematical error. Considering these issues, there is a need for a versatile computer program that is accurate, robust, and user-friendly to perform the required computations automatically. In the present work, we developed and benchmarked an open-source computer program entitled CompVision that was able to simulate five-compartmental systems. The present software had an easy-to-use graphical user interface (GUI) for the users. The executable program and the source codes were made available publicly under GPLv3 license, which would allow everyone to use, modify, and distribute without any restriction. The present program would be useful in a variety of research fields and applications.

In response to the Fukushima Daiichi Nuclear Power Station (FDNPS) accident, the treated water from which the primary radioactive substances were removed contained tritium, and the Japanese government discussed how to treat this water. As the storage capacity of the treated water reached its limit, the Japanese government decided on a method to discharge the treated water into the sea in 2023. Herein, a basic study was conducted to develop a tritiated monitor to directly measure tritium in wastewater for preparing the release of tritiated water from the FDNPS. Two plastic scintillators with different shapes (sheet and pellet types) were compared as detectors. The pellet-type detector was found to be more sensitive to tritiated water than the sheet-type, with an efficiency of 2.95 × 10−5 cps Bq−1 L in the test configuration. In the future, optimizing the design for background reduction should achieve a minimum detectable radioactivity of 1,500 Bq L−1, the emission standard set by nuclear power plant operators. Through this study, we could obtain basic data for developing such a practical tritiated monitor. [ABSTRACT FROM AUTHOR]

Previously, we have developed DynamicMC for modeling relative movement of Oak Ridge National Laboratory phantom in a radiation field for the Monte Carlo N-Particle package (Health Physics. 2023,124(4):301–309). Using this software, three-dimensional dose distributions in a phantom irradiated by a certain mono-energetic (Mono E) source can be deduced through its graphical user interface. In this study, we extended DynamicMC to be used in combination with the Particle and Heavy Ion Transport code System (PHITS) by providing it with a higher flexibility for dynamic movement for an anthropomorphic phantom. For this purpose, we implemented four new functions into the software, which are (1) to generate not only Mono E sources but also those having an energy spectrum of an arbitrary radioisotope (2) to calculate the absorbed doses for several radiologically important organs (3) to automatically average the calculated absorbed doses along the path of the phantom and (4) to generate user-defined slab shielding materials. The first and third items utilize the PHITS-specific modalities named radioisotope-source and sumtally functions, respectively. The computational cost and complexity can be dramatically reduced with these features. We anticipate that the present work and the developed open-source tools will be in the interest of nuclear radiation physics community for research and teaching purposes. [ABSTRACT FROM AUTHOR]

Rhodium-103m is one of the most attractive Auger electron emitters for internal radiotherapy. The half-life of 103mRh is relatively short (56.114 min). Therefore, it needs to be produced using a generator for clinical use. Most studies of 103Pd/103mRh generators using anion-exchange resins were carried out over 50 years ago. However, these resins are no longer commercially available. In the present study, we tested a 103Pd/103mRh generator using alternative anion-exchange resins (i.e., IRA904, IRA410, SA20A, and SA11AL). No-carrier-added 103Pd was used to make the generators. The 103mRh product was eluted from the generators using 6 mL of 0.1 M HCl with a flow rate 0.5 mL/min. The generator made from SA11AL showed good performance, with a yield of 39 %, an impurity level of 103Pd in the product of 0.29 %, and an operation time of 14 min. This makes this generator competitive with previously developed ones. [ABSTRACT FROM AUTHOR]