Simulation study of medical isotope production by accelerator induced reactions.

Trends of isotope yields observed in reactions induced by 16O ions of 140, 315 and 33600 MeV

Energy deposition calculated by PHITS code in Pb spallation target

Calculated results are presented for the number of neutrons produced, the neutron production spectra, and energy deposition as a function of depth in the target when protons in the energy range 190 to 268 MeV are incident on a water-cooled tantalum target.

Independent isotopic yields for elements from Zn to La in the 25 MeV proton-induced fission of ${}^{nat}U$ were determined with the JYFLTRAP facility. In addition, isotopic yields for Zn, Ga, Rb, Sr, Zr, Pd and Xe in the 50 MeV proton-induced fission of ${}^{nat}U$ were measured. The deduced isotopic yield distributions are compared with a Rubchenya model, the GEF model with universal parameters and the semi-empirical Wahl model. Of these, the Rubchenya model gives the best overall agreement with the obtained data. Combining the isotopic yield data with mass yield data to obtain the absolute independent yields was attempted. The result depends on the mass yield distribution.

A more accurate knowledge of heavy fission product yields is needed to improve our understanding of the fission process and to increase the efficiency in nuclear reactor operation. High resolution measurements of fission observables can be done with the recoil mass spectrometer Lohengrin at the Institut Laue-Langevin in Grenoble, France, which was designed to measure fission fragment characteristics from neutron induced fission. The mass separator is situated at the research reactor of the institute and permits the placement of an actinide layer in a high thermal neutron flux. It separates fragments according to atomic mass, kinetic energy and ionic charge state by the action of magnetic and electric fields, and allows to determine these distributions, isotopic yields, and the fragment gamma-decay characteristics. Almost all fissile isotopes rangings from Th to Cf have been investigated with Lohengrin, and in particular mass and nuclear charge distributions for light fission products have been determined. The experimental set-up used to investigate the mass yield and the fission fragment kinetic energy distributions in the heavy mass region, or in the light mass region, is done by coupling a high resolution ionization chamber to the spectrometer. For low mass fission products a double anode ionization chamber is used to determine furthermore isotopic yields within a mass line. For fission fragments of higher mass this separation is no longer possible, and gamma-spectrometry is used instead to identify the contributing nuclear charges. The experimental set-up is shortly described in the present paper, and we present preliminary results for measurements of thermal neutron induced fission in 235 U(nth, f), 239 Pu(nth ,f ) and 241 Pu(nth, f).

Isotope yields have been analyzed within the framework of a Modified Fisher Model to study the power law yield distribution of isotopes in the multifragmentation regime. Using the ratio of the mass dependent symmetry energy coefficient relative to the temperature, $a_{sym}/T$, extracted in previous work and that of the pairing term, $a_{p}/T$, extracted from this work, and assuming that both reflect secondary decay processes, the experimentally observed isotope yields have been corrected for these effects. For a given I = N - Z value, the corrected yields of isotopes relative to the yield of $^{12}C$ show a power law distribution, $Y(N,Z)/Y(^{12}C) \sim A^{-\tau}$, in the mass range of $1 \le A \le 30$ and the distributions are almost identical for the different reactions studied. The observed power law distributions change systematically when I of the isotopes changes and the extracted $\tau$ value decreases from 3.9 to 1.0 as I increases from -1 to 3. These observations are well reproduced by a simple de-excitation model, which the power law distribution of the primary isotopes is determined to $\tau^{prim} = 2.4 \pm 0.2$, suggesting that the disassembling system at the time of the fragment formation is indeed at or very near the critical point.

Osteons are the primary sites of cortical bone lesions. However, many aspects of osteon microstructure remain poorly understood. This study aimed to explores interindividual differences in the osteon morphotype distributions in the human femoral diaphysis by evaluating the secondary osteon distributions in samples from human femurs. Two anonymized bone fragments from two modern Japanese femurs were examined. Twelve continuous transverse femoral diaphysis specimens were prepared from each fragment. Imaging examinations were conducted using a circularly polarized light microscope, and cross-sectional images were rendered using graphical synthesis software. Osteons in the images were identified as either bright-type osteons, dark-type osteons, or an others type. The two femurs were compared, and the secondary osteon morphotype distributions in different regions of their cross-sections were analyzed. When the two femurs were compared, significant differences in osteon density were observed in some regions and cross-sections. The dark-type osteon presence was strongest in the anterior and posterior regions of the femurs. The analytical method used in this study was found to be able to evaluate osteon microstructure. The results suggest that examining additional specimens and analyzing the biomechanical underpinnings of interindividual differences in osteon distribution patterns may help to improve our understanding of osteon microstructure.

Recent successful results in passive carbon-ion radiotherapy allow the patient to live for a longer time and allow younger patients to receive the radiotherapy. Undesired radiation exposure in normal tissues far from the target volume is considerably lower than that close to the treatment target, but it is considered to be non-negligible in the estimation of the secondary cancer risk. Therefore, it is very important to reduce the undesired secondary neutron exposure in passive carbon-ion radiotherapy without influencing the clinical beam. In this study, the source components in which the secondary neutrons are produced during passive carbon-ion radiotherapy were identified and the method to reduce the secondary neutron dose effectively based on the identification of the main sources without influencing the clinical beam was investigated. A Monte Carlo study with the PHITS code was performed by assuming the beamline at the Heavy-Ion Medical Accelerator in Chiba (HIMAC). At first, the authors investigated the main sources of secondary neutrons in passive carbon-ion radiotherapy. Next, they investigated the reduction in the neutron dose with various modifications of the beamline device that is the most dominant in the neutron production. Finally, they investigated the use of an additional shield for the patient. It was shown that the main source is the secondary neutrons produced in the four-leaf collimator (FLC) used as a precollimator at HIAMC, of which contribution in the total neutron ambient dose equivalent is more than 70%. The investigations showed that the modification of the FLC can reduce the neutron dose at positions close to the beam axis by 70% and the FLC is very useful not only for the collimation of the primary beam but also the reduction in the secondary neutrons. Also, an additional shield for the patient is very effective to reduce the neutron dose at positions farther than 50 cm from the beam axis. Finally, they showed that the neutron dose can be reduced by approximately 70% at any position without influencing the primary beam used in treatment. This study was performed by assuming the HIMAC beamline; however, this study provides important information for reoptimizing the arrangement and the materials of beamline devices and designing a new facility for passive carbon-ion radiotherapy and probably passive proton radiotherapy.

2018 ACC/HRS/NASCI/SCAI/SCCT Expert Consensus Document on Optimal Use of Ionizing Radiation in Cardiovascular Imaging: Best Practices for Safety and Effectiveness.

The yields of Kr (A = 87–93) and Xe (A = 138–143) primary fission fragments produced in 232Th, 238U, and 244Pu photofission upon the scission of a target nucleus and neutron emission were measured in an experiment with bremsstrahlung from electrons accelerated to 25 MeV by a microtron, and the results of these measurements are presented. The experimental procedure used involved the transportation of fragments that escaped from the target by a gas flow through a capillary and the condensation of Kr and Xe inert gases in a cryostat at liquid-nitrogen temperature. The fragments of all other elements were retained with a filter at the capillary inlet. The isotopes of Kr and Xe were identified by the γ spectra of their daughter products. The mass-number distributions of the independent yields of Kr and Xe isotopes are obtained and compared with similar data on fission induced by thermal and fast neutrons; the shifts of the fragment charges with respect to the undistorted charge distribution are determined. Prospects for using photofission fragments in studying the structure of highly neutron-rich nuclei are discussed.

Nuclear medicine is an integrative field encompassing nuclear physics, chemistry, and medicine, utilizing radioactive materials (radiopharmaceuticals) for disease diagnosis and treatment. It provides both anatomical and functional information simultaneously, aiding in early disease detection and treatment planning. The principles of nuclear medicine involve the use of various radiopharmaceuticals, including Technetium-99m (Tc-99m), Fluorine-18 (F-18), Iodine-131 (I-131), and Gallium-67 (Ga-67), targeting specific organs or tissues for diagnostic and therapeutic purposes. Imaging techniques such as Single-Photon Emission Computed Tomography (SPECT), Positron Emission Tomography (PET), Planar Scintigraphy, and Hybrid Imaging play key roles in visualizing physiological processes. Pharmacists are integral in radiopharmaceutical preparation, quality control, dispensing, and radiation safety, ensuring compliance with regulatory standards. Nurses support patient education, preparation, monitoring, and post-procedure care, contributing to comprehensive patient management. Collaboration between pharmacists and nurses optimizes nuclear medicine's diagnostic and therapeutic benefits, emphasizing patient safety and effective healthcare delivery. This integrated approach underscores the significance of nuclear medicine in modern medical practice.

Fission yield measurements of Rb, Sr, Cs and Ba isotopes far from the center of the isotopic yield distributions in 235U( nth, f)

Research Organization for Information Science – Technology (RIST), 2-4 Shirane, Tokai-mura, Ibaraki, 319-1106, JapanParticle and Heavy Ion Transport code System (PHITS) support a broad range of research activities: radiation shielding and dosimetry, radiotherapy and space science as well as the high-energy physics. In this paper, various benchmark calculations based on high-energy collision experiments are carried out using the PHITS code: particle production (positive and negative pion) on thin or thick targets (hydrogen, carbon and aluminum), energy deposition in target and peripheral equipment. On the whole, the good agreement between PHITS calculations and experimental data is shown for many cases.

Calculation of the ORELA neutron moderator spectrum and resolution function

The problem of measuring the gamma heating in a mixed DT neutron and gamma ray environment was explored. A new detector technique was developed to make this measurement. Gamma heating measurements were made in a low-Z assembly irradiated with 14-Mev neutrons and (n, n{prime}) gammas produced by a Texas Nuclear Model 9400 neutron generator. Heating measurements were made in the mid-line of the lattice using a proportional counter operating in the Continuously-varied Bias-voltage Acquisition mode. The neutron-induced signal was separated from the gamma-induced signal by exploiting the signal rise-time differences inherent to radiations of different linear energy transfer coefficient, which are observable in a proportional counter. The operating limits of this measurement technique were explored by varying the counter position in the low-Z lattice, hence changing the irradiation spectrum observed. The experiment was modelled numerically to help interpret the measured results. The transport of neutrons and gamma rays in the assembly was modelled using the one- dimensional radiation transport code ANISN/PC. The cross-section set used for these calculations was derived from the ENDF/B-V library using the code MC{sup 2}-2 for the case of DT neutrons slowing down in a low-Z material. The calculated neutron and gamma spectra in the slab and the relevant mass-stopping powers were used to construct weighting factors which relate the energy deposition in the counter fill-gas to that in the counter wall and in the surrounding material. The gamma energy deposition at various positions in the lattice is estimated by applying these weighting factors to the measured gamma energy deposition in the counter at those locations.