High-energy Beta Research Articles

In-situ detection of high-energy beta ray emitter 90Sr/90Y inside the Fukushima Daiichi Nuclear Power Station Unit 3 reactor building using a liquid light guide Cherenkov counter

We have developed a method to directly detect 90Sr/90Y under a high gamma ray background using a liquid light guide Cherenkov counter. Cherenkov radiation has the characteristic that the angle of radiation varies depending on the energy of the charged particles. Using this feature, we have developed a surface contamination detector capable of discriminating between 662 keV gamma rays from 137Cs and beta rays from 90Sr/90Y through time-of-flight analysis of the Cherenkov radiation generated inside the liquid light guide. With this detector, we conducted a measurement test of 90Sr/90Y inside the Fukushima Daiichi Nuclear Power Station Unit 3 reactor building and achieved the first in-situ detection of 90Sr/90Y under a high gamma-ray background.

Tissue Dose-rate Kernels for Bremsstrahlung Exposure from Internal Electron Emitters.

Radionuclides emitting high-energy beta rays are frequently employed for therapeutic purposes in the field of medicine. However, it is widely recognized that such radionuclides have the potential to generate in vivo bremsstrahlung radiation. This research study focused on investigating the dose rate of bremsstrahlung radiation emanating from a radioactive source embedded in a patient. To accomplish this, we estimate the spectral energy distribution of the generated bremsstrahlung. By employing this spectral distribution, we present a novel method for estimating the bremsstrahlung dose rate kernel applicable to a given combination of source and material. This method considers photon buildup and attenuation, as well as the encapsulation of the radiation source. Furthermore, we provide formulas for both monoenergetic electrons and beta-transition electrons that account for radioactive decay.

Dose rate conversion coefficients for ocular contamination in nuclear medicine: A Monte Carlo simulation with experimental validation.

Since 2011, the International Commission on Radiological Protection (ICRP) has recommended an annual eye lens dose limit of 20 mSv for radiation workers, averaged over 5 years, with no year exceeding 50 mSv. However, limited research has been conducted on dose rate conversion coefficients (DCCs) for direct contamination of the eye. This study aimed to accurately determine DCCs for the eye lens and cornea for ocular contamination with radionuclides used in nuclear medicine. DCCs for 37 radionuclides used in nuclear medicine were determined using two different methods. Method 1 involved conducting Monte Carlo (MC) simulations of an ICRU cylinder to determine the absorbed dose at a depth of 3mm resulting from a point source. The accuracy of this simulation approach was validated by experimental thermoluminescent dosimeter (TLD) measurements for 18F, 68Ga, 99mTc, and 177Lu. In method 2, average DCCs were calculated for the eye lens (complete and radiosensitive parts) and the cornea for both a point source and thin surface contamination centered on the cornea using MC simulations on the adult mesh-type reference computational phantom of the eye from the ICRP (MRCP). DCCs determined from TLD measurements showed excellent agreement (deviations: +1.4%, +4.7%, -3.1%, and -2.5% for 18F, 68Ga, 99mTc, and 177Lu, respectively) compared to MC simulations of the experimental set-up. For the 37 radionuclides, DCCs of the complete eye-lens for a point source ranged from 2.53×10-7 to 4.15×10-2 mGy MBq-1 s-1 for the adult MRCPs, being substantially smaller compared to DCCs determined via MC simulations of a ICRU cylinder. In general, point source and surface contamination showed comparable DCCs for the eye lens. Radionuclides emitting low-energy beta radiation or conversion electrons (e.g., 177Lu, 99mTc) showed low DCCs as the radiation does not penetrate to the depth of the eye lens, while radionuclides emitting high-energy beta radiation (e.g., 90Y) showed high DCCs. Overall, DCCs for the radiosensitive part of the eye lens were larger (up to a factor of 3) compared to the complete eye lens. DCCs for the cornea were larger than for the eye lens with a factor that strongly depended on the emitted radiation type. Especially alpha emitters (e.g., 211At, 223Ra) showed high DCCs for the cornea because of the short range of alpha radiation, leading to local maxima in the cornea and not reaching the eye lens. DCCs at a depth of 3mm in an ICRU cylinder and adult MRCP DCCs for both the complete and sensitive parts of the eye lens and cornea were determined for 37 radionuclides having applications in nuclear medicine. These DCCs are highly useful in radiation safety assessments and radiation dose calculations in ocular contamination incidents.

Evaluation of radiation dose caused by bremsstrahlung photons generated by high-energy beta rays using the PHITS and GEANT4 simulation codes

ABSTRACT High-energy beta-ray sources generate bremsstrahlung photons in the building materials, generated by the radioactive nuclides inside the nuclear reactor buildings emitted by the Fukushima Daiichi nuclear reactor accident. Therefore, evaluating the bremsstrahlung dose subjected to the workers in the building is crucial for radiation protection. The precision for assessing the bremsstrahlung dose was investigated by comparing the Particle and Heavy Ion Transport code System (PHITS) and the GEometry ANd Tracking (GEANT4) simulation code results. Behind various shielding plates (lead, copper, aluminum, glass, and polyethylene with multiple thicknesses), the water cylinder was set to obtain the absorbed dose and the deposited energy spectrum by the bremsstrahlung photons. In comparing the deposited energy spectrum, the spectral shapes have consistent trends. Below several tens of keV, a peak is observed in the PHITS spectrum for lead. While comparing the absorbed dose, most of the results from both codes correlate within an ~10% difference for 2.280 MeV beta-ray sources and an ~20% difference for 0.5459 MeV beta-ray sources, except for ~30% for 20 mm thick lead. Although some differences occurred, the evaluation results of both codes correlated well with the above precision.

Laminated Flow-Cell Detector with Granulated Scintillator for the Detection of Tritiated Water

Nuclear sites require regular measurements of the air, soil, and groundwater to ensure the safety of the surrounding environment from potentially hazardous levels of contamination. Although high-energy beta and gamma emitters can often be detected instantly using fixed dosimeters, the detection of low-energy beta emitters is a difficult challenge, especially in groundwater, as its radiation is easily self-absorbed by the surrounding medium. Therefore, it is common practice to sample groundwater and transfer it to a laboratory for analysis using Liquid Scintillation Counting. This work demonstrates a new detector design for the real-time monitoring of tritiated water, a weak beta emitter. This design utilizes a flow cell filled with a granulated scintillator to maximize the surface area of the sample. The cavity is made from plastic sheets, which allow rapid manufacture using readily available lamination sheets. A column of SiPMs in coincidence counting mode has been implemented to reduce noise and allow future extensions to the flow cell for greater detection rates while allowing the detector to fit within limited spaces such as groundwater monitoring boreholes. Using multiple concentrations of tritiated water, this detector has been validated and calibrated, obtaining a minimum detection activity of 26.356 ± 0.889 Bq/mL for a 1-day counting period.

Oxygen vacancies and local amorphization introduced by high fluence neutron irradiation in β -Ga2O3 power diodes

Beta phase gallium oxide (β-Ga2O3) is emerging as a promising material for space applications due to its unique properties and potential high performance in extreme environments. In this work, we systematically study the impact of β-Ga2O3 Schottky barrier diodes (SBDs) under a high fluence neutron irradiation to explore the degradation mechanism of the devices. After irradiated by neutrons with an average energy of 1–2 MeV and a dose rate of 1.3 × 1012 cm−2 s−1, SBDs with a homoepitaxial layer suffered serious performance degradation. The main manifestation of this degradation was a substantial increase in on-resistance, which rose from 3.9 to 3.5 × 108 mΩ·cm2 under the aforementioned irradiation conditions. The appearance of amorphous/polycrystalline striped lattice damage in the epitaxial layer as well as the presence of deep-level defects caused by oxygen vacancies are factors related to this phenomenon. The simulation revealed that the capture reaction of neutrons and Ga elements is the primary cause of neutron irradiation. This reaction generates high-energy beta- particles (β-particles) resulting in the formation of defects. This paper reveals the degradation mechanism of β-Ga2O3 SBDs under neutron irradiation and provides a possible design roadmap for radiation-resistant β-Ga2O3 power devices. Moreover, a high-temperature oxygen annealing process was implemented, which proved to be in restoring the device performance.

Практичні аспекти застосування методу черенковського лічення з корекцією кольорового гасіння

Cerenkov counting is a convenient and effective method of counting high-energy beta radiation, which has long been used to measure a number of radionuclides, such as, in particular, 90Sr+90Y, in environmental objects. The traditional Cerenkov method requires the use of radiochemical sample preparation procedures, but these procedures may be simpler than those used, for example, for the liquid scintillation counting (LSC) method. We proposed the Cerencov method, which corrects color quench effect. The method is based on the correlation between the counting rates of the radiation of the sample and its external standard, which is observed for a wide range of color quenching of the samples. The use of such a Cerencov method allows measurement of high-energy -emitters, in particular, its use as an express method for the study of 90Sr+90Y in surface water. For a number of cases, the method makes it possible to avoid the use of long lasting and expensive sample preparation procedures. The results of the cross-testing of the samples obtained by the Cerencov method and direct measurement by the liquid scintillation counting method are in good agreement with each other.

A new method based on selective fluorescent polymers (PSresin) for the analysis of 90Sr in presence of 210Pb in environmental samples

90Sr is of major concern in emergency and environmental control plans. It is one of the main fission products in nuclear facilities and is a high-energy beta emitter that presents chemical properties similar to those of calcium. 90Sr is commonly detected using methods based on liquid scintillation counting (LSC) following a chemical separation to remove potential interferences. However, these methods generate mixed wastes (hazardous and radioactive). In recent years, an alternative strategy using PSresins has been developed. For 90Sr analysis with PSresins, 210Pb is the main interferent that should be considered, as it is also strongly retained in the PSresin. In this study, a procedure was developed involving a precipitation with iodates to separate lead from strontium before the PSresin separation. Moreover, the method developed was compared with well-established and routinely used methods based on LSC, revealing that the new method produced equivalent results in less time and with less waste generation.

In-beam gamma -ray spectroscopy of ^{94}Ag

A recoil-beta-tagging experiment has been performed to study the excited T=0 and T=1 states in the odd–odd N=Z nucleus ^{94}Ag, populated via the ^{40}Ca(^{58}Ni,1p3n)^{94}Ag reaction. The experiment was conducted using the MARA recoil separator and JUROGAM3 array at the Accelerator Laboratory of the University of Jyväskylä. Through correlating fast, high-energy beta decays at the MARA focal plane with prompt gamma rays emitted at the reaction target, a number of transitions between excited states in ^{94}Ag have been identified. The timing characteristics of these transitions confirm that they fall within decay sequences that feed the short-lived T=1 ground state of ^{94}Ag. The transitions are proposed to proceed within and between the sets of states with T=0 and T=1. Possible correspondence between some of these transitions from analog states in ^{94}Pd has been discussed, and shell-model calculations including multipole and monopole electromagnetic effects have been presented, in order to enable predictions of the decay patterns between the T=0 and T=1 states and to allow a theoretical set of Coulomb energy differences to be calculated for the A = 94T=1 analog states.

Fundamentals of Rhenium-188 Radiopharmaceutical Chemistry.

The β- emitter, rhenium-188 (188Re), has long been recognized as an attractive candidate for targeted cancer radionuclide therapy (TRNT). This transition metal shares chemical similarities with its congener element technetium, whose nuclear isomer technetium-99m (99mTc) is the current workhorse of diagnostic nuclear medicine. The differences between these two elements have a significant impact on the radiolabelling methods and should always receive critical attention. This review aims to highlight what needs to be considered to design a successful radiopharmaceutical incorporating 118Re. Some of the most effective strategies for preparing therapeutic radiopharmaceuticals with 188Re are illustrated and rationalized using the concept of the inorganic functional group (core) and a simple ligand field theoretical model combined with a qualitative definition of frontiers orbitals. Of special interest are the Re(V) oxo and Re(V) nitrido functional groups. Suitable ligands for binding to these cores are discussed, successful clinical applications are summarized, and a prediction of viable future applications is presented. Rhenium-188 decays through the emission of a high energy beta particle (2.12 MeV max energy) and a half-life of 16.9 h. An ideal biological target would therefore be a high-capacity target site (transporters, potential gradients, tumour microenvironment) with less emphasis on saturable targets such as overexpressed receptors on smaller metastases.

Application and development of liquid argon detector in rare event detection

Rare event detection is a frontier subject in particle physics and nuclear physics. In particular, dark matter detection, neutrino-free double beta decay and neutrino-nucleon coherent elastic scattering are being planned and implemented gradually. Rare event detection requires not only the detectors to possess excellent performances but also extremely low environmental background, so the selection of detectors and related materials is an important issue in rare event detection. Liquid argon has become an important scintillator material for scintillator detectors because of its low cost, good scintillation performance and large volume. Liquid argon was first studied in the 1940s as a sensitive material for ionizing radiation detectors. The first measurements of high-energy beta particles were obtained by using a liquid argon ionization chamber in 1953. The ICARUS group put forward the idea of constructing liquid argon temporal projection chamber, and made attempt to construct liquid argon temporal projection chamber in 1977. The scintillation light signals were collected for the first time in a liquid argon temporal projection chamber in 1999. Thus, the drift time of the particle can be obtained to determine the particle track. After development, single-phase liquid argon scintillator detector and two-phase argon time projection chamber have become two common types of liquid argon detectors, and have been extensively used in rare event detection experiments in recent years. For dark matter detection, the DEAP group and DarkSide group have achieved good results with single-phase liquid argon scintillation detector and two-phase argon time projection chamber, respectively. For neutrino-free double beta decay experiments, the GERDA group has done a lot of researches of liquid argon anti-coincidence system and applied the said system to experiments. The LEGEND group, which is the combination of GERDA and MAJORANA experimental group, upgraded the liquid argon anti-coincidence system which was applied to the following LEGEND-200 project. For neutrino-nucleon elastic scattering experiments, COHERENT obtained the latest results by using the liquid argon detectors. The Taishan neutrino-nucleon coherent elastic scattering project of the High Energy Institute of Chinese Academy of Sciences has also begun to study the feasibility of liquid argon anti-coincidence system. Finally, this paper discusses the direction of optimizing the liquid argon detector, such as exposure, background level and optical readout scheme, and gives a good prospect of liquid argon detector applied to rare event detection in the future.

Biokinetic Model Development of 177Lu-labeled Methylene Diphosphonate as a Radiopharmaceutical Treatment

177Lu is a lanthanide radionuclide. In recent years, the possibility of applying a drug based on the 177Lu radionuclide as a palliative treatment for bone metastases has increased. 177Lu has many prospects in terms of its applications in nuclear medicine. The high-energy beta particles and the relatively short half-life of the radionuclide are used to provide an effective treatment. In this work, a comparison of organ and tissue doses is performed with two different drugs: 177Lu in an ionic radionuclide form and 177Lu labeled methylene diphosphonate (177Lu-MDP). 177Lu in an ionic form actively accumulates in the liver and bones. Phosphonate compounds form stable radio-labeled complexes. This suggests that 177Lu-MDP is a non-dissociated form of the drug. The distribution and elimination of the drug occur according to the kinetics of the carrier, i.e., methylene diphosphonate. It is shown that the use of an osteotropic complex (describing any drug that is attracted to and targets bone) allows for the concentration of a large dose in pathological areas and minimizes damage to healthy organs and tissues.

Psoralen as a Photosensitizers for Photodynamic Therapy by Means of In Vitro Cherenkov Light

Possible enhancements of DNA damage with light of different wavelengths and ionizing radiation (Rhenium-188-a high energy beta emitter (Re-188)) on plasmid DNA and FaDu cells via psoralen were investigated. The biophysical experimental setup could also be used to investigate additional DNA damage due to photodynamic effects, resulting from Cherenkov light. Conformational changes of plasmid DNA due to DNA damage were detected and quantified by gel electrophoresis and fluorescent staining. The clonogene survival of the FaDu cells was analyzed with colony formation assays. Dimethyl sulfoxide was chosen as a chemical modulator, and Re-188 was used to evaluate the radiotoxicity and light (UVC: λ = 254 nm and UVA: λ = 366 nm) to determine the phototoxicity. Psoralen did not show chemotoxic effects on the plasmid DNA or FaDu cells. After additional treatment with light (only 366 nm-not seen with 254 nm), a concentration-dependent increase in single strand breaks (SSBs) was visible, resulting in a decrease in the survival fraction due to the photochemical activation of psoralen. Whilst UVC light was phototoxic, UVA light did not conclude in DNA strand breaks. Re-188 showed typical radiotoxic effects with SSBs, double strand breaks, and an overall reduced cell survival for both the plasmid DNA and FaDu cells. While psoralen and UVA light showed an increased toxicity on plasmid DNA and human cancer cells, Re-188, in combination with psoralen, did not provoke additional DNA damage via Cherenkov light.

RADT-20. REPORT OF THE RESPECT-GBM™ PHASE I/IIA DOSE ESCALATION TRIAL OF RHENIUM-186 NANOLIPOSOME (186RNL) IN RECURRENT GLIOMA VIA CONVECTION ENHANCED DELIVERY (CED) & PLANNED PHASE IIB TRIAL

Abstract A phase I/IIa dose escalation trial was initiated to determine the safety and recommended phase II dose (RP2D) of 186RNL in patients with recurrent glioma. Liposomal rhenium-186 (186RNL) is a source of high energy beta particles and gamma photons with attractive properties for brain CED.Patients with biopsy proven recurrent glioma had computerized treatment planning and placement of up to 4 intracranial catheter(s). Each patient received a single administration of 186RNL by CED. Whole body planar and SPECT/CT imaging from days 1-8 following treatment was performed. Patients were followed for safety, sufficiency of delivery and overall survival. Twenty-one patients across 6 dose escalation cohorts received 1.0-22.3mCi in a volume of 0.6-8.8mL. Mean tumor volume was 8.3mL, patients were heavily pretreated (mean 1.7 recurrences) with poor prognostic factors. There were no CED failures. Mean absorbed radiation dose to the tumor (MARDT) was 271Gy. No dose limiting toxicities were observed. Patients were stratified by MARDT. Those receiving > 100Gy MARDT (n=12) had a median and mean overall survival of 129.9 (95% CI 35.1 to 169.3) and 99.5 ± 19 weeks respectively with 3 patients alive. Patients receiving ≤ 100Gy MARDT (n=9) had a median and mean overall survival of 22.4 (95% CI 6.6 to 45.4) and 24.7 ± 4.8 weeks respectively, none are alive. Kaplan Meier analysis of overall survival for patients receiving MARDT greater than 100Gy vs. those with ≤ 100Gy showed a statistically significant difference in overall survival (p< 0.001).A single administration of 186RNL by CED in recurrent glioma patients is feasible, safe, and potentially effective in increasing overall survival when > 100Gy radiation is delivered to the tumor. A RP2D of 22.3mCi in 8.8mL was selected for patients with tumor size of ≤ 15mL in the planned phase 2b trial. The PIIb trial design and comparative survival data will also be presented.

277O The ReSPECT-GBM™ phase I/IIa trial of rhenium-186 nanoliposome (186RNL) in recurrent glioma via convection enhanced delivery (CED) and planned phase IIb trial

A phase I/IIa dose escalation trial was initiated to determine the safety and recommended phase II dose (RP2D) of 186RNL in patients with recurrent glioma. 186RNL is a source of high energy beta and gamma particles. We report the safety, feasibility, overall survival (OS), RP2D and proposed phase IIb clinical plan.

Beta-Ray-Bremsstrahlung Contributions to Short-Lived Delayed Photoneutron Groups in Heavy Water Reactors

Hard bremsstrahlung produced during the deceleration of fission-product beta rays in nuclear fuel is proposed as a source of delayed photoneutrons (PNs) in heavy water reactors. Electron Gamma Shower (EGS5) code simulations of coupled electron-photon transport in seven fuel element geometries immersed in an infinite heavy water medium confirm high-energy beta rays produce sufficient bremsstrahlung yields with photon energies greater than the D(γ,n)1H reaction threshold such that the beta-ray contribution to an isotopic PN yield can be comparable to or greater than yields from hard gamma rays emitted during the isomeric transition of the daughter, especially for some short-lived fission products with high-intensity direct-to-ground-state beta transitions where the beta ray and antineutrino carry away the majority of the Q-value. Some fission products that do not have hard gamma rays in their decay schemes are in fact PN precursors due to the beta-ray-bremsstrahlung contribution. The lack of evaluated nuclear data for many short-lived fission products, data reliability issues of fission products with decay scheme data, cross-section library effects, and possible decay-chain/parent-feeding phenomenon are affecting the accuracy of PN group parameters derived from a small number of legacy experiments. The reanalysis of two legacy PN experiments supports the existence of a very-short-lived direct-delayed neutron group.

Radiation Monitoring Using Personal Dosimeter Devices in Terms of Long-Term Compliance and Creating a Culture of Safety

IntroductionRadiation-emitting devices are commonplace in the hospital with their ability to produce imaging for diagnoses, However, they hold a risk for device operators due to radiation exposure. Hospital systems have programs where physicians exposed to radiation are required to wear dosimeters to help record total radiation over time. Dosimetry readings over standardized recommendations can lead to hospital image issues and disciplinary action for physicians. This study aimed to discover the true values recorded on dosimeters with radiation exposure and discuss effective ways to encourage compliance with dosimeter usage.MethodologyThe study was completed over a course of 12 months with physicians from three different hospitals. Selection criteria included physicians considered to be “radiation workers” including those who operate x-ray machines, fluoroscopy units, unsealed and sealed isotopes, or those exposed to other sources of gamma or high-energy beta radiation. Two Plan-Do-Study-Act (PDSA) cycles were implemented. The first cycle was the first six months of the study and the second cycle was the second six months of the study. The first PDSA cycle had planned dosimeter reading check-ins every month. After this cycle ended, physicians were sent a survey anonymously asking if they had ever intentionally left behind their dosimeter. In the second PDSA cycle, a planned policy change was put into action where penalties for physicians who went over the recommended dosage were stopped. A monthly educational meeting where a discussion on the risks of radiation as well as protective mechanisms was implemented instead. The same monthly check-ins for dosimeter reading monitoring were employed again with the same survey regarding dosimeter adherence and usage being sent out at the end of the second cycle. Run charts were created to determine whether the policy change showed statistically significant differences in dosimetry readings.ResultsProtocol changes led to statistically significant (p<0.05) differences in radiation exposure recorded throughout the hospital systems. The primary PDSA cycle readings showed that hospital systems one (n=118), two (n=71), and three (n=32) had readings of 3.90 mSv, 2.55 mSv, and 2.02 mSv, respectively, which were all under the annual recommended dose limit of 10 mSv maximum per six months. However, an average of 94.4% (n=221) of physicians across all hospitals admitted to not using the dosimeter. In the second PDSA cycle after the policy change, the radiation doses were higher with an increase in the average cumulative dose at hospital system one of 255%, 328% at system two, and 323% at system three. Hospital systems one and two were both over the yearly limit of 20.0 mSv (7.70 mSv over for system one and 1.86 mSv over for system two) while system three remained under. The number of physicians who stated they always used the dosimeter during the second PDSA cycle increased to 83.9% in-hospital system one, 90.2% in-hospital system two, and 93.8% in-hospital system three.ConclusionCreating a culture of safety is critical for physician compliance. A comfortable work environment without unreasonable consequences creates an environment where physicians can focus on their health and safety while also doing what is in the workplace’s best interest. This culture can best be made with more collaboration between administrative staff and workers to create a trustworthy experience in hospital systems.

Cherenkov radiation technique for the determination of fission product 90Sr in milk

ABSTRACT Monitoring of the anthropogenic radionuclides (90Sr, 135Cs and 137Cs) in different components such as spinach, milk, meat, soil and the grass is important for the environmental radiological survey. Nuclear weapons testing in the atmosphere, nuclear power plant accidents and leaks from the nuclear fuel cycle are the main sources of these radionuclides. The amounts of 90Sr/90Y detected in the environment are mostly due to fallout from nuclear weapons testing. Because of its long physical (28.5 years) and biological half-lives (approximately 12 years) and high fission yield, the measurement of 90Sr is also necessary for radiation protection purposes. It accumulates in bone tissue when ingested by humans through the food chain, and 90Y, a daughter nuclide of 90Sr, emits high-energy beta particles, raising the risk of bone cancer. Strontium has been widely measured in milk samples by using various classical methods. In this study, the procedure we used is based on the separation of 90Y by HDEHP extraction and counting the Cherenkov radiation using a liquid scintillation spectrometer, Quantulus 1220. Prior to analyses, spiked milk samples were dried and prepared as milk powder. The microwave ashing programme was optimised, and recovery of the radiochemical separation steps was tested for spiked milk powder samples before routine analysis. This method is found to be applicable for the routine analysis of 90Sr in milk samples after validation of the method by measuring IRMM milk powder samples, too. A lower limit of detection of about 0.02 Bq.kg−1 was obtained for samples in the case of 84–99% Y chemical yield, 1.45 cpm reagent blank, 4 × 60 minutes counting time and about 83.5 ± 2.1% counting efficiency.

Hybrid kernelised expectation maximisation for Bremsstrahlung SPECT reconstruction in SIRT with 90Y micro-spheres

BackgroundSelective internal radiation therapy with Yttrium-90 microspheres is an effective therapy for liver cancer and liver metastases. Yttrium-90 is mainly a high-energy beta particle emitter. These beta particles emit Bremsstrahlung radiation during their interaction with tissue making post-therapy imaging of the radioactivity distribution feasible. Nevertheless, image quality and quantification is difficult due to the continuous energy spectrum which makes resolution modelling, attenuation and scatter estimation challenging and therefore the dosimetry quantification is inaccurate. As a consequence a reconstruction algorithm able to improve resolution could be beneficial.MethodsIn this study, the hybrid kernelised expectation maximisation (HKEM) is used to improve resolution and contrast and reduce noise, in addition a modified HKEM called frozen HKEM (FHKEM) is investigated to further reduce noise. The iterative part of the FHKEM kernel was frozen at the 72nd sub-iteration. When using ordered subsets algorithms the data is divided in smaller subsets and the smallest algorithm iterative step is called sub-iteration. A NEMA phantom with spherical inserts was used for the optimisation and validation of the algorithm, and data from 5 patients treated with Selective internal radiation therapy were used as proof of clinical relevance of the method.ResultsThe results suggest a maximum improvement of 56% for region of interest mean recovery coefficient at fixed coefficient of variation and better identification of the hot volumes in the NEMA phantom. Similar improvements were achieved with patient data, showing 47% mean value improvement over the gold standard used in hospitals.ConclusionsSuch quantitative improvements could facilitate improved dosimetry calculations with SPECT when treating patients with Selective internal radiation therapy, as well as provide a more visible position of the cancerous lesions in the liver.

Birth of the Beta-knife Thyroidectomy: The Radiance of Saul Hertz.

This is the story of how one man's life's work allowed for Iodine-131 (I-131) to become a therapy for hyperthyroidism and thyroid cancer. What is now a standard in our times arose from Saul Hertz's rather challenging and humble beginnings. Thyroid lobectomy and total thyroidectomy were therapeutic mainstays for thyroid disease until Hertz treated his first patient with radioactive iodine (RAI) ablation therapy at Massachusetts General Hospital (MGH) on March 31, 1941. His concepts for using beta particle emission from RAI to ablate thyroid tissue were revolutionary. Hertz's RAI therapy translated to research with thyroid cancer by the mid-1940s. The high-energy beta particles produced cytolethal effects on remnant thyroid tissue left behind by total thyroidectomy, thereby accomplishing completion thyroidectomy in some patients. Progressive surgeons from the Hertz era incorporated RAI into their practice. MGH surgery resident Francis Moore took sabbatical from clinical training to do translational research with RAI and other radioisotopes. Irving Ariel of New York became known as a nuclear surgeon in the wake of Hertz's work. George Crile Jr of Cleveland became an RAI advocate for the surgical community, implementing several paradigm-changing concepts in thyroid disease along the way. Hertz was a visionary who sparked this movement, predicting many of the molecular dilemmas with RAI-tumor avidity that clinical researchers continue to navigate today. This timely history for surgical oncologists and endocrine surgeons traces the development of RAI therapy through the life of Saul Hertz, a biographical window influenced by social stigma, political controversy, and mainstream media.