Radiation Dose Limits Research Articles

Preclinical Positron Emission Tomography (PET) of Prosthetic Joint Infection Using a Nitro-Prodrug of 2-[18F]F-p-Aminobenzoic Acid ([18F]F-PABA).

Deep-seated bacterial infections are difficult to detect and diagnose due to the lack of specific clinical imaging modalities. Therefore, the bacteria-specific positron emission tomography radiotracer 2-[18F]fluoro-4-nitrobenzoic acid ([18F]FNB) was developed, which is reduced to 2-[18F]fluoro-4-aminobenzoic acid ([18F]F-PABA) by bacterial nitroreductases and has improved pharmacokinetics compared to the parent compound. PET imaging demonstrated that the uptake of 2-[18F]fluoro-4-nitrobenzoic acid in a clinically relevant Staphylococcus aureus prosthetic joint infection model was up to ∼4-fold higher in the infected joint compared to the contralateral joint. 2-[18F]Fluoro-4-nitrobenzoic acid was also able to distinguish infection from inflammation in a surgical inflammation model. Based on the mouse radiation dosimetry results, the calculated effective dose of 2-[18F]fluoro-4-nitrobenzoic acid was well below the whole-body radiation dose limit established by the Food and Drug Administration for humans. In addition, no treatment-related microscopic changes in organ histopathology were observed in a mouse acute toxicity study. Overall, these data suggest that 2-[18F]fluoro-4-nitrobenzoic acid is a specific and effective imaging agent for noninvasively diagnosing prosthetic joint infections.

Patients’ effective doses assessment during low-dose computed tomography

Computed tomography has become increasingly common for diagnosing socially significant diseases in recent years. In foreign practice, screening schemes for lung cancer in people belonging to risk categories have been developed and implemented. These schemes have been successfully used over the past 10 years. In this case, “low-dose” scanning protocols are used, which make it possible to perform examination with patient effective dose several times lower compared to standard protocols. Lung cancer screening methods using low-dose computed tomography are beginning to be introduced in the Russian Federation. To ensure the radiation safety of those individuals eligible for inclusion in screening programs or participating in biomedical research testing lung cancer screening, it is necessary to evaluate effective doses from low-dose computed tomography and compare these doses to established radiation dose limits. This study assessed the patients’ effective doses who underwent different types of low-dose computed tomography of chest at two medical organizations. The results of the study show that it is possible to achieve non-exceedance of the current annual effective dose limit of 1 mSv only for patients weighing less than 90 kg. For patients with higher body weight, the minimum effective dose will be in the range of 1.2 – 1.4 mSv. The results of the study indicate the need to make changes to the current regulatory and methodological documents of Rospotrebnadzor to ensure the possibility of using low-dose computed tomography as part of screening for all categories of people.

A PHITS based-computational model of a TRIGA-fueled subcritical reactor for gamma dose mapping

Since 1988, the Philippines lacked local access to a nuclear facility, creating a significant void in this field of study for Filipinos. However, after a hiatus of 34 years, this gap was addressed with the recent authorization granted to Philippine Research Reactor 1 (PRR-1) Subcritical Assembly for Training, Education, and Research (SATER), allowing it to resume operations. In this work, a PHITS-based computational model was developed for the recently commissioned PRR-1 SATER. The model utilized a simplified model of the Training, Research, Isotope, General Atomics (TRIGA) fuel that releases photons with 0.6617 MeV energy from the Cs-137 fission product in the fuel. Compared to previous works on photon transport mapping, which utilized average source definition, this study employed individually defined fuel intensities and compared them with the averaged source definition for the fuel. The two fuel source definitions showed noticeable differences inside the reactor tank which is relevant for mixed-field irradiation applications of a research reactor. However, defining the fuel rods by their average strength is sufficient for radiation protection purposes. Simulations were also performed for fuel source definitions based on the average and ±1 standard deviation of the gamma intensity. Gamma doses received by cylindrical phantoms positioned at 0.5 m from the surface of the reactor tank for 500 h were found to be 1 % of the radiation dose limits per year and 4 % of the average dose limit for 5 years as stipulated by the Code of Philippine Nuclear Research Institute (PNRI) Regulations. Loss of water accident was also analyzed based on a conservative exposure time of 500 h. This resulted in a dose value that is only 45.5 % of the dose identified as the emergency turnback guidance of the IAEA. Lastly, PHITS calculated values of gamma doses were found to agree well, with 0.98 ratio, when compared with gamma doses measured at specified locations in the reactor. Results of this study confirm the inherent safety of the PRR-1 SATER in terms of radiological shielding for Cs-137 photons.

Melanoma in Pregnancy-Diagnosis, Treatment, and Consequences for Fetal Development and the Maintenance of Pregnancy.

Cutaneous malignant melanoma is one of the most common neoplasms among pregnancy-associated cancers (PACs). Risk factors include excessive exposure to ultraviolet radiation, the presence of benign and dysplastic nevi, and a patient or family history of melanoma. Self-examination and careful inspection of nevi are crucial, especially in the context of their progression over time. Physiological changes that occur during pregnancy, such as the darkening and enlargement of the nevi, delay the diagnosis of CMM. In the fetus, metastases are very rare, and if they do occur, they concern the placenta or fetal tissues. The choice of treatment is influenced by the cancer stage, symptoms, the time of termination of pregnancy, and the patient's decision. Essential procedures which are safe for the fetus are diagnostic biopsy, ultrasound, and the therapeutic excision of the lesion and the affected lymph nodes. Other imaging methods can be used with a safe radiation dose limit of 100 mGy. Immunotherapy and targeted treatments must be carefully considered, because of their possible adverse effects on the fetus. An interdisciplinary approach to the problem of melanoma during pregnancy is necessary, involving doctors of various specialties.

Radiation exposure of patients during endourological procedures.

Considering the existing gaps in the literature regarding patient radiation dose (RD) and its associated risks, a systematic review of the literature on RD was conducted, focusing on percutaneous nephrolithotomy (PCNL), extracorporeal shock wave lithotripsy (SWL), and ureteroscopy (URS). Two authors conducted a literature search on PubMed, Web of Science, and Google Scholar to identify studies on RD during endourological procedures. Two thousand two hundred sixty-six articles were screened. Sixty-five publications met the inclusion criteria using the PRISMA standards. RD was generally highest for PCNL, reaching levels up to 33mSv, 28,700 mGycm2, and 430.8mGy. This was followed by SWL, with RD reaching up to 7.32mSv, 13,082 mGycm2, and 142mGy. URS demonstrated lower RD, reaching up to 6.07mSv, 8920 mGycm2, and 46.99mGy. Surgeon experience and case load were inversely associated with RD. Strategies such as optimizing fluoroscopy settings, implementing ultrasound (US), and following the ALARA (As Low As Reasonably Achievable) principle minimized RD. This is the first systematic review analyzing RD, which was generally highest during PCNL, followed by SWL and URS. There is no specific RD limit for these procedures. Implementation of strategies such as optimizing fluoroscopy settings, utilizing US, and adhering to the ALARA principle proved effective in reducing RD. However, further research is needed to explore the factors influencing RD, assess their impact on patient outcomes, and establish procedure-specific reference levels for RD.

Feasibility of Liver Transplantation after 90 Y Radioembolization: Lessons from a Radiation Protection Incident.

Radioembolization using 90 Y is a growing procedure in nuclear medicine for treating hepatocellular carcinoma. Current guidelines suggest postponing liver transplantation or surgical resection for a period of 14 to 30 d after radioembolization to minimize surgeons' exposure to ionizing radiation. In light of a radiation protection incident, we reevaluated the minimum delay required between radioembolization and subsequent liver transplantation. A patient with a hepatocellular carcinoma underwent a liver transplantation 44 h after undergoing radioembolization using 90 Y (860 MBq SIR-Spheres). No specific radioprotection measures were followed during surgery and pathological analysis. We subsequently (1) evaluated the healthcare professionals' exposure to ionizing radiation by conducting dose rate measurements from removed liver tissue and (2) extrapolated the recommended interval to be observed between radioembolization and surgery/transplantation to ensure compliance with the radiation dose limits for worker safety. The surgeons involved in the transplantation procedure experienced the highest radiation exposure, with whole-body doses of 2.4 mSv and extremity doses of 24 mSv. The recommended delay between radioembolization and liver transplantation was 8 d when using SIR-Spheres and 15 d when injecting TheraSphere. This delay can be reduced further when considering the specific 90 Y activity administered during radioembolization. This dosimetric study suggests the feasibility of shortening the delay for liver transplantation/surgery after radioembolization from the 8th or 15th day after using SIR-Spheres or TheraSphere, respectively. This delay can be decreased further when adjusted to the administrated activity while upholding radiation protection standards for healthcare professionals.

Radiation Exposure to the Interventional Echocardiographers and Sonographers: A Call to Action

Interventional echocardiography is a rapidly growing field within the disciplines of cardiology and anesthesiology, with the rise of advanced transcatheter procedures making skilled imagers more important than ever. However, these procedures also involve frequent manipulation of the transesophageal echocardiography probe, which means interventional echocardiographers (IEs) are at risk of long-term occupational radiation exposure. Studies have shown that radiation exposure is linked to various health issues, including cancer, cataracts, hypertension, hyperlipidemia, endothelial dysfunction, vascular aging, and early atherosclerosis. While there is increasing awareness of the occupational radiation dose limits and the need for better shielding methods, the importance of radiation safety for the IE is still not sufficiently prioritized in most cardiac catheterization laboratories/hybrid operating rooms. This is partly due to a paucity of studies looking at long-term radiation exposure to the IE, as this field is newer than that of interventional cardiologists.

Radiation dose in radiologist from cerebral angiography using optically stimulated luminescence dosimeter

Background: The number of cerebral angiography procedures is increasing, resulting in higher X-ray radiation doses received by radiologists. Consequently, understanding the radiation doses received by radiologists and the accumulation of radiation in control rooms is crucial for guiding prevention strategies against radiation hazards. Objectives: This study aimed to measure and evaluate radiation doses to the hands, lenses of the eyes, and thyroids of radiologists performing cerebral angiography procedures, as well as to measure the accumulated radiation dose in the control room. Materials and methods: OSL dosimeters were placed on the eyeglass frames, thyroids, hands, and legs of radiologists performing 20 cerebral angiography procedures, as well as on the wall and window of the control room. Results: Radiologists’ average radiation doses were measured at specific body parts as follows: left eye (49 µSv), right eye (15 µSv), left hands (34 µSv), right hands (16 µSv), left legs (27 µSv), right legs (7 µSv), and thyroid glands (14 µSv). Notably, the received doses remained well within the maximum radiation dose limit established by the International Commission on Radiological Protection (ICRP). When calculating the maximum number of procedures that can be performed annually, we based it on the limit of the radiation dose that the eyes’ lenses should not exceed. Our findings revealed that the permissible number of procedures determined by the lens radiation dose limit, should not surpass 405 cases annually (equivalent to 34 cases per month). The radiation dose from therapeutic angiography procedures was discovered to be up to 5 times higher than that from diagnostic angiography procedures. The maximum accumulated radiation dose in the control room was 1.18 µSv/hr, which remained below the limit of the Department of Medical Sciences (< 3 µSv/hr). Conclusion: Radiologists receive less radiation from cerebral diagnostic angiography than therapeutic angiography. Organs on the left side were exposed to greater radiation levels than those on the right side. Wearing radiation protection devices during each procedure can reduce radiation exposure and mitigate long-term effects on radiologists. It is recommended to monitor and calculate the accumulated radiation dose of workers to ensure their exposure remains within safety limits.

90Y Contamination in the Interventional Radiology Suite: VARSKIN Estimation of Skin and Eye Injury and Review of Mitigation Strategies.

Our objective was to demonstrate, through computer simulations, radiation exposure levels from a 90Y contamination event during radioembolization procedures to calculate the radiation doses from various contamination scenarios. We also provide reasonable safety protocols to prevent contamination and minimize radiation exposure during decontamination. Methods: Simulations were performed using the computer code VARSKIN+, version 1.0, to determine the amount of radiation exposure resulting from different contamination scenarios. Results: The annual radiation dose limit to the skin and the lens of the eye was exceeded within 23 s of exposure to a 44-MBq droplet. Double layers of surgical gloves and level 3 gowns provided some attenuation of radiation from 90Y contamination by reducing the dose rate by 39% and 44%, respectively. Two layers of surgical gloves offered the best ratio of radiation protection without compromising dexterity. Conclusion: This study demonstrated that radiation exposures during 90Y spills or contamination events can be considerable. Interventional radiology and nuclear medicine personnel must be mindful of the risks, follow strategies to prevent spills, and be familiar with recommended decontamination procedures for spills in the interventional radiology suite.

Reassessing lead protective garment assessment using ICRP 103 tissue weighting factors

Lead protective garments worn by medical staff in the presence of x-rays develop defects over time. This work proposes a novel method of assessing the protective efficacy of the garments as defects develop. The proposed method applies updated radiobiology data from ICRP 103. This work applied the as low as reasonably achievable principle to devise a formula through which a maximum allowed defect area in lead protective garments can be calculated. This formula depends on the cross-sectional areas () and ICRP 103 tissue weighting factors () of the most radiosensitive and overlapping organs protected by the garment, the maximum allowed additional effective dose to the garment wearer due to the defects (), and the unattenuated absorbed dose at the surface of the garment (). The maximum allowed defect areas are separated into three regions: above the waist, below the waist, and thyroid. To be conservative, it was assumed that = 50 mGy yr−1, and = 0.3 mSv yr−1. Also conservatively, transmission was assumed to be 0%, as employing a non-zero transmission factor would increase the maximum allowed defect area. Maximum allowed defect areas were as follows: 370 mm2 for above the waist, 37 mm2 for below the waist, and 279 mm2 for the thyroid. These values can be compared to commonly published values which are 670 mm2 for an apron, 15 mm2 over the gonads, and 11–20 mm2 for the thyroid. The proposed method for lead protective garment assessment is highly adaptable as values can be adjusted as radiobiology data are updated, and as values such as radiation dose limits vary across jurisdictions. Future works will include collection of data for unattenuated dose to apron () as it varies across professions, so that garments may be allowed different defect areas if relegated to individuals of specific professions.

Determination of lower radiation dose limit for automatic measurement of adipose tissue.

The purpose of this study was to determine the lower limit of radiation dose required to measure visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) volumes when a fat quantification and noise reduction techniques (NRTs) are combined. For this purpose, we utilized CT colonography (CTC) images taken at low doses and manually segmented VAT and SAT fat volumes as ground truth. In order to derive the acceptable precision of the measurements needed to estimate the lower limit of radiation dose, we estimated the effect of different positioning during CT scanning on fat measurements using manually segmented VAT and SAT against normal dose. As a result, the acceptable accuracy of SAT and VAT was found to be 94.5% and 85.2%, respectively. Using these thresholds, the lower radiation dose limit required to accurately measure SAT using 5.25-mm slice-thick images was 1.5mGy of size-specific dose estimates (SSDE), while the lower radiation dose limit required to accurately measure VAT was 0.4mGy of SSDE. The lower dose limit for SAT and VAT combined was 1.5mGy, which was equivalent to an estimated effective dose of 0.38mSv. Alternatively, without noise reduction, SAT could not achieve acceptable accuracy even for images with a slice thickness of 5.25mm, while VAT required noise reduction for images with a slice thickness of 1.25mm, but could achieve acceptable accuracy without noise reduction for images with a slice thickness of 5.25mm.

Assessment of radiation exposure in a nuclear medicine department of an oncology hospital

BackgroundMedical personnel in nuclear medicine departments are exposed to ionizing radiation which is associated with cancer induction and mortality risks. Examples of such personnel are those working in the hot-areas where radioisotopes for nuclear medicine examinations are prepared. This work aims to estimate the occupational radiation exposure for workers at the Nuclear Medicine department in Da Nang Oncology Hospital, Vietnam. Materials and methodsThe study was conducted from 2020 to 2021. The personal dose equivalents (Hp) were quantified for soft tissues for deep dose (Hp(10)), eye lens dose (Hp(3)), skin dose (and Hp(0.07)) were quantified utilizing optically stimulated luminescence dosimeters (OSLD) crystals. In this study, the dose equivalent at the hot area is measured by 9 OSLD, while that for staff was measured using 16 OSLD. ResultsIn 2020, the annual average Hp(10) was (0.38 mSv ± 1.39); in 2021 Hp(10) was (0.25 mSv ± 1.27). The average Hp(10) was well below the annual occupational dose limits (20 mSv.year−1). Regarding the annual dose, all recorded values were quite low compared to the annual radiation dose limits for radiation staff (20 mSv annual ∼ 1.67 mSv.month−1). Nevertheless, some points of measurement revealed a high-value dose of 5.69 mSv ± 2.83. This suggests that rigorous evaluation of the workplace is essential to ensuring workers' exposure is kept within safe levels. ConclusionsIt is concluded that the Hp(10) and Hp(0.07) for the working environment and radiation workers were below the dose limits from ICRP. In addition, it is recommended that continuous monitoring of the occupational dose in nuclear medicine department is essential to reduce the dosimetric hazards of personnel working in the department.

Evaluation of a New Real-Time Dosimeter Sensor for Interventional Radiology Staff.

In 2011, the International Commission on Radiological Protection (ICRP) recommended a significant reduction in the lens-equivalent radiation dose limit, thus from an average of 150 to 20 mSv/year over 5 years. In recent years, the occupational dose has been rising with the increased sophistication of interventional radiology (IVR); management of IVR staff radiation doses has become more important, making real-time radiation monitoring of such staff desirable. Recently, the i3 real-time occupational exposure monitoring system (based on RaySafeTM) has replaced the conventional i2 system. Here, we compared the i2 and i3 systems in terms of sensitivity (batch uniformity), tube-voltage dependency, dose linearity, dose-rate dependency, and angle dependency. The sensitivity difference (batch uniformity) was approximately 5%, and the tube-voltage dependency was <±20% between 50 and 110 kV. Dose linearity was good (R2 = 1.00); a slight dose-rate dependency (~20%) was evident at very high dose rates (250 mGy/h). The i3 dosimeter showed better performance for the lower radiation detection limit compared with the i2 system. The horizontal and vertical angle dependencies of i3 were superior to those of i2. Thus, i3 sensitivity was higher over a wider angle range compared with i2, aiding the measurement of scattered radiation. Unlike the i2 sensor, the influence of backscattered radiation (i.e., radiation from an angle of 180°) was negligible. Therefore, the i3 system may be more appropriate in areas affected by backscatter. In the future, i3 will facilitate real-time dosimetry and dose management during IVR and other applications.

Retinoblastoma Radiotherapy Treatment Optimizations Through GATE Simulations

One of the most frequent children tumors in the area around the eyes is defined as retinoblastoma. Proton radiotherapy treatment is a particularly effective type of radiation therapy due to the prolonged survival rates of children with childhood cancers such as retinablastoma, continued growth of nearby organs and tissues, low radiation dose restriction of vision-related tissues and systems of these tissues. In this study, a geometry phantom including eyeball, lens, lacrimal gland, optic nerve, optic chiasm, retina, cancer, cornea and bone structures was modeled with Monte Carlo simulation tool GATE (vGATE 9.0). With this simulation, the doses absorbed by the tissues were calculated using the DoseActor and TLEDoseActor algorithms. Secondary doses were determined by the TLEDoseActor algorithm. Determination of secondary radiations is important because of the low radiation dose limit of tissues and systems that affect vision. The best treatment results were tried to be obtained by giving the beam thickness of the radiation used in our study, 4 different angles towards the target and different energies. These results show that it can be helpful in calculating a treatment plan for proton therapy in clinical practice.

Low Toxicity and Disease Responses in Systemic AL-Amyloidosis Using an Yttrium-90 Labelled Anti-CD66 Monoclonal Antibody TLX66 As the Only Conditioning Prior to Autologous Stem Cell Transplantation

Despite the introduction of new therapies Systemic AL-amyloidosis (AL) remains incurable and the majority of patients will relapse. Autologous stem cell transplantation (ASCT) remains an important treatment option with improvement of organ function and survival in responding patients, however the toxicity of ASCT using conventional chemotherapy results in high morbidity and mortality limiting the application in this vulnerable patient group. We tested the use of a monoclonal anti-CD66 radiolabelled with yttrium-90, TLX66 (90Y-besilesomab) as the sole conditioning agent prior to ASCT in a phase I study in patients with AL. The study had full ethical and regulatory approvals (EudraCT 2015-002231-18; ISRCTN 13400668). The study consisted of three radiation activity levels, 30, 40 and 45 Mega Becquerels (MBq) per kg body weight with 3 patients treated at each activity level. Patients entered the study after fulfilling entry requirements and with informed consent. Prior to receiving the 90Y-besilesomab organ dosimetry and biodistribution were determined using the same anti-CD66 radiolabelled with indium-111 (111In-anti-CD66) with sequential gamma camera imaging. Estimated absorbed radiation to critical organs was determined from an established dosimetry model, organ radiation dose expressed in Gray (Gy). Radiation dose limits of 45Gy for the bone marrow and 15Gy for the liver were used as safety measures. Table 1 summarises patient details. The median previous lines of treatment were 2 (range 1-5) including three who had previous ASCT using high dose melphalan. The primary end-point was treatment related toxicity as determined using CTCAE v4.0. Haematological toxicities (cytopenia) were excluded as adverse events (AEs) unless considered life-threatening. Secondary end-points: Disease response determined by changes in clonal free light chain assay (FLCa), malignant plasma cell percentage in BM as determined by multi-colour flow cytometry; cardiac toxicity from NT-proBNP assay; overall survival and time to disease progression; biodistribution and dosimetry SPECT-CT imaging; engraftment using the European Blood and Marrow Transplant (EBMT) criteria for neutrophil and platelet engraftment. Results: Ten patients underwent dosimetry with 111In-anti-CD66, 9 received the 90Y-besilesomabwith infused activity determined by study cohort and patient body weight; one patient failed dosimetry with excessive hepatic uptake, two received reduced activity to keep the marrow dose within the 45Gy limit. There were no serious adverse events (SAE's) in the trial. There were 3 grade 4 AE's (mainly cytopenias during transplantation) and no SUSAR's were reported. A total of 41 grade 1-4 AE's were recorded. There were no transplant related deaths. All patients became profoundly cytopenic consistent with bone marrow suppression due to the targeted radiation. All patients engrafted with median neutrophils recovery by D+13 and platelets by D+11. Importantly, no patients experienced any mucositis or therapy related diarrhoea. All maintained oral nutrition. Only two patients experienced a fever post-transplant, neither were life-threatening. Table 2 summarises the estimated absorbed radiation dose to critical organs and disease responses. Of the 9 patients treated with 90Y-besilesomaband ASCT 7 had haematologic responses with 2 complete responses (CR), 5 partial responses (PR), 1 stable disease (SD) and 1 progressive disease (PD) as determined. Six of 8 evaluable patients showed a reduction in percentage of malignant plasma cells in the BM. The study collected data up to D+100 post-transplant but 2 patients showed continuing slow reduction in clonal FLCa beyond D+100 with 1 achieving a CR 5 months post-transplant. No radiation dose limiting toxicity was seen. No consistent changes were seen in NT-proBNP. Importantly no cardiac AEs were recorded. All patients are alive. The long term follow up data will be presented. Acknowledgement: The native anti CD66 MAb (Besilesomab) was provided by Telix Pharmaceuticals. TLX66 (90Y-besilesomab) was acquired by Telix Pharmaceuticals in 2021. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Current situation survey for establishing personally acceptable radiation dose limits for nuclear disaster responders.

When responding to disasters, emergency preparedness is essential to ensure that disaster activities are performed smoothly, safely and efficiently. Investigations on the Fukushima accident revealed that lack of preparedness, poor communication and unsuitable emergency measures contributed to an inadequate emergency response to the nuclear disaster. In this study, we conducted a questionnaire survey on the establishment of a personal radiation exposure dose among Disaster Medical Assistance Team (DMAT) members in Japan who might be involved in the initial response to a nuclear disaster. Establishing personal exposure doses for personnel can encourage emergency preparedness and inform decisions on appropriate role assignments during nuclear response activities. Valid responses were obtained from 178 participants, and the response distribution was as follows: ‘Already have own acceptable dose standard,’ 16 (9%); ‘Follow own institution’s standard (and know its value),’ 30 (17%); ‘Follow own institution’s standard (but do not know its value),’ 59 (33%); ‘Haven’t decided,’ 63 (35%) and ‘Don’t understand question meaning,’ 10 (6%). We also assessed intention to engage in nuclear disaster activities among respondents via engagement intent scores (EIS) and found that participants who had established personal exposure standards had significantly higher EIS scores than those who had not decided or who did not understand the question. Thus, educating potential nuclear disaster responders on personal exposure doses may contribute to a higher intention to engage in emergency responses and improve preparedness and response efficiency.

Risk Assessment of Exposure to Natural Radiation in Soil Using RESRAD-ONSITE and RESRAD-BIOTA in the Cobalt-Nickel Bearing Areas of Lomié in Eastern Cameroon

Nkamouna-Kongo is a cobalt–nickel deposit located in Lomié, Eastern Cameroon. Mining creates radiation exposure pathways that must be considered in risk management scenarios. RESRAD-ONSITE and RESRAD-BIOTA, developed by the US DOE, assess contaminated sites by deriving cleanup criteria and estimating the radiation dose and risk associated with residual radioactive materials using site-specific parameters. This paper evaluated the radiation dose in biota and the health risk from exposure to naturally occurring radionuclides. The activity of 226Ra, 232Th, and 40K was determined by γ-spectrometry. The internal doses were 2.13 × 10−07, 1.42 × 10−06, and 8.38 × 10−05 Gy d−1 for animals and 2.38 × 10−07, 2.04 × 10−06, and 9.07 × 10−05 Gy d−1 for plants. The maximum total dose of 0.7234 mSv yr−1 was obtained at t = 1 year. The external dose contribution obtained at t = 1 year for all nuclides summed and all component pathways was 0.4 mSv yr−1, above the background radiation dose limit of 2.5 × 10−01 mSv yr−1. A maximum cancer risk of 1.36 × 10−03 was observed at t = 1 year. It was also shown in the RESRAD calculations that the total cancer morbidity risks from plant ingestion, radon (independent of water), and external gamma exposure pathways were greater than those from other exposure pathways. The high risk calculated for 226Ra relative to 232Th and 40K makes it the primary human health concern in the study area. The use of a 1 m cover thickness would remediate the contaminated site to a dose on the order of 10−5 mSv yr−1 for a period of 0 to 100 years. The values of these doses are below the US DOE recommended limits.

Quantifying the x-ray dark-field signal in single-grid imaging.

X-ray dark-field imaging reveals the sample microstructure that is unresolved when using conventional methods of x-ray imaging. In this paper, we derive a new method to extract and quantify the x-ray dark-field signal collected using a single-grid imaging set-up, and relate the signal strength to the number of sample microstructures, N. This was achieved by modelling sample-induced changes to the shadow of the upstream grid, and fitting experimental data to this model. Our results suggested that the dark-field scattering angle from our spherical microstructures deviates slightly from the theoretical model of N, which was consistent with results from other experimental methods. We believe the approach outlined here can equip quantitative dark-field imaging of small samples, particularly in cases where only one sample exposure is possible, either due to sample movement or radiation dose limitations. Future directions include an extension into directional dark-field imaging.

THE MEASUREMENT OF ENVIRONMENTAL RADIATION EXPOSURE AROUND THE LINAC RADIOTHERAPY BUNKER

Radiotherapy is cancer therapy using radiation. One of the tools used for radiotherapy is the Linac. Using Linac also can have a detrimental effect on radiation workers, patients, and the public. The reaction can cause activation around the room to become radioactive. Therefore, radiation protection is needed. This research aimed to measure environmental radiation exposure as a radiation protection effort around the Linac bunker. This research uses a quantitative method by collecting data directly on the area around the Linac bunker, with a distance of ± 30 cm from the bunker wall, using the STEP OD-02 Detector. The average Linac operation is 2000 hours/year, while the safe dose limit used is 1/2 dose Limit from Nuclear Power Monitoring Agency. Based on measurements of environmental radiation exposure, there are eight areas classified as safe and four other regions experiencing radiation leakage, including Doors with a radiation exposure difference of 0.078 Sv/hour; West Field (0.074 Sv/hour); TPS Room (0.302 Sv/hour); and Meeting Rooms (0.199 Sv/hour), but still within the safe limit of radiation dose. The environmental radiation exposure around the Linac Radiotherapy bunker is safe.

Autologous Stem Cell Transplantation in AL-Amyloidosis Following Yttrium-90 Labelled Anti-CD66 Monoclonal Antibody As Sole Conditioning Is Associated with Low Toxicity and Demonstrable Disease Responses

▪Delayed diagnosis and lack of effective therapies results in the death of approximately 30% of patients with AL-amyloidosis (AL-A) within the first year of diagnosis. Autologous stem cell transplantation (ASCT) remains an important treatment option, resulting in improved organ function and survival in responders, however its utility is restricted due to the substantial toxicity of conventional ASCT conditioning in the vulnerable AL-A population. We report here the use of a monoclonal anti-CD66 monoclonal antibody (Besilesomab)radiolabelled with yttrium-90 (90Y-anti-CD66) as the sole conditioning agent prior to ASCT in a phase I study in AL-A patients. The study had full ethical and regulatory approvals (EudraCT 2015-002231-18; ISRCTN 13400668) and comprised 3 ascending radiation activity levels, 30, 40 and 45 MBq per kg body weight, each with 3 patients. Patients entered the study after fulfilling entry requirements and with informed consent. Prior to receiving 90Y-anti-CD66, organ dosimetry and biodistribution were determined using anti-CD66 labelled with indium-111 (111In-anti-CD66) with sequential gamma camera imaging. Estimated absorbed radiation to critical organs was determined from an established dosimetry model, organ radiation dose expressed in Gray (Gy). Radiation dose limits of 45Gy for the bone marrow, 15Gy for the liver were used as safety measures.Table 1 summarises patient characteristics, the majority of whom had received multiple lines of treatment including three who had previously undergone ASCT using high dose melphalan (HDM) conditioning. The primary end-point was treatment related toxicity as determined using CTCAE v4.0. Haematological toxicities (cytopenia) were excluded as adverse events (AEs) unless considered life-threatening. Secondary end-points were: clonal disease response determined by changes in serum free light chain assay (FLCa) and malignant plasma cell percentage in bone marrow (BM) as determined by multi-colour flow cytometry; cardiac toxicity using NT-proBNP measurements; overall survival and time to disease progression; biodistribution and dosimetry using SPECT-CT imaging; neutrophil and platelet engraftment (European Blood and Marrow Transplant criteria).Results: Ten patients were studied with 111In-anti-CD66, of whom 9 proceeded to 90Y-anti-CD66 conditioning with infused activity determined by study cohort and body weight; one patient failed dosimetry with excessive hepatic uptake and 2 received reduced activity to keep the BM dose within the 45Gy limit. In total 47 AEs were recorded the majority (41) grades 1-2 with no Serious Adverse Events (SAEs); 3 AEs recorded as grade 4; no transplant related deaths and all patients engrafted with median neutrophil recovery by D+13, platelets by D+11. Importantly no patients experienced mucositis or therapy related diarrhoea maintaining oral nutrition. All patients became profoundly cytopenic consistent with bone marrow suppression due to the targeted radiation. Only two patients experienced a fever post-transplant, neither life-threatening. Table 2 summarises the estimated absorbed radiation dose to critical organs and disease responses. Of the 9 patients treated with 90Y-anti-CD66 and ASCT, 2 had complete responses (CR) and 5 had partial responses (PR); 1 stable disease and 1 progressive disease determined by FLCa. Six of 8 evaluable patients showed a reduction in percentage of malignant plasma cells in the BM. The study collected data to D+100 post-transplant but 4 patients showed continuing reduction in clonal FLCa beyond D+100 with one achieving a near CR 9 months post-transplant. No dose limiting toxicity was seen. No cardiac AEs were recorded. All patients are alive with median follow-up of 32.8 months (15.3 - 58.4).Summary: We have demonstrated that 90Y-anti-CD66 therapy can be used safely as sole conditioning agent prior to ASCT in pre-treated AL patients, associated with low toxicity and promising disease response rates, including patients who previously had undergone ASCT using HDM. BM radiation doses of up to 45Gy were achieved using this targeted approach with acceptably low doses delivered to other critical organs. Further trials are required to determine the full potential of this agent in the context of stem cell transplantation for AL amyloidosis and other haematological diseases. This research was funded by the charity Blood Cancer UK. [Display omitted] DisclosuresOrchard: GSK: Current holder of individual stocks in a privately-held company; Pfizer: Speakers Bureau. Cook: BMS: Current Employment, Honoraria; Celegene: Honoraria, Other: Travel support, Research Funding; Jansen: Honoraria; Takeda: Honoraria, Other: Travel support. Jackson: amgen: Consultancy, Honoraria, Speakers Bureau; takeda: Consultancy, Honoraria, Research Funding, Speakers Bureau; celgene BMS: Consultancy, Honoraria, Research Funding, Speakers Bureau; GSK: Consultancy, Honoraria, Speakers Bureau; J and J: Consultancy, Honoraria, Speakers Bureau; oncopeptides: Consultancy; Sanofi: Honoraria, Speakers Bureau.