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Following the permanent shutdown of Kori Unit 1 in June 2017, the Republic of Korea has been preparing for full‐scale decommissioning work. In addition, the design life of 12 units will expire by 2030. If decommissioning begins without initially extending the lifespan of nuclear reactors, massive amounts of decommissioning wastes will be generated in a short period. The total amount of radioactive wastes generated during the dismantling of a pressurized water reactor is estimated as 6200 tons, and approximately 70% of the total radioactive wastes are classified as metal wastes. Self‐disposal through the decontamination of contaminated metals can contribute to the economic feasibility of decommissioning nuclear power plants because it can reduce the disposal cost of medium‐ and low‐level radioactive wastes. Therefore, this study evaluated the possibility of self‐disposal of steam generators that may occur during future decommissioning. The radioactivity analysis data on transferring the replaced steam generator of Hanul Unit 1 were used as the source term. The decontamination factor was calculated by applying 200 units from 1200 to 2000, and the radiation dose was evaluated using the RESRAD‐RECYCLE code. Consequently, the single‐nuclide concentration and sum of the allowable concentration fraction for mixed radionuclides at a decontamination factor of 1400 were below the regulatory requirements; however, the dose evaluation results exceeded the allowable dose in some scenarios. The decontamination factor was 2000, when the dose evaluation results for all scenarios met the regulatory requirements.

Radiation has been utilized as a direct cytotoxic tumorcidal modality, however, the effect of radiation on tumor vasculature influences response to anticancer therapies. Although numerous reports have demonstrated vascular changes in irradiated tumors, the findings and implications are extensive and at times contradictory depending on the radiation dose, timing, and models used. In this review, we focus on the radiation-mediated effects on tumor vasculature with respect to doses used, timing postradiation, vasculogenesis, adhesion molecule expression, permeability, and pericyte coverage, including the latest findings.

Human papillomavirus (HPV)-mediated oncogenesis confers increased sensitivity to radiotherapy and HPV head and neck cancer is associated with improved patient outcomes. As such, management of HPV-related head and neck cancer requires a multidisciplinary approach that balances maximizing locoregional control with minimizing treatment-related toxicity. We highlight considerations in radiation dose and target delineation, as well as considerations for chemoradiation, postoperative radiotherapy, and single modality, definitive radiotherapy.

PURPOSE Cardiac computed tomography has a clear clinical role in the evaluation of coronary artery disease and assessment of coronary artery calcium (CAC) but the use of ionizing radiation limits the clinical use. Beam-shaping "bow-tie" filters determine the radiation dose and the effective scan field-of-view diameter (SFOV) by delivering higher X-ray fluence to a region centered at the isocenter. A method for positioning the heart near the isocenter could enable reduced SFOV imaging and reduce dose in cardiac scans. However, a predictive approach to center the heart, the extent to which heart centering can reduce the SFOV, and the associated dose reductions have not been assessed. The purpose of this study is to build a heart-centered patient positioning model, to test whether it reduces the SFOV required for accurate CAC scoring, and to quantify the associated reduction in radiation dose. METHODS The location of 38,184 calcium lesions (3151 studies) in the Multi-Ethnic Study of Atherosclerosis was utilized to build a predictive heart-centered positioning model and compare the impact of SFOV on CAC scoring accuracy in heart-centered and conventional body-centered scanning. Then, the positioning model was applied retrospectively to an independent, contemporary cohort of 118 individuals (81 with CAC > 0) at our institution to validate the model's ability to maintain CAC accuracy while reducing the SFOV. In these patients, the reduction in dose associated with a reduced SFOV beam-shaping filter was quantified. RESULTS Heart centering reduced the SFOV diameter 25.7% relative to body centering while maintaining high CAC scoring accuracy (0.82% risk reclassification rate). In our validation cohort, imaging at this reduced SFOV with heart-centered positioning and tailored beam-shaping filtration led to a 26.9% median dose reduction (25-75th percentile: 21.6%-29.8%) without any calcium risk reclassification. CONCLUSIONS Heart-centered patient positioning enables a significant radiation dose reduction while maintaining CAC accuracy.

Introduction Carers and comforters frequently remain with children during paediatric general radiographic examinations. As well as improving the likelihood of overall success of the procedure, this can be important for minimising stress and anxiety of the child. Wearing lead aprons can contribute to additional stress and anxiety about the procedure for both carer and child, specifically due to radiation risk. It also introduces some practical challenges for radiographers. This study quantified a carers exposure to scattered radiation for general radiographic examinations when remaining with a child to assist in positioning or to comfort them. Methods Scattered radiation was measured at four common locations where a carer may stand, with a range of tube potentials (40 kVp to 100 kVp ) and PMMA thicknesses of 2.5-22.5 cm. This was then matched to our clinical protocols to estimate the radiation dose a carer could be exposed to while assisting a patient during general radiographic examinations. Results The effective dose received by a carer standing 20 cm from the centre of the patient varies from 11 min of Australian natural BERT for a finger radiograph on a patient 70 kg. Conclusion This dosimetric data allowed an evidence-based assessment of radiation protection requirements for the carer using the ALARA principle. At our institution, it was decided that a lead apron is not required if the carer is unlikely to receive more than 2 µSv. A new policy, presented here, was developed to implement this decision.

Background Left atrial appendage occlusion (LAAO) is usually performed via the guidance of procedural transesophageal echocardiography (TEE) companied by general anesthesia (GA). Objective To investigate the feasibility and safety of LAAO guided by procedural fluoroscopy only. Methods The patients eligible for LAAO were enrolled into the current study and received implantation of either Watchman device or LAmbre device. The procedure was carried out with procedural fluoroscopy only and no companied GA; the position, shape, and leakage of the device were assessed by contrast angiography. TEE was performed after three-months follow-up to evaluate the thrombosis, and leakage of device. Results Ninety-seven patients with atrial fibrillation with either Watchman device (n = 49) or LAmbre device (n = 48) were consecutively enrolled. Watchman device group was of lower CHA2 DS2 -VASc and HAS-BLED scores compared with LAmbre device groups (P 0.05), including procedural success rate (98.0% vs. 97.9%), mean procedure time, mean fluoroscopy time, total radiation dose, contrast medium dose, percentage of peri-device leakage. Pericardial effusions requiring intervention occurred in two of the Watchman group. TEE follow-up found no patient with residual leakage ≥5 mm at 3 months and no device related thrombosis. During the 22.0±11.1 months follow-up, 2 patients experienced ischemic stroke. Conclusions LAAO with the procedural imaging of fluoroscopy only exhibited the promising results of efficacy and safety. A prospective randomized multicenter study would be required to verify the observations in this study. This article is protected by copyright. All rights reserved.

Purpose There is an increased interest in using non‐coplanar beams for radiotherapy, including SBRT and SRS. This approach can significantly reduce doses to organs‐at‐risk, however, it requires stringent quality assurance, especially when a dynamic treatment couch is used. In this work, new functionality that allows using non‐coplanar beam arrangements in addition to conventional coplanar beams was added and validated to the previously developed in vivo dose verification system. Methods The existing program code was modified to manage the additional treatment couch parameters: angle and positions. Ten non‐coplanar test plans that use a static couch were created in the treatment planning system. Also, two plans that use a dynamic treatment couch were created and delivered using Varian Developer mode, since the treatment planning system does not support a dynamic couch. All non‐coplanar test trajectories were delivered on a simple geometric phantom, using an Edge linear accelerator (Varian Medical Systems) with the megavoltage imager deployed and acquiring megavoltage transmission images that were used to calculate the delivered 3D dose distributions in the phantom with the updated dose calculation algorithm. The reconstructed dose distributions were compared using the 3D chi‐comparison test with 2%/2mm tolerances to the corresponding reference dose distributions obtained from the treatment planning system. Results The chi‐comparison test resulted in at least a 97.0% pass rate over the entire 3D volume for all tested trajectories. For static gantry, static couch non‐coplanar fields, and non‐coplanar arcs using dynamic couch the pass rates observed were at least 98%, while for the static couch, non‐transverse coplanar arc fields, pass rates were at least 97%. Conclusions A model‐based 3D dose calculation algorithm has been extended and validated for a variety of non‐coplanar beam trajectories of different complexities. This system can potentially be applied for quality assurance of treatment delivery systems that use complex, non‐coplanar beam arrangements.

Purpose A clinical-prototype, dedicated, cone-beam breast computed tomography (CBBCT) system with offset detector is undergoing clinical evaluation at our institution. This study is to estimate the normalized glandular dose coefficients ( DgN CT ) that provide air kerma-to-mean glandular dose conversion factors using Monte Carlo simulations. Materials and methods The clinical prototype CBBCT system uses 49 kV x-ray spectrum with 1.39 mm 1st half-value layer thickness. Monte Carlo simulations (GATE, version 8) were performed with semi-ellipsoidal, homogeneous breasts of various fibroglandular weight fractions ( f g = 0.01 , 0.15 , 0.5 , 1 ) , chest wall diameters ( d = 8 , 10 , 14 , 18 , 20 cm), and chest wall to nipple length ( l = 0.75 d ), aligned with the axis of rotation (AOR) located at 65 cm from the focal spot to determine the DgN CT . Three geometries were considered - 40 × 30 -cm detector with no offset that served as reference and corresponds to a clinical CBBCT system, 30 × 30 -cm detector with 5 cm offset, and a 30 × 30 -cm detector with 10 cm offset. Results For 5 cm lateral offset, the DgN CT ranged 0.177 - 0.574 mGy/mGy and reduction in DgN CT with respect to reference geometry was observed only for 18 cm ( 6.4 % ± 0.23 % ) and 20 cm ( 9.6 % ± 0.22 % ) diameter breasts. For the 10 cm lateral offset, the DgN CT ranged 0.221 - 0.581 mGy/mGy and reduction in DgN CT was observed for all breast diameters. The reduction in DgN CT was 1.4 % ± 0.48 % , 7.1 % ± 0.13 % , 17.5 % ± 0.19 % , 25.1 % ± 0.15 % , and 27.7 % ± 0.08 % for 8, 10, 14, 18, and 20 cm diameter breasts, respectively. For a given breast diameter, the reduction in DgN CT with offset-detector geometries was not dependent on f g . Numerical fits of DgN CT d , l , f g were generated for each geometry. Conclusion The DgN CT and the numerical fit, D g N CT d , l , f g would be of benefit for current CBBCT systems using the reference geometry and for future generations using offset-detector geometry. There exists a potential for radiation dose reduction with offset-detector geometry, provided the same technique factors as the reference geometry are used, and the image quality is clinically acceptable.

It is important to employ radiation dose reduction techniques in pediatric computed tomography (CT) to reduce potential risks of radiation‐induced malignancy. Automatic tube potential (kV) selection tools have been developed and become available on many CT scanners, which select the optimum kV based on the patient size and clinical task to improve the radiation dose efficiency. However, its use in pediatric CT has been mostly empirical, following manufacturer’s default recommendation without solid demonstration for quality improvement. This study aimed to implement an automatic tube potential tool (CAREkV, Siemens Healthcare) into routine pediatric CT practice, using the “Plan‐Do‐Study‐Act” quality improvement process, in place of an existing kV/mAs technique chart. The design of this quality improvement project involved Plan‐Do‐Study‐Act stages. Plan and Do stages identified the criteria for optimal automatic kV selection; a range of phantoms representing typical pediatric groups were scanned on a dual‐source 128‐slice scanner using a fast‐pitch scanning mode. The identified CAREkV settings were implemented into the CT protocol and evaluated after a 6‐month period. In the Study stage, an objective evaluation of the image metrics and radiation dose for two similar patient cohorts using CAREkV and the technique‐chart, respectively, were compared. The kV selected, image quality and radiation dose determined by CAREkV were comparable to those obtained while using the technique‐chart. The CAREkV was successfully implemented into our pediatric abdominopelvic CT practice. By utilizing the “PDSA” process optimal image quality and radiation dose reduction were achieved with an automatic kV selection tool to improve CT workflow.

X-ray radiation is commonly employed in clinical practice for diagnostic and therapeutic applications. Over the past decade, developments in nanotechnology have led to the use of high-Z elements as the basis for innovative new treatment platforms that enhance the clinical efficacy of X-ray radiation. Nanoscale metal–frameworks (nMOFs) are coordination networks containing organic ligands that have attracted attention as therapeutic platforms in oncology and other areas of medicine. In cancer therapy, X-ray activated, high-Z nMOFs have demonstrated potential as radiosensitizers that increase local radiation dose deposition and generation of reactive oxygen species (ROS). This mini-review summarizes current research on high-Z nMOFs in cancer theranostics and discusses factors that may influence future clinical application.

Introduction Uterine artery embolisation (UAE) is regarded as a safe and effective treatment for symptomatic uterine fibroids and/or adenomyosis. Dose reduction during UAE is critical for this reproductive‐age patient population to minimise the risks of radiation‐induced effects. The aim of this study was to identify the predictors of radiation dose which can be controlled and optimised for patients during UAE. Methods A total of 150 patients between June 2018 and August 2019 were included in this study. Demographic and clinical information such as age, body mass index (BMI), total number of fibroids, total fibroid volume, total uterus volume and dosimetric measurements on Dose Area Product (DAP), Air Kerma (AK) and fluoroscopy time were recorded. Total digital subtraction angiography (DSA), total conventional roadmap (CRM), total last‐image hold (LIH) and total fluoroscopy were calculated from the dose report. Multiple linear regression analysis was used to identify the independent predictor variables of total dose (DAP) using a regression model. Results Total DSA, total CRM and total LIH were identified as the determinants of dose for UAE (P, The predictors of patient radiation dose have been identified for the interventional radiology procedure known as uterine artery embolisation (UAE). A regression model entered and identified total digital subtraction angiography (DSA), total conventional roadmap (CRM) and total last‐image hold (LIH) as the determinants of dose over demographic and other angiographic variables. Control of these dose predictors can potentially minimise radiation dose exposure to this reproductive‐age patient population. Dose optimisation can be attained to reduce the risks of tissue effects and/or stochastic effects associated with irradiating the pelvis region.

Radiotherapy remains a mainstay of cancer treatment, being used in roughly 50% of patients. The precision with which the radiation dose can be delivered is rapidly improving. This precision allows the more accurate targeting of radiation dose to the tumor and reduces the amount of surrounding normal tissue exposed. Although this often reduces the unwanted side effects of radiotherapy, we still need to further improve patients’ quality of life and to escalate radiation doses to tumors when necessary. High‐precision radiotherapy forces one to choose which organ or functional organ substructures should be spared. To be able to make such choices, we urgently need to better understand the molecular and physiological mechanisms of normal tissue responses to radiotherapy. Currently, oversimplified approaches using constraints on mean doses, and irradiated volumes of normal tissues are used to plan treatments with minimized risk of radiation side effects. In this review, we discuss the responses of three different normal tissues to radiotherapy: the salivary glands, cardiopulmonary system, and brain. We show that although they may share very similar local cellular processes, they respond very differently through organ‐specific, nonlocal mechanisms. We also discuss how a better knowledge of these mechanisms can be used to treat or to prevent the effects of radiotherapy on normal tissue and to optimize radiotherapy delivery., Here, we discuss the complexity of radiotherapy‐induced side effects and approaches for prevention or treatment. Radiation damage develops at a cellular level, progresses to intercellular interactions resulting in intra‐ and interorgan functional responses. These need different approaches for prevention or treatment, for instance intracellular signaling modification, sparing of specific stem cell‐containing areas or contributing organs, and stem cell therapies.

Background Radiation effective dose to the red bone-marrow, a critical organ in the therapy of differentiated thyroid carcinoma (DTC) with radioiodine-131 (131 I), cannot be measured directly. As radioiodine concentration is comparable in blood and most organs, and is believed to be similar in red marrow, the effective dose to the blood seems to be a good first-order approximation of the radiation effective dose to the hematopoietic system and a better means to quantifying exposure from therapy compared to the total amount of activity administered. Purpose We applied four formulas (Lassmann et al (standard) [2008], Eur J Nucl Med Molecul Imaging, 35:1405-1412), (Thomas et al. [1993], Nucl Med Biol, 20:157-162), (Sisson et al. [2003], J Nucl Med, 44:898-903; Ha¨nscheid et al. [2009], Endocr Relat Cancer, 16:1283-1289) and (Ha¨nscheid et al. [2006], J Nucl Med, 47:648-654) and compared between the estimated values of the effective dose that were obtained by three formulas and those obtained by the standard one. Materials and methods Twenty-seven patients, 22 women and 5 men, suffering from DTC were enrolled in this study. Whole-body probe measurements and blood collections (2 mL whole-blood samples) were conducted at 2, 6, 24, 48, 72-96 h after the administration of 131 I to obtain time-activity curves. Whole-body measurements were performed as conjugate view (anterior and posterior) counts by scintillation camera imaging. Results By comparing the values of blood effective dose that were obtained by applying Thomas et al. [1993], Nucl Med Biol, 20:157-162; Sisson et al. [2003], J Nucl Med, 44:898-903 and Ha¨nscheid et al. [2009], Endocr Relat Cancer, 16:1283-1289, and Ha¨nscheid et al. [2006], J Nucl Med, 47:648-654, techniques, with those obtained by (Lassmann et al (standard technique) [2008], Eur J Nucl Med Molecul Imaging, 35:1405-1412), we found that these values are, respectively, 15.0%, 40.0%, and 41.0% more than those obtained by using the standard method. To our knowledge no papers have been published previously that compare between these dosimetric approaches. Conclusion Highly overestimated or highly underestimated results obtained by a certain method or technique, compared with those obtained by the standard method, are not desirable, they tend to exaggerate in applying radiation protection procedures, by increasing or decreasing, which, in both cases, become far from the realistic or recommended procedures. As an operating philosophy, the objective of radiation safety practices simply should not be to keep radiation doses within legal limits or maximum permissible doses (MPDs ), but to keep them "as low as reasonably achievable" (ALARA concept). MPDs should not be considered as thresholds below which exposure to radiation is of no concern, they are not assumed to be totally risk free, and any reasonable technique for reducing radiation dose may have potential benefits in the long run.

Uncrossable lesions are those that cannot be crossed with a balloon after successful guidewire crossing. These lesions are challenging and are commonly encountered in tortuous and calcified arteries as well as chronic total occlusions. They are the second most common barrier to successful PCI in CTO intervention after inability to cross the CTO segment with a guidewire. Procedures involving balloon uncrossable lesions during routine and CTO PCI utilise longer procedural times, radiation dose and contrast volumes with a lower likelihood of procedural success. In this article, we describe a pragmatic approach of managing balloon uncrossable lesions utilising the most contemporary equipment available in an algorithmic fashion beginning with simple, cost effective techniques right up to complex strategies for advanced operators. In addition, some of these lesions, even when crossed by any technique, they may remain difficult to dilate and prepare for stent insertion. We describe an approach of how to manage these undilatable lesions.

Aim To describe patients' and radiographers' experiences of abdominal compression using conventional and patient‐controlled compression methods. Design Qualitative descriptive design. Methods Forty‐five patients who had used both a conventional and a patient‐controlled compression device answered questionnaires. Five radiographers were interviewed. The data‐collection took place between September 2015 and February 2017. Data were analysed by qualitative content analysis. Results Patient‐controlled compression was preferred by slightly more patients because of fear of pain due to excessively hard pressure, maintaining control over the pressure and shorter duration. It was more comfortable, and patients felt they could participate in the examinations. Conventional compression was preferred by some because of more stable pressure and uncertainty of own capacity to provide the optimal compression. Discomfort was more often mentioned concerning the conventional compression method. The radiographers experienced the patient‐controlled method as less time‐consuming and more comfortable, but uncertainty about correct compression technique and its effect on radiation dose and image quality was reported.

Purpose We compare the effect of tube current modulation (TCM) and fixed tube current (FTC) on size‐specific dose estimates (SSDE) and image quality in lung cancer screening with low‐dose CT (LDCT) for patients of all sizes. Methods Initially, 107 lung screening examinations were performed using FTC, which satisfied the Centers for Medicare & Medicaid Services' volumetric CT dose index (CTDIvol) limit of 3.0 mGy for standard‐sized patients. Following protocol modification, 287 examinations were performed using TCM. Patient size and examination parameters were collected and water‐equivalent diameter (Dw) and SSDE were determined for each patient. Regression models were used to correlate CTDIvol and SSDE with Dw. Objective and subjective image quality were measured in 20 patients who had consecutive annual screenings with both FTC and TCM. Results CTDIvol was 2.3 mGy for all FTC scans and increased exponentially with Dw (range = 0.96–4.50 mGy, R2 = 0.73) for TCM scans. As patient Dw increased, SSDE decreased for FTC examinations (R2 = 1) and increased for TCM examinations (R2 = 0.54). Image quality measurements were superior with FTC for smaller sized patients and with TCM for larger sized patients (R2 > 0.5, P

A critical factor for clinical practice is the production of 68 Ga radiopharmaceuticals manufactured manually or through an automated procedure. 68 Ga radiopharmaceuticals are often prepared manually, although this method can lead to an increased operator's radiation dose and potential variability within production. The present work compares 68 Ga-radiolabelling (PSMA-11; DOTA-TOC) utilizing a cassette module (GAIA; Elysia-Raytest; Germany) with a manual setup for routine clinical production with regard to process reliability and reproducibility.

Introduction Digital radiography (DR) systems enable radiographers to reduce the radiation dose to patients while maintaining optimised image quality. However, concerns still exist about paediatric patients who may be exposed to an increased level of radiation dose which is not needed for clinical practice. The purpose of this study was to evaluate the knowledge, awareness and attitudes, in terms of image quality optimisation of radiographers undertaking paediatric DR in Australia and Saudi Arabia. Methods A survey‐based study was devised and distributed to radiographers from Australia and Saudi Arabia. Questions focused on Australian and Saudi Arabian radiographers’ knowledge and attitude of paediatric DR examinations. Results There were 376 participants who responded to the survey from both countries. A major finding showed that most participants lack knowledge in the area of paediatric DR examinations. Most participants from Australia had received no formal training in paediatric digital radiography (79%), whereas nearly half of the participants from Saudi Arabia received no training (45%). Approximately three out of four radiographers from both countries believed that when using DR they did not need to change the way they collimate the beam as DR images can be cropped using post‐processing methods. Conclusion The finding of this study demonstrates that radiographers from both countries should improve their understanding and clinical use of DR in paediatric imaging. More education and training for both students and clinicians is needed to enhance radiographer performance in digital radiography and improve their clinical practices., The purpose of this work was to evaluate the knowledge, awareness and attitudes of radiographers with paediatric digital radiography in terms of image quality optimisation between radiographers in Australia and Saudi Arabia. This study demonstrates that radiographers from both countries should endeavour to improve their perceptions and understanding of paediatric digital radiography. More education and training is recommended to enhance radiographer performance in paediatric digital radiography.

PURPOSE: The development and clinical employment of a computed tomography (CT) imaging system benefit from a thorough understanding of the statistical properties of the output images; cerebral CT perfusion (CTP) imaging system is no exception. A series of articles will present statistical properties of CTP systems and the dependence of these properties on system parameters. This Part I paper focuses on the signal and noise properties of cerebral blood volume (CBV) maps calculated using a nondeconvolution-based method. METHODS: The CBV imaging chain was decomposed into a cascade of subimaging stages, which facilitated the derivation of analytical models for the probability density function, mean value, and noise variance of CBV. These models directly take CTP source image acquisition, reconstruction, and postprocessing parameters as inputs. Both numerical simulations and in vivo canine experiments were performed to validate these models. RESULTS: The noise variance of CBV is linearly related to the noise variance of source images and is strongly influenced by the noise variance of the baseline images. Uniformly partitioning the total radiation dose budget across all time frames was found to be suboptimal, and an optimal dose partition method was derived to minimize CBV noise. Results of the numerical simulation and animal studies validated the derived statistical properties of CBV. CONCLUSIONS: The statistical properties of CBV imaging systems can be accurately modeled by extending the linear CT systems theory. Based on the statistical model, several key signal and noise characteristics of CBV were identified and an optimal dose partition method was developed to improve the image quality of CBV.

Background Because the x‐ray property of patient longitudinal axis in area detector computed tomography (ADCT) depends on a heel effect, radiation dose and beam quality are not uniform along the long axis of the patient. Objective This study aimed to measure the longitudinal beam properties and contrast uniformity of ADCT scanners in the 160‐mm nonhelical volume‐acquisition (NVA) mode and provide useful datasets for the radiation dose reduction in ADCT examinations. Materials and Methods Two different types of ADCT scanners were used in this study. To assess the heel effect in 256‐ and 320‐row ADCT scanners, we measured dose profile, half‐value layer, and iodine contrast uniformity along longitudinal beam direction. Results The maximum effective energy difference within a 160‐mm x‐ray beam is approximately 4 keV. Maximum radiation dose on the anode side of the x‐ray tube showed approximately 40%–45% reduction compared with that on the isocenter position; the heel effect properties longitudinally differed throughout the x‐ray beam, and the decrease in the radiation dose in 256‐ and 320‐row ADCT scanners was observed on the patient table side and gantry side respectively. The CT numbers of iodinated solutions for 256‐row ADCT scanner were independent of the heel effect; nevertheless, the CT numbers of 320‐row ADCT scanner tended to increase on the patient table (cathode) side. Conclusion This study reveals that the radiation dose on the anode side of the x‐ray tube shows approximately 40%–45% reduction compared with that on the isocenter position, and the heel effect properties for 256‐ and 320‐row ADCT scanners longitudinally differ throughout the x‐ray beam. The x‐ray tube for individual ADCT scanners is mounted in an opposite direction along the long axis of the patient.

Background: Currently, there is an increasing interest in noninvasive imaging of cardiovascular system such as computed tomography coronary angiography (CCTA). The risks of radiation-induced cancer and contrast-induced nephropathy (CIN) have always been regarded as concerns which increased demand for CCTA using reduced radiation dose and iodine intake. We aimed to evaluate the image quality and radiation dose of CCTA by modifying tube voltage and concentration of contrast media. Methods: The present study includes 105 patients who underwent CCTA for clinical indications. Specific inclusion and exclusion criteria in terms of patient's weight, body mass index, calcium score, and stenting were used. First group of patients scanned by 120 kV and 370 mg I/mL contrast medium, compared with second and third groups for which scanning was performed using 100 kV and 370 mg I/mL and 100 kV and 300 mg I/mL, respectively. Image quality was evaluated both subjectively and objectively. The effective dose and iodine intake were also measured. Results: Using low kV protocols led to radiation dose reduction up to 38 and applying low contrast medium concentration with consequent reduced iodine intake up to 21. Moreover, there were significant differences in image quality of new scanning protocols. Conclusion: Reduction in tube voltage with lowering of contrast medium concentration can reduce radiation dose and iodine intake with acceptable image quality. © 2019 Wiley Periodicals, Inc.

Purpose A contrast-detail phantom such as CDRAD is frequently used for quality assurance, optimization of image quality, and several other purposes. However, it is often used without considering the uncertainty of the results. The aim of this study was to assess two figure of merits (FOM) originating from CDRAD regarding the variations of the FOMs by dose utilized to create the x-ray image. The probability of overlapping (assessing an image acquired at a lower dose as better than an image acquired at a higher dose) was determined. Methods The CDRAD phantom located underneath 12, 20, and 26 cm PMMA was imaged 16 times at five dose levels using an x-ray system with a flat-panel detector. All images were analyzed by CDRAD Analyser, version 1.1, which calculated the FOM inverse image quality figure (IQFinv ) and gave contrast detail curves for each image. Inherent properties of the CDRAD phantom were used to derive a new FOM h, which describes the size of the hole with the same diameter and depth that is just visible. Data were analyzed using heteroscedastic regression of mean and variance by dose. To ease interpretation, probabilities for overlaps were calculated assuming normal distribution, with associated bootstrap confidence intervals. Results The proportion of total variability in IQFinv , explained by the dose (R2 ), was 91%, 85%, and 93% for 12, 20, and 26 cm PMMA. Corresponding results for h were 91%, 89%, and 95%. The overlap probability for different mAs levels was 1% for 0.8 vs 1.2 mAs, 5% for 1.2 vs 1.6 mAs, 10% for 1.6 vs 2.0 mAs, and 10% for 2.0 mAs vs 2.5 mAs for 12 cm PMMA. For 20 cm PMMA, it was 0.5% for 10 vs 16 mAs, 13% for 16 vs 20 mAs, 14% for 20 vs 25 mAs, and 14% for 25 vs 32 mAs. For 26 cm PMMA, the probability varied from 0% to 6% for various mAs levels. Even though the estimated probability for overlap was small, the 95% confidence interval (CI) showed relatively large uncertainties. For 12 cm PMMA, the associated CI for 0.8 vs 1.2 mAs was 0.1-3.2%, and the CI for 1.2 vs 1.6 mAs was 2.1-7.8%. Conclusions Inverse image quality figure and h are about equally related to dose level. The FOM h, which describes the size of a hole that should be seen in the image, may be a more intuitive FOM than IQFinv . However, considering the probabilities for overlap and their confidence intervals, the FOMs deduced from the CDRAD phantom are not sensitive to dose. Hence, CDRAD may not be an optimal phantom to differentiate between images acquired at different dose levels.

One of the key features of good practice in medicine is the doctor-patient communication. Radiation protection standards for radiosynovectomy (RS) is limited. Yttrium-90 is a beta-emitting radioisotope used in RS to treat joint pain from haemophilic arthritis. ICRP 94 states that if a patient is treated with up to 200 MBq, there is no need for further precautions when it comes to public exposure, however, activities can go up to 370 MBq in RS for the knee. This study analysed 119 family members' safety (16.7% pregnant women). The ambient dose equivalent rate was measured within four distances. A survey was carried analysing risk groups and time spent next to patients. Results showed that family members should be advised to remain at 1.0 m from the patient to decrease accumulated dose by 97.6%. The dose per activity factors estimated in this study is also a useful tool during the risk assessment and doctor/patient communication. Pamphlets were distributed with radiation protection recommendations. Ambient dose equivalent was low enough to show that RS is a safe procedure for family members, which is essential to promote adherence to RS in countries where it is needed but not performed due to lack of information on radiation safety.

Purpose In recent years, health risks concerning high-dose x-ray radiation have become a major concern in dental computed tomography (CT) examinations. Therefore, adopting low-dose computed tomography (LDCT) technology has become a major focus in the CT imaging field. One of these LDCT technologies is downsampling data acquisition during low-dose x-ray imaging processes. However, reducing the radiation dose can adversely affect CT image quality by introducing noise and artifacts in the resultant image that can compromise diagnostic information. In this paper, we propose an artifact correction method for downsampling CT reconstruction based on deep learning. Method We used clinical dental CT data with low-dose artifacts reconstructed by conventional filtered back projection (FBP) as inputs to a deep neural network and corresponding high-quality labeled normal-dose CT data during training. We trained a generative adversarial network (GAN) with Wasserstein distance (WGAN) and mean squared error (MSE) loss, called m-WGAN, to remove artifacts and obtain high-quality CT dental images in a clinical dental CT examination environment. Results The experimental results confirmed that the proposed algorithm effectively removes low-dose artifacts from dental CT scans. In addition, we showed that the proposed method is efficient for removing noise from low-dose CT scan images compared to existing approaches. We compared the performances of the general GAN, convolutional neural networks, and m-WGAN. Through quantitative and qualitative analysis of the results, we concluded that the proposed m-WGAN method resulted in better artifact correction performance preserving the texture in dental CT scanning. Conclusions The image quality evaluation metrics indicated that the proposed method effectively improves image quality when used as a postprocessing technique for dental CT images. To the best of our knowledge, this work is the first deep learning architecture used with a commercial cone-beam dental CT scanner. The artifact correction performance was rigorously evaluated and demonstrated to be effective. Therefore, we believe that the proposed algorithm represents a new direction in the research area of low-dose dental CT artifact correction.

Purpose This study aims to characterize the performance of a prototype rapid kilovoltage (kV) x-ray image guidance system onboard the newly released Halcyon 2.0 linear accelerator (Varian Medical Systems, Palo Alto, CA) by use of conventional and innovatively designed testing procedures. Methods Basic imaging system performance tests and radiation dose measurements were performed for all eleven kV-cone beam computed tomography (CBCT) imaging protocols available on a preclinical Halcyon 2.0 LINAC. Both conventional CBCT reconstruction using the Feldkamp-Davis-Kress (FDK) algorithm and a novel, advanced iterative reconstruction (iCBCT) available on this platform were evaluated. Standard image quality metrics, including slice thickness accuracy, high-contrast resolution, low-contrast resolution, regional uniformity and noise, and CT Hounsfield unit (HU) number accuracy and linearity were evaluated using a manufacturer-supplied QUART phantom (GmbH, Zorneding, Germany) and an independent image quality phantom (Catphan 500, The Phantom Laboratory, New York, NY). Due to the simplified design of the QUART phantom, we developed surrogate and clinically feasible strategies for measuring slice thickness and high- and low-contrast resolution. Imaging dose delivered by these eleven protocols was measured using a computed tomography dose index phantom and pencil chamber with commonly accepted methods and procedures. A subset of measurements were repeated on a conventional C-arm LINAC (TrueBeam and Trilogy, Varian Medical System) for comparison. Clinical patient images of pelvic and abdominal regions are also presented for qualitative assessment as part of a feasibility study for clinical implementation. Results Image acquisition time was 17-42 s on the Halcyon system compared with 60 s on the C-arm LINAC systems. The kV imager projection offset, imaging and treatment isocenter coincidence and the couch three-dimensional match movement all achieved less than1 mm mechanical accuracy. All major image quality metrics were within either the national guideline or vendor-recommended tolerances. The designed surrogate approach with the QUART phantom showed a range of 0.24-0.35 cycles/mm for spatial resolution, a contrast-to-noise ratio (CNR) of 2-20 for FDK reconstruction and a tolerance of 0.5 mm for slice thickness. Other metrics derived from the Catphan images obtained on the Halcyon and C-arm LINACs showed comparable values for the FDK reconstruction. The iterative reconstruction tended to reduce noise, as evidenced by a higher CNR ratio. The fast scan pelvis protocols for Halcyon resulted in 50% lower dose compared to the standard scans, and the thorax fast protocol similarly delivered 10% lower dose than the standard thoracic scan. Preliminary patient images indicated that rapid kV CBCT with breath-hold is feasible, with improved imaging quality compared to free-breathing scans. Conclusion Independent and comprehensive characterization of the kV imaging guidance system on the Halcyon 2.0 system demonstrated acceptable image quality for clinical use. The imaging unit onboard the Halcyon meets vendor specifications and satisfies requirements for routine clinical use. The fast kV imaging system enables the potential for volumetric CBCT acquisition during a single breath-hold and the iterative reconstruction tends to reduce the noise therefore has the potential to improve the CNR for normal size patient.

To evaluate the possibility of lowering radiation dose from a localizer radiograph (LR) using a tin spectral shaping filter and to investigate the effect of this adaptation on the radiation dose and image quality of subsequent computed tomography (CT) examination.The study utilized a set of semianthropomorphic abdomen phantoms, representing small, medium, and large patients. The LR scans were performed with and without a tin spectral shaping filter using various kVp/mA settings. The tube current values of spiral CT examinations following the LR were assessed to evaluate the effect of LR settings on automatic exposure control (AEC). The image quality of CT examinations with various LRs was evaluated by measuring image noise in several regions-of-interest. Organ dose values from LR scans were derived from Monte Carlo simulations performed on a set of virtual anthropomorphic phantoms and the effective dose (ED) values were calculated.The radiation dose from the LR can be strongly reduced by using a tin spectral shaping filter (P 0.001). The optimal settings of the LR scan depend on the size of the scanned subject: for small and medium size subjects, the combination of a tin spectral shaping filter with 100 kVp and 20 mA resulted in the lowest possible radiation dose (ED = 0.007 mGy) without compromising the AEC and image quality of subsequent CT. In contrast, the LR settings of 100 kVp with a tin spectral shaping filter and the tube current values of 20 and 35 mA in large subject (47.4 cm in diameter) resulted in significant variation of the TCM values (11.1% and 8.4%, respectively) and the corresponding increase of noise by5% in subsequent CT examination. For all investigated phantom sizes, the combination of 100 Sn kV with a tin spectral shaping filter and tube current values of 75 mA results in the lowest possible radiation dose, while still keeping the AEC function unchanged.The study indicated that tin spectral shaping filtration can be applied to LRs for radiation dose reduction, but such adaptation needs to take patient size into account.

Purpose Wide bore CT scanners use extended field-of-view (eFOV) reconstruction algorithms to attempt to recreate tissue truncated due to large patient habitus. Radiation therapy planning systems rely on accurate CT numbers in order to correctly plan and calculate radiation dose. This study looks at the impact of eFOV reconstructions on CT numbers and radiation dose calculations in real patient geometries. Methods A large modular phantom based on real patient geometries was created to surround a CIRS Model 062M phantom. The modular sections included a smooth patient surface, a skin fold in the patient surface, and the addition of arms for simulation of the patient in arms up or arms down position. This phantom was used to evaluate the accuracy of CT numbers for three extended FOV algorithms implemented on Siemens CT scanners: eFOV, HDFOV, and HDProFOV. Six different configurations of the phantoms were scanned and images were reconstructed for the three different extended FOV algorithms. The CIRS phantom inserts and overall phantom geometry were contoured in each image, and the Hounsfield units (HU) numbers were compared to an image of the phantom within the standard scan FOV (sFOV) without the modular sections. To evaluate the effect on dose calculations, six radiotherapy patients previously treated at our institution (three head and neck and three chest/pelvis) whose body circumferences extended past the 50 cm sFOV in the treatment planning CT were used. Images acquired on a Siemens Sensation Open scanner were reconstructed using sFOV, eFOV and HDFOV algorithms. A physician and dosimetrist identified the radiation target, critical organs, and external patient contour. A benchmark CT was created for each patient, consisting of an average of the 3 CT reconstructions with a density override applied to regions containing truncation artifacts. The benchmark CT was used to create an optimal radiation treatment plan. The plan was copied onto each CT reconstruction without density override and dose was recalculated. Results Tissue extending past the sFOV impacts the HU numbers for tissues inside and outside the sFOV when using extended FOV reconstructions. On average, the HU for all CIRS density inserts in the arms up (arms down) position varied by 43 HU (67 HU), 39 HU (73 HU), and 18 HU (51 HU) for the eFOV, HDFOV, and HDProFOV scans, respectively. In the patient dose calculations, patients with a smooth patient contour had the least deviation from the benchmark in the HDFOV (0.1-0.5%) compared to eFOV (0.4-1.8%) reconstructions. In cases with large amounts of tissue and irregular skin folds, the eFOV deviated the least from the benchmark (range 0.2-0.6% dose difference) compared to HDFOV (range 1.3-1.8% dose difference). Conclusions All reconstruction algorithms demonstrated good CT number accuracy in the center of the image. Larger artifacts are seen near and extending outside the scan FOV, however, dose calculations performed using typical beam arrangements using the extended FOV reconstructions were still mostly within 2.5% of best estimated reference values.

Bolus materials are commonly used for both human and veterinary radiation therapy (RT). Commercially available bolus materials often leave an air gap between the bolus and the skin which can lead to underdosing of the tumor. This prospective exploratory study evaluated the 6 MV X-ray and electron beam (6, 9, and 12 MeV) attenuating properties for two alternative bolus materials: McKesson lubricating jelly® (MLJ) and Aquasonic 100 Ultrasound gel® (AUG). The results comparing MLJ and water for 12 MeV and 9 MeV electron beams showed

The labeling of peptides with gallium-68 is often initially performed by manual labeling, but with high clinical demand, other alternatives are needed. Cold-kits or automated synthesis are viable options for standardized methods and deemed pharmaceutically more acceptable. This study compares these [68 Ga]Ga-PSMA-11 production methods. Data from 40 kit-based and 40 automated syntheses of [68 Ga]Ga-PSMA-11 were analyzed. Pre-set criteria were evaluated including radiochemical purity, radionuclidic purity, chemical purity, physiological acceptability and sterility. The operator time and radiation dose received were measured. The robustness and repeatability of each method were assessed and a comparison of the running costs of each method is also provided. For both the methods all the analyzed products met the release criteria. No differences were found in radiochemical purity, radiochemical identity, radionuclidic purity, and sterility. However, radiochemical yield and apparent molar activity showed significant differences. For both methods, whole body radiation exposure to operators was lower than with manual labeling (25 - 40 μSv). The exposure during kit-based labeling (14.5 ± μSv) was seven times higher than that of automated synthesis (2.05 ± 0.99 μSv). The automated synthesis was the more expensive method. Both methods are sound alternatives to manual synthesis and offer higher quality, better radiation protection and a more reliable manufacturing of radiopharmaceuticals.

Introduction Diagnostic coronary angiography (CA) uses ionising radiation with relatively high doses, which impact on both patients and staff. This study sought to identify which patient and procedural factors impact patient and operator dose the most during CA. Methods Patient and procedure related variables impacting on Kerma area product (PKA) and operator dose (OD) were collected for 16 months. Procedures were separated into 10 different procedure categories. PKA was used for patient dose and OD was measured with an instantly downloadable dosimeter (IDD) – downloaded at the end of each procedure. High and low radiation dose was defined by binary variables based on the 75th percentile of the continuous measures. Univariate and multivariate regression were used to identify predictors. Results Of 3860 patients included, the IDD was worn for 2591 (61.7%). Obesity (BMI > 30 compared to BMI

This study was conducted to optimize the cone beam computed tomography image quality in implant dentistry using both clinical and quantitative image quality evaluation with measurement of the radiation dose. A natural bone human skull phantom and an image quality phantom were used to evaluate the images produced after changing the exposure parameters (kVp and mA). A 10 × 5 cm2 field of view was selected for average adult. Five scans were taken with varying kVp (70–90 kVp) first at fixed 4 mA. After assessment of the scans and selecting the best kVp, nine scans were taken with 2–12 mA, and the kVp was fixed at the optimal value. A clinical assessment of the implant‐related anatomical landmarks was done in random order by two blinded examiners. Quantitative image quality was assessed for noise/uniformity, artifact added value, contrast‐to‐noise ratio, spatial resolution, and geometrical distortion. A dosimetry index phantom and thimble ion chamber were used to measure the absorbed dose for each scan setting. The anatomical landmarks of the maxilla had good image quality at all kVp settings. To produce good quality images, the mandibular landmarks demanded higher exposure parameters than the maxillary landmarks. The quantitative image quality values were acceptable at all selected exposure settings. Changing the exposure parameters does not necessarily produce higher image quality outcomes but does affect the radiation dose to the patient. The image quality could be optimized for implant treatment planning at lower exposure settings and dose than the default settings.