Dose Reduction Measures Research Articles

Factors affecting radiographers' use of dose-reduction measures.

This study investigates radiographers' views on implementing dose-reduction measures, with a focus on verifying patient identity and pregnancy status, practising gonad shielding in men and using compression. An electronic questionnaire was distributed to radiographers working in general radiography and/or computed tomography. The questionnaire was based on factors from a framework for analysing risk and safety in clinical medicine. Ordered logistic regressions were used to analyse associations among factors and use of dose-reduction measures. In total, 466 questionnaires were distributed and 170 radiographers (36%) completed them. Clear instructions and routines, support from colleagues, knowledge and experience, a strong safety culture, managerial support and access to proper equipment influence the likelihood of using dose-reduction measures. The strongest associations were found between support from colleagues and verifying pregnancy status (OR = 5.65,P= 0.026), safety culture and use of gonad shielding (OR = 2.36,P= 0.042), and having enough time and use of compression (OR = 2.11,P= 0.003). A strong safety culture and a supportive work environment appears to be essential for the use of dose-reduction measures, and education, training and stress management can improve utilisation of dose-reduction measures.

Trends in Radiation Dose to the Contralateral Breast During Breast Cancer Radiation Therapy.

Over 4 million survivors of breast cancer live in the United States, 35% of whom were treated before 2009. Approximately half of patients with breast cancer receive radiation therapy, which exposes the untreated contralateral breast to radiation and increases the risk of a subsequent contralateral breast cancer (CBC). Radiation oncology has strived to reduce unwanted radiation dose, but it is unknown whether a corresponding decline in actual dose received to the untreated contralateral breast has occurred. The purpose of this study was to evaluate trends in unwanted contralateral breast radiation dose to inform risk assessment of second primary cancer in the contralateral breast for long-term survivors of breast cancer. Individually estimated radiation absorbed doses to the four quadrants and areola central area of the contralateral breast were estimated for 2,132 women treated with radiation therapy for local/regional breast cancers at age <55 years diagnosed between 1985 and 2008. The two inner quadrant doses and two outer quadrant doses were averaged. Trends in dose to each of the three areas of the contralateral breast were evaluated in multivariable models. The population impact of reducing contralateral breast dose on the incidence of radiation-associated CBC was assessed by estimating population attributable risk fraction (PAR) in a multivariable model. The median dose to the inner quadrants of the contralateral breast was 1.70 Gy; to the areola, 1.20 Gy; and to the outer quadrants, 0.72 Gy. Ninety-two percent of patients received ≥1 Gy to the inner quadrants. For each calendar year of diagnosis, dose declined significantly for each location, most rapidly for the inner quadrants (0.04 Gy/year). Declines in dose were similar across subgroups defined by age at diagnosis and body mass index. The PAR for CBC due to radiation exposure >1 Gy for women <40 years of age was 17%. Radiation dose-reduction measures have reduced dose to the contralateral breast during breast radiation therapy. Reducing the dose to the contralateral breast to <1 Gy could prevent an estimated 17% of subsequent radiation-associated CBCs for women treated under 40 years of age. These dose estimates inform CBC surveillance for the growing number of breast cancer survivors who received radiation therapy as young women in recent decades. Continued reductions in dose to the contralateral breast could further reduce the incidence of radiation-associated CBC.

Early design validation on the Vacuum Vessel ports sealing interface installation and removal with Virtual Reality in ITER TBM port cells

Port Cell (PC) rooms in the ITER tokamak building host the devices required for the Port Plugs operation and provide connection to services. During Plasma Operation State, the Vacuum Vessel ports sealing interface provides vacuum tightness and first confinement barrier as essential functions. When a Port Plug needs to be replaced or maintained, this significant sealing component must be removed and reinstalled. The general strategy for this operation has been reviewed resulting in modification proposals to address the requirements for static and dynamic confinement and management of radiation considering the ALARA (As Low As Reasonably Achievable) approach. As Dose Reduction Measures (DRM), additional provisions have been proposed to ensure a robust confinement control during the machine shutdown operation. They mostly consist in an airlock that allows the extension of the first confinement barrier equipped with specific handling equipment to perform human-assisted operations on the sealing flanges. In particular, this paper presents the study carried out in TBM dedicated PC during the conceptual design phase of the maintenance cabin airlock and the handling tools by means of Virtual Reality (VR). VR techniques allow working with virtual prototypes at full scale from the early design stage to ease the design process and the concepts validation with important results concerning the assessments of accessibility issues. The study describes also the outcomes of the VR studies and explains how VR can be an effective instrument to conduct integration studies with complex kinematics and human access operations in the execution of the engineering validation process.

Computational study of the dose-rate field of an ITER heat exchanger due to activated corrosion products

In ITER (Nuclear Facility INB-174), ACPs (Activated Corrosion Products) deposited in the cooling channels will represent a major contribution to the radiation field during machine shutdown. The primary cooling circuit includes eight Heat Exchangers (HXs) which host thousands of small pipes in the so-called bundles, where the heat is transferred from the primary to the secondary circuit and where ACPs accumulate. The accurate calculation of the radiation associated with these hot spots is needed, to ensure that the radiological zoning is respected during the planned maintenance activities in the ITER Equipment Vault. To characterize the impact of one HX on the radiation levels, three computational models were produced and simulated. The first one, called no-bundle model, was an unrealistically conservative model that omitted the steel of the bundle pipes, which resulted in extremely high dose rates surrounding this component. In the second one, called simplified-bundle model, the mass of the bundle pipes was considered by defining a bundle cell with a homogeneous material. To ensure the validity of this computational representation, a third model, called detailed-bundle model, was produced with the most realistic up-to-date model of the HX. The detailed-bundle model included an explicit representation of the complete bundle realized with automated modelling techniques. The radiation source deposited onto the thousands of surfaces of the bundle pipes was simulated explicitly using dedicated developments in D1SUNED. The dose field surrounding one HX was calculated with the detailed model and compared with the simplified, second model, showing good agreement. The simulation of the detailed-bundle model allowed us to reliably lower the dose rates estimates, by a factor of 8-10, compared to the first, unrealistic model. The validation of the simplified-bundle model will be used to practically evaluate the Occupational Radiation Exposure and to assess dose reduction measures for this component.

Characterization of patient dose distributions and probabilistic risk analysis in cardiovascular catheterization laboratories

Purpose: Patient radiation doses in cardiovascular and interventional radiology are highly variable for similar procedures. This random nature may be better described by a distribution function, compared to a linear regression. This study develops a distribution function to characterize patient dose distributions and estimate probabilistic risk. Methods: Reference air kerma from 8647 patients over six years were retrospectively collected from an EP lab and two Cath labs. Data was first sorted into low dose (<100mGy) and high dose cases (>100mGy), and histograms of the data created. Dagum and Inverse gamma distributions were chosen to initially fit to both low and high dose cases. Fits between model and the data was optimized, and a linear regression analysis performed to obtain R squared values and standard errors for the correlation between model and data. Risk probabilities were estimated according to the modeled distribution function. BMI and time distributions were analyzed to understand their influence on the inverse gamma distribution error found in the data. 75th percentiles from both descriptive statistics and model were calculated. Results: The inverse gamma distribution can be used to characterize radiation dose distributions. Model predicted cases for radiation dose 3000mGy< x <5000mGy and >5000mGy are approximately 42 and 0 for 3651 cases for lab#1, and 14 and 1 for 3197 cases for lab#2, respectively, while the actual cases are 10 and 0, and 16 and 2. Descriptive and model statistics generated different 75th percentile levels for sorted data compared to unsorted data. Time has a greater influence on inverse gamma distribution function than BMI. Conclusion: This study creates a framework to understand the random error present in radiology practices that cause wide variations in patient radiation doses. It also provides an approach to evaluate different IR areas in terms of effectiveness of dose reduction measures.

Radiation exposure estimation in pediatric patients during computed tomography imaging procedures

Computed tomography (CT) procedures are the largest source of medical radiation exposure in children and adults. Numerous children undergo high-radiation-dose examinations due to the increasing utilization of CT in children and the wide range of radiation doses. It is therefore necessary to protect pediatric patients, because of their higher sensitivity to ionizing radiation. This study aimed to establish a multicenter cohort of pediatric patients who received CT scans and predict the radiation-related cancer risk. Ninety-five patients who underwent various CT scans [brain 64 (67.4%), chest 14 (14.7%), abdomen 17 (17.9%)] were referred to one of three hospitals. All patients were examined using one of three identical multi-detector CT machines (Toshiba Aquilion 64) according to standard departmental imaging protocols. The average effective doses per scan for brain, chest, and abdominal procedures were 49.7, 34, and 40 mSv, respectively. Dose-reduction measures might significantly decrease the number of radiation-induced malignancies in children.

ITER Test Blanket Module—Engineering Investigations for Port Cell Pipe Forest Replacement

The ITER Test Blanket Modules (TBMs) are installed and operated inside the vacuum vessel (VV) at the equatorial ports located within port plugs (PP), and each of them includes two TBMs. After each plasma operation campaign, the TBM research plan testing program requires the replacement of the TBMs by new ones during the ITER long-term shutdown (LTM). The replacement of a TBM requires the removal/reinstallation of all test blanket system (TBS) equipment present in the port cell (PC), including those in the port interspace called pipe forest (PF). The TBS equipment in PC shall be designed so that occupational radiation exposure can be as low as reasonably achievable (ALARA) over the life of the plant to follow the ITER Policy. To implement ALARA process requirements, a design shall consider careful integration assessment since early phase to address all engineering aspects of the replacement sequence. The design of the TBS equipment in PC shall optimize the reconfiguration operation by including human factor considerations and providing adequate space. Provisions for dose reduction measures (DRMs) considering protection means and minimization of occupancy times in radiation fields are also investigated by assessing remote technics to reduce operator exposure. This article describes engineering investigations for optimized PF replacement operations in various engineering fields. Results on the design of the TBS equipment in the TBM-PC are discussed. The PF design shall implement nuclear engineering aspects. Design options shall demonstrate constructability and maintainability meaning compliance with ALARA process and adequate construction codes (RCC-MRx, EN 13480). TBM-PP replacement sequence drives several elements of the TBM-PC component design and associated integration. Concepts are discussed with regard to nuclear engineering and operation aspects. Use of prototyping demo, including virtual reality (VR), will support the preliminary validation during the system engineering process in order to prepare the full-scale mock-up validation phase.

Comparative analysis of occupational radiation doses when decommissioning nuclear power plants

AbstractKori 1, the first commercial reactor in Korea, was permanently shut down in 2017 and is preparing for decommissioning in the mid‐2020s. Although Kori 1 is shut down, some radiation sources remain in the system; as such, the dismantling workers are exposed to radiation until decommissioning is completed. Unexpected radiation events have been reported in some decommissioning nuclear power plants (NPPs), which resulted in additional radiation exposure to workers and significant financial losses due to delays in the decommissioning schedule. Hence, an appropriate radiation protection program must be established to minimize radiation exposure as well as the economic burden. In this study, radiation doses from precedent decommissioning NPPs worldwide are compared with those estimated from Kori 1 to determine dose reduction measures that can achieve radiation exposure as low as reasonably achievable to decommissioning workers.

Cumulative radiation doses from recurrent PET-CT examinations.

Positron emission tomography (PET–CT) is an essential imaging modality for the management of various diseases. Increasing numbers of PET–CT examinations are carried out across the world and deliver benefits to patients; however, there are concerns about the cumulative radiation doses from these examinations in patients. Compared to the radiation exposure delivered by CT, there have been few reports on the frequency of patients with a cumulative effective radiation dose of ≥100 mSv from repeated PET–CT examinations. The emerging dose tracking system facilitates surveys on patient cumulative doses by PET–CT because it can easily wrap up exposure doses of PET radiopharmaceuticals and CT. Regardless of the use of a dose tracking system, implementation of justification for PET–CT examinations and utilisation of dose reduction measures are key issues in coping with the cumulative dose in patients. Despite all the advantages of PET/MRI such as eliminating radiation exposure from CT and providing good tissue contrast in MRI, it is expensive and cannot be introduced at every facility; thus, it is still necessary to utilise PET–CT with radiation reduction measures in most clinical situations.

Fludarabine-Cyclophosphamide-Rituximab Treatment in Chronic Lymphocytic Leukemia, Focusing on Long Term Cytopenias Before and After the Era of Targeted Therapies.

The widespread application of fludarabine, cyclophosphamide, and rituximab combination is limited due to its toxicity, particularly the prolonged cytopenias. The study aimed to compare the prolonged cytopenias depending on fitness and report real-life data on dose reduction measures and efficacy. According to our database, 120 and 14 patients were treated with FCR between 2011 and 2015 and between 2016 and 2019. Out of the first cohort, 34 patients were treated in subsequent lines. The complete and partial remission rate after first-line treatment was 79%, 16% in the first cohort and 86%, 14% in the second cohort, respectively; and 47%, 35% after non first-line treatment. Based on today’s standards, only 37.5% of the patients were fit for FCR. The frequency of persistent cytopenia was 14%, and it was significantly associated with fitness (χ 2 (1) = 6.001, p = 0.014 for all patients). The small number of FCR treated patients after 2016 shows how the availability of targeted therapies, mostly ibrutinib, in later lines changed the first-line choice. Recently, it is recommended first-line for fit patients with mutated IGHV and no TP53 aberrations. With this narrow indication, a decrease in the frequency of persistent cytopenias is predicted.

Pediatric Cardiothoracic CT Guideline Provided by the Asian Society of Cardiovascular Imaging Congenital Heart Disease Study Group: Part 2. Contemporary Clinical Applications.

The use of pediatric cardiothoracic CT for congenital heart disease (CHD) was traditionally limited to the morphologic evaluation of the extracardiac thoracic vessels, lungs, and airways. Currently, the applications of CT have increased, owing to technological advancements in hardware and software as well as several dose-reduction measures. In the previously published part 1 of the guideline by the Asian Society of Cardiovascular Imaging Congenital Heart Disease Study Group, we reviewed the prerequisite technical knowledge for clinical applications in a user-friendly and vendor-specific manner. Herein, we present the second part of our guideline on contemporary clinical applications of pediatric cardiothoracic CT for CHD based on the consensus of experts from the Asian Society of Cardiovascular Imaging CHD Study Group. This guideline describes up-to-date clinical applications effectively in a systematic fashion.

Measurements of CTDI and DLP from CT image data for paediatrics radiological performance evaluation and dose optimisation in Ghana

Risk of developing cancer in paediatric patients is higher compared with adults and hence need for optimization strategies in paediatric medical imaging is very critical. The higher risk is attributable to the fact that children have developing organs and tissues which are more sensitive to the effects of radiation, and also they have longer life expectancy which allows more time for any harmful effects of radiation to manifest. Optimization of radiological protection is a means of adjusting imaging parameters and instituting protective measures such that required images are obtained with lowest possible radiation dose, and net benefit is maximized to maintain sufficient image quality for diagnostic purposes. Special consideration is given to the availability of dose reduction measures for paediatric imaging equipment. A unique aspect of paediatric imaging is with regards to the wide range in patient sizes and weights, therefore requiring special attention to optimization and modification of equipment, technique, and imaging parameters. Good radiographic technique for paediatrics include attention to patient positioning, field size and adequate collimation, use of protective shielding, optimization of exposure factors etc. In CT, dose reduction is optimized by the adjustment of scan parameters such as mA, kVp, and pitch in accordance with patient weight, age, region scanned, and study indication. Paediatric radiological imaging should therefore be performed by trained and experienced health personnel in the medical imaging department. The overall aim of the research was to enhance the capability of Ghana to improve the efficiency of existing modalities for paediatric medical imaging and to implement and enhance optimization techniques and methodologies for advanced paediatric medical imaging in CT. In addition to providing appropriate clinical recommendation for clinicians for dose management during CT scan. MVL DICOM application software was used to access image data during abdominal CT scan. Effective dose estimates were estimated as developed by ICRP 103 recommendations. The data collection was based on retrospective extraction of image data, using MVL platform where detailed information of the CTDIvol and DLP were available for recording. The weighted CTDI (CTDIW) was estimated by multiplying the volumetric CTDI (CTDIVOL) by the pitch factor. The effective dose was estimated by the product of the region-specific normalizing constant and the dose length product on each image. For image quality Signal to Noise Ratio was estimated and compare with effective dose for dose optimisation. In conclusion, the mean dose parameters exceeded the recommended dose parameter and hence an urgent need for an action to minimise radiation dose to paediatric patients.

Measurement strategies for radon in indoor air of waterworks – a review

In waterworks, 222 Rn can exhale in large amounts through open water surfaces and cause a significant dose contribution. Annual effective doses up to 56 mSv y −1 are documented in literature. This paper gives a literature review on studies associated with radon measurements in indoor air of waterworks − covering more than 800 waterworks in nine regions. Special attention is given to the assessment of the workers' effective dose, which can be done either on basis of the personal exposure or on basis of the local activity concentrations and the residence times. Especially at facilities with a water treatment, large diurnal variations depending on its operation mode were reported. The average 222 Rn concentrations may considerably differ during the time spent of the staff and do not allow to determine the correct annual effective doses. Personal detectors avoid this problem and do not require the survey of the residence times, while the determination of the local exposure allows for the identification of spots with high activity concentrations to set dose reduction measures.

SPECT/CT radiation dosimetry

Single-photon emission computed tomography combined with X-ray computed tomography (SPECT/CT) improves diagnostic accuracy by allowing better localization and definition of scintigraphic findings. However, the combined acquisition of functional and anatomical images can substantially increase radiation exposure to patients, particularly when using a hybrid system with diagnostic CT capabilities. At the same time, the introduction of new SPECT and CT reconstruction techniques (based on the use of iterative algorithms), and of CT automatic dose modulation techniques, has opened the way for possible reductions in patient dose and/or improvements of image quality. It is, therefore, essential to carefully balance the diagnostic needs and the radiation protection requirements, optimizing the choice of radiopharmaceutical and administered activity, and the image acquisition and processing modalities both in SPECT and in CT. This is particularly important in the case of pediatric examinations. In short, to maximize benefit to patients, SPECT/CT studies have to be optimized, adopting dose-reduction measures both from CT and SPECT practices. In SPECT, shorter lived gamma emitters should be preferred and the amount of activity administered must be carefully adjusted to the patient’s size. In CT, scanning parameters (scanning length, tube current, tube voltage, filtration, collimation, slice thickness, pitch, automatic dose modulation method, reconstruction technique, and image processing) must be chosen carefully, remembering that normally the scanned images are used only for the purposes of attenuation correction and/or a more precise localization of scintigraphic findings, which require lower quality and consequently entail a lower dose to the patient. On the other hand, good quality diagnostic CT images, obtained at higher dose levels, are necessary if a diagnostic CT examination must still be planned for the patient. The purpose of this review on SPECT/CT radiation dosimetry is to provide updated information on the total effective dose and total equivalent doses to critical organs due to both radiopharmaceutical administration and CT scan modality for both adults and pediatric patients. The use of new solid-state detectors (cadmium zinc telluride) for SPECT cameras will also be considered. Finally, the means of easily determining SPECT/CT dose to patients will be provided.

Radiation risk and protection of patients in clinical SPECT/CT

Clinical studies have demonstrated that hybrid single photon emission computed tomography (SPECT)/CT for various diagnostic issues has an added value as compared to SPECT alone. However, the combined acquisition of functional and anatomical images can substantially increase radiation exposure to patients, in particular when using a hybrid system with diagnostic CT capabilities. It is, therefore, essential to carefully balance the diagnostic needs and radiation protection requirements. To this end, the evidence on health effects induced by ionizing radiation is outlined. In addition, the essential concepts for estimating radiation doses and lifetime attributable cancer risks associated with SPECT/CT examinations are presented taking into account both the new recommendations of the International Commission on Radiological Protection (ICRP) as well as the most recent radiation risk models. Representative values of effective dose and lifetime attributable risk are reported for ten frequently used SPECT radiopharmaceuticals and five fully diagnostic partial-body CT examinations. A diagnostic CT scan acquired as part of a combined SPECT/CT examination contributes considerably to, and for some applications even dominates, the total patient exposure. For the common SPECT and CT examinations considered in this study, the lifetime attributable risk of developing a radiation-related cancer is less than 0.27 %/0.37 % for men/women older than 16 years, respectively, and decreases markedly with increasing age at exposure. Since there is no clinical indication for a SPECT/CT examination unless an emission scan has been indicated, the issue on justification comes down to the question of whether it is necessary to additionally acquire a low-dose CT for attenuation correction and anatomical localization of tracer uptake or even a fully diagnostic CT. In any case, SPECT/CT studies have to be optimized, e.g. by adapting dose reduction measures from state-of-the-art CT practice, and exposure levels should not exceed the national diagnostic reference levels for standard situations.

Multiple opportunities to reduce radiation dose from myocardial perfusion imaging

Multiple opportunities to reduce radiation dose from myocardial perfusion imaging

ICRP PUBLICATION 121: Radiological Protection in Paediatric Diagnostic and Interventional Radiology

Paediatric patients have a higher average risk of developing cancer compared with adults receiving the same dose. The longer life expectancy in children allows more time for any harmful effects of radiation to manifest, and developing organs and tissues are more sensitive to the effects of radiation. This publication aims to provide guiding principles of radiological protection for referring clinicians and clinical staff performing diagnostic imaging and interventional procedures for paediatric patients. It begins with a brief description of the basic concepts of radiological protection, followed by the general aspects of radiological protection, including principles of justification and optimisation. Guidelines and suggestions for radiological protection in specific modalities – radiography and fluoroscopy, interventional radiology, and computed tomography – are subsequently covered in depth. The report concludes with a summary and recommendations.The importance of rigorous justification of radiological procedures is emphasised for every procedure involving ionising radiation, and the use of imaging modalities that are non-ionising should always be considered. The basic aim of optimisation of radiological protection is to adjust imaging parameters and institute protective measures such that the required image is obtained with the lowest possible dose of radiation, and that net benefit is maximised to maintain sufficient quality for diagnostic interpretation. Special consideration should be given to the availability of dose reduction measures when purchasing new imaging equipment for paediatric use. One of the unique aspects of paediatric imaging is with regards to the wide range in patient size (and weight), therefore requiring special attention to optimisation and modification of equipment, technique, and imaging parameters. Examples of good radiographic and fluoroscopic technique include attention to patient positioning, field size and adequate collimation, use of protective shielding, optimisation of exposure factors, use of pulsed fluoroscopy, limiting fluoroscopy time, etc. Major paediatric interventional procedures should be performed by experienced paediatric interventional operators, and a second, specific level of training in radiological protection is desirable (in some countries, this is mandatory). For computed tomography, dose reduction should be optimised by the adjustment of scan parameters (such as mA, kVp, and pitch) according to patient weight or age, region scanned, and study indication (e.g. images with greater noise should be accepted if they are of sufficient diagnostic quality). Other strategies include restricting multiphase examination protocols, avoiding overlapping of scan regions, and only scanning the area in question. Up-to-date dose reduction technology such as tube current modulation, organ-based dose modulation, auto kV technology, and iterative reconstruction should be utilised when appropriate.It is anticipated that this publication will assist institutions in encouraging the standardisation of procedures, and that it may help increase awareness and ultimately improve practices for the benefit of patients.

Application of adaptive non-linear 2D and 3D postprocessing filters for reduced dose abdominal CT

Abdominal computed tomography (CT) is a frequently performed imaging procedure, resulting in considerable radiation doses to the patient population. Postprocessing filters are one of several dose reduction measures that might help to reduce radiation doses without loss of image quality. To assess and compare the effect of two- and three-dimensional (2D, 3D) non-linear adaptive filters on reduced dose abdominal CT images. Two baseline abdominal CT image series with a volume computer tomography dose index (CTDI (vol)) of 12 mGy and 6 mGy were acquired for 12 patients. Reduced dose images were postprocessed with 2D and 3D filters. Six radiologists performed blinded randomized, side-by-side image quality assessments. Objective noise was measured. Data were analyzed using visual grading regression and mixed linear models. All image quality criteria were rated as superior for 3D filtered images compared to reduced dose baseline and 2D filtered images (P < 0.01). Standard dose images had better image quality than reduced dose 3D filtered images (P < 0.01), but similar image noise. For patients with body mass index (BMI) < 30 kg/m(2) however, 3D filtered images were rated significantly better than normal dose images for two image criteria (P < 0.05), while no significant difference was found for the remaining three image criteria (P > 0.05). There were no significant variations of objective noise between standard dose and 2D or 3D filtered images. The quality of 3D filtered reduced dose abdominal CT images is superior compared to reduced dose unfiltered and 2D filtered images. For patients with BMI < 30 kg/m(2), 3D filtered images are comparable to standard dose images.

A Computed Tomography (CT) wish list, from a medical physicist’s perspective

Significant advances in computed tomography (CT) technology have been made since the first clinical images were published in 1973. The initial clinical applications were brain scans where the patient’s head was immobilised by a water bag that compensated for the large changes in flux adjacent to the head. Body imaging became feasible as improvements led to better image quality and reduced scan times. Improved computing technology has allowed for image reconstruction, including rendering and 3D reconstruction, to all occur in real time. Perfusion studies, cardiac imaging and CT angiography are now common and interventional procedures can be performed using CT fluoroscopy guidance. Some of the major scanner developments that have contributed to this progress are slip-ring technology, which facilitated helical scanning, and multidetector CT systems with capabilities for volume scanning. In addition, increasingly complex X-ray tube designs and novel CT detector materials and configurations have also contributed to changes in CT imaging. Dose reporting began to address concerns raised regarding the risks from radiation exposure and other practical dose reduction measures such as the adaptation of parameters to the patient size were implemented. This included modulating the tube current throughout the scan. More recent CT developments include dual-energy imaging and iterative reconstruction techniques, which are used instead of or in combination with traditional filtered back-projection image formation. All of these improvements in technologies combined have resulted in dose reductions for some CT procedures in the order of 90 %! The changes to image quality, dose and the way in which CT scans are performed have been extensive. However, there are always further enhancements that can be made, especially as user requirements or objectives change. For diagnostic medical physicists, there will always be a wish list of what we would like on a CT scanner. This is largely driven by the work that we undertake and the needs of our colleagues, who request, perform or interpret CT scans. Inevitably, achieving the best health outcome for the patient is the primary concern. The wish list is also influenced by current opinions and attitudes towards CT imaging. Hence, the desirable features for a CT scanner are discussed below, with the rationale for these first explored. A small straw poll of radiologists and radiographers from a variety of workplaces was also undertaken to gauge opinions. Z. Brady (&) Radiology Department, The Alfred, P.O. Box 315, Prahran, VIC 3181, Australia e-mail: z.brady@alfred.org.au

Diagnostic Performance of High-Definition Coronary Computed Tomography Angiography Performed With Multiple Radiation Dose Reduction Strategies

Background Numerous radiation dose reduction measures have been proposed for coronary computed tomographic angiography (CCTA). Although these techniques allow for imaging with reduced radiation, it is unknown whether diagnostic performance is maintained. A new high-definition CCTA (HD-CCTA) allows higher spatial resolution, reduced image noise, and lower radiation doses. Objectives The aim of this study was to determine the diagnostic performance of HD-CCTA, in combination with multiple radiation dose reduction strategies, for the detection of obstructive coronary artery disease. Methods Consecutive patients (N = 43, aged 60 ± 10 years, 83% male) with chest pain and referred for quantitative coronary angiography (QCA) underwent HD-CCTA with radiation dose reduction measures, including prospective electrocardiographic triggering, reduction of additional tube on-time, and minimization of tube voltage and current. Intraluminal diameter stenosis ≥ 50% was considered significant. QCA served as the reference standard. The area under the receiver-operating-characteristic curve (AUC) was used to evaluate diagnostic accuracy. Results All scans demonstrated diagnostic image quality, with 99% (543/548) of included coronary segments interpretable by HD-CCTA. Median effective radiation dose was 2.8 mSv (interquartile range, 1.3-3.9). The AUC for the per-patient assessment for stenosis ≥ 50% was 0.90 (95% confidence interval [CI], 0.77-0.96), with sensitivity of 95% (95% CI, 85%-100%), specificity of 79% (95% CI, 63%-95%), positive predictive value of 78% (95% CI, 61%-95%), and negative predictive value of 95% (95% CI, 85%-100%). Conclusions Compared with QCA, HD-CCTA with multiple dose reduction measures resulted in low radiation doses and high diagnostic accuracy to detect and exclude obstructive coronary artery disease.