Establishment of Local Diagnostic Reference Levels of Pediatric Abdominopelvic and Chest CT Examinations Based on the Body Weight and Size in Korea

ObjectiveThe purposes of this study were to analyze the radiation doses for pediatric abdominopelvic and chest CT examinations from university hospitals in Korea and to establish the local diagnostic reference levels (DRLs) based on the body weight and size.Materials and MethodsAt seven university hospitals in Korea, 2494 CT examinations of patients aged 15 years or younger (1625 abdominopelvic and 869 chest CT examinations) between January and December 2017 were analyzed in this study. CT scans were transferred to commercial automated dose management software for the analysis after being de-identified. DRLs were calculated after grouping the patients according to the body weight and effective diameter. DRLs were set at the 75th percentile of the distribution of each institution''s typical values.ResultsFor body weights of 5, 15, 30, 50, and 80 kg, DRLs (volume CT dose index [CTDI_vol]) were 1.4, 2.2, 2.7, 4.0, and 4.7 mGy, respectively, for abdominopelvic CT and 1.2, 1.5, 2.3, 3.7, and 5.8 mGy, respectively, for chest CT. For effective diameters of < 13 cm, 14–16 cm, 17–20 cm, 21–24 cm, and > 24 cm, DRLs (size-specific dose estimates [SSDE]) were 4.1, 5.0, 5.7, 7.1, and 7.2 mGy, respectively, for abdominopelvic CT and 2.8, 4.6, 4.3, 5.3, and 7.5 mGy, respectively, for chest CT. SSDE was greater than CTDI_vol in all age groups. Overall, the local DRL was lower than DRLs in previously conducted dose surveys and other countries.ConclusionOur study set local DRLs in pediatric abdominopelvic and chest CT examinations for the body weight and size. Further research involving more facilities and CT examinations is required to develop national DRLs and update the current DRLs.     

我国CT检查成年人辐射剂量诊断参考水平的建立历程及解读

经过放射诊断专家、影像技术专家、辐射防护专家和专业技术人员10多年的探索,一项基于大规模国内调查数据而建立的CT检查成年人辐射剂量诊断参考水平(diagnostic reference level,DRL)以国家卫生行业标准(WS/T 637-2018)形式发布。其制定原则和方法符合国际惯例和我国的实际情况,基本上涵盖了我国成年人常见CT检查项目,与国外的DRL比较,整体处于一个合理或较低的剂量水平。给出的50%分位数(可能达到水平)和25%分位数(异常低剂量的提示水平)作为辐射剂量优化指导的额外工具。在日常放射诊断活动中,使辐射剂量与图像质量、临床诊断任务相匹配,降低非正当过高或过低剂量的发生频率。     

Strahlendosis in der Computertomographie

The exponentially growing performance of newer scanner generations has increased diagnostic opportunities and utilization of computed tomography. The excellent clinical results with CT, however, have to be weighed against a high radiation exposure. While radiation exposure with modern scanners is well below the diagnostic reference values of the EU for most organ systems, radiation dose for retrospectively gated cardiac examinations can be substantially higher: organ doses can reach 100 mGy, a dose for which cancer induction been proven. For children, the situation may also be critical if scanning parameters are not adapted to their smaller size and increased radiation risk: the risk-benefit ratio may then no longer favor CT. The application of CT for young patients, patients with favorable prognosis and for frequent follow-up examinations will increase the radiation risk to the individual and the population. The growth rates for CT utilization in Germany are well below those in the United States but the increasing number of exams will lead to a substantial increase in population dose even if the dose per individual exam can be reduced. The combination of optimum scanning parameters, automated dose modulation and dose adaptation to the individual patient will help contain radiation dose. Further reduction is possible by reducing the number of scan phases, limiting the scan length and choosing a lower tube voltage. Most important, however, is the close collaboration with referring physicians: scanning technique and choice of imaging modality can only be adapted if the clinical question is clearly defined. In the light of radiation exposure the critical and knowledgeable use of CT becomes the more important the easier it is to request an exam and the better the clinical results.     

Establishment of CT diagnostic reference levels in Ireland

Objective To propose Irish CT diagnostic reference levels (DRLs) by collecting radiation doses for the most commonly performed CT examinations. Methods A pilot study investigated the most frequent CT examinations. 40 CT sites were then asked to complete a survey booklet to allow the recording of CT parameters for each of 9 CT examinations during a 12-week period. Dose data [CT volume index (CTDI(vol)) and dose-length product (DLP)] on a minimum of 10 average-sized patients in each category were recorded to calculate a mean site CTDI(vol) and DLP value. The rounded 75th percentile was used to calculate a DRL for each site and the country by compiling all results. Results are compared with international DRL data. Results Data were collected for 3305 patients. 30 sites responded with data for 34 scanners, representing 54% of the national total. All equipment had multislice capability (2-128 slices). DRLs are proposed using CTDI(vol) (mGy) and DLP (mGy cm) for CT head (66/58 and 940, respectively), sinuses (16 and 210, respectively), cervical spine (19 and 420, respectively), thorax (9/11 and 390, respectively), high resolution CT (7 and 280, respectively), CT pulmonary angiography (13 and 430, respectively), multiphase abdomen (13 and 1120, respectively), routine abdomen/pelvis (12 and 600, respectively) and trunk examinations (10/12 and 850, respectively). These values are lower than current DRLs and comparable to other international studies. Wide variations in mean doses are noted across sites. Conclusions Baseline figures for Irish CT DRLs are provided on the most frequently performed CT examinations. The variations in dose between CT departments as well as between identical scanners suggest a large potential for optimisation of examinations.     

Diagnostic reference levels for thorax X-ray examinations of paediatric patients

Based on the Medical Exposure Directive of the European Commission, 97/43/Euratom, The Radiation and Nuclear Safety Authority (STUK) in Finland has the responsibility for setting national diagnostic reference levels (DRLs) for the most common radiological examinations. Paediatric patients deserve special attention because of the higher radiation risk compared with adults. The purpose of this paper is to present a method that takes into account patient size when setting DRLs in paediatric patients. The overall data consisted of patient doses collected from six hospitals during the years 1994-2001, and new measurements in two hospitals in 2004. In total, there were 700 chest examinations. The method established by the National Radiological Protection Board (UK) for setting DRLs was not considered feasible in Finnish practice. Patient doses correlated exponentially with the projection thickness, which was measured directly for each patient. Since 1 January 2006, paediatric DRLs for conventional chest examinations have been specified in Finland as a DRL curve by using both dose quantities (entrance surface doses (ESD) and dose-area product (DAP)) as a function of patient projection thickness.     

Patient dose from CT: a literature review

CONTEXT: Computed tomography (CT) exams are increasingly common and account for a significant portion of individuals' mounting exposure to medical radiation. OBJECTIVE: To explore issues surrounding patient radiation dose, including techniques for minimizing dose and the feasibility of tracking lifetime exposure to medical radiation from CT and other imaging exams. METHODS: The authors conducted a review of the recent literature to assess current knowledge of dose levels, protocols for minimizing patient dose and possible systems for tracking cumulative dose. RESULTS: Currently, no regulations are in place to track cumulative patient radiation dose. However, the authors discuss possible means of recording, tracking and storing this data, such as standardizing its inclusion in DICOM headers and transmitting it to electronic personal health records. CONCLUSION: More research is needed to develop and implement uniform dose tracking procedures and protocols for minimizing patient dose.     

Patient doses from CT examinations in Turkey

PURPOSE

We aimed to establish the first diagnostic reference levels (DRLs) for computed tomography (CT) examinations in adult and pediatric patients in Turkey and compare these with international DRLs.

METHODS

CT performance information and examination parameters (for head, chest, high-resolution CT of the chest [HRCT-chest], abdominal, and pelvic protocols) from 1607 hospitals were collected via a survey. Dose length products and effective doses for standard patient sizes were calculated from the reported volume CT dose index (CTDI_vol).

RESULTS

The median number of protocols reported from the 167 responding hospitals (10% response rate) was 102 across five different age groups. Third quartile CTDI_vol values for adult pelvic and all pediatric body protocols were higher than the European Commission standards but were comparable to studies conducted in other countries.

CONCLUSION

The radiation dose indicators for adult patients were similar to those reported in the literature, except for those associated with head protocols. CT protocol optimization is necessary for adult head and pediatric chest, HRCT-chest, abdominal, and pelvic protocols. The findings from this study are recommended for use as national DRLs in Turkey.Computed tomography (CT) scanners have been used in diagnostic radiology since the early 1970s and have gained popularity worldwide owing to their substantial and life-saving clinical benefits. However, the increase in the use of CT applications has led to the emergence of radiologic concerns, such as cancer risk, because of the incremental collective effective dose (ED) associated with its use. Even if the number of CT exams is small among all radiography procedures, a large proportion of medical radiation exposure comes from CT applications. CT contributes the biggest part of radiation from medical sources in the United States (~66%), United Kingdom (~47%), and Germany (~60%) (1, 2). Owing to these concerns, protection of patients of all age groups from the effects of unnecessary and harmful radiation has become a priority in CT examinations (1–3).Dose constraint is one of the fundamental radiation protection principles; however, this cannot be applied in radiologic examinations (3). Therefore, the optimization principle has become increasingly important and needs to be performed with considerable attention in medical practice. Comparison of CT application parameters and patient radiation doses with diagnostic reference levels (DRLs) is a recommended method often considered the first step for optimization in CT examinations (4). Medical practitioners utilize national DRLs as an indicator of dose, in accordance with hospital CT protocols. When patient doses exceed the national DRL, CT examinations should be re-evaluated and optimized (5). The establishment of DRLs for individual countries has been recommended by international organizations such as the International Commission on Radiological Protection (ICRP) and the European Commission (EC) (6–8).The justification of CT examinations may necessitate the willingness of radiology personnel to participate in decision-making regarding the use of radiographic examinations; however, more important input may be derived from the optimization of scanning protocols. Patient radiation doses originating from radiologic examinations can exhibit large variations, even when they are performed in the same hospital department (9, 10). The existence of DRLs for specific radiologic examinations enables standardization across the majority of patients. However, DRLs are neither realistic boundaries for CT technicians nor are they regarded as an indicator of good medical practice. Determination of actual dose levels for targeted patient groups and attempts to maintain radiation exposure below the DRLs may reduce the detrimental health effects associated with radiologic procedures (11, 12).A recent study performed in Turkey investigated patients who underwent CT examinations while pregnant, unbeknownst to the patient and technicians. Mean patient radiation doses from abdominal CT examinations were reported to be approximately three-fold higher than those published in the literature (13). Therefore, there is an urgent need for establishment of national DRLs and for the optimization of CT scanning protocols. In 2012, there were more than 1600 CT devices used in Turkey and a technical report from the country’s national authority revealed that there is insufficient information concerning radiation doses from CT devices (14).     

Establishment of CT diagnostic reference levels (DRLs) for a Singapore healthcare cluster

IntroductionThe use of computed tomography (CT) in healthcare institutions has increased rapidly in recent years. The Singapore Health Services (SingHealth) cluster of healthcare institutions has taken the first step in establishing a local cluster-wide CT Diagnostic Reference Levels (DRL) in Singapore. CT dose data from each institution were collected through two primary dosimetry metrics: volume CT dose index (CTDI_vol measured in mGy) and dose-length product (DLP measured in mGy.cm).MethodsData from 19 CT scanners in seven institutions under one of Singapore healthcare cluster were retrospectively collected and analysed. The five common adult CT examinations analysed were CT Brain (non-contrast enhanced), CT Chest (IV contrast enhanced), CT Kidney-Ureter-Bladder (CT KUB, non-contrast enhanced), CT Pulmonary Angiogram (CT PA, IV contrast enhanced) and CT Abdomen-Pelvis (CT AP, IV contrast enhanced, single phase). Median CTDI_vol and DLP values for the five CT examinations from each institution were derived, with the cluster DRLs determined as the 75th percentile of the distribution of the institution median dose values.ResultsA total of 2413 dose data points were collected over a six-month period from June to November 2020. The cluster CT DRLs for the five CT examinations were determined to be 47 mGy and 820 mGy.cm for CT Brain, 5.4 mGy and 225 mGy.cm for CT Chest, 6.7 mGy and 248 mGy.cm for CT PA, 4.6 mGy and 190 mGy.cm for CT KUB and 6.9 mGy and 349 mGy.cm for CT AP.ConclusionThe establishment of the cluster CT DRLs provided individual institutions with a better understanding if their CT doses are unusually high or low, while emphasising that these DRLs are not meant as hard dose limits or constraints to follow strictly.     

Computed tomography diagnostic reference levels for adult brain,chest and abdominal examinations: A systematic review

ObjectivesRadiation dose variation within and among Computed Tomography (CT) centres is commonly reported. This work systematically reviewed published articles on adult Diagnostic Reference Levels (DRLs) for the brain, chest and abdomen to determine the causes and extent of variation. A systematic literature search and review was performed in selected databases containing leading journals in radiography, radiology and medical physics using carefully defined search terms related to CT and DRLs. The quality of the included articles was determined using the Effective Public Health Practise Project tool for quantitative studies.Key findingsThe 54 articles reviewed include: 45 studies using human data, 8 studies using phantom data, and one study with both human and phantom data. The main comparator in between studies was the dose indices used in reporting DRLs. DRL variations of up to a factor of 2 for the same procedure were noted in phantom studies, and up to a factor of 3 in human studies. Sources of variation include the type of scanner, the age of the scanner, differences in protocols, variations in patients, as well as variations in study design. Different combinations of dose indices were reported: volume computed tomography dose index (CTDIvol) and dose length product (DLP) (59%); DLP only (11%); weighted computed tomography dose index (CTDIw) and DLP (9%); CTDIvol only (7%); CTDIvol, DLP and effective dose (ED) (6%); CTDIw only (4%); CTDIvol, DLP and size specific dose estimate (SSDE) (1%) and CTDIw, CTDIvol and DLP (1%). The use of different dose indices limited dose comparison between studies.ConclusionThe study noted a 2–3 fold variation in DRLs between studies for the same procedure. The causes of variation are reported and include study design, scanner technology and the use of different dose indices.Implications for practiceThere is a need for standardisation of CT DRLs in line with the International Commission on Radiological Protection recommendations to reduce dose variation and facilitate dose comparison.     

CT Radiation Dose Optimization and Tracking Program at a Large Quaternary-Care Health Care System

PurposeThe authors report the implementation and outcomes of a CT radiation dose optimization and tracking program at a large quaternary-care health care system.MethodsA committee reviewed, optimized, and released standardized imaging protocols for the most common CT examinations across the health system. Volume CT dose index and dose-length product (DLP) diagnostic reference levels (DRLs) were established, with the goal of decreasing the percentage of outliers (CT scans with DLPs greater than the established DRLs) to <5% of tracked CT examinations. Baseline radiation dose data were manually extracted for 5% of total examinations. A semiautomated process to analyze all DLP data was then implemented to monitor outliers.ResultsThe baseline percentage of outliers was slightly higher than 10% for pediatric scans but nearly 26.5% for adult scans. Over the first year, after standardized protocols were distributed, the percentage of outliers decreased for pediatric brain (from 22% to 6%), adult brain (from 23% to 3%), and adult chest (from 22% to 11%) examinations. Over the next 2 years, after the dose-tracking program was implemented, the percentage of outliers decreased for adult (brain, from 3% to 1%; chest, from 11% to 1%; abdomen, from 24% to 1%) and pediatric (brain, from 6% to 2%; chest, from 11% to 0%; abdomen, from 7% to 1%) examinations.ConclusionsThe reported CT protocol optimization and dose-tracking program enabled a sustainable reduction in the proportion of CT examinations being performed above established DRLs from as high as 26% to <1% over a period of 2 years.     

Survey of volume CT dose index in Japan in 2014

Objective:

The aims of this study are to propose a new set of Japanese diagnostic reference levels (DRLs) for 2014 and to study the impact of tube voltage and the type of reconstruction algorithm on patient doses. The volume CT dose index (CTDI_vol) for adult and paediatric patients is assessed and compared with the results of a 2011 national survey and data from other countries.

Methods:

Scanning procedures for the head (non-helical and helical), chest and upper abdomen were examined for adults and 5-year-old children. A questionnaire concerning the following items was sent to 3000 facilities: tube voltage, use of reconstruction algorithms and displayed CTDI_vol.

Results:

The mean CTDI_vol values for paediatric examinations using voltages ranging from 80 to 100 kV were significantly lower than those for paediatric examinations using 120 kV. For adult examinations, the use of iterative reconstruction algorithms significantly reduced the mean CTDI_vol values compared with the use of filtered back projection. Paediatric chest and abdominal scans showed slightly higher mean CTDI_vol values in 2014 than in 2011. The proposed DRLs for adult head and abdominal scans were higher than those reported in other countries.

Conclusion:

The results imply that further optimization of CT examination protocols is required for adult head and abdominal scans as well as paediatric chest and abdominal scans.

Advances in knowledge:

Low-tube-voltage CT may be useful for reducing radiation doses in paediatric patients. The mean CTDI_vol values for paediatric scans showed little difference that could be attributed to the choice of reconstruction algorithm.Since the introduction of CT in the 1970s, it has been established worldwide as one of the most important imaging modalities in diagnostic radiology. In the past decade, various dose-reduction techniques, such as tube current modulation¹ and low tube voltage,² have been shown to reduce radiation exposure. In particular, the use of an iterative reconstruction (IR) algorithm, in contrast to a filtered back projection (FBP) algorithm, has provided diagnostically acceptable images using low-radiation-dose CT.^3,4Since estimates of the cancer risk attributable to the use of diagnostic X-rays have been reported,^5,6 radiological technologists should aim to optimize scan parameters in order to avoid excessive radiation exposure. One powerful tool in this optimization applies the concept of diagnostic reference levels (DRLs). The DRLs of CT examinations are generally expressed in terms of the volume CT dose index (CTDI_vol) or dose–length product. The DRL is used in medical imaging with ionizing radiation to indicate whether, in routine conditions, the patient dose from a specified procedure is unusually high or low; DRLs are usually reviewed at regular intervals and could be specific to a country or region.⁷ Surveys of DRLs for CT examination of adults^8–11 and children^12,13 have been reported in several countries.The current DRLs in Japan were established as target values by the Japan Association of Radiological Technologists in 2006. The DRLs refer to a set of medical exposure guidelines, although there are several issues with these guidelines.¹⁴ First, no more than two examinations (head and abdomen) are listed in DRLs, and they contain no information about the CT examination of children. Second, the DRL for abdomen examination employs a 30-cm phantom, whereas a 32-cm phantom is more commonly used worldwide. Therefore, a new set of Japanese DRLs has become an urgent necessity. In 2011, Asada et al¹⁵ reported mean CTDI_vol values for the head (non-helical and helical), chest and upper abdomen of both adults and children, which were obtained using a nationally distributed questionnaire. The aims of this study are to propose a new set of Japanese DRLs for 2014 and to study the impact of tube voltage and the type of reconstruction algorithm on patient doses. The CTDI_vol for both adults and children have been assessed and compared with both the results of the 2011 survey and data from other countries.     

National reference doses for dental cephalometric radiography

Objectives

Diagnostic reference levels (DRLs) are an important tool in the optimisation of clinical radiography. Although national DRLs are provided for many diagnostic procedures including dental intra-oral radiography, there are currently no national DRLs set for cephalometric radiography. In the absence of formal national DRLs, the Health Protection Agency (HPA) has previously published National Reference Doses (NRDs) covering a wide range of diagnostic X-ray examinations. The aim of this study was to determine provisional NRDs for cephalometric radiography.

Methods

Measurements made by the Dental X-ray Protection Service (DXPS) of the HPA, as part of the cephalometric X-ray equipment testing service provided to dentists and dental trade companies throughout the UK, were used to derive provisional NRDs.

Results

Dose–area product measurements were made on 42 X-ray sets. Third quartile dose–area product values for adult and child lateral cephalometric radiography were found to be 41 mGy cm² and 25 mGy cm², respectively, with individual measurements ranging from 3 mGy cm² to 108 mGy cm².

Conclusion

This report proposes provisional NRDs of 40 mGy cm² and 25 mGy cm² for adult and child lateral cephalometric radiographs, respectively; these doses could be considered by employers when establishing their local DRLs.Since the introduction of the Ionising Radiation (Medical Exposure) Regulations in 2000 (IR(ME)R 2000) [1], employers responsible for the use of dental and medical X-ray equipment have been required to establish local diagnostic reference levels (DRLs) for each common radiographic procedure undertaken. Reviews of their radiography practices are required if DRLs are consistently exceeded. In effect, a diagnostic reference level can be considered the level of dose expected not to be exceeded for a standard procedure when good and normal practice regarding diagnostic and technical performance is applied. Local DRLs should be established by the employer in consultation with the appointed medical physics expert (MPE).To assist employers to set appropriate local DRLs, the Department of Health adopted national DRLs for many common X-ray examinations [2]. National DRLs are normally set at the third quartile value of the patient dose distribution observed for a particular type of X-ray examination during a widescale survey (i.e. the patient dose value that only 25% of assessed X-ray sets exceed).The national DRLs adopted by the Department of Health were primarily based on the Health Protection Agency’s (HPA) 2000 review of the National Patient Dose Database (NPDD) [3]. However, at the time of the review, dental X-ray examinations were not included in the NPDD. Subsequently, the national DRL for dental intra-oral examinations was based on separate patient dose data published by the HPA in 1999 [4].The NPDD was designed to collate measurements of patient radiation doses from common diagnostic X-ray examinations carried out throughout the UK and to provide a major source of information for the review and adoption of new national DRLs. In July 2007, the HPA published the 2005 review of the NPDD [5]; this time, the review included dose data from dental X-ray examinations and proposed new National Reference Doses (NRDs) for intra-oral and panoramic examinations, which updated those first proposed in 1999 [4]. Although these NRDs for intra-oral and panoramic examinations have not been formally adopted by the Department of Health as national DRLs, the data collected are representative of current practice.When setting a local DRL, national DRLs and NRDs should be considered and it would be expected that the local DRL should not normally exceed the national level. However, just ensuring that patient doses are below the national DRL or NRD does not mean that local practices are being optimised. Dental surgeries using modern equipment and techniques should be able to set a local DRL significantly lower than the national level, based on their local circumstances.A national review of doses arising from dental cephalometric examinations has never been undertaken in the UK and cephalometric doses have not, to date, been included in the NPDD. For many years, however, the Dental X-ray Protection Service (DXPS) of the HPA has carried out the commissioning and routine quality assurance testing of cephalometric equipment installed throughout the UK. As part of the testing procedures, measurements are made of representative patient doses. This report proposes a patient dose measurement method together with rounded third quartile dose values for adult and child lateral cephalometric radiography based on the patient dose measurements made by DXPS.Owing to the specialist applications of cephalometric radiography, there are only a relatively small number of units in use in the UK compared with intra-oral or panoramic equipment; consequently, the sample size considered in this report is fairly small. However, the dose measurements are considered reasonably representative of UK practice so that the third quartile values can be considered as provisional NRDs and provide a useful guide to employers when establishing their local DRLs. Furthermore, it is anticipated that the patient dose data presented in this report and any data subsequently collected on cephalometric radiography doses will be included in the NPDD so that future reviews of the database can propose NRDs for cephalometric radiography.     

Adult patient radiation doses from non-cardiac CT examinations: a review of published results

Objectives

CT is a valuable tool in diagnostic radiology but it is also associated with higher patient radiation doses compared with planar radiography. The aim of this article is to review patient dose for the most common types of CT examinations reported during the past 19 years.

Methods

Reported dosimetric quantities were compared with the European diagnostic reference levels (DRLs). Effective doses were assessed with respect to the publication year and scanner technology (i.e. single-slice vs multislice).

Results

Considerable variation of reported values among studies was attributed to variations in both examination protocol and scanner design. Median weighted CT dose index (CTDI_w) and dose length product (DLP) are below the proposed DRLs; however, for individual studies the DRLs are exceeded. Median reported effective doses for the most frequent CT examinations were: head, 1.9 mSv (0.3–8.2 mSv); chest, 7.5 mSv (0.3–26.0 mSv); abdomen, 7.9 mSv (1.4–31.2 mSv); and pelvis, 7.6 mSv (2.5–36.5 mSv).

Conclusion

The introduction of mechanisms for dose reduction resulted in significantly lower patient effective doses for CT examinations of the head, chest and abdomen reported by studies published after 1995. Owing to the limited number of studies reporting patient doses for multislice CT examinations the statistical power to detect differences with single-slice scanners is not yet adequate.The use of CT in medicine is now firmly established and represents one of the most important radiological procedures performed worldwide. A consequence of the wide adoption of CT in clinical practice is that radiation dose from CT is growing as a component of the total radiation dose received by patients and the general population [1^,2]. Data from various national surveys have proved that CT is a major source of radiation exposure and provides a substantial proportion of the collective dose from medical exposure, e.g. approximately 35% in Germany [3] and 47% in the UK [4]. The introduction of faster multislice and dual source CT technology has allowed cardiac CT, large-volume high-resolution CT and improved z-plane resolution [5-8]. The speed and ease of CT imaging and the ambition to obtain quality images and cover larger areas of the patient''s anatomy can lead to increased patient doses; although technological developments provide the opportunity to decreases individual CT doses [9]. Patient radiation dose owing to CT examination is expected to be highly variable because of the use of different imaging protocols and the intrinsic differences among makes and models of CT scanners [10^,11]. To limit radiation exposure arising from CT procedures to as low as reasonably achievable (ALARA), European guidelines on quality criteria were published and specific diagnostic reference levels (DRLs) were proposed for routine CT examinations [12]. The purpose of this study is to review published literature on patient radiation doses from common non-cardiac CT examinations, to compare findings with DRLs, to identify whether patient doses are reduced or increased for newer studies and to comment on the impact of multislice technology on patient doses.     

Assessment of computed tomography radiation doses for paediatric head and chest examinations using paediatric phantoms of three different ages

IntroductionWith the rapid development of computed tomography (CT) scanners, the assessment of the radiation dose received by the patient has become a heavily researched topic and may result in a reduction in radiation exposure risk. In this study, radiation doses were measured using three paediatric phantoms for head and chest CT examinations in Najran, Saudi Arabia.MethodsThirteen scanners were included in the study to estimate the CT radiation doses using three phantoms representing three age groups (1-, 5-, and 10-year-old patients).ResultsThe volume CT dose index (CTDI_vol) estimated for each phantom ranged from 6.56 to 41.12 mGy and 0.292 to 11.10 mGy for the head and chest examinations, respectively. The estimation of lifetime attributable risk (LAR) indicated that the cancer risk could reach approximately 0.02–0.16% per 500 children undergoing head and chest CT examinations.ConclusionThe comparison with the published data of the European Commission (EC) and countries reported in this study revealed that the mean CTDI_vol for the head examinations was within the recommended dose reference levels (DRLs). Meanwhile, chest results exceeded the international DRLs for the one-year-old phantoms, suggesting that optimisation work is required at a number of sites.Implications for practiceThe variation among CT doses reported in this study showed that substantial standardisation is needed.     

Renal Colic Imaging: Myths,Recent Trends,and Controversies

There has been a substantial increase in the utilization of imaging, particularly of multi-detector computed tomography (MDCT), for the evaluation of patients with suspected urolithiasis over the past 2 decades. While the diagnostic accuracy of computed tomography (CT) for urolithiasis is excellent, it has also resulted in substantial medical expenditures and increased ionizing radiation exposure. This is especially concerning in patients with known nephrolithiasis and in younger patients. This pictorial review will focus on recent trends and controversies in imaging of patients with suspected urolithiasis, including the current roles of ultrasound (US), MDCT, and magnetic resonance imaging, the estimated radiation dose from MDCT and dose reduction strategies, as well as imaging of suspected renal colic in pregnant patients. The current epidemiological, clinical, and practice management literature will be appraised.     

Radiation doses for barium enema and barium meal examinations in Ireland: potential diagnostic reference levels

Wide variations in patient dose for the same examinations have been demonstrated by several studies throughout Europe. By investigating patient dose, variations can be acknowledged, causal agents sought and the necessary adjustments made. Diagnostic reference levels (DRLs) provide a framework with which dose levels from individual hospitals are compared, and when exceeded, corrective actions can be taken where appropriate. This study aimed to establish DRLs for barium enema and barium meal examinations in Ireland. Measurements were recorded using a dose-area product meter in 12 hospitals representing 33% of relevant hospitals. Results demonstrated wide mean hospital dose variation, by up to a factor of 7.8 and 4.2 for barium enema and barium meal examinations, respectively. Minimum and maximum individual patient dose values varied by a factor of 45 for barium enemas and 90 for barium meal examinations. Reasons for dose variations were complex, but major factors for both examinations were fluoroscopy time, secondary radiation grid type and level of filtration. Some examination-specific factors were also noted. DRLs, established using the quantity dose-area product, were calculated to be 47 Gy cm(2) for barium enemas and 17 Gy cm(2) for barium meal examinations. Although the DRL value for barium meals was the same as the reference value established in the UK for that examination in 1996, the barium enema DRL in this study was 45% higher than the relevant UK value.     

Mammography Diagnostic Reference Levels (DRLs) in Ghana

IntroductionDiagnostic Reference Levels (DRLs) are essential for optimisation in mammography. A local DRL for screen-film mammography has been established in Ghana but none exists for the digital mammography systems. Furthermore, technological advancement is phasing out the use of screen-film mammography and replacing it with digital mammography systems. This study aims to establish the local DRLs used in digital mammography across three institutions in Ghana to guide mammography practice.MethodsAverage glandular dose (AGD), compressed breast thickness (CBT), age of patients, entrance surface exposure (ESE), kVp, and mAs were retrospectively extracted from three digital mammography systems. The 75th and 95th percentile values were obtained for the AGD of each mammography projection and at CBT of 60 ± 5 mm. The correlation between the AGD and CBT, kVp, mAs, and ESE were investigated.ResultsThe 75th percentile for the AGD at CBT of 60 ± 5 mm for Centres 1, 2, 3, and all centres were 2.3, 1.8, 2.1, and 2.0 mGy respectively. The DRLs obtained were comparably higher than international studies except those of the United Kingdom. The AGD showed a strong positive correlation with the CBT, kVp, mAs, and ESE. There was variability in the AGD applied across the three centres for the craniocaudal (CC) and mediolateral oblique (MLO) projections. The mean AGD, mAs, and ESE for all the three centres and per centre recorded were higher than previous studies, but the mean kVp and CBT were lower than previous studies.ConclusionThe higher DRLs estimated in this preliminary study indicates that there is a need for dose optimisation in digital mammography practice in Ghana to improve radiation protection.Implications for practiceThe findings will guide the process of optimisation and limit the variations in the radiation dose during mammography practice.     

Survey of pediatric MDCT radiation dose from university hospitals in Thailand: a preliminary for national dose survey

Background Increasing pediatric CT usage worldwide needs the optimization of CT protocol examination. Although there are previous published dose reference level (DRL) values, the local DRLs should be established to guide for clinical practice and monitor the CT radiation. Purpose To determine the multidetector CT (MDCT) radiation dose in children in three university hospitals in Thailand in four age groups using the CT dose index (CTDI) and dose length product (DLP). Material and Methods A retrospective review of CT dosimetry in pediatric patients (<15 years of age) who had undergone head, chest, and abdominal MDCT in three major university hospitals in Thailand was performed. Volume CTDI (CTDI(vol)) and DLP were recorded, categorized into four age groups: <1 year, 1-< 5 years, 5-<10 years, and 10-<15 years in each scanner. Range, mean, and third quartile values were compared with the national reference dose levels for CT in pediatric patients from the UK and Switzerland according to International Commission on Radiological Protection (ICRP) recommendation. Results Per age group, the third quartile values for brain, chest, and abdominal CTs were, respectively, in terms of CTDI(vol): 25, 30, 40, and 45 mGy; 4.5, 5.7, 10, and 15.6 mGy; 8.5, 9, 14, and 17 mGy; and in terms of DLP: 400, 570, 610, and 800 mGy cm; 80, 140, 305, and 470 mGy cm; and 190, 275, 560,765 mGy cm. Conclusion This preliminary national dose survey for pediatric CT in Thailand found that the majority of CTDI(vol) and DLP values in brain, chest, and abdominal CTs were still below the diagnostic reference levels (DRLs) from the UK and Switzerland regarding to ICRP recommendation.     

Impact of new technologies on dose reduction in CT

The introduction of slip ring technology enables helical CT scanning in the late 1980's and has rejuvenated CT's role in diagnostic imaging. Helical CT scanning has made possible whole body scanning in a single breath hold and computed tomography angiography (CTA) which has replaced invasive catheter based angiography in many cases because of its easy of operation and lesser risk to patients. However, a series of recent articles and accidents have heightened the concern of radiation risk from CT scanning. Undoubtedly, the radiation dose from CT studies, in particular, CCTA studies, are among the highest dose studies in diagnostic imaging. Nevertheless, CT has remained the workhorse of diagnostic imaging in emergent and non-emergent situations because of their ubiquitous presence in medical facilities from large academic to small regional hospitals and their round the clock accessibility due to their ease of use for both staff and patients as compared to MR scanners. The legitimate concern of radiation dose has sparked discussions on the risk vs benefit of CT scanning. It is recognized that newer CT applications, like CCTA and perfusion, will be severely curtailed unless radiation dose is reduced. This paper discusses the various hardware and software techniques developed to reduce radiation dose to patients in CT scanning. The current average effective dose of a CT study is ∼10 mSv, with the implementation of dose reduction techniques discussed herein; it is realistic to expect that the average effective dose may be decreased by 2-3 fold.