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

Patient size as a parameter for determining Diagnostic Reference Levels for paediatric Computed Tomography (CT) procedures

INTRODUCTION

The paediatric radiation dose has never been studied in Sri Lanka, nor has a national diagnostic reference level (NDRL) established. Therefore, the primary aim of this study was to propose diagnostic reference levels (DRL) and achievable dose (AD) values for paediatric CT examinations based on size.

METHODS

A total of 658 paediatric (0-15 years) non-contrast-enhanced (NC) studies of head, chest and abdomen regions performed during six months in two dedicated paediatric hospitals (out of the three such institutions in the country) were included. For head examinations, the dose indexes were analysed based on age, while for body examinations, both age and effective diameter (D_eff) were used. The median and the third quartile of the pooled dose distribution were given as AD and NDRL, respectively.

RESULTS

The AD ranges for the head, chest and abdomen regions based on CTDI_vol were 45.8-57.2 mGy, 2.9-10.0 mGy and 3.8-10.3 mGy. The corresponding NDRL ranges were 45.8-95.8 mGy, 3.5-14.1 mGy and 4.5-11.9 mGy. The AD ranges based on SSDE_deff and d_eff were 3.5-9.6 mGy and 4.1-10.3 mGy in chest and abdomen regions. The corresponding NDRL were 4.5-14.1 mGy and 6.1-10.6 mGy.

CONCLUSION

Other institutions can use the present study DRLs as a reference dose for paediatric CT. The AD values can be used as a baseline for target dose optimisations, reducing doses up to 90%.

Factors affecting high cumulative radiation exposure from paediatric computed tomography

Purpose

To estimate occurrence rate of high cumulative radiation exposure from paediatric computed tomography (CT), and to determine influential factors on high-dose inclination.

Material and methods

Patients below 18 years old receiving at least 50 mSv of a cumulative dose during a 5-year period in a tertiary care centre were retrospectively enrolled. Individual patient characteristics, diagnoses, frequency of exa-minations, scanner sites, designated scans, and effective doses were recorded. Collective doses were compared among groups of the diagnoses and scanner sites, and regression analyses were applied.

Results

Of 2771 patients, 3.2% received individual cumulative doses between 50 and 303 mSv (median, 74 mSv). Frequency of examinations ranged from 1 to 13 times (median, 4 times) per patient. About 70% of the patients had oncological illness. Radiation was predominantly high in a CT simulator that could contribute the percentage of collective dose to twice that of examinations owing to higher scanning parts and CT dose index. Some scanner sites used higher acquisition phases. Regression analysis showed that the number of scanning parts and phases significantly influenced the cumulative dose inclination (p < 0.05) while frequent examinations did not.

Conclusions

There was a low occurrence of paediatrics with high dose accumulation. Significant factors affecting potentially high exposure were customized CT protocols in the specific scanners.

ESTIMATION OF DIAGNOSTIC REFERENCE LEVELS AND ACHIEVABLE DOSES FOR PEDIATRIC PATIENTS IN COMMON COMPUTED TOMOGRAPHY EXAMINATIONS: A MULTI-CENTER STUDY

This study was conducted to determine first local diagnostic reference levels (DRLs) and achievable doses (ADs) for pediatric patients during the most common computed tomography (CT) procedures in Yazd province. The DRL was obtained based on volume CT dose index (CTDIvol) and dose length product (DLP) for four various age groups of children. Data were collected from the most commonly performed pediatric CT scans, including abdomen-pelvis, chest, brain and sinus examinations, at six high-loaded institutes. The patients' data (766 no.) in terms of CTDIvol and DLP were obtained from four age groups: ≤1-, 1-5-, 5-10- and 10-15-y-old. The 75th percentiles of CTDIvol and DLP were considered as DRL values and the 50th percentiles were described as ADs for those parameters. Consequently, the acquired DRLs were compared with other national and international published values. The DRLs in terms of CTDIvol for abdomen-pelvis, chest, brain and sinus examinations were 3, 8, 9 and 10 mGy; 4, 5, 5 and 5 mGy; 25, 28, 29 and 38 mGy; and 23, 24, 26 and 27 mGy for four different age groups of ≤1-, 1-5-, 5-10- and 10-15-y-old, respectively. The DRL values in terms of DLP were 75, 302, 321 and 342 mGy.cm; 109, 112, 135 and 170 mGy.cm, 352, 355, 360 and 481 mGy.cm; and 206, 211, 228 and 245 mGy.cm, respectively, for the mentioned age groups. In this study, the DRL and AD values in the brain examination were greater among the other studied regions. The DRL plays a critical role in the optimization of radiation doses delivered to patients and in improving their protection. This study provides the local DRLs and ADs for the most common pediatric CT scanning in Yazd province to create optimum situation for the clinical practice.

Paediatric diagnostic reference levels in computed tomography: a systematic review

This study aims to review the existing literature on diagnostic reference levels (DRLs) in paediatric computed tomography (CT) procedures and the methodologies for establishing them. A comprehensive literature search was done in the popular databases such as PubMed and Google Scholar under the key words 'p(a)ediatric DRL', 'dose reference level', 'diagnostic reference level' and 'DRL'. Twenty-three articles originating from 15 countries were included. Differences were found in the methods used to establish paediatric CT DRLs across the world, including test subjects, reference phantom size, anatomical regions, modes of data collection and stratification techniques. The majority of the studies were based on retrospective patient surveys. The head, chest and abdomen were the common regions. The volume computed tomography dose index (CTDI_vol) and dose-length product (DLP) were the dosimetric quantities chosen in the majority of publications. However, the size-specific dose estimate was a growing trend in the DRL concept of CT. A 16 cm diameter phantom was used by most of the publications when defining DRLs for head, chest and abdomen. The majority of the DRLs were given based on patient age, and the common age categories for head, chest and abdomen regions were 0-1, 1-5, 5-10 and 10-15 years. The DRL ranges for the head region were 18-68 mGy (CTDI_vol) and 260-1608 mGy cm (DLP). For chest and abdomen regions the variations were 1.0-15.6 mGy, 10-496 mGy cm and 1.8-23 mGy, 65-807 mGy cm, respectively. All these DRLs were established for children aged 0-18 years. The wide range of DRL distributions in chest and abdomen regions can be attributed to the use of two different reference phantom sizes (16 and 32 cm), failure to follow a common methodology and inadequate dose optimisation actions. Therefore, an internationally accepted protocol should be followed when establishing DRLs. Moreover, these DRL variations suggest the importance of establish a national DRL for each country considering advanced techniques and dose reduction methodologies.

PEDIATRIC REGIONAL DRL ASSESSMENT IN COMMON CT EXAMINATIONS FOR MEDICAL EXPOSURE OPTIMIZATION IN TEHRAN, IRAN

The main purpose of this pilot study was to assess the regional diagnostic reference level (RDRL) of computed tomography (CT) examinations to optimise medical exposure in five pediatric medical imaging centers in Tehran, Iran where the most frequent CT examinations were investigated. For each patient, CT volume dose indexes (CTDIvol) and dose length product (DLP) in each group were recorded and their third quartile was calculated and set as RDRL. Pediatrics were divided into four age groups (<1; 1-5; 5-10 and 10-15 years). Then, the third quartile values for head, chest and abdomen-pelvic CTs were, respectively, calculated for each group in terms of CTDIvol: 21.3, 24.4, 24.2 and 36.3 mGy; 2.9, 3.2, 3.7 and 5.7 mGy; 3.7, 5.7, 6.3 and 6.8 mGy; and in terms of DLP: 322.2, 390.1, 424.9 and 694.1 mGy.cm; 53.1, 115.2, 145.3 and 167.6 mGy.cm and 128.7, 317.7, 460.2 and 813.8 mGy.cm. Finally, RDRLs were compared with other countries and preceding data in Iran. As a result, CTDIVOL values were lower than other national and international studies except for chest and abdomen-pelvic values obtained in Europe. Moreover, this matter applied to DLP so that other formerly reported values were higher than the present study but European values for chest and abdomen-pelvic scans and also Tehran studies conducted in 2012. Variation of scan parameters (tube voltage (kVp), tube current (mAs) and scan length), CTDIvol and DLP of different procedures among different age groups were statistically significant (P-value < 0.05). The variations in dose between CT departments as well as between identical scanners suggest a large potential for optimization of examinations relative to which this study provides helpful data.

A survey of pediatric CT doses in the Shanghai metropolitan area

The purpose of this study was to evaluate computed tomography (CT) doses in child examinees at different ages throughout the Shanghai metropolitan area. The head and body CT dose indices (CTDIs) of 50 CT scanners were tested by phantom measurements using standard imaging protocols. The values of CTDI_w, CTDI_vol and dose length product (DLP) were calculated and saved in a table along with the parameters of routine head and chest scans for different age groups of children and adults. The effective doses were estimated from the K-factors by age and DLP. The CTDI_vol, DLP and effective dose for multi-detector row CT (MDCT) in children during routine head scans were larger than those for single-detector row CT (SDCT) and dual-detector row CT (DDCT). The CTDI_vol, DLP and effective dose for MDCT and DDCT in children during routine chest scans were lower than those for SDCT. Radiation risks are higher for children in CT examinations compared to adults.

AUTOMATIC ACQUISITION OF CT RADIATION DOSE DATA: USING THE DIAGNOSTIC REFERENCE LEVEL FOR RADIATION DOSE OPTIMIZATION

The present work describes that we try to construct a system that collects dose information that performed CT examination from multiple facilities and unified management. The results of analysis are compared with other National diagnostic reference level (DRL), and the results are fed back to each facility and the cause of the abnormal value is investigated for dose optimization. Medical information collected 139 144 tests from 33 CT devices in 13 facilities. Although the DRL of this study is lower than that of Japan DRL, it was higher than the DRL of each country. When collecting all the examination, it is thought that the variation of the dose due to the error other than the intended imaging site is large. In future, we should continue to collect information in order to DRL renewal and we also think that it is desirable to collect information on physique and detailed scan region as well.

USEFULNESS OF SIZE-SPECIFIC DOSE ESTIMATES IN PEDIATRIC COMPUTED TOMOGRAPHY: REVALIDATION OF LARGE-SCALE PEDIATRIC CT DOSE SURVEY DATA IN JAPAN

The objective of this research is to calculate the organ equivalent dose and effective dose from the scanning conditions at 165 centers in Japan using computed tomography (CT) Dose software and compare the results with the CT dose index volume (CTDIvol), dose length product (DLP) and size-specific dose estimates (SSDE) to validate the usefulness of SSDE. The CTDIvol and DLP were significantly lower in infants than in children (p < 0.05). No significant differences were found in the bone marrow equivalent dose and effective dose for the torso between infants and children (p > 0.05), and the bone marrow equivalent dose and effective dose for the head were higher in infants than children (p < 0.05). No significant difference was found in SSDE for the torso between infants and children (p > 0.05). Organ equivalent and effective doses for head CT scans are higher in infants than in children (I/P ratio ≥ 1). The I/P ratios of CTDIvol and DLP for chest and abdominal CT scans are also higher in Japan than in other countries. CTDIvol and DLP are not accurate when used as a dose index, and SSDE was considered suitable for dose assessment of the torso. However, for head CT in infants, a further reduction in radiation exposure is required.

The present state of radiation exposure from pediatric CT examinations in Japan-what do we have to do?

The use of computed tomography (CT) has increased dramatically over the past several decades and has resulted in a concurrent increase in medical exposure to ionizing radiation. Several recent studies have examined the link between medical radiation and the risk of cancer, especially in children. The cancer risk associated medical exposure has not been definitively confirmed. However, we have to reduce unwarranted medical radiation exposure in pediatric patients. Justification and optimization are of great importance in order to minimize these risks, and the standardization of CT usage is essential. However, in Japan no clinical guidelines for the use of CT have been commonly agreed upon, especially in children. Furthermore, the CT-associated radiation exposure in Japan varies widely among the different facilities. Further studies based on a nationwide survey in Japan will be required in order to establish simple and useful clinical guidelines.

Individual radiation exposure from computed tomography: a survey of paediatric practice in French university hospitals, 2010-2013

OBJECTIVES

To describe computed tomography (CT) scanning parameters, volume CT dose index (CTDIvol) and dose-length product (DLP) in paediatric practice and compare them to current diagnostic reference levels (DRLs).

METHODS

The survey was conducted in radiology departments of six major university hospitals in France in 2010-2013. Data collection was automatised to extract and standardise information on scanning parameters from DICOM-header files. CTDIvol and DLP were estimated based on Monte Carlo transport simulation and computational reference phantoms.

RESULTS

CTDIvol and DLP were derived for 4,300 studies, four age groups and 18 protocols. CTDIvol was lower in younger patients for non-head scans, but did not vary with age for routine head scans. Ratios of 95th to 5th percentile CTDIvol values were 2-4 for most body parts, but 5-7 for abdominal examinations and 4-14 for mediastinum CT with contrast, depending on age. The 75th percentile CTDIvol values were below the national DRLs for chest (all ages) and head and abdominal scans (≥10 years).

CONCLUSION

The results suggest the need for a better optimisation of scanning parameters for routine head scans and infrequent protocols with patient age, enhanced standardisation of practices across departments and revision of current DRLs for children.

KEY POINTS

 • CTDIvol varied little with age for routine head scans.  • CTDIvol was lowest in youngest children for chest or abdominal scans.  • Individual and inter-department variability warrant enhanced standardisation of practices.  • Recent surveys support the need for revised diagnostic reference levels.  • More attention should be given to specific protocols (sinuses, neck, spine, mediastinum).

Asian consortium on radiation dose of pediatric cardiac CT (ASCI-REDCARD)

BACKGROUND

With incremental utilization of pediatric cardiac CT in congenital heart disease, it is imperative to define its current radiation dose levels in clinical practice in order to help imagers optimize CT protocols, particularly in Asia and other developing countries where CT physicists are not readily available.

OBJECTIVE

To evaluate current radiation dose levels and influencing factors in cardiac CT in children with congenital heart disease in Asia by conducting a retrospective multi-center, multi-vendor study.

MATERIALS AND METHODS

We included 1,043 pediatric cardiac CT examinations performed in 8 centers between January 2014 and December 2014 to evaluate congenital heart disease. In five weight groups, we calculated radiation dose metrics including volume CT dose index, size-specific dose estimate, dose-length product and effective dose. Age at CT exam, gender, tube voltage, scan mode, CT indication and image reconstruction algorithm were analyzed to learn whether they influenced CT radiation dose.

RESULTS

Volume CT dose index, size-specific dose estimate, dose-length product and effective dose of pediatric cardiac CT showed variations in the range of 4.3-23.8 mGy, 4.9-17.6 mGy, 55.8-501.3 mGy∙cm and 1.5-3.2 mSv, respectively, within five weight groups. Gender, tube voltage, scan mode and cardiac function assessment significantly influenced CT radiation dose.

CONCLUSION

This multi-center, multi-vendor study demonstrated variations in radiation dose metrics of pediatric cardiac CT reflecting current practice in Asia. Gender, tube voltage, scan mode and cardiac function assessment should be considered as essential radiation dose-influencing factors in developing optimal pediatric cardiac CT protocols.

Radiation dose levels in pediatric chest CT: experience in 499 children evaluated with dual-source single-energy CT

BACKGROUND

The availability of dual-source technology has introduced the possibility of scanning children at lower kVp with a high-pitch mode, combining high-speed data acquisition and high temporal resolution.

OBJECTIVE

To establish the radiation dose levels of dual-source, single-energy chest CT examinations in children.

MATERIALS AND METHODS

We retrospectively recorded the dose-length product (DLP) of 499 consecutive examinations obtained in children <50 kg, divided into five weight groups: group 1 (<10 kg, n = 129); group 2 (10-20 kg, n = 176); group 3 (20-30 kg, n = 99), group 4 (30-40 kg, n = 58) and group 5 (40-49 kg, n = 37). All CT examinations were performed with high temporal resolution (75 ms), a high-pitch mode and a weight-adapted selection of the milliamperage.

RESULTS

CT examinations were obtained at 80 kVp with a milliamperage ranging between 40 mAs and 90 mAs, and a pitch of 2.0 (n = 162; 32.5%) or 3.0 (n = 337; 67.5%). The mean duration of data acquisition was 522.8 ± 192.0 ms (interquartile range 390 to 610; median 490). In the study population, the mean CT dose index volume (CTDIvol₃₂) was 0.83 mGy (standard deviation [SD] 0.20 mGy; interquartile range 0.72 to 0.94; median 0.78); the mean DLP₃₂ was 21.4 mGy.cm (SD 9.1 mGy.cm; interquartile range 15 to 25; median 19.0); and the mean size-specific dose estimate (SSDE) was 1.7 mGy (SD 0.4 mGy; interquartile range 1.5 to 1.9; median 1.7). The DLP₃₂, CTDI_vol32 and SSDE were found to be statistically significant in the five weight categories (P < 0.0001).

CONCLUSION

This study establishes the radiation dose levels for dual-source, single-kVp chest CT from a single center. In the five weight categories, the median values varied 15-37 mGy.cm for the DLP₃₂, 0.78-1.25 mGy for the CTDI_vol32 and 1.6-2.1 mGy for the SSDE.

Nationwide survey of radiation exposure during pediatric computed tomography examinations and proposal of age-based diagnostic reference levels for Japan

BACKGROUND

Diagnostic reference levels (DRLs) have not been established in Japan.

OBJECTIVE

To propose DRLs for CT of the head, chest and abdomen for three pediatric age groups.

MATERIALS AND METHODS

We sent a nationwide questionnaire by post to 339 facilities. Questions focused on pediatric CT technology, exposure parameters, CT protocols, and radiation doses for age groups <1 year, 1-5 years, and 6-10 years.

RESULTS

For the three age groups in the 196 facilities that responded, the 75th percentile values of volume CT dose index based on a 16-cm phantom (CTDIvol 16 [mGy]) for head, chest and abdominal CT were for infants 39.1, 11.1 and 12.0, respectively; for 1-to 5-year-olds 46.9, 14.3 and 16.7, respectively; and for 6-to 10-year-olds 67.7, 15.0 and 17.0, respectively. The corresponding dose–length products (DLP 16 [mGy・cm]) for head, chest and abdominal CT were for infants 526.1, 209.1 and 261.5, respectively; for 1-to 5-year-olds 665.5, 296.0 and 430.8, respectively; and for 6-to 10-year-olds 847.9, 413.0 and 532.2, respectively.

CONCLUSION

The majority of CTDIvol 16 and DLP 16 values for the head were higher than DRLs reported from other countries. For risk reduction, it is necessary to establish DRLs for pediatric CT in Japan.

Optimised paediatric CT dose at a tertiary children's hospital in Japan: a 4-y single-centre analysis

Since diagnostic reference levels (DRLs) for children are not currently established in Japan, the authors determined local DRLs for the full range of paediatric CT examinations in a single tertiary care children's hospital. A retrospective review of 4801 CT performance records for paediatric patients (<15 y old) who had undergone CT examinations from 2008 to 2011 was conducted. The most frequent examinations were of the head (52 %), followed by cardiac (15 %), temporal bone (9 %), abdomen (7 %), chest (6 %) and others (11 %). Approximately one-third of children received two or more CT scans. The authors' investigation showed that mean CTDIvol and DLP for head, chest and abdomen increased as a function of age. Benchmarking of the results showed that CTDIvol, DLP and effective dose for chest and abdomen examinations in this hospital were below average, whereas those for the head tended to be at or slightly above average of established DRL values from five countries. The results suggest that CT examinations as performed in a tertiary children's hospital in Japan are well optimised.

A Survey of Pediatric CT Protocols and Radiation Doses in South Korean Hospitals to Optimize the Radiation Dose for Pediatric CT Scanning

Children are at greater risk of radiation exposure than adults because the rapidly dividing cells of children tend to be more radiosensitive and they have a longer expected life time in which to develop potential radiation injury. Some studies have surveyed computed tomography (CT) radiation doses and several studies have established diagnostic reference levels according to patient age or body size; however, no survey of CT radiation doses with a large number of patients has yet been carried out in South Korea. The aim of the present study was to investigate the radiation dose in pediatric CT examinations performed throughout South Korea. From 512 CT (222 brain CT, 105 chest CT, and 185 abdominopelvic CT) scans that were referred to our tertiary hospital, a dose report sheet was available for retrospective analysis of CT scan protocols and dose, including the volumetric CT dose index (CTDIvol), dose-length product (DLP), effective dose, and size-specific dose estimates (SSDE). At 55.2%, multiphase CT was the most frequently performed protocol for abdominopelvic CT. Tube current modulation was applied most often in abdominopelvic CT and chest CT, accounting for 70.1% and 62.7%, respectively. Regarding the CT dose, the interquartile ranges of the CTDIvol were 11.1 to 22.5 (newborns), 16.6 to 39.1 (≤1 year), 14.6 to 41.7 (2-5 years), 23.5 to 44.1 (6-10 years), and 31.4 to 55.3 (≤15 years) for brain CT; 1.3 to 5.7 (≤1 year), 3.9 to 6.8 (2-5 years), 3.9 to 9.3 (6-10 years), and 7.7 to 13.8 (≤15 years) for chest CT; and 4.0 to 7.5 (≤1 year), 4.2 to 8.9 (2-5 years), 5.7 to 12.4 (6-10 years), and 7.6 to 16.6 (≤15 years) for abdominopelvic CT. The SSDE and CTDIvol were well correlated for patients <5 years old, whereas the CTDIvol was lower in patients ≥6 years old. Our study describes the various parameters and dosimetry metrics of pediatric CT in South Korea. The CTDIvol, DLP, and effective dose were generally lower than in German and UK surveys, except in certain age groups.

Diagnostic value of CT compared to ultrasound in the evaluation of acute abdominal pain in children younger than 10 years old

To assess the diagnostic value of ultrasound compared to CT in evaluating acute abdominal pain of different causes in children 10 years of age and under, hospital records and imaging files of 4052 patients under age of 10 who had imaging for abdominal pain were reviewed. One-hundred-thirty-two patients (3 %), (74 males/58 females) who underwent ultrasound and CT within 24 h were divided by age: group I, ages 0-48 months (25 patients); group II, 49-84 months (53 patients); and group III, 85-120 months (54 patients). Diagnoses at ultrasound, CT, and discharge were compared. Cases of a change in diagnosis following CT and impact of the changed diagnosis on patient management were assessed. Non-diagnostic ultrasound or a diagnostic conundrum was present in a small percentage (3 %) of our patients. In the group of patients imaged with two modalities, CT changed the diagnosis in 73/132 patients (55.3 %). Patient management changed in 63/132 patients (47.7 %). CT changed the diagnosis in 46/64 patients with surgical conditions (71.8 %, p < 0.001). Among patients with surgical conditions, the difference between ultrasonography (US) and CT diagnoses was significant in groups 2 (p = 0.046) and 3 (p =  .001). The impact of the change in diagnosis in surgical patients imaged with two modalities was significant in the group as a whole and in each age group separately. Non-diagnostic or equivocal US in a small percentage of patients is probably sufficient to justify the additional radiation burden.

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.

A study to establish international diagnostic reference levels for paediatric computed tomography

The article reports results from the largest international dose survey in paediatric computed tomography (CT) in 32 countries and proposes international diagnostic reference levels (DRLs) in terms of computed tomography dose index (CTDI vol) and dose length product (DLP). It also assesses whether mean or median values of individual facilities should be used. A total of 6115 individual patient data were recorded among four age groups: <1 y, >1-5 y, >5-10 y and >10-15 y. CTDIw, CTDI vol and DLP from the CT console were recorded in dedicated forms together with patient data and technical parameters. Statistical analysis was performed, and international DRLs were established at rounded 75th percentile values of distribution of median values from all CT facilities. The study presents evidence in favour of using median rather than mean of patient dose indices as the representative of typical local dose in a facility, and for establishing DRLs as third quartile of median values. International DRLs were established for paediatric CT examinations for routine head, chest and abdomen in the four age groups. DRLs for CTDI vol are similar to the reference values from other published reports, with some differences for chest and abdomen CT. Higher variations were observed between DLP values, based on a survey of whole multi-phase exams. It may be noted that other studies in literature were based on single phase only. DRLs reported in this article can be used in countries without sufficient medical physics support to identify non-optimised practice. Recommendations to improve the accuracy and importance of future surveys are provided.

Patient grouping for dose surveys and establishment of diagnostic reference levels in paediatric computed tomography

There has been confusion in literature on whether paediatric patients should be grouped according to age, weight or other parameters when dealing with dose surveys. The present work aims to suggest a pragmatic approach to achieve reasonable accuracy for performing patient dose surveys in countries with limited resources. The analysis is based on a subset of data collected within the IAEA survey of paediatric computed tomography (CT) doses, involving 82 CT facilities from 32 countries in Asia, Europe, Africa and Latin America. Data for 6115 patients were collected, in 34.5 % of which data for weight were available. The present study suggests that using four age groups, <1, >1-5, >5-10 and >10-15 y, is realistic and pragmatic for dose surveys in less resourced countries and for the establishment of DRLs. To ensure relevant accuracy of results, data for >30 patients in a particular age group should be collected if patient weight is not known. If a smaller sample is used, patient weight should be recorded and the median weight in the sample should be within 5-10 % from the median weight of the sample for which the DRLs were established. Comparison of results from different surveys should always be performed with caution, taking into consideration the way of grouping of paediatric patients. Dose results can be corrected for differences in patient weight/age group.

Pediatric Computed Tomography Dose Optimization Strategies: A Literature Review

INTRODUCTION

Computed tomography (CT) dose optimization is an important issue in radiography because CT is the largest contributor to medical radiation dose and its use is increasing. However, CT dose optimization for pediatric patients could be more challenging than their adult counterparts. The purpose of this literature review was to identify and discuss the current pediatric CT dose saving techniques. Optimized pediatric protocols were also proposed.

METHODS

A comprehensive literature search was conducted using the Medline, ProQuest Health and Medical Complete, PubMed, ScienceDirect, Scopus, Springer Link, and Web of Science databases and the keywords CT, pediatric, optimization, protocol, and radiation dose to identify articles focusing on pediatric CT dose optimization strategies published between 2004 and 2014.

RESULTS AND SUMMARY

Seventy-seven articles were identified in the literature search. Strategies for optimizing a range of scan parameters and technical considerations including tube voltage and current, iterative reconstruction, diagnostic reference levels, bowtie filters, scout view, pitch, scan collimation and time, overscanning, and overbeaming for pediatric patients with different ages and body sizes and compositions were discussed. An example of optimized pediatric protocols specific to age and body size for the 64-slice CT scanners was devised. It is expected that this example could provide medical radiation technologists, radiologists, and medical physicists with ideas to optimize their pediatric protocols.

Local diagnostic reference level based on size-specific dose estimates: assessment of pediatric abdominal/pelvic computed tomography at a Japanese national children's hospital

BACKGROUND

A child's body size is not accurately reflected by volume CT dose index (CTDIvol) and dose-length product (DLP). Size-specific dose estimation (SSDE) was introduced recently as a new index of radiation dose. However, it has not yet been established as a diagnostic reference level (DRL).

OBJECTIVE

To calculate the SSDE of abdominal/pelvic CT and compare the SSDE with CTDIvol. To calculate the DRLs of CTDIvol and SSDE. Our hypotheses are: SSDE values will be greater than CTDIvol, and our DRL will be smaller than the known DRLs of other countries.

MATERIALS AND METHODS

The CTDIvol and DLP of 117 children who underwent abdominal/pelvic CT were collected retrospectively. The SSDE was calculated from the sum of the lateral and anteroposterior diameters. The relationships between body weight and effective diameter and between effective diameter and CTDIvol/SSDE were compared. Further, the local DRL was compared with the DRLs of other countries.

RESULTS

Body weight and effective diameter and effective diameter and SSDE were positively correlated. In children ages 1, 5 and 10 years, the SSDE is closer to the exposure dose of CTDIvol for the 16-cm phantom, while in children ages 15 years, the SSDE falls between CTDIvol for the 16-cm phantom and that for the 32-cm phantom. The local DRL was lower than those of other countries.

CONCLUSION

With SSDE, the radiation dose increased with increasing body weight. Since SSDE takes body size into account, it proved to be a useful indicator for estimating the exposure dose.

Nationwide radiation dose survey of computed tomography for fetal skeletal dysplasias

BACKGROUND

Recently, computed tomography (CT) has been used to diagnose fetal skeletal dysplasia. However, no surveys have been conducted to determine the radiation exposure dose and the diagnostic reference level (DRL).

OBJECTIVE

To collect CT dose index volume (CTDIvol) and dose length product (DLP) data from domestic hospitals implementing fetal skeletal 3-D CT and to establish DRLs for Japan.

MATERIALS AND METHODS

Scan data of 125 cases of 20 protocols from 16 hospitals were analyzed. The minimum, first-quartile, median, third-quartile and maximum values of CTDIvol and DLP were determined. The time-dependent change in radiation dose setting in hospitals with three or more cases with scans was also examined.

RESULTS

The minimum, first-quartile, median, third-quartile and maximum CTDIvol values were 2.1, 3.7, 7.7, 11.3 and 23.1 mGy, respectively, and these values for DLP were 69.0, 122.3, 276.8, 382.6 and 1025.6 mGy·cm, respectively. Six of the 12 institutions reduced the dose setting during the implementation period.

CONCLUSIONS

The DRLs of CTDIvol and DLP for fetal CT were 11.3 mGy and 382.6 mGy·cm, respectively. Institutions implementing fetal CT should use these established DRLs as the standard and make an effort to reduce radiation exposure by voluntarily decreasing the dose.

Can a revised paediatric radiation dose reduction CT protocol be applied and still maintain anatomical delineation, diagnostic confidence and overall imaging quality?

OBJECTIVE

To compare multidetector CT (MDCT) radiation doses between default settings and a revised dose reduction protocol and to determine whether the diagnostic confidence can be maintained with imaging quality made under the revised protocol in paediatric head, chest and abdominal CT studies.

METHODS

The study retrospectively reviewed head, chest, abdominal and thoracoabdominal MDCT studies, comparing 231 CT studies taken before (Phase 1) and 195 CT studies taken after (Phase 2) the implemented revised protocol. Image quality was assessed using a five-point grading scale based on anatomical criteria, diagnostic confidence and overall quality. Image noise and dose-length product (DLP) were collected and compared.

RESULTS

The relative dose reductions between Phase 1 and Phase 2 were statistically significant in 35%, 51% and 54% (p < 0.001) of head, chest and abdominal CT studies, respectively. There were no statistically significant differences in overall image quality score comparisons in the head (p = 0.3), chest (p = 0.7), abdominal (p = 0.7) and contiguous thoracic (p = 0.1) and abdominal (p = 0.2) CT studies, with the exception of anatomical quality in definition of bronchial walls and delineation of intrahepatic portal branches in thoracoabdominal CTs, and diagnostic confidence in mass lesion in head CTs, liver lesion (>1 cm), splanchnic venous thrombosis, pancreatitis in abdominal CTs, and emphysema and aortic dissection in thoracoabdominal CTs.

CONCLUSION

Paediatric CT radiation doses can be significantly reduced from manufacturer's default protocol while still maintaining anatomical delineation, diagnostic confidence and overall imaging quality.

ADVANCES IN KNOWLEDGE

Revised paediatric CT protocol can provide a half DLP reduction while preserving overall imaging quality.