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

Prospective dose monitoring using a manual dose management system: experience in brain computed tomography from a tertiary hospital in Nigeria

A manual radiation dose management system was developed to track the radiation dose and scan parameters of patients for brain computed tomography (CT). Radiation dose in volume computed tomography dose index (CTDIvol) and dose length product (DLP) were monitored to identify procedures that may require optimisation using notification values. The data were analysed and compared with national and international diagnostic reference levels (DRLs). A total of 596 brain CTs were monitored and grouped as <1: 36, 1-<5: 38, 5-<10: 25, 10-<15: 31 and adult: 466. The CTDIvol notification value identified the following number of examinations having high CTDIvol in <1 y: 1, 1-<5: 1, 5-<10: 0, 10-<15: 0 and adult (>15): 11. Furthermore, the DLP notification values identified the following examinations with high DLP in <1 y: 1, 1-<5:1, 5-<10:1, 10-<15: 1 and adults (>15): 18. The established local paediatric DLP DRLs were 2-3 times higher than the international paediatric DLP DRLs. This calls for a total protocol review and optimisation considering the local CT practices for paediatric imaging.

Estimation of diagnostic reference levels for pediatric head computed tomography in Yaoundé

The diagnostic reference levels (DRLs) are determined from dosimetry studies to compare and manage patient doses in medical imaging procedures. The aim of this work was to establish the first DRLs for pediatric patients during the most common computed tomography (CT) procedures in Yaoundé, Cameroon during routine head CT examinations to know how to improve our clinical practice tomorrow. The sample was classified per age group: ≤ 1-, 1-5-, 5-10- and 10-15-y-old. The retrospective study was used. The proposed DRLs were defined as 75th percentile of the median values of the distributions. In terms of Volume CT Dose Index (CTDIvol) and dose length product (DLP), the DRLs obtained for the ages groups were: 28.6 mGy and 545.8 mGy.cm, 32.6 mGy and 735 mGy.cm, 37.1 mGy and 761.6 mGy.cm and 44.2 mGy and 1081.2 mGy.cm, respectively. DRLs in Yaoundé for DLP were higher than those of comparison literatures. The Yaoundé CTDIvol was higher than the comparison literatures except for the IAEA (2015) values for the three older age groups. The DRLs reported in Yaoundé were compared to Morocco 2020, Switzerland 2018, IAEA 2015 and Iran 2020 values. The estimation of this first DRL for pediatric head CT scan in Yaoundé must be a starting point to spread this investigation towards other examinations and imaging modalities across the country. Therefore, optimization of the CT scan procedures and orderly updates of local DRLs are necessary to improve radioprotection.

Results and analysis of examination doses for paediatric CT procedures based on a nationwide survey in China

OBJECTIVE

To report the results of a dose survey conducted across 31 provinces in mainland China from 2017 to 2018 and to analyse the dose level to determine the national diagnostic reference levels (DRLs) for paediatric CT procedures.

METHODS

At least ten patients for each age group (0- < 1, 1- < 5, 5- < 10, 10- < 15 years) and each procedure (head, chest and abdomen) for each CT scanner were selected from four to eight hospitals in each province. The dose information (CTDIvol and DLP) was collected from the HIS or RIS-PACS systems. The median values in each CT scanner were considered the representative dose values for the paediatric patients in CT scanning. The national DRLs were estimated based on the 75th percentile distribution of the median values.

RESULTS

A total of 24,395 patients and 319 CT scanners were investigated across 262 hospitals. For paediatric CT scanning in 4 different age groups, the median (P50) and the 75th percentile (P75) of CTDIvol and DLP for each scanning procedure were calculated and reported. National DRLs were then proposed for each procedure and age group.

CONCLUSION

The dose level of CT scanning for children in mainland China was reported for the first time. The DRLs for paediatric CT in the present study are similar to those in some Asian countries but higher than those in European countries.

CLINICAL RELEVANCE STATEMENT

The paediatric CT is an extensively used tool in diagnosing paediatric disease; however, children are more sensitive to radiation. Establishing the diagnostic reference level of paediatric CT examination is necessary to reduce the dose of CT in children and promote the optimisation of medical exposure.

KEY POINTS

• The DRLs for 3 paediatric CT procedures (head, chest and abdomen) and 4 age groups (0- < 1, 1- < 5, 5- < 10, 10- < 15 years) were proposed in mainland China first time. • The examination parameter and dose for children need to be further optimised in China, especially to lower the tube voltage in paediatric CT.

Ultra-low-dose computed tomography with deep learning reconstruction for craniosynostosis at radiation doses comparable to skull radiographs: a pilot study

BACKGROUND

Craniofacial computed tomography (CT) is the diagnostic investigation of choice for craniosynostosis, but high radiation dose remains a concern.

OBJECTIVE

To evaluate the image quality and diagnostic performance of an ultra-low-dose craniofacial CT protocol with deep learning reconstruction for diagnosis of craniosynostosis.

MATERIALS AND METHODS

All children who underwent initial craniofacial CT for suspected craniosynostosis between September 2021 and September 2022 were included in the study. The ultra-low-dose craniofacial CT protocol using 70 kVp, model-based iterative reconstruction and deep learning reconstruction techniques was compared with a routine-dose craniofacial CT protocol. Quantitative analysis of the signal-to-noise ratio and noise was performed. The 3-dimensional (D) volume-rendered images were independently evaluated by two radiologists with regard to surface coarseness, step-off artifacts and overall image quality on a 5-point scale. Sutural patency was assessed for each of six sutures. Radiation dose was compared between the two protocols.

RESULTS

Among 29 patients (15 routine-dose CT and 14 ultra-low-dose CT), 23 patients had craniosynostosis. The 3-D volume-rendered images of ultra-low-dose CT without deep learning showed decreased image quality compared to routine-dose CT. The 3-D volume-rendered images of ultra-low-dose CT with deep learning reconstruction showed higher noise level, higher surface coarseness but decreased step-off artifacts, comparable signal-to-noise ratio and overall similar image quality compared to the routine-dose CT images. Diagnostic performance for detecting craniosynostosis at the suture level showed no significant difference between ultra-low-dose CT without deep learning reconstruction, ultra-low-dose CT with deep learning reconstruction and routine-dose CT. The estimated effective radiation dose for the ultra-low-dose CT was 0.05 mSv (range, 0.03-0.06 mSv), a 95% reduction in dose over the routine-dose CT at 1.15 mSv (range, 0.54-1.74 mSv). This radiation dose is comparable to 4-view skull radiography (0.05-0.1 mSv) and lower than previously reported effective dose for craniosynostosis protocols (0.08-3.36 mSv).

CONCLUSION

In this pilot study, an ultra-low-dose CT protocol using radiation doses at a level similar to skull radiographs showed preserved diagnostic performance for craniosynostosis, but decreased image quality compared to the routine-dose CT protocol. However, by combining the ultra-low-dose CT protocol with deep learning reconstruction, image quality was improved to a level comparable to the routine-dose CT protocol, without sacrificing diagnostic performance for craniosynostosis.

Pediatric computed tomography doses in Germany from 2016 to 2018 based on large-scale data collection

PURPOSE

Accumulating evidence from epidemiological studies that pediatric computed tomography (CT) examinations can be associated with a small but non-zero excess risk for developing leukemia or brain tumor highlights the need to optimize doses of pediatric CT procedures. Mandatory dose reference levels (DRL) can support reduction of collective dose from CT imaging. Regular surveys of applied dose-related parameters are instrumental to decide when technological advances and optimized protocol design allow lower doses without sacrificing image quality. Our aim was to collect dosimetric data to support adapting current DRL to changing clinical practice.

METHOD

Dosimetric data and technical scan parameters from common pediatric CT examinations were retrospectively collected directly from Picture Archiving and Communication Systems (PACS), Dose Management Systems (DMS), and Radiological Information Systems (RIS).

RESULTS

We collected data from 17 institutions on 7746 CT series from the years 2016 to 2018 from examinations of the head, thorax, abdomen, cervical spine, temporal bone, paranasal sinuses and knee in patients below 18 years of age. Most of the age-stratified parameter distributions were lower than distributions from previously-analyzed data from before 2010. Most of the third quartiles were lower than German DRL at the time of the survey.

CONCLUSIONS

Directly interfacing PACS, DMS, and RIS installations allows large-scale data collection but relies on high data-quality at the documentation stage. Data should be validated by expert knowledge or guided questionnaires. Observed clinical practice in pediatric CT imaging suggests lowering some DRL in Germany is reasonable.

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%.

ESTABLISHMENT OF LOCAL DIAGNOSTIC REFERENCE LEVEL FOR ROUTINE PAEDIATRIC COMPUTED TOMOGRAPHY EXAMINATIONS IN BAFOUSSAM WEST CAMEROON

The main purpose of this study was to determine local diagnostic reference level (LDRL) for routine computed tomography (CT) examination in Bafoussam, western Cameroon. The exposure parameters and dose quantities were collected manually. This retrospective, evaluative and comparative study was conducted to determine LDRLs for routine head CT examination in Bafoussam, to optimize these procedures in the region. The 75th percentile values of the calculated volume CT dose index (CTDIvol) and dose length product (DLP) were proposed as LDRL. The sample was classified in four age groups: < 1, 1-5, 5-10 and 10-15 y. The LDRLs obtained for the four age groups were: 24 mGy and 381.32 mGy.cm, 42.5 mGy and 875.55 mGy.cm, 45.85 mGy and 939.62 mGy.cm, 57.12 mGy and 1222.3 mGy.cm, respectively. The 75th percentile CTDIvol and DLP dose values for this study are higher than international values. We propose a coordinating discussions and collaboration about patient's and specific equipment's change information's, between radiologists, medical imaging technicians and medical physicist, which can reduce absorbed doses and improved medical practice in hospitals.

Towards the establishment of national diagnostic reference levels in Tunisia: a multicentre survey in paediatric CT

This work focuses on the determination of the radiation doses for a total sample of 916 children, categorised into four age groups (<1, 1-5, <5-10, <10-15 years) undergoing the most frequent paediatric CT scans performed in different scan facilities in Tunisia in order to establish the national diagnostic reference levels (DRLs). Dose evaluation concerned the dosimetric indicators: volume computed tomography dose index (CTDI_vol)and dose-length product (DLP). The different paediatric CT protocols and practices were also evaluated. The results show a large variation in doses between different radiology departments. For head scans, the respective DRLs for children aged <1, 1-5, 5-10 and 10-15 years were 26, 38, 51 and 51 mGy, respectively, for CTDI_voland 384, 664, 873 and 978 mGy cm, respectively, for DLP. For the chest, the equivalent respective DRLs were 8, 10, 12 and 15 mGy for CTDI_voland 118, 330, 442 and 526 mGy cm for DLP. For the abdomen, the respective DRLs were 9, 13, 19 and 18 mGy for CTDI_voland 353, 485, 592 and 1073 mGy cm for DLP. This study shows that the optimisation of paediatric CT procedures should be a priority, especially within regional hospitals. The implementation of corrective actions will take place after the initial DRLs. These actions, including recommendations and guidelines to good practice, should be a joint effort of all stakeholders, including health authorities, the radiation protection regulator, professional societies and universities.

2021 NATIONAL DIAGNOSTIC REFERENCE LEVELS FOR PAEDIATRIC COMPUTED TOMOGRAPHY IN EGYPT

OBJECTIVE

To establish national diagnostic reference levels (NDRLs) for most common paediatric computed tomography (CT) examinations in Egypt.

METHODS

This was a prospective study that included all dedicated paediatric imaging centers in Egypt. Data from 1680 individual paediatric patients undergoing CT scanning of the head, chest and abdomen-pelvis were collected. Computed tomography dose indices were recorded, data were analysed and compared with the internationally published paediatric DRLs in14 countries.

RESULTS

The Egyptian NDRLs of the CTDIvol (mGy) for head, chest and abdomen-pelvis scans among four paediatric age groups were found to be (23, 27, 28, 32, 4, 5, 6, 8, 5, 6, 7, 9) mGy, respectively; and the corresponding NDRLs of the DLP (mGycm) for head, chest and abdomen-pelvis scans were found to be (345, 428, 499, 637, 67, 85, 145, 215, 97, 135, 240, 320) mGycm, respectively. There were variations in the radiation doses between CT centers and identical scanners indicating the need for dose optimization. The NDRLs of the CTDIvol (mGy) and the DLP (mGycm) values were similar to or lower than international DRLs.

CONCLUSION

This study summarizes the results of the first Egyptian Computed Tomography survey that provides national diagnostic reference levels for paediatric patients in Egypt. Despite the reasonable NDRLs values, the study depicted certain pros and cons concerning CT practice, and identified some problems that hinder the process of optimization as well as justification in children.

Analysis and results from a UK national dose audit of paediatric CT examinations

OBJECTIVE

To present the results following a UK national patient dose audit of paediatric CT examinations, to propose updated UK national diagnostic reference levels (DRLs) and to analyse current practice to see if any recommendations can be made to assist with optimisation.

METHODS

A UK national dose audit was undertaken in 2019 focussing on paediatric CT examinations of the head, chest, abdomen/pelvis and cervical spine using the methods proposed by the International Commission on Radiological Protection. The audit pro-forma contained mandatory fields, of which the post-examination dosimetry (volume CT dose index and dose-length product) and the patient weight (for body examinations) were the most important.

RESULTS

Analysis of the data submitted indicates that it is appropriate to propose national DRLs for CT head examinations in the 0-<1, 1-<5, 5-<10 and 10-<15 year age ranges. This extends the number of age categories of national DRLs from those at present and revises the existing values downwards. For CT chest examinations, it is appropriate to propose national DRLs for the first time in the UK for the 5-<15, 15-<30, 30-<50 and 50-<80 kg weight ranges. There were insufficient data received to propose national DRLs for abdomen/pelvis or cervical spine examinations. Recommendations towards optimisation focus on the use of tube current (mA) modulation, iterative reconstruction and the selection of examination tube voltage (kV_p).

CONCLUSION

Updated UK national DRLs are proposed for paediatric CT examinations of the head and chest.

ADVANCES IN KNOWLEDGE

A national patient dose audit of paediatric CT examinations has led to the proposal of updated national DRLs.

Paediatric diagnostic reference levels for common radiological examinations using the European guidelines

OBJECTIVE

The purpose of this study was to explore the feasibility to determine regional diagnostic reference levels (RDRLs) for paediatric conventional and CT examinations using the European guidelines and to compare RDRLs derived from weight and age groups, respectively.

METHODS

Data were collected from 31 hospitals in 4 countries, for 7 examination types for a total of 2978 patients. RDRLs were derived for each weight and age group, respectively, when the total number of patients exceeded 15.

RESULTS

It was possible to derive RDRLs for most, but not all, weight-based and age-based groups for the seven examinations. The result using weight-based and age-based groups differed substantially. The RDRLs were lower than or equal to the European and recently published national DRLs.

CONCLUSION

It is feasible to derive RDRLs. However, a thorough review of the clinical indications and methodologies has to be performed previous to data collection. This study does not support the notion that DRLs derived using age and weight groups are exchangeable.

ADVANCES IN KNOWLEDGE

Paediatric DRLs should be derived using weight-based groups with access to the actual weight of the patients. DRLs developed using weight differ markedly from those developed with the use of age. There is still a need to harmonize the method to derive solid DRLs for paediatric radiological examinations.

Diagnostic reference levels for computed tomography examinations in pediatric population - A systematic review

Computed tomography (CT) has vital role in diagnosis of various pathologies using cross sectional images. Besides the advantages of CT in pediatric radiology, radiation dose has a significant adverse effect as children are more vulnerable than adults. Establishing Diagnostic Reference levels (DRLs) will determine unusual increase in radiation doses and therefore helps in optimizing the radiation dose by maintaining optimum diagnostic image quality. The objective of the review is to explore the literature on DRLs in pediatric CT examinations and techniques that have been used to establish them. Detailed search was done in PubMed-Medline, Scopus CINAHL, Web of Science, and the Cochrane Library databases to find studies that have established DRLs for pediatric CT examinations. The Preferred Reporting Items for Systematic Review and Meta-Analyses methodology was used to assess the relevant articles. The articles which assessed DRLs in pediatric CT examinations were included. A total of 501 articles were identified, of which 21 articles were included after a detailed screening process. Our review showed increased in pediatric patient dose surveys across the world and also increased in awareness for establishing DRLS among pediatric CT examinations. The review also demonstrated wide variation in DRLs and also deviation in the scanning techniques, protocols used and categorization methods used for establishing DRLs. As the pediatric population is more sensitive to radiation, the current review emphasizes the need for optimization of protocols and international standardization for establishing DRLs to facilitate a more feasible way of comparison of dose globally across CT sites.

DERIVATION OF LOCAL DIAGNOSTIC REFERENCE LEVELS FOR COMMON ADULT COMPUTED TOMOGRAPHY EXAMINATIONS IN MOROCCAN HOSPITAL

The purpose was to derive local diagnostic reference levels (LDRLs) for adults common computed tomography (CT) examinations in Moroccan hospital. The data of patients were collected retrospectively from one facility for 2 months period. The proposed LDRLs were defined as 75th percentile of spreads for CT dose index-volume (CTDIvol) and dose length product (DLP). Findings were compared with diagnostic reference levels (DRLs) of France, Australia and Egypt. A total of 259 cases were enrolled including 53% of male and 47% of female. The corresponding LDRLs in terms of CTDIvol (mGy) were 58, 15, 15 and 14 for head, chest, abdomen-pelvis and chest-abdomen-pelvis CT examinations, respectively. For DLP (mGy.cm) were 1298, 944, 1874 and 2026, respectively. The proposed LDRLs for CTDIvol were almost similar to DRLs of Australia, higher than those of France and lower than Egyptian DRLs. In terms of DLP, LDRLs were higher than compared studies with exception of head CT, which were lower and higher for CTDIvol than Egyptian DRLs. The results highlight higher radiation doses during adult CT scans, indicating the need to spread the same investigation regarding other imaging procedures including different radiological examinations across Moroccan hospitals.

Assessment of patients' cumulative doses in one year and collective dose to population through CT examinations

PURPOSE

To estimate percentage of patients undergoing multiple CT exams leading to cumulative effective dose (CED) of more than 25, 50, 75 and 100 mSv in one year and assess per capita and the collective effective dose.

METHODS

Data from a regional hospital network was collected retrospectively using radiation dose monitoring system at 6 facilities with 8 CT scanners. The data was analyzed to find number of patients in different dose groups, their age, gender, number of CT exams and exams needed to reach 100 mSv based on age groups.

RESULTS

In one year 43,010 patients underwent 75,252 CT examinations. The number of exams per 1000 population was 153. Further 27% of the patients were younger than 55- years and 15.9% of them were younger than 45-year-old. A total of 0.67% of patients received a CED > 100 mSv; 3.5% had CED > 50 mSv, 11.9% with CED > 25 mSv and the maximum CED was 529 mSv. The minimum time to reach 100 mSv was a single CT exam. Seven patients received > 100 mSv in a single CT exam. 0.36% of patients had 10 or more CT exams in one year and 3.8% had 5 or more CT exams. The mean CED was 12.3 mSv, the average individual effective dose was 1.1 mSv and the collective effective dose was 521.3 person-Sv.

CONCLUSIONS

The alarming high CED received by large number of patients and with high collective dose to population requires urgent actions by all stake holders in the best interest of patient radiation safety.

Simplified size adjusted dose reference levels for adult CT examinations: A regional study

PURPOSE

To investigate retrospective classification of adult patients into small, average, and large based on effective diameter (EDia) from localizer image of computed tomography (CT) scans and to develop regional diagnostic reference levels (DRLs) and achievable doses (AD).

METHOD

The patients falling within the mean ± standard deviation (SD) of EDia were classified as average; those below this range as small and above as large. The CTDI_vol,dose-length-product (DLP) and size-specific dose estimates (SSDE) of all adult patients undergoing CT examinations in 8 CT facilities for 11 months (Dec. 2019 - Oct. 2020) were evaluated. The 75th and 50th percentile values were compared with national and international values.

RESULTS

Of the total of 69,434 CT examinations, nearly 80% fell within average size. The 75th percentile values of CTDI_vol and DLP for small patients for abdomen-pelvic exams were nearly half of average sized patients. Similarly, the 75th percentile values for large patients were nearly double. Similar findings were not found for chest exams. Analysis of image quality and dose factors such as noise, mean axial length, slice thickness, mean number of sequences, use of iterative reconstruction and tube current modulation (TCM) resulted in identification of opportunities for improvement and optimization of different CT facilities.

CONCLUSIONS

DRLs for adult patients were found to vary widely with patient size and thus establishing DRLs only for standard sized patient is not adequate. Simplified and intuitive methods for size classification was shown to provide meaningful information for optimization for patients outside the standard size adult.

Establishing paediatric diagnostic reference levels using reference curves - A feasibility study including conventional and CT examinations

PURPOSE

To derive Regional Diagnostic Reference Levels (RDRL) for paediatric conventional and CT examinations using weight-based DRL curves and compare the outcome with DRL derived using the weight groups.

METHODS

Data from 1722 examinations performed at 29 hospitals in four countries were included. DRL was derived for four conventional x-ray (chest, abdomen, pelvis, hips/joints) and two types of CT examinations (thorax, abdomen). DRL curves were derived using an exponential fit to the data using weight as an independent variable and the respective radiation dose indices (P_KA, CTDI_vol, DLP) as dependent variables. DRL was also derived for weight groups for comparison. The result was compared with national diagnostic reference level (NDRL) curves.

RESULTS

The derived curves show similarities with the NDRL curves available and corresponded sufficiently well with DRL for weight groups using the same data set, if sufficient number of data was available.

CONCLUSIONS

We conclude that weight-based DRL curves are a feasible approach and could be used together with DRL for weight groups. The main advantage of DRL curves is its application in the clinic. When the examination frequency is low, time to collect enough data to establish typical values for one or several weight groups may be unreasonably long. The curve provides the means to compare dose level faster and with fewer data points.

Old enemy, new threat: you can't solve today's problems with yesterday's solution

The radiation protection principles of justification, optimization, and dose limitation as enumerated by the International Commission on Radiological Protection have been guiding light for the profession for over three decades. The dose limitation does not apply to medical exposure but keeping patients' doses low is achieved through optimization, particularly by developing and using diagnostic reference levels (DRLs). There are new findings that demonstrate that despite using the best possible approaches to justification and optimization including as well use of DRLs, a very large number of patients are receiving doses in excess of 100 mSv of effective dose or organ doses exceeding 100 mGy. A non-ignorable fraction of patients is receiving such high doses in a single day. The magnitude of such patients creates the need for a relook into the principles with the intent to understand what can be done to attend to today's problems. A look at other areas such as approaches, and principles used in the pharmaceutical industry and in traffic management throws some light into what can be learnt from these examples. It appears that the system needs to be enriched to deal with the protection of the individual patient. The currently available approaches and even the principles are largely based on the protection of the population or group of patients. The third level of justification for individual needs further refinement to take into account series of imaging many patients are needing, and cumulative radiation doses involved, many of which happen in a short duration of 1 to 5 years. There is every likelihood of patient radiation doses continuing to increase further that underscores the need for timely attention. This paper provides several suggestions to deal with the situation.

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.

Multicentric study of patients receiving 50 or 100 mSv in a single day through CT imaging-frequency determination and imaging protocols involved

OBJECTIVES

To assess the magnitude and characterization of CT imaging protocols of patients receiving 50 or 100 mSv in a single day.

METHODS

In this multicentric retrospective study covering up to 279 hospitals from January 2015 to December 2019, the effective dose (E) as estimated by dose management system from dose length product of patients was filtered and grouped into per-day dose bands (≤ 20, > 20-50, > 50-70, > 70-100, > 100-200, > 200 mSv). Information on patient's age and imaging protocol was noted. The data were analyzed to determine the frequency of occurrence in each dose band. Top 20 CT imaging protocols that led to patients with a dose of ≥ 50 mSv in a single acquisition were identified and their relative frequency was estimated.

RESULTS

A total of approx. 4.3 million (4,283,738) CT exams were performed in approx. 3.9 million (3,880,524) patient-days indicating 9.41% had more than one CT exam in a single day. There were 31,058 (0.8%) patient-days with ≥ 50 mSv and 1191 (0.03%) with ≥ 100 mSv. Nearly 1/3^rd patient-days reaching ≥ 50 mSv were of patients aged 50 years or younger. The top 20 CT imaging protocols that led to ≥ 50 mSv in a single day belonged to the body region (chest or abdomen and pelvis) and nearly one-third were angiographic studies.

CONCLUSIONS

In the first study of its kind, we report that patients with 50 mSv+ in a single day or a single exam are not rare. The information on imaging protocols leading to such doses and their frequency has been provided to help develop dose management strategies.

KEY POINTS

• Our study of 4,283,738 CT exams performed in 3,880,524 patient-days indicates 0.8% with 50 mSv+ and 0.03% with 100 mSv+ in a single day. • A total of 9.41% underwent more than one CT exam in a single day; nearly 1/3^rd of those with 50 mSv+ were ≤ 50 years of age. • Identified top 20 CT imaging protocols that led to 50 mSv+ doses in a single exam. All belong to chest or abdomen and pelvis and nearly 1/3^rd were angiographic studies.

Higher patient doses through X-ray imaging procedures

Medical imaging using X-rays has been one of the most popular imaging modalities ever since the discovery of X-rays 125 years ago. With unquestionable benefits, concerns about radiation risks have frequently been raised. Computed tomography (CT) and fluoroscopic guided interventional procedures have the potential to impart higher radiation exposure to patients than radiographic examinations. Despite technological advances, there have been instances of increased doses per procedure mainly because of better diagnostic information in images. However, cumulative dose from multiple procedures is creating new concerns as effective doses >100 mSv are not uncommon. There is a need for action at all levels. Manufacturers must produce equipment that can provide a quality diagnostic image at substantially lesser dose and better implementation of optimization strategies by users. There is an urgent need for the industry to develop CT scanners with sub-mSv radiation dose, a goal that has been lingering. It appears that a new monochromatic X-ray source will lead to replacement of X-ray tubes all over the world in coming years and will lead to a drastic reduction in radiation doses. This innovation will impact all X-ray imaging and will help dose reduction. For interventional procedures, the likely employment of robotic systems in practice may drastically reduce radiation exposures to operators- but patient exposure will still remain an issue. Training needs always need to be emphasized and practiced.

Development of a computational phantom for validation of automated noise measurement in CT images

The purpose of this study was to develop a computational phantom for validation of automatic noise calculations applied to all parts of the body, to investigate kernel size in determining noise, and to validate the accuracy of automatic noise calculation for several noise levels. The phantom consisted of objects with a very wide range of HU values, from -1000 to +950. The incremental value for each object was 10 HU. Each object had a size of 15 × 15 pixels separated by a distance of 5 pixels. There was no dominant homogeneous part in the phantom. The image of the phantom was then degraded to mimic the real image quality of CT by convolving it with a point spread function (PSF) and by addition of Gaussian noise. The magnitude of the Gaussian noises was varied (5, 10, 25, 50, 75 and 100 HUs), and they were considered as the ground truth noise (N_G). We also used a computational phantom with added actual noise from a CT scanner. The phantom was used to validate the automated noise measurement based on the average of the ten smallest standard deviations (SD) from the standard deviation map (SDM). Kernel sizes from 3 × 3 up to 27 × 27 pixels were examined in this study. A computational phantom for automated noise calculations validation has been successfully developed. It was found that the measured noise (N_M) was influenced by the kernel size. For kernels of 15 × 15 pixels or smaller, the N_Mvalue was much smaller than the N_G. For kernel sizes from 17 × 17 to 21 × 21 pixels, the N_Mvalue was about 90% of N_G. And for kernel sizes of 23 × 23 pixels and above, N_Mis greater than N_G. It was also found that even with small kernel sizes the relationship between N_Mand N_Gis linear with R²more than 0.995. Thus accurate noise levels can be automatically obtained even with small kernel sizes without any concern regarding the inhomogeneity of the object.

Establishment of CTPA Local Diagnostic Reference Levels with Noise Magnitude as a Quality Indicator in a Tertiary Care Hospital

This study aimed to establish the local diagnostic reference levels (LDRLs) of computed tomography pulmonary angiography (CTPA) examinations based on body size with regard to noise magnitude as a quality indicator. The records of 127 patients (55 males and 72 females) who had undergone CTPAs using a 128-slice CT scanner were retrieved. The dose information, scanning acquisition parameters, and patient demographics were recorded in standardized forms. The body size of patients was categorized into three groups based on their anteroposterior body length: P1 (14–19 cm), P2 (19–24 cm), and P3 (24–31 cm), and the radiation dose exposure was statistically compared. The image noise was determined quantitatively by measuring the standard deviation of the region of interest (ROI) at five different arteries—the ascending and descending aorta, pulmonary trunk, and the left and right main pulmonary arteries. We observed that the LDRL values were significantly different between body sizes (p < 0.05), and the median values of the CT dose index volume (CTDI_vol) for P1, P2, and P3 were 6.13, 8.3, and 21.40 mGy, respectively. It was noted that the noise reference values were 23.78, 24.26, and 23.97 HU for P1, P2, and P3, respectively, which were not significantly different from each other (p > 0.05). The CTDI_vol of 9 mGy and dose length product (DLP) of 329 mGy∙cm in this study were lower than those reported by other studies conducted elsewhere. This study successfully established the LDRLs of a local healthcare institution with the inclusion of the noise magnitude, which is comparable with other established references.

Radiation dose to the lens from CT of the head in young people

AIM

To determine cumulative scan frequencies and estimate lens dose for paediatric computed tomography (CT) head examinations in the context of potential cataract risk.

MATERIALS AND METHODS

The cumulative number of head-region CT examinations among a cohort of 410,997 children and young adults who underwent CT in the UK between 1985 and 2014 was calculated. Images from a sample of these head examinations (n=668) were reviewed to determine the level of eye inclusion. Lens dose per scan was estimated using the computer program, NCICT V1.0, for different levels of eye inclusion and exposure settings typical of past and present clinical practice.

RESULTS

In total 284,878 patients underwent 448,108 head-region CT examinations. The majority of patients (72%) had a single recorded head-region examination. A small subset (∼1%, n=2,494) underwent ≥10 examinations, while 0.1% (n=387) underwent ≥20. The lens was included within the imaged region for 57% of reviewed routine head examinations. In many cases, this appeared to be intentional, i.e. protocol driven. In others, there appeared to have been an attempt to exclude the eyes through gantry angulation. Estimated lens doses were 20-75 mGy (mean: 47 mGy) where the eye was fully included within the examination range and 2-7 mGy (mean: 3.1 mGy) where the lens was fully excluded. Potential cumulative lens doses ranged from ∼3 mGy to ∼4,700 mGy, with 2,335 patients potentially receiving >500 mGy.

CONCLUSION

The majority of young people will receive cumulative lens doses well below 500 mGy, meaning the risk of cataract induction is likely to be very small.

Development and validation of image quality scoring criteria (IQSC) for pediatric CT: a preliminary study

OBJECTIVE

To develop and assess the value and limitations of an image quality scoring criteria (IQSC) for pediatric CT exams.

METHODS

IQSC was developed for subjective assessment of image quality using the scoring scale from 0 to 4, with 0 indicating desired anatomy or features not seen, 3 for adequate image quality, and 4 depicting higher than needed image quality. Pediatric CT examinations from 30 separate patients were selected, five each for routine chest, routine abdomen, kidney stone, appendicitis, craniosynostosis, and ventriculoperitoneal (VP) shunt. Five board-certified pediatric radiologists independently performed image quality evaluation using the proposed IQSC. The kappa statistics were used to assess the interobserver variability.

RESULTS

All five radiologists gave a score of 3 to two-third (67%) of all CT exams, followed by a score of 4 for 29% of CT exams, and 2 for 4% exams. The median image quality scores for all exams were 3 and the interobserver agreement among five readers (acceptable image quality [scores 3 or 4] vs sub-optimal image quality ([scores 1 and 2]) was moderate to very good (kappa 0.4-1). For all five radiologists, the lesion detection was adequate for all CT exams.

CONCLUSIONS

The image quality scoring criteria covering routine and some clinical indication-based imaging scenarios for pediatric CT examinations has potential to offer a simple and practical tool for assessing image quality with a reasonable degree of interobserver agreement. A more extensive and multi-centric study is recommended to establish wider usefulness of these criteria.

Long-term experience and analysis of data on diagnostic reference levels: the good, the bad, and the ugly

OBJECTIVES

To analyze 11-year data of France for temporal trends in dose indices and dose optimization and draw lessons for those who are willing to work on creation and update of diagnostic reference levels (DRLs).

METHODS

The data from about 3000 radiology departments leading to about 750,000 imaging exams between 2004 and 2015 was analyzed, and patterns of reductions in dose for those below and above the DRLs were estimated and correlated with technology change.

RESULTS

Dose optimization achieved was important and significant in departments which were above or just below the DRL (p = .006) but not in those which were around half of the DRL values. The decrease in 75th percentile value of Kerma air product (KAP) for chest radiography by 27.4% between 2004 and 2015 was observed with the number of flat panel detectors increase from 6 to 43%. A good correlation between the detector type distribution and the level of patient radiation exposure is observed. Otherwise, setting DRLs for standard-sized patient excludes patients lower and higher weighted than "standard."

CONCLUSIONS

The concept of DRL may become obsolete unless lessons drawn from the experience of users are taken into account. While establishing DRLs should be part of the regulations, setting up and updating values should be governed by bodies whose decision-making cycle is short, at the most 1 year. A local rather than national approach, taking into account body habitus and image quality, needs to be organized.

KEY POINTS

• The technology changes faster than regulations. Requirement of DRL establishment should be part of the regulations; however, setting and updating values should be the role of professional societies. • The concept of DRL, highlighting the 75th percentile values and dedicated to standard-sized adult, misses optimization opportunities in the majority of patients who are below the 75th percentile value and outside the range of standard-sized adult. • The ugly aspects of the DRL concept include its non-applicability to individuals, no customization to clinical indications, and lack of consideration of image quality.

PEDIATRIC HEAD CT EXPOSURE DOSES IN TUNISIA: A PILOT STUDY TOWARDS THE ESTABLISHMENT OF NATIONAL DIAGNOSTIC REFERENCE LEVELS

The purpose of this study was to assess and analyze the radiation doses during head pediatric CT from different CT units within six Tunisian hospitals representing different geographic regions in order to optimize the dose given and minimize the radiology risk to this category of patients and towards the derivation of national diagnostic reference levels. Patient data and exposure parameters were collected for four age groups (<1, 1-5, 5-10 and 10-15 y). Clinical protocols and exposure settings were analyzed. Doses were collected in terms of CTDIvol and DLP values. Effective and Organ doses to specific radiosensitive organs were estimated using the Monte Carlo simulation software 'Impact CTDosimetry'. Results showed large variations in CT protocols and doses between different radiology departments. CTDIvol and DLP values demonstrated a broad range between the CT units and between the axial and helical scan techniques in the same unit. CTDI vol values were estimated to be 24.9, 31.7, 45.5 and 47.8 mGy for <1, 1-5, 5-10 and 10-15 y age groups, respectively. In term of DLP, median values were ~346, 528, 824, 897 mGy cm for the same age groups, respectively. Effective dose ranged from 1.4 to 5 mSv. Dose values were comparable with those reported in the literature. The study shows an evident need for continuous training of staff in radiation protection concepts, especially within the regional hospitals, emphasizes the importance of the production and the update of recommendations and good practice guidelines using interdisciplinary working groups and opens the way for the establishment of national DRLs.

Children's Environmental Health in Thailand: Past, Present, and Future

Background:

There is increasing evidence of a link between environmental pollution and preventable diseases in developing countries, including Thailand. Economic development has generated several types of pollution that can affect population health. While these environmental health effects can be observed throughout life, pregnant women and children represent particularly vulnerable and sensitive groups.

Methods:

The published epidemiological literature investigating environmental chemical exposure in Thai children was reviewed, highlighting those that investigated associations between exposure and subsequent health outcomes.

Results:

The majority of the Thai epidemiological studies on environmental health in children were cross-sectional in design, with some demonstrating associations between exposure and outcome. The three main types of chemical exposure in Thai children were pesticides, heavy metals, and air pollution, which resulted from agricultural activities in countryside areas, industrial zones (both registered and unregistered establishments), mining, and traffic in inner cities. Major health outcomes included detrimental effects on cognitive function and cancer risk. Pesticide exposure was focused on, but not limited to, agricultural areas. The success of the Thai environmental policy to introduce lead–free petrol can be demonstrated by the decline of mean blood lead levels in children, particularly in urban areas. However, unregistered lead-related factories and smelters act as hidden sources. In addition, there is increasing concern, but little acknowledgement, about the effects of chronic arsenic exposure related to mining. Lastly, air pollution remains a problem in both dense city populations due to traffic and in rural areas due to contamination of indoor air and house dust with heavy metals, endotoxins and other allergens.

Conclusions:

The increasing number of published articles demonstrates an improved awareness of children’s environmental health in Thailand. Chemical hazards, including the improper use of pesticides, environmental contamination with heavy metals (lead and arsenic), and air pollution in inner cities and indoor air, continue to be growing issues.

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).

Patient dose monitoring and the use of diagnostic reference levels for the optimization of protection in medical imaging: current status and challenges worldwide

Optimization is one of the key concepts of radiation protection in medical imaging. In practice, it involves compromising between the image quality and dose to the patient; the dose should not be higher than necessary to achieve an image quality (or diagnostic information) needed for the clinical task. Monitoring patient dose is a key requirement toward optimization. The concept of diagnostic reference level (DRL) was introduced by the International Commission on Radiological Protection as a practical tool for optimization. Unfortunately, this concept has not been applied consistently worldwide. To review the current strengths and weaknesses worldwide and to promote improvements, the International Atomic Energy Agency organized a Technical Meeting on patient dose monitoring and the use of DRLs on May 2016. This paper reports a summary of the findings and conclusions from the meeting. The strengths and weaknesses were generally different in less-developed countries compared with developed countries. Possible improvements were suggested in six areas: human resources and responsibilities, training, safety and quality culture, regulations, funding, and tools and methods. An overall conclusion was that radiation protection requires a patient-centric approach and a transfer from purely reactive to increasingly proactive optimization, whereby the best outcome is expected from good teamwork.

Review of the current status of radiation protection in diagnostic radiology in Africa

The aim of this paper is to review the available published studies from African countries on patient doses and medical radiation protection and identify strengths, weaknesses, and challenges. Papers on radiation doses to patients published until 2016 pertaining to studies in African countries were reviewed. Radiography, interventional radiology, computed tomography (CT), and mammography modalities were covered. In radiography, the entrance surface air kerma values were below the established diagnostic reference levels (DRLs) provided by the International Atomic Energy Agency, European Commission, and National Council on Radiation Protection and Measurements. Patient and staff doses in interventional procedures were not on the higher side when compared with other published reports from developed countries. The dose length product values in CT in many situations were higher than established DRLs. In mammography, the variations of clinical image quality and dose to standard breast between African countries and other countries were insignificant. In conclusion, like in any continent, not all countries in Africa are active, but some have produced good results. The potential for optimization of radiation protection using simple and inexpensive techniques has been demonstrated. The lack of medical physicists is one of the important challenges.

Validation of the Australian diagnostic reference levels for paediatric multi detector computed tomography: a comparison of RANZCR QUDI data and subsequent NDRLS data from 2012 to 2015

The national diagnostic reference level service (NDRLS), was launched in 2011, however no paediatric data were submitted during the first calendar year of operation. As such, Australian national diagnostic reference levels (DRLs), for paediatric multi detector computed tomography (MDCT), were established using data obtained from a Royal Australian and New Zealand College of Radiologists (RANZCR), Quality Use of Diagnostic Imaging (QUDI), study. Paediatric data were submitted to the NDRLS in 2012 through 2015. An analysis has been made of the NDRLS paediatric data using the same method as was used to analyse the QUDI data to establish the Australian national paediatric DRLs for MDCT. An analysis of the paediatric NDRLS data has also been made using the method used to calculate the Australian national adult DRLs for MDCT. A comparison between the QUDI data and subsequent NDRLS data shows the NDRLS data to be lower on average for the Head and AbdoPelvis protocol and similar for the chest protocol. Using an average of NDRLS data submitted between 2012 and 2015 implications for updated paediatric DRLS are considered.

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.