ICRP Publication 135: Diagnostic Reference Levels in Medical Imaging

A MULTICENTRE SURVEY OF LOCAL DIAGNOSTIC REFERENCE LEVELS AND ACHIEVABLE DOSE FOR CORONARY ANGIOGRAPHY AND PERCUTANEOUS TRANSLUMINAL CORONARY INTERVENTION PROCEDURES IN KOREA

Interventional cardiology procedures can involve relatively high radiation doses compared to general radiography. During coronary angiography (CAG) and percutaneous transluminal coronary intervention (PCI), the same area is exposed to radiation for a long period. In this study, radiation exposure data of 1071 examinations in Korean hospitals were collected, and the achievable dose (AD) and diagnostic reference levels (DRLs) in actual medical practice for two types of interventional cardiology procedures in Korea were established. In CAG, 75th percentile DRLs and AD of the total kerma-area product were 47.0 and 33.1 Gy·cm 2, respectively. In PCI, those values were 171.3 and 102.6 Gy·cm2, respectively. This is the first study to introduce the DRLs for cardiovascular interventional procedures in Korea. These results will help optimise the interventional cardiology procedures for Korean cardiac centres.

DOSE BENCHMARKS FOR PAEDIATRIC HEAD COMPUTED TOMOGRAPHY EXAMINATION IN NIGERIA

Diagnostic reference levels (DRLs) provide benchmarks for dose optimisation. We aimed to propose DRLs for paediatric head computed tomography (CT) in Nigeria and assess if facilities adapt protocols to age-specific standardisations. Volume CT dose index (CTDIvol) and dose-length-product (DLP) of at least 20 paediatric patients per age group were extracted from 11 facilities and used to propose DRLs. Kruskal-Wallis and Median tests were used to assess the contribution of age to paediatric dose variations. CTDIvol (mGy)/DLP (mGy.cm) ranged 16-31/100-1603 (newborn), 10-92/75-4072 (1-y-old), 10-81/169-2603 (5-y-olds) and 14-86/119-3945 (≥10-y-olds). The 75th percentile CTDIvol/DLP values were 27/1040, 37/988, 48/1493 and 54/1824 for newborn, 1-y, 5-y, ≥10-y-olds, respectively. Age accounted for 18.4 and 5.3% variations in median CTDIvol and DLP, respectively. Paediatric head CT doses in Nigeria are higher than reported internationally, suggesting a need for dose optimisation interventions.

Eye lens radiation exposure in paediatric interventional treatment of retinoblastoma

Retinoblastoma represents 3% of cancers in children under fifteen years of age. The standard paediatric treatment for saving the affected eye is supraselective intra-arterial chemotherapy performed in interventional rooms. In order to address the radiation toxicity due to the angiography, the aim of this study was to determine the typical dose value corresponding to the procedure, estimate the paediatric patients' eye lens dose and study the relationship between dose indicators and dose to the lens. An automatic dose management software was installed in two interventional rooms to obtain the distribution of the dose indicators kerma-area product and reference-point air kerma, getting a typical value 16 Gy·cm2 and 130 mGy, respectively (n = 35). The eye lens dose estimates were obtained with photoluminescent dosimeters placed on the patient's eyelids. In the left eye, the entrance surface air kerma was 44.23 ± 2.66 mGy, and 12.72 ± 0.89 mGy in the right eye (n = 10). There was a positive correlation between dose to the lens per procedure and dose indicators, with R2 > 0.65 for both eyes. Based on this information, the threshold for the onset of radiation-induce cataracts (500 mGy) will be exceeded if the treatment is performed for more than 8 sessions.

INSTITUTIONAL BREAST DOSES IN DIGITAL MAMMOGRAPHY

The objective of this study was to survey breast dose in screening mammography, establish institutional doses and compare them with the corresponding dose values. Three hundred women between the ages of 40 and 80 years old participated in the study. All mammographic examinations were performed with a digital mammography system. The women characteristics (age, weight, height, BMI), technical and exposure parameters (anode/filter material, projection, compressed breast thickness (CBT), compression force, tube voltage, tube load), the entrance surface dose (ESD) and the average glandular dose (AGD) were recorded. The mean, median, 75th and 95th percentiles of the AGD and ESD distributions were estimated for all examinations, for right and left breast, as well as for CBT within 55-65 mm, for Cranio-Caudal (CC) and Medio-Lateral Oblique (MLO) projections. A statistical analysis was also performed, to investigate the impact of the recorded parameters on the ESD and AGD. The mean/median values of the ESD and AGD for all examinations, for CC and MLO projections were 4.60/4.29 and 5.42/5.25 mGy and 1.18/1.13 and 1.32/1.30 mGy, respectively. The mean/median values of the ESD and AGD for CC and MLO projections at CBT range 55-65 mm were 5.29/5.08 and 5.56/5.42 mGy and 1.30/1.24 and 1.36/1.32 mGy, respectively. The 75th percentile for CC and MLO projections were estimated 5.79 and 6.17 mGy, as well as 1.41 and 1.48 mGy in terms of ESD and AGD values, respectively. The 95th percentile of the ESD and AGD for CC and MLO projections were also 7.40 and 7.53 mGy and 1.76 and 1.78 mGy, respectively. The tube voltage, tube load, age and CBT had a significant influence on the dose values. The estimated values were found to be comparable, or in most cases lower, than the corresponding 75th and 95th percentile values from previous studies.

PATIENT DOSE SURVEY BASED ON SIZE-SPECIFIC DOSE ESTIMATE AND ACCEPTABLE QUALITY DOSE IN CHEST AND ABDOMEN/PELVIS CT EXAMINATIONS

The practical aspects of two recently developed patient dose optimization methods in computed tomography (CT) examinations, size-specific dose estimate (SSDE) and acceptable quality dose (AQD), were verified for the chest and abdomen/pelvis examinations. A dose survey was performed in a CT institute by considering patients lateral diameter, weight and body mass index (BMI). The AQD tables for weight and BMI groups and SSDE threshold curves were obtained. The mean of volume CT dose index and dose length product for standard-size patients were compared with the national diagnostic reference levels (NDRLs) of Iran. The results show that patient doses are below the NDRLs. It is more reliable to report the AQDs based on SSDE and for BMI groups which can well take into account patient size in the dose optimization process. The SSDE threshold curves can be determined with more precision by including dose data of all possible sizes in the curves.

A Nordic survey of CT doses in hybrid PET/CT and SPECT/CT examinations

Background

Computed tomography (CT) scans are routinely performed in positron emission tomography (PET) and single photon emission computed tomography (SPECT) examinations globally, yet few surveys have been conducted to gather national diagnostic reference level (NDRL) data for CT radiation doses in positron emission tomography/computed tomography (PET/CT) and single photon emission computed tomography/computed tomography (SPECT/CT). In this first Nordic-wide study of CT doses in hybrid imaging, Nordic NDRL CT doses are suggested for PET/CT and SPECT/CT examinations specific to the clinical purpose of CT, and the scope for optimisation is evaluated. Data on hybrid imaging CT exposures and clinical purpose of CT were gathered for 5 PET/CT and 8 SPECT/CT examinations via designed booklet. For each included dataset for a given facility and scanner type, the computed tomography dose index by volume (CTDI_vol) and dose length product (DLP) was interpolated for a 75-kg person (referred to as CTDI_vol,75kg and DLP_75kg). Suggested NDRL (75th percentile) and achievable doses (50th percentile) were determined for CTDI_vol,75kg and DLP_75kg according to clinical purpose of CT. Differences in maximum and minimum doses (derived for a 75-kg patient) between facilities were also calculated for each examination and clinical purpose.

Results

Data were processed from 83 scanners from 43 facilities. Data were sufficient to suggest Nordic NDRL CT doses for the following: PET/CT oncology (localisation/characterisation, 15 systems); infection/inflammation (localisation/characterisation, 13 systems); brain (attenuation correction (AC) only, 11 systems); cardiac PET/CT and SPECT/CT (AC only, 30 systems); SPECT/CT lung (localisation/characterisation, 12 systems); bone (localisation/characterisation, 30 systems); and parathyroid (localisation/characterisation, 13 systems). Great variations in dose were seen for all aforementioned examinations. Greatest differences in DLP_75kg for each examination, specific to clinical purpose, were as follows: SPECT/CT lung AC only (27.4); PET/CT and SPECT/CT cardiac AC only (19.6); infection/inflammation AC only (18.1); PET/CT brain localisation/characterisation (16.8); SPECT/CT bone localisation/characterisation (10.0); PET/CT oncology AC only (9.0); and SPECT/CT parathyroid localisation/characterisation (7.8).

Conclusions

Suggested Nordic NDRL CT doses are presented according to clinical purpose of CT for PET/CT oncology, infection/inflammation, brain, PET/CT and SPECT/CT cardiac, and SPECT/CT lung, bone, and parathyroid. The large variation in doses suggests great scope for optimisation in all 8 examinations.

A Scalable Database of Organ Doses for Common Diagnostic Fluoroscopy Procedures of Children: Procedures of Historical Practice for Use in Radiation Epidemiology Studies

Assessment of health effects from low-dose radiation exposures in patients undergoing diagnostic imaging is an active area of research. High-quality dosimetry information pertaining to these medical exposures is generally not readily available to clinicians or epidemiologists studying radiation-related health risks. The purpose of this study was to provide methods for organ dose estimation in pediatric patients undergoing four common diagnostic fluoroscopy procedures: the upper gastrointestinal (UGI) series, the lower gastrointestinal (LGI) series, the voiding cystourethrogram (VCUG) and the modified barium swallow (MBS). Abstracted X-ray film data and physician interviews were combined to generate procedure outlines detailing X-ray beam projections, imaged anatomy, length of X-ray exposure, and presence and amount of contrast within imaged anatomy. Monte Carlo radiation transport simulations were completed for each of the four diagnostic fluoroscopy procedures across the 162-member (87 males and 75 females) University of Florida/National Cancer Institute pediatric phantom library, which covers variations in both subject height and weight. Absorbed doses to 28 organs, including the active marrow and bone endosteum, were assigned for all 162 phantoms by procedure. Additionally, we provide dose coefficients (DCs) in a series of supplementary tables. The DCs give organ doses normalized to procedure-specific dose metrics, including: air kerma-area product (µGy/mGy · cm2), air kerma at the reference point (µGy/µGy), number of spot films (SF) (µGy/number of SFs) and total fluoroscopy time (µGy/s). Organs accumulating the highest absorbed doses per procedure were as follows: kidneys between 0.9-25.4 mGy, 1.1-16.6 mGy and 1.1-9.7 mGy for the UGI, LGI and VCUG procedures, respectively, and salivary glands between 0.2-3.7 mGy for the MBS procedure. Average values of detriment-weighted dose, a phantom-specific surrogate for the effective dose based on ICRP Publication 103 tissue-weighting factors, were 0.98 mSv, 1.16 mSv, 0.83 mSv and 0.15 mSv for the UGI, LGI, VCUG and MBS procedures, respectively. Scalable database of organ dose coefficients by patient sex, height and weight, and by procedure exposure time, reference point air kerma, kerma-area product or number of spot films, allows clinicians and researchers to compute organ absorbed doses based on their institution-specific and patient-specific dose metrics. In addition to informing on patient dosimetry, this work has the potential to facilitate exposure assessments in epidemiological studies designed to investigate radiation-related risks.

Implementation of Institutional Size-Specific Diagnostic Reference Levels for CT Angiography

RATIONALE AND OBJECTIVES

To generate institutional size-specific diagnostic reference levels (DRLs) for computed tomography angiography (CTA) examinations and assess the potential for dose optimization compared to size-independent DRLs.

MATERIALS AND METHODS

CTA examinations of the aorta, the pulmonary arteries and of the pelvis/lower extremity performed between January 2016 and January 2017 were included in our retrospective study. Water equivalent diameter (Dw) was automatically calculated for each patient. The relationship between Dw and computed tomography dose index (CTDI_vol) was analyzed and the 75th percentile was chosen as the upper limit for institutional DRLs. Size-specific institutional DRLs were compared to national size-independent DRLs from Germany and the UK.

RESULTS

A total of 1344 examinations were included in our study (n = 733 aortic CTA, n = 406 pulmonary CTA, n = 205 pelvic/lower extremity CTA). Mean Dw was 26 ± 9 cm and mean CTDI_vol was 7.0 ± 4.6 mGy. For all CTA protocols, there was a linear progression of CTDI_vol with increasing Dw with an R² = 0.95 in aortic CTA, R² = 0.94 in pulmonary CTA and R² = 0.93 in pelvic/lower extremity CTA. Median CTDI_vol increased by 0.57 mGy per additional cm Dw in aortic CTA, by 1.1 mGy in pulmonary CTA and by 0.31 mGy in pelvic/lower extremity CTA. Institutional DRLs were lower than national DRLs for average size patients (aortic CTA: Dw 28.2 cm, CTDI_vol 7.6 mGy; pulmonary CTA, Dw 27.9 cm, CTDI_vol 11.8 mGy; pelvic/lower extremity CTA, Dw 20.0 cm, CTDI_vol 6.4 mGy). More dose outliers in small patients were detected with size-specific DRLs compared to national size-independent DRLs (56.4% vs 16.2%).

CONCLUSION

We implemented institutional size-specific DRLs for CTA examinations which enabled a more precise analysis compared to national sizeindependent DRLs.

Conversion factors to estimate effective doses from kerma area product in interventional cardiology. Impact of added filtration

There is a large variation in the factors used to estimate effective doses from kerma area product (KAP) for interventional cardiology. These factors are required to estimate population doses. This paper presents the results for this conversion factor for cardiac procedures using tissue weighting factors of ICRP-103 and the impact of the added copper filtration in the X-ray beam. The data from 925 cardiac procedures and 75,347 radiation events were collected from two angiography laboratories using the DICOM Radiation Dose Structured Reports (RDSR). Effective doses were calculated with Monte Carlo software and the dosimetric, technical and geometrical information included in the RDSR. In one laboratory, with an X-ray system without Cu filtration for the cine runs, a factor of 0.21 ± 0.05 mSv/(Gy·cm²) was obtained. In other laboratory, incorporating a patient dose reduction technique, and 0.4 mm of Cu filtration for cine runs, the conversion factor was 0.29 ± 0.05 mSv/(Gy·cm²). The analysis of the radiation events for the different Cu filtrations (0.0; 0.1; 0.4 and 0.9 mm) resulted in conversion factors of: 0.16; 0.27; 0.34 and 0.40 mSv/(Gy·cm²) respectively. The estimation of effective and population doses from KAP should take into account the Cu filtration in the X-ray beam. For the X-ray system with patient dose reduction technique, using 0.4 mm Cu for cine runs, the global conversion factor increased by 38%, from 0.21 to 0.29 mSv/(Gy·cm²) in comparison to the standard X-ray system with a protocol that did not include copper filtration for cine acquisitions.

IAEA survey of dental cone beam computed tomography practice and related patient exposure in nine Central and Eastern European countries

OBJECTIVES

Cone beam CT (CBCT) in dentistry and maxillofacial surgery is a widely used imaging method for the assessment of various maxillofacial and dental pathological conditions. The objective of this study was to summarize the results of a multinational retrospective-prospective study that focused on patient exposure in this modality.

METHODS

The study included 27 CBCT units and 325 adult and paediatric patients, in total. Data on patients, clinical indications, technical parameters of exposure, patient dose indicator, or, alternatively, dose to phantom were collected. The dose indicator used was air kerma-area product, P_KA.

RESULTS

In most scanners operators are offered with a variety of options regarding technical parameters, especially the field of view size. The median and the third quartile value of P_KA for adult patients in 14 different facilities were 820 mGy cm² and 1000 mGy cm² (interquartile range = 1058 mGy cm²), and 653 mGy cm² and 740 mGy cm² (interquartile range = 1179 mGy cm²) for children, as reported by four different institutions. Phantom dose data were reported from 15 institutions, and median P_KA ranged from 125 mGy cm² to 1951 mGy cm². Median P_KA values varied by more than a 10-fold between institutions, mainly due to differences in imaging protocol used, in particular field of view and tube current-exposure time product.

CONCLUSIONS

The results emphasize the need for a cautious approach to using dental CBCT. Imaging only when the clinical indications are clear, accompanied with the appropriate radiographic techniques and the optimum imaging protocol, will help reduce radiation dose to patients.

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.

The usefulness of large sample size patient dose audits for optimisation of CT automatic exposure control (AEC) settings

The aim of this study was to demonstrate the usefulness of large sample size patient dose audits for optimisation of CT automatic exposure control (AEC) settings, even when the investigation is limited to only three scanners at a single institution. Pre-optimisation patient dose audits of common CT examinations (n > 200 for each protocol) on three CT scanners (two Philips Brilliance and one Toshiba Aquilion) using radiology information system (RIS) data were conducted showing sub-optimal CT AEC performance on the Toshiba scanner. Based on these results, an optimisation exercise was carried out on the non-optimally performing scanner by phantom measurement and investigation of system configuration. Post-optimisation patient dose audits were subsequently carried out to assess the success of the optimisation exercise demonstrating standardisation of doses; median dose-length-product values were reduced by up to 43% on the sub-optimal scanner without any adverse effect on clinical image quality. This study has demonstrated that large sample patient dose audits using RIS data can be instrumental in identifying and rectifying sub-optimal CT AEC performance, even when the investigation is limited to only three scanners at a single institution.

Validation of algorithmic CT image quality metrics with preferences of radiologists

PURPOSE

Automated assessment of perceptual image quality on clinical Computed Tomography (CT) data by computer algorithms has the potential to greatly facilitate data-driven monitoring and optimization of CT image acquisition protocols. The application of these techniques in clinical operation requires the knowledge of how the output of the computer algorithms corresponds to clinical expectations. This study addressed the need to validate algorithmic image quality measurements on clinical CT images with preferences of radiologists and determine the clinically acceptable range of algorithmic measurements for abdominal CT examinations.

MATERIALS AND METHODS

Algorithmic measurements of image quality metrics (organ HU, noise magnitude, and clarity) were performed on a clinical CT image dataset with supplemental measures of noise power spectrum from phantom images using techniques developed previously. The algorithmic measurements were compared to clinical expectations of image quality in an observer study with seven radiologists. Sets of CT liver images were selected from the dataset where images in the same set varied in terms of one metric at a time. These sets of images were shown via a web interface to one observer at a time. First, the observer rank ordered the CT images in a set according to his/her preference for the varying metric. The observer then selected his/her preferred acceptable range of the metric within the ranked images. The agreement between algorithmic and observer rankings of image quality were investigated and the clinically acceptable image quality in terms of algorithmic measurements were determined.

RESULTS

The overall rank-order agreements between algorithmic and observer assessments were 0.90, 0.98, and 1.00 for noise magnitude, liver parenchyma HU, and clarity, respectively. The results indicate a strong agreement between the algorithmic and observer assessments of image quality. Clinically acceptable thresholds (median) of algorithmic metric values were (17.8, 32.6) HU for noise magnitude, (92.1, 131.9) for liver parenchyma HU, and (0.47, 0.52) for clarity.

CONCLUSIONS

The observer study results indicated that these algorithms can robustly assess the perceptual quality of clinical CT images in an automated fashion. Clinically acceptable ranges of algorithmic measurements were determined. The correspondence of these image quality assessment algorithms to clinical expectations paves the way toward establishing diagnostic reference levels in terms of clinically acceptable perceptual image quality and data-driven optimization of CT image acquisition protocols.

Diagnostic reference levels for paediatric CT in Jordan

This study aimed to investigate the current status of Diagnostic Reference Levels (DRLs) in paediatric CT across Jordan. The dose data for four main CT examinations (brain, chest, abdominopelvic, and chest, abdomen and pelvis (CAP)) in hospitals and imaging centres (n = 4) were measured. The volume CT dose index (CTDIvol) and Dose Length Product (DLP) values were compared within the different hospitals and age groups (<1 year, 1-4 years, 5-10 years and 11-18 years). DRLs in Jordan were compared to international DRLs. The paediatric population consisted of 1818 children; 61.4% of them were male. There were significant variations between the DRLs for each CT scanner with an up to four-fold difference in dose between hospitals. There were apparent significant differences between Jordan and other countries with the DLPs in Jordan being relatively high. However, for CTDIvol, the values in Jordan were close to those of other countries. This study confirmed variations in the CTDIvol and DLP values of paediatric CT scans in Jordan. These variations were attributed to the different protocols and equipment used. There is a need to optimise paediatric CT examinations doses in Jordan.

U.S. PET/CT and Gamma Camera Diagnostic Reference Levels and Achievable Administered Activities for Noncardiac Nuclear Medicine Studies

Existing surveys of radiopharmaceutical doses for U.S. nuclear medicine laboratories are of limited scope and size. Dose data are important because they can be used to benchmark individual laboratories, understand geographic variations in practice, and provide source data for societal guidelines and appropriateness criteria. Diagnostic reference levels (DRLs) and achievable administered activities (AAAs) for 13 noncardiac adult gamma camera and PET/CT examinations were derived retrospectively from American College of Radiology accreditation data (January 1, 2015, to December 31, 2017). The calculated DRL and AAA are consistent with previously published surveys. The distributions of radiopharmaceutical doses across facilities are in general consistent but show variation within a particular examination. Analysis of dose distribution suggests this variation results from differences in clinical protocols, educational gaps, and/or equipment factors. The AAA for the surveyed facilities exceeds dose ranges proposed in societal practice guidelines for several common nuclear medicine studies. Compared with similar surveys from Europe and Japan, geographic variation is observed, with some doses greater and others lower than used in the United States. Overall, radiopharmaceutical dose variation within the United States and internationally, and deviation from societal guidelines, imply that these dose-related benchmarks may be used to further standardize and improve clinical practice.

Analysis of a multicentre cloud-based CT dosimetric database: preliminary results

BACKGROUND

To manage and analyse dosimetric data provided by computed tomography (CT) scanners from four Italian hospitals.

METHODS

A radiation dose index monitoring (RDIM) software was used to collect anonymised exams stored in a cloud server. Since hospitals use different names for the same procedure, digital imaging and communications in medicine (DICOM) tags more appropriate to describe exams were selected and associated to study common names (SCNs) from a radiology playbook according to scan region and use of contrast media. Retrospective analysis was carried out to describe population and to evaluate dosimetric indexes and inaccuracies associated with SCNs.

RESULTS

More than 400 procedures were clustered into 95 SCNs, but 78% of exams on adults were described with only 10 SCNs. Median values of dose-length product (DLP) and volumetric CT dose index (CTDI_vol) for three analysed SCNs were in agreement with those previously published. The percentage of inaccuracies does not heavily affect the dosimetric analysis on the whole cloud, since variations in median values reached at most 8%.

CONCLUSIONS

Implementation of a cloud-based RDIM software and related issues were described, showing the strength of the chosen playbook-based clustering and its usefulness for homogeneous data analysis. This approach may allow for optimisation actions, accurate assessment of the risk associated with radiation exposure, comparison of different facilities, and, last but not least, collection of information for the implementation of the 2013/59 Euratom Directive.

Patient radiation dose in percutaneous biliary interventions: recommendations for DRLs on the basis of a multicentre study

OBJECTIVE

Percutaneous biliary interventions (PBIs) can be associated with a high patient radiation dose, which can be reduced when national diagnostic reference levels (DRLs) are kept in mind. The aim of this multicentre study was to investigate patient radiation exposure in different percutaneous biliary interventions, in order to recommend national DRLs.

METHODS

A questionnaire asking for the dose area product (DAP) and the fluoroscopy time (FT) in different PBIs with ultrasound- or fluoroscopy-guided bile duct punctures was sent to 200 advanced care hospitals. Recommended national DRLs are set at the 75th percentile of all DAPs.

RESULTS

Twenty-three facilities (9 interventional radiology depts. and 14 gastroenterology depts.) returned the questionnaire (12%). Five hundred sixty-five PBIs with 19 different interventions were included in the analysis. DAPs (range 4-21,510 cGy·cm2) and FTs (range 0.07-180.33 min) varied substantially depending on the centre and type of PBI. The DAPs of initial PBIs were significantly (p < 0.0001) higher (median 2162 cGy·cm2) than those of follow-up PBIs (median 464 cGy·cm2). There was no significant difference between initial PBIs with ultrasound-guided bile duct puncture (2162 cGy·cm2) and initial PBIs with fluoroscopy-guided bile duct puncture (2132 cGy·cm2) (p = 0.85). FT varied substantially (0.07-180.33 min).

CONCLUSIONS

DAPs and FTs in percutaneous biliary interventions showed substantial variations depending on the centre and the type of PBI. PBI with US-guided bile duct puncture did not reduce DAP, when compared to PBI with fluoroscopy-guided bile duct puncture. National DRLs of 4300 cGy·cm2 for initial PBIs and 1400 cGy·cm2 for follow-up PBIs are recommended.

KEY POINTS

• DAPs and FTs in percutaneous biliary interventions showed substantial variations depending on the centre and the type of PBI. • PBI with US-guided bile duct puncture did not reduce DAP when compared to PBI with fluoroscopy-guided bile duct puncture. • DRLs of 4300 cGy·cm2for initial PBIs (establishing a transhepatic tract) and 1400 cGy·cm2for follow-up PBIs (transhepatic tract already established) are recommended.

Estimation of the radiation dose in pregnancy: an automated patient-specific model using convolutional neural networks

OBJECTIVES

The conceptus dose during diagnostic imaging procedures for pregnant patients raises health concerns owing to the high radiosensitivity of the developing embryo/fetus. The aim of this work is to develop a methodology for automated construction of patient-specific computational phantoms based on actual patient CT images to enable accurate estimation of conceptus dose.

METHODS

We developed a 3D deep convolutional network algorithm for automated segmentation of CT images to build realistic computational phantoms. The neural network architecture consists of analysis and synthesis paths with four resolution levels each, trained on manually labeled CT scans of six identified anatomical structures. Thirty-two CT exams were augmented to 128 datasets and randomly split into 80%/20% for training/testing. The absorbed doses for six segmented organs/tissues from abdominal CT scans were estimated using Monte Carlo calculations. The resulting radiation doses were then compared between the computational models generated using automated segmentation and manual segmentation, serving as reference.

RESULTS

The Dice similarity coefficient for identified internal organs between manual segmentation and automated segmentation results varies from 0.92 to 0.98 while the mean Hausdorff distance for the uterus is 16.1 mm. The mean absorbed dose for the uterus is 2.9 mGy whereas the mean organ dose differences between manual and automated segmentation techniques are 0.07%, - 0.45%, - 1.55%, - 0.48%, - 0.12%, and 0.28% for the kidney, liver, lung, skeleton, uterus, and total body, respectively.

CONCLUSION

The proposed methodology allows automated construction of realistic computational models that can be exploited to estimate patient-specific organ radiation doses from radiological imaging procedures.

KEY POINTS

• The conceptus dose during diagnostic radiology and nuclear medicine imaging procedures for pregnant patients raises health concerns owing to the high radiosensitivity of the developing embryo/fetus. • The proposed methodology allows automated construction of realistic computational models that can be exploited to estimate patient-specific organ radiation doses from radiological imaging procedures. • The dosimetric results can be used for the risk-benefit analysis of radiation hazards to conceptus from diagnostic imaging procedures, thus guiding the decision-making process.

Expanding the Concept of Diagnostic Reference Levels to Noise and Dose Reference Levels in CT

OBJECTIVE. Diagnostic reference levels were developed as guidance for radiation dose in medical imaging and, by inference, diagnostic quality. The objective of this work was to expand the concept of diagnostic reference levels to explicitly include noise of CT examinations to simultaneously target both dose and quality through corresponding reference values. MATERIALS AND METHODS. The study consisted of 2851 adult CT examinations performed with scanners from two manufacturers and two clinical protocols: abdominopelvic CT with IV contrast administration and chest CT without IV contrast administration. An institutional informatics system was used to automatically extract protocol type, patient diameter, volume CT dose index, and noise magnitude from images. The data were divided into five reference patient size ranges. Noise reference level, noise reference range, dose reference level, and dose reference range were defined for each size range. RESULTS. The data exhibited strong dependence between dose and patient size, weak dependence between noise and patient size, and different trends for different manufacturers with differing strategies for tube current modulation. The results suggest size-based reference intervals and levels for noise and dose (e.g., noise reference level and noise reference range of 11.5-12.9 HU and 11.0-14.0 HU for chest CT and 10.1-12.1 HU and 9.4-13.7 HU for abdominopelvic CT examinations) that can be targeted to improve clinical performance consistency. CONCLUSION. New reference levels and ranges, which simultaneously consider image noise and radiation dose information across wide patient populations, were defined and determined for two clinical protocols. The methods of new quantitative constraints may provide unique and useful information about the goal of managing the variability of image quality and dose in clinical CT examinations.

Local clinical diagnostic reference levels for chest and abdomen CT examinations in adults as a function of body mass index and clinical indication: a prospective multicenter study

OBJECTIVES

To compare institutional dose levels based on clinical indication and BMI class to anatomy-based national DRLs (NDRLs) in chest and abdomen CT examinations and to assess local clinical diagnostic reference levels (LCDRLs).

METHODS

From February 2017 to June 2018, after protocol optimization according to clinical indication and body mass index (BMI) class (< 25; ≥ 25), 5310 abdomen and 1058 chest CT series were collected from 5 CT scanners in a Swiss multicenter group. Clinical indication-based institutional dose levels were compared to the Swiss anatomy-based NDRLs. Statistical significance was assessed (p < 0.05). LCDRLs were calculated as the third quartile of the median dose values for each CT scanner.

RESULTS

For chest examinations, dose metrics based on clinical indication were always below P75 NDRL for CTDI_vol (range 3.9-6.4 vs. 7.0 mGy) and DLP (164.0-211.2 vs. 250 mGycm) in all BMI classes except for DLP in BMI ≥ 25 (248.8-255.4 vs. 250.0 mGycm). For abdomen examinations, they were significantly lower or not different than P50 NDRLs for all BMI classes (3.8-9.0 vs. 10.0 mGy and 192.9-446.8 vs. 470mGycm). The estimated LCDRLs show a drop in CTDI_vol (21% for chest and 32% for abdomen, on average) with respect to current DRLs. When considering BMI stratification, the largest LCDRL difference within the same clinical indication is for renal tumor (4.6 mGy for BMI < 25 vs. 10.0 mGy for BMI ≥ 25; - 117%).

CONCLUSION

The results suggest the necessity of estimating clinical indication-based DRLs, especially for abdomen examinations. Stratifying per BMI class allows further optimization of the CT doses.

KEY POINTS

• Our data show that clinical indication-based DRLs might be more appropriate than anatomy-based DRLs and might help in reducing large variations in dose levels for the same type of examinations. • Stratifying the data per patient-size subgroups (non-overweight, overweight) allows a better optimization of CT doses and therefore the possibility to set LCDRLs based on BMI class. • Institutions who are fostering continuous dose optimization and LDRLs should consider defining protocols based on clinical indication and BMI group, to achieve ALARA.

CT diagnostic reference levels: are they appropriately computed?

OBJECTIVES

To estimate the variability of CT diagnostic reference levels (DRLs) according to the methods used for computing collected data.

METHODS

Dose-length products (DLP) were collected by our national nuclear control agency from the 250 devices installed in 140 medical centers in the country. In 2015, the number of head, thorax, abdomen, and lumbar spine examinations collected in these centers ranged from approximately 20,000 to 42,000. The impact on DRLs of the number of devices considered, as well as the differences in descriptive statistics (mean vs. median DLP) or methods of pooling DLP data (all devices vs. all patients), was investigated. Variability in DRLs was investigated using a bootstrapping method as a function of the numbers of devices and examinations per device.

RESULTS

As expected, DRLs derived from means were higher than those from medians, with substantial differences between device- and patient-related DRLs. Depending on the numbers of devices and DLP data per device, the variability ranged from 10 to 40% but was stabilized at a level of 10-20% if the number of devices was higher than 50 to 60, regardless of the number of DLP data per device.

CONCLUSION

Number of devices and of DLP data per device, descriptive statistics, and pooling data influence DRLs. As differences in methods of computing survey data can artificially influence DRLs, harmonization among national authorities should be recommended.

KEY POINTS

• Due to CT dose variability, that of DRLs is at least of 10%. • DRLs derived from medians are lower than from means and differ from those obtained by pooling all patient data. • Fifty to 60 devices should be sufficient for estimating national DRLs, regardless of the number of data collected per device.

CT beam dosimetric characterization procedure for personalized dosimetry

Personalized dosimetry in computed tomography (CT) can be realized by a full Monte Carlo (MC) simulation of the scan procedure. Essential input data needed for the simulation are appropriate CT x-ray source models and a model of the patient's body which is based on the CT image. The purpose of this work is to develop comprehensive procedures for the determination of CT x-ray source models and their verification by comparison of calculated and measured dose distributions in physical phantoms. Mobile equipment together with customized software was developed and used for non-invasive determination of equivalent source models of CT scanners under clinical conditions. Standard and physical anthropomorphic CT dose phantoms equipped with real-time CT dose probes at five representative positions were scanned. The accumulated dose was measured during the scan at the five positions. ImpactMC, an MC-based CT dose software program, was used to simulate the scan. The necessary inputs were obtained from the scan parameters, from the equivalent source models and from the material-segmented CT images of the phantoms. 3D dose distributions in the phantoms were simulated and the dose values calculated at the five positions inside the phantom were compared to measured dose values. Initial results were obtained by means of a General Electric Optima CT 660 and a Toshiba (Canon) Aquilion ONE. In general, the measured and calculated dose values were within relative uncertainties that had been estimated to be less than 10%. The procedures developed were found to be viable and rapid. The procedures are applicable to any scanner type under clinical conditions without making use of the service mode with stationary x-ray tube position. Results show that the procedures are well suited for determining and verifying the equivalent source models needed for personalized CT dosimetry based on post-scan MC calculations.

The skin dose of pelvic radiographs since 1896

OBJECTIVES

To derive conversions of antiquated exposure data into modern equivalents and to apply these in the assessment of the skin dose of pelvic radiographs since 1896.

METHODS

The literature 1896-2018 was searched for implicit and explicit dose information. The early implicit dose data contained now obsolete descriptions of radiation quality and quantity for long since disappeared X-ray systems of limited efficiency. Converting the old information into modern specifications was achieved using contemporary data and computer simulations. Final dose calculations were done with modern software. Explicit radiation doses of later date reported in old quantities and units were adapted according to current recommendations.

RESULTS

For the period before 1927 conversion algorithms for spark gap data and penetrometer hardnesses to high voltage could be derived. Electrical and X-ray efficiencies of several old röntgen systems were determined. Together they allowed reconstruction of 53 doses. After 1927 doses were generally explicitly specified; 114 were retrieved. Although an enormous spread was observed, the average skin dose was reduced by a factor of about 400.

CONCLUSIONS

Antiquated exposure data were successfully used for dose reconstruction. Extreme dose variability was a constant. Efforts to cut down doses were effective as skin doses went down from sub-erythema values to about one milligray.

[The First Step in the Optimization of Radiation Protection of Patients in Cerebral Angiography: Investigate the Possibility of Constructing the Diagnostic Reference Level by Imaging Objective/Disease Group Using Display Value of the Blood Vessel Imaging Apparatus]

To optimize the radiation protection of patients, we investigated the possibility of constructing the diagnostic reference levels (DRLs) by imaging objective/disease group using display value of the blood vessel imaging apparatus (air kerma-area product: P_KA, air kerma at the patient entrance reference point: K_{a, r}) in cerebral angiography. We used P_KA and K_{a, r} recorded during surgery of 997 patients at our hospital, and classified them according to the purpose of imaging (diagnostic cerebral angiography or neuro interventional radiology) and disease group. Neuro interventional radiology (P_KA: 268±155 Gy・cm², K_{a, r}: 2420±1462 mGy) was significantly higher than that of diagnostic cerebral angiography (P_KA: 161±70 Gy・cm², K_{a, r}: 1112±485 mGy), (Mann-Whitney test, P<0.01). Significant difference was found between P_KA and K_{a, r} for imaging purpose and disease group (Kruskal-Wallis test, P<0.05). It is highly probable that the DRL for cerebral angiography can be constructed by imaging purpose/disease group using display value (P_KA, K_{a, r}) of the blood vessel imaging apparatus.

X-ray examination dose surveys: how accurate are my results?

OBJECTIVES

To determine the variabilities of dose-area-products (DAP) of frequent X-ray examinations collected for comparison with diagnostic reference levels (DRLs).

METHODS

DAP values of chest, abdomen, and lumbar spine examinations obtained on devices from two manufacturers were collected in three centers over 1 to 2 years. The variability of the average DAP results defined as the 95% confidence interval in percentage of their median value was calculated for increasing sample sizes, each examination and center. We computed the sample sizes yielding variabilities lower or equal to 25% and 10%. The effect of narrowing patient selection based on body weight was also investigated (ranges of 67-73 Kg, or 60-80 Kg).

RESULTS

DAP variabilities ranged from 75 to 170% of the median value when collecting small samples (10 to 20 DAP). To reduce this variability, larger samples are needed, collected over up to 2 years, regardless of the examination and center. A variability ≤ 10% could only be reached for chest X-rays, requiring up to 800 data. For the abdomen and lumbar spine, the lowest achievable variability was 25%, regardless of the body weight selection, requiring up to 400 data.

CONCLUSION

Variabilities in DAP collected through small samples of ten data as recommended by authorities are very high, but can be reduced down to 25% (abdomen and lumbar spine) or even 10% (chest) through a substantial increase in sample sizes. Our findings could assist radiologists and regulatory authorities in estimating the reliability of the data obtained when performing X-ray dose surveys.

KEY POINTS

• Low but reasonable variabilities cannot be reached with samples sized as recommended by regulatory authorities. Higher numbers of DAP values are required to reduce the variability. • Variabilities of 10% for the chest and 25% for abdomen and lumbar spine examinations are achievable, provided large samples of data are collected over 1 year. • Our results could help radiologists and authorities interpret X-rays dose surveys.

An Australian local diagnostic reference level for paediatric whole-body 18F-FDG PET/CT

OBJECTIVE:

The aim of this study is to report a local diagnostic reference level (DRL) for paediatric whole-body (WB) fludeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) CT examinations.

METHODS:

The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) national DRL (NDRL) age category (0-4 years and 5-14 years), the International Commission on Radiological Protection age category (ICRP age) (<1, >1-5, >5-10, and >10-15 years), and European guideline weight category ( EG weight) (<5, 5-<15, 15-<30, 30-<50, and 50-<80 kg) were used to determine a local DRL for WB ¹⁸F FDG PET/CT studies. Two-structured questionnaires were designed to collect dose data, patient demographics, equipment details, and acquisition protocols for WB ¹⁸F-FDG PET/CT procedures. The local DRL was based on the median ¹⁸F-FDG administered activity (MBq), dose-length product (DLP), and the CT dose index volume (CTDI_vol), values. The effective dose (E) was also calculated and reported.

RESULTS:

The local DRLs for ¹⁸F-FDG administered activity, CTDI_vol and DLP values based on ARPANSA age and ICRP age were increased from lower to higher age categories. For the EG weight category, the local DRL for ¹⁸F-FDG administered activity, CTDI_vol and DLP values were increased from the low EG weight category to the high EG weight category. The mean administered activity in our study based on ICRP age category >1-5, >5-10, and >10-15 years is 79.97, 119.40, and 176.04 MBq, which is lower than the mean administered activity reported in the North American Consensus guideline published in 2010 (99, 166, and 286 MBq) and European Association of Nuclear Medicine and Dosage Card (version 1.5.2008) (120, 189, and 302 MBq). However, the mean administered activity in our study based on ICRP age category <1 year was 55 MBq compared to the EANM Dosage card (version 1.5.2008) (70 MBq) and the NACG 2010 (51 MBq). Our study shows that the finding for ICRP age category <1 year was similar to the NACG 2010 value.

CONCLUSION:

The determined local DRL values for the radiation doses associated with WB ¹⁸F FDG PET/CT examinations are differed considerably between the ARPANSA and ICRP age category and EG weight category. Although, the determined ¹⁸F-FDG value for ICRP < 1 year is in good agreement with available publish data, it is preferable to optimise the ¹⁸F-FDG administered activity while preserving the diagnostic image quality.

ADVANCES IN KNOWLEDGE:

The local DRL value determined from WB ¹⁸F-FDG PET/CT examinations may help to establish the ARPANSA NDRL for WB FDG ¹⁸F-PET/CT examinations.

Diagnostic reference levels for 18 F-FDG whole body PET/CT procedures: Results from a survey of 12 centres in Australia and New Zealand

INTRODUCTION

The aim of this work is to report diagnostic reference levels (DRLs) for hybrid positron emission tomography and x-ray computed tomography (PET/CT) exams in Australia (AU) for Queensland (QLD) and Western Australia (WA) (AU QLD/WA) and New Zealand (NZ).

METHODS

Two-structured booklets were designed to collect dose information, patient demographics, equipment details and acquisition protocols for fluoride-18 fluorodeoxyglucose (¹⁸ F-FDG) PET/CT procedures, and any additional diagnostic CT routinely performed as part of ¹⁸ F-FDG whole-body examination. The DRL was reported based on the 75^th percentile and achievable dose for ¹⁸ F-FDG, CT dose index volume (CTDI_vol ) and dose length product (DLP). The effective dose and total effective dose was reported for ¹⁸ F-FDG whole-body PET/CT examination. Also, the effective dose was reported separately for identified additional diagnostic CT.

RESULTS

The findings of this study show that the current DRL for ¹⁸ F-FDG in AU QLD/WA and NZ was 333.75 MBq and 332.87 MBq, respectively. The reported AU QLD/WA CTDI_vol and DLP associated with ¹⁸ F-FDG whole-body PET/CT examinations from vertex to thigh (VT) was 4.41 mGy and 474 mGy.cm. In NZ, the reported VT CTDI_vol and DLP was 13.07 mGy and 1319.05 mGy.cm. The effective dose for ¹⁸ F-FDG and CT component was 5.6 mSv and 4.7 mSv for AU QLD/WA. For NZ, the effective dose was 5.7 mSv and 10.9 mSv for ¹⁸ F-FDG and CT component. The total effective dose delivered from the ¹⁸ F-FDG whole-body scan from the AU QLD/WA PET/CT centres (10.44 mSv) were lower than the radiation doses delivered from the NZ (16.65 mSv).

CONCLUSIONS

The current DRLs were proposed for AU QLD/WA and NZ for ¹⁸ F-FDG whole-body PET/CT examinations. Variations existed in the current practice of AU QLD/WA and NZ PET/CT examinations. There is a need to optimize the radiation doses delivered from PET/CT examinations.

Diagnostic Reference Levels for Adult Nuclear Medicine Imaging Established from the National Survey in Korea

PURPOSE

There is substantial need for optimizing radiation protection in nuclear medicine imaging studies. However, the diagnostic reference levels (DRLs) have not yet been established for nuclear medicine imaging studies in Korea.

MATERIALS AND METHODS

The data of administered activity in 32 nuclear medicine imaging studies were collected from the Korean Society of Nuclear Medicine (KSNM) dose survey database from 2013 and 2014. Through the expert discussions and statistical analyses, the 75th quartile value (Q3) was suggested as the preliminary DRL values. Preliminary DRLs were subjected to approval process by the KSNM Board of Directors and KSNM Council, followed by clinical applications and performance rating by domestic institutes.

RESULTS

DRLs were determined through 32 nuclear medicine imaging studies. The Q3 value was considered as appropriate selection as it was generally consistent with the most commonly administered activity. In the present study, the final version of initial DRL values for nuclear medicine imaging in Korean adults is described including various protocols of the brain and myocardial perfusion imaging.

CONCLUSION

The first DRLs for nuclear medicine imaging in Korean adults were confirmed. The DRLs will enable optimized radiation protection in the field of nuclear medicine imaging in Korea.

The associated factors for radiation dose variation in cardiac CT angiography

OBJECTIVE:

This study aimed to examine the associated factors for dose variation and influence cardiac CT angiography (CCTA) dose benchmarks in current CT imaging centres.

METHODS:

A questionnaire was distributed to CT centres across Australia and Saudi Arabia. All participating centres collected data for adults who underwent a CCTA procedure. The questionnaire gathered information about the examination protocol, scanning parameters, patient parameters, and volume CT dose index (CTDI vol) and dose-length product (DLP). A stepwise regression analysis was performed to assess the contribution of tube voltage (kV), padding time technique, cross-sectional area (CSA) of chest and weight to DLP.

RESULTS:

A total of 17 CT centres provided data for 423 CCTA examinations. The median CTDI_vol, DLP and effective dose were 18 mGy, 256 mGy.cm and 5.2 mSv respectively. There was a statistically significant difference in DLP between retrospective and prospective ECG-gating modes (p = 0.001). Median DLP from CCTA using padding technique was 61% higher than CCTA without padding (p = 0.001). The stepwise regression showed that kV was the most significant predictor of DLP followed by padding technique then CSA while patient weight did not statistically significantly predict DLP. Correlation analysis showed a strong positive correlation between weight and CSA (r = 0.78), and there was a moderate positive correlation between weight and DLP (r = 0.42), as well as CSA and DLP (r = 0.48).

CONCLUSION:

Findings show radiation dose variations for CCTA. The associated factors for dose variation found in this study are scanning mode, kV, padding time technique and CSA of the chest. This results support the need to include CSA measurements in future dose survey and for setting DRLs.

ADVANCES IN KNOWLEDGE:

The study provides baseline information that helps to understand the associated factors for dose variations and high doses within and between centres performing CCTA.

International variation in radiation dose for computed tomography examinations: prospective cohort study

OBJECTIVE

To determine patient, institution, and machine characteristics that contribute to variation in radiation doses used for computed tomography (CT).

DESIGN

Prospective cohort study.

SETTING

Data were assembled and analyzed from the University of California San Francisco CT International Dose Registry.

PARTICIPANTS

Standardized data from over 2.0 million CT examinations of adults who underwent CT between November 2015 and August 2017 from 151 institutions, across seven countries (Switzerland, Netherlands, Germany, United Kingdom, United States, Israel, and Japan).

MAIN OUTCOME MEASURES

Mean effective doses and proportions of high dose examinations for abdomen, chest, combined chest and abdomen, and head CT were determined by patient characteristics (sex, age, and size), type of institution (trauma center, care provision 24 hours per day and seven days per week, academic, private), institutional practice volume, machine factors (manufacturer, model), country, and how scanners were used, before and after adjustment for patient characteristics, using hierarchical linear and logistic regression. High dose examinations were defined as CT scans with doses above the 75th percentile defined during a baseline period.

RESULTS

The mean effective dose and proportion of high dose examinations varied substantially across institutions. The doses varied modestly (10-30%) by type of institution and machine characteristics after adjusting for patient characteristics. By contrast, even after adjusting for patient characteristics, wide variations in radiation doses across countries persisted, with a fourfold range in mean effective dose for abdomen CT examinations (7.0-25.7 mSv) and a 17-fold range in proportion of high dose examinations (4-69%). Similar variation across countries was observed for chest (mean effective dose 1.7-6.4 mSv, proportion of high dose examinations 1-26%) and combined chest and abdomen CT (10.0-37.9 mSv, 2-78%). Doses for head CT varied less (1.4-1.9 mSv, 8-27%). In multivariable models, the dose variation across countries was primarily attributable to institutional decisions regarding technical parameters (that is, how the scanners were used).

CONCLUSIONS

CT protocols and radiation doses vary greatly across countries and are primarily attributable to local choices regarding technical parameters, rather than patient, institution, or machine characteristics. These findings suggest that the optimization of doses to a consistent standard should be possible.

STUDY REGISTRATION

Clinicaltrials.gov NCT03000751.

Radiation exposure during image-guided endoscopic procedures: The next quality indicator for endoscopic retrograde cholangiopancreatography

Endoscopic retrograde cholangiopancreatography (ERCP) is one of the most frequently used image-guided procedures in gastrointestinal endoscopy. Post-ERCP pancreatitis is an important concern, and prophylaxis, cannulation and other related technical procedures have been well documented by endoscopists. In addition, medical radiation exposure is of great concern in the general population because of its rapidly increasing frequency and its potential carcinogenic effects. International organizations and radiological societies have established diagnostic reference levels, which guide proper radiation use and serve as global standards for all procedures that use ionizing radiation. However, data on gastrointestinal fluoroscopic procedures are still lacking because the demand for these procedures has recently increased. In this review, we present the current status of quality indicators for ERCP and the methods for measuring radiation exposure in the clinical setting as the next quality indicator for ERCP. To reduce radiation exposure, knowledge of its adverse effects and the procedures for proper measurement and protection are essential. Additionally, further studies on the factors that affect radiation exposure, exposure management and diagnostic reference levels are necessary. Then, we can discuss how to manage medical radiation use in these complex fluoroscopic procedures. This knowledge will help us to protect not only patients but also endoscopists and medical staff in the fluoroscopy unit.

[Evaluation of Radiation Exposure on Mass Screening Examination for Gastric Cancer Using an Air Kerma-area Product Meter]

The present study grasped the radiation exposure per examination by incident air kerma (air kerma-area product; KAP and incident air kerma; K_{a, e}) using an air kerma-area product meter of our division with mobile population based gastric cancer screening. Initially, we measured the air kerma rate at the patient entrance reference point using an air kerma-area product meter and calibrated dosimeter, for three devices which an air kerma-area product meter was equipped, inspected the indication error of them. The error was 4.3% at the maximum, and accuracy was confirmed. The 816 patients who underwent gastric cancer screening in our division, the median values of KAP and K_{a, e} of the standard gastrography method 1 were 645.7 mGy·cm², 37.4 mGy, respectively. The radiation dose of males were significantly higher than females, and the radiation dose increased in proportion to the BMI. The median values of calculated KAP and K_{a, e} of the standard gastrography method 1 for standard body size were 633.8 mGy·cm², 37.0 mGy, respectively. We suggest that the patient exposure in gastrography can be optimized using an air kerma-area product meter.

Determining and updating PET/CT and SPECT/CT diagnostic reference levels: A systematic review

The aim of this systematic review is to investigate the national diagnostic reference level (NDRL) methods for positron emission tomography/computed tomography (PET/CT) and single photon emission tomography/computed tomography (SPECT/CT) procedures. A search strategy was based on the preferred, reporting items for systematic review and meta-analysis (PRISMA). Relevant articles retrieved from Medline, Scopus, Web of Science, Embase, Cinahl, and Google Scholar published up to October 2017. The search yielded 1057 articles. Fourteen articles were included in the review after a screening process. Relevant information from the selected articles were summarised and analysed. Discrepancies were found between the methodologies utilised to establish and report both PET/CT and SPECT/CT NDRLs, e.g. patient sampling and administered activity. Further research should focus on reporting more NDRLs for hybrid PET/CT and SPECT/CT examinations, and establish a robust NDRL standard for the CT portion associated with PET/CT and SPECT/CT examinations. This review provides updated NDRL reommndations to deliver more comparable international radation doses for administered activity and CT dose across PET/CT and SPECT/CT clinics.

DIAGNOSTIC REFERENCE LEVELS FOR CARDIAC CT ANGIOGRAPHY IN AUSTRALIA

This study aims to assess patient radiation dose from cardiac computed tomography angiography (CCTA) with the aim of proposing a national diagnostic reference levels (NDRLs) for CCTA procedures in Australia. A questionnaire was used to retrospectively gather baseline information related to CCTA scanning and patient parameters in CT centres across the country. The 75th percentile of both volumetric CT dose index (CTDIvol) and dose length-product (DLP) was used as DRL values for CCTA. A DRL for CT calcium scoring test was also determined. NDRLs were compared with international published data. Data sets of 338 patients from nine CT centres were used for analysis. The CCTA DRL for the CTDIvol and the DLP were 22 mGy and 268 mGy cm, respectively. The CT calcium scoring test DRL for DLP was 137 mGy cm. The DRL values for CCTA in Australia have been recommended for the first time. DRLs are lower than those in most published studies due to the implementation of dose-saving technologies such as prospective ECG-gated mode and iterative reconstruction algorithms. Considerable variations remain in patient doses between hospitals for the most frequently used CCTA protocols, indicating the potential for DRLs to prompt dose optimisation strategies in CT facilities.

Optimization of CT protocols using cause-and-effect analysis of outliers

The aim of this study was to implement an outlier marking and analysis methodology to optimize CT examination protocols. CT Head examination data, including dose metrics along with technical parameters, were stored in an automatic dose registry system. Reference dose metrics distribution was obtained throughout a 1-year period. Outlier thresholds were calculated taking into account the specific shape of the distribution, by using a robust measure of the skewness; the medcouple parameter. Subsequently, outliers from a 4-month period were marked and Cause-and-Effect analysis was carried out by a multidisciplinary dose committee. Reference Dose metrics distributions were obtained from 3690 CT Head examinations. Both CTDIvol and DLP showed a certain degree of skewness, with a medcouple value of 0.05 and 0.11, respectively. All of the upper-outliers fell within 3 identifiable groups of causes, ordered by relative importance: i) inadequate protocol selection, ii) arms or objects in the field-of-view, and iii) abnormal scanning region diameter. Regarding the lower-outliers, 90% were attributable to the inclusion of additional series in the original head protocol and the remaining 10% to unknown causes. Also, a general Cause-and-Effect diagram for outliers was elaborated. While the Dose Reference Level method applies to the general performance of a CT protocol and allows comparison with other centers, the outlier method represents a step further in the optimization process. The proposed method focuses on detecting incorrect utilization of the CT, which mainly arises from inadequate knowledge of CT technology.

[Survey of Recognition, Utilization, and Evaluation for Diagnostic Reference Levels in the Field of X-ray Computed Tomography]

A survey on recognition, utilization, and evaluation for diagnostic reference levels (DRLs) after establishing Japan DRLs 2015 in the field of X-ray computed tomography (CT) was conducted for members of Japanese Society of Radiological Technology using web-based questionnaire system. The survey consisted of provincial branches to which respondents belong, their occupation, years of professional experience, years of experience in X-ray CT section, recognition of DRLs, and utilization and evaluation of DRLs in the field of X-ray CT section. Each survey item had one to eight questions. A total of 369 members completed the questionnaire. Among them, 295 out of 369 (79.9%) members knew that DRLs were released in Japan. After establishing the DRLs, 226 of 330 (68.5%) and 123 of 319 (38.6%) members investigated the doses used for adult and pediatric CT at their facilities, respectively. Although 345 of 369 (93.5%) members answered that DRLs are necessary for the field of X-ray CT, only 142 of 369 (38.5%) members thought that the established DRLs are enough to use in the field of X-ray CT. The survey has clarified the current status of recognition, utilization, and evaluation for DRLs in the field of X-ray CT after establishing the DRLs in Japan.