ICRP Publication 135: Diagnostic Reference Levels in Medical Imaging

Factors affecting dose-length product of computed tomography component in whole-body positron emission tomography/computed tomography

In whole-body positron emission tomography (PET)/computed tomography (CT), it is important to optimise the CT radiation dose. We have investigated factors affecting the dose-length product (DLP) of the CT component of whole-body PET/CT and derived equations to predict the DLP. In this retrospective study, 1596 whole-body oncology PET/CT examinations with¹⁸F-fluorodeoxyglucose were analysed. Automatic exposure control was used to modulate radiation dose in CT. Considering age, weight, sex, arm position (up, down, one arm up), scan range (up to the mid-thigh or feet), scan mode (spiral or respiratory-triggered nonspiral) and the presence of a metal prosthesis as potential factors, multivariate analysis was performed to identify independent predictors of DLP and to determine equations to predict DLP. DLP values were predicted using the obtained equations, and compared with actual values. Among body size indices, weight best correlated with DLP in examinations performed under the standard imaging conditions (arms: up; scan range: up to the mid-thigh; scan mode: spiral; and no metal prosthesis). Multivariate analysis indicated that weight, arm position, scan range and scan mode were substantial independent predictors; lowering the arms, extending the scan range and using respiratory-triggered imaging, as well as increasing weight, increased DLP. The degree of the DLP increase tended to increase with increasing weight. The DLP values were predicted using equations that considered these parameters were in excellent agreement with the actual values. The DLP for the CT component of whole-body PET/CT is affected by weight, arm position, scan range and scan mode, and can be predicted with excellent accuracy using these factors.

Comparison of patient effective doses from multiple CT examinations based on different calculation methods

The aim of this study is to compare effective dose (E) estimations based on different methods for patients with recurrent computed tomography (CT) examinations. Seventeen methods were used to determine the E of each phase as well as the total E of the CT examination. These included three groups of estimations: based on the use of published E, calculated from typical or patient-specific values of volume computed tomography dose index (CTDI_vol) and dose-length product (DLP) multiplied by conversion coefficients, and based on patient-specific calculations with use of software. The E from a single phase of the examination varied with a ratio from 1.3 to 6.8 for small size patients, from 1.2 to 6.5 for normal size patients, and from 1.7 up to 18.1 for large size patients, depending on the calculation method used. The cumulative effective dose (CED) ratio per patient for the different size groups varied as follows: from 1.4 to 2.5 (small), from 1.7 to 4.3 (normal), and from 2.2 up to 6.3 (large). The minimum CED across patients varied from 38 up to 200 mSv, while the variation of maximum CED was from 122 up to 538 mSv. Although E is recommended for population estimations, it is sometimes needed and used for individual patients in clinical practice. Its value is highly dependent on the method applied. Individual estimations of E can vary up to 18.1 times and CED estimations can differ up to 6 times. The related large uncertainties should always be taken into account.

Benefits and limitations for the use of radiation dose management systems in medical imaging. Practical experience in a university hospital

OBJECTIVES

Radiation dose management systems (DMS) are currently used to help improve radiation protection in medical imaging and interventions. This study presents our experience using a homemade DMS called DOLQA (Dose On-Line for Quality Assurance).

METHODS

Our DMS is connected to 14 X-ray systems in a university hospital linked to the central data repository of a large network of 16 public hospitals in the Autonomous Community of Madrid, with 6.7 million inhabitants. The system allows us to manage individual patient dose data and groups of procedures with the same clinical indications, and compare them with diagnostic reference levels (DRLs). The system can also help to prioritise optimisation actions.

RESULTS

This study includes results of imaging examinations from 2020, with 37,601 procedures and 286,471 radiation events included in the radiation dose structured reports (RDSR), for computed tomography (CT), interventional procedures, positron emission tomography-CT (PET-CT) and mammography.

CONCLUSIONS

The benefits of the system include: automatic registration and management of patient doses, creation of dose reports for patients, information on recurrent examinations, high dose alerts, and help to define optimisation actions.The system requires the support of medical physicists and implication of radiologists and radiographers. DMSs must undergo periodic quality controls and audit reports must be drawn up and submitted to the hospital's quality committee.The drawbacks of DMSs include the need for continuous external support (medical physics experts, radiologists, radiographers, technical services of imaging equipment and hospital informatics services) and the need to include data on clinical indication for the imaging procedures.

ADVANCES IN KNOWLEDGE

DMS perform automatic management of radiation doses, produces patient dose reports, and registers high dose alerts to suggest optimisation actions. Benefits and limitations are derived from the practical experience in a large university hospital.

[Scientific Research Group Report: Nationwide Survey on Radiation Exposure of Pediatric CT Examination in Japan (2018)]

PURPOSE

To understand the latest pediatric computed tomography (CT) exposure required for the revision of national DRLs.

METHODS

A questionnaire was sent to 409 facilities where the members of the Japanese Society of Radiological Technology and the Japanese Society of Pediatric Radiology are enrolled. We investigated the imaging conditions, CTDI_vol, and DLP of the pediatric head, chest, and abdominal CT examinations.

RESULTS

In all, 43 facilities (11%) responded to our survey. multi detector-row CT (MDCT) systems were available in all surveyed facilities. More than 98% of the MDCT systems had more than 64 detector rows. The CTDI_vol of all CT protocols was lower than the NDRL due to the progress of updating to MDCTs with radiation exposure reduction functions such as an iterative reconstruction, but the DLP of head and abdominal CT protocols of some age group were higher than NDRL.

CONCLUSION

It is necessary to review the imaging protocol with the attending physician and radiologist and consider further optimization of medical exposure.

Radiation doses from low-dose CT scans in SPECT/CT and PET/CT examinations: A survey in Germany

AIM

Recently, dose reference levels (DRLs) have been defined in Germany for auxiliary low-dose CT scans in hybrid SPECT/CT and PET/CT examinations, based on data from 2016/17. Here, another survey from 2020 was evaluated and compared with the new DRLs as well as with similar surveys from foreign countries.

METHODS

The survey, which had already been conducted in the Nordic countries, queried for various examinations including the following values: patient weight and height, volume CT dose index (CTDI_vol), dose length product (DLP). For each examination, statistical parameters such as the third quartile (Q3) were determined from all submitted CTDI_vol and DLP values. Additionally, for examinations comprising datasets from at least 10 systems, the third quartile (Q3-Med) of the respective median values of each system was calculated. Q3 and Q3-Med were compared with the newly published DRLs from Germany and values from similar studies from other countries.

RESULTS

Data from 15 SPECT/CT and 13 PET/CT systems from 15 nuclear medicine departments were collected. For the following examinations datasets from more than 10 systems were submitted: SPECT lung VQ, SPECT bone, SPECT&PET cardiac, PET brain, PET oncology. Especially for examinations of the thorax and heart, the new DRLs are very strict compared to this study. The CTDI_vol values for examinations of the head were lower in this study than the DRLs prescribe now.

CONCLUSIONS

For certain examination types, there is a need for dose optimization at some clinics and devices in order to take into account the new DRLs in Germany in the future.

T-shirt size as a classification for body habitus in computed tomography (CT) and development of size-based dose reference levels for different indications

PURPOSE

To examine the impact of patient size on dose indices and develop size-based reference levels (50th and 75th percentiles) for 20 body CT exams for routine and organ-specific clinical indications.

METHODS

Based on effective diameter estimated from adult body CT, each acquisition was classified into T-shirt size as XXS, XS, S, M, L, XL, and XXL. Radiation dose indices for each size and each exam type were correlated.

RESULTS

About 0.93 million CT exams from 256 CT facilities in the United States were analysed. Taking T-shirt size M as a reference, the CTDI_vol for other sizes were: XXS (∼60%), XS (∼65%), S (∼75%), L (∼130%), XL (∼165%), XXL (∼210%), or grossly small patients received about 60% of the dose as compared to M sized patients and XXL required doubling the dose. Taking ratio of the dose indices of the largest to smallest size, it was evident that SSDE variation was much less (about 50%) than that in CTDI_vol, but there was still nearly 40 to 220% variation in SSDE across the range of t-shirt sizes. The 50th and 75th percentile values are presented for CTDI_vol, SSDE and DLP for each of the 20 CT exams and for each of the seven T-shirt sizes.

CONCLUSIONS

A novel approach expressing body habitus in terms of T-shirt size is not only simple and intuitive, but it also provides a tool to have a perception of differences in dose metrices among patients of different body build.

10-year experience of Paediatric varicocele embolization in a tertiary centre with long-term follow-up

INTRODUCTION

Paediatric varicocele embolization has many benefits over surgical ligation, but lacks published long-term data. We investigated technical and clinical outcomes in this under reported patient group.

OBJECTIVE

To evaluate technical success, complications and recurrence rates following varicocele embolization in paediatric patients.

MATERIALS AND METHODS

A single-centre retrospective review of procedural data and electronic notes of consecutive patients referred for varicocele embolization over a 10-year period was performed (February 2010-March 2020). The primary outcomes were technical success and clinical efficacy (lack of symptom recurrence). Secondary outcomes included complications, testicular vein size reduction and procedural parameters including radiation exposure. Chi-square analysis was used to identify predictors of clinical success. Follow-up involved outpatient clinical assessment and telephone interview.

RESULTS

40 patients (median age 15) were referred for left-sided symptomatic varicocele. Technical embolization success was achieved in 36/40 patients (90%), with 4 procedures abandoned (inaccessible vein). Embolization technique was platinum-based coils ± sclerosant. There were no immediate or long-term procedural complications. 32/36 patients completed short term follow-up at a median interval of 2.8 months. 30/32 (93.78%) experienced early clinical success. We found a significant reduction in peritesticular vein size following embolization (pre-3.70 vs post-2.56 mm, p = 0.00017) and a significant relationship between varicocele grade and early clinical success (χ2 = 4.2, p = 0.04), but not pre-treatment peritesticular vein size (χ2 = 0.02, p = 0.88). 33/36 patients completed long-term follow-up (median 4.2 years, range 0.36-9.9 years) producing a late clinical success rate of 93.9% (31/33). No post procedural complications including hydroceles were identified.

DISCUSSION

This study demonstrates technical success, matching rates described in adult patients which is reassuring and in support of embolization in the younger patient cohort. More importantly, the overall clinical success rate is comparable with previous embolization studies. Reassuringly, all symptom recurrences occurred early in follow-up, and there is a cogent argument for a single follow-up appointment at this juncture. Our long-term average follow-up duration, primarily gained via telephone interview, exceeds other studies. Although our study has the longest follow-up for varicocele embolization in children, it is limited by a few patients being lost to early and long-term follow-up. This is a recognised issue faced by studies attempting to follow-up benign conditions with a high clinical success rate.

CONCLUSION

Paediatric varicocele embolization is a successful alternative to surgical ligation, with no complications and good clinical outcomes over a long-term follow-up.

Radiation Dose Management in Pediatric Brain CT According to Age and Weight as Continuous Variables

The diagnostic reference levels (DRLs) for pediatric brain computed tomography (CT) are provided for groups divided according to age. We investigated the relationships of radiation dose indices (volume CT dose index and dose length product) with age and weight, as continuous variables, in pediatric brain CT. In a retrospective analysis, 980 pediatric brain CT examinations were analyzed. Curve fitting was performed for plots of the CT dose indices versus age and weight, and equations to estimate age- and weight-dependent standard dose indices were derived. Standard dose indices were estimated using the equations, and the errors were calculated. The results showed a biphasic increase in dose indices with increasing age and weight, characterized by a rapid initial and subsequent slow increase. Logarithmic, power, and bilinear functions were well fitted to the plots, allowing estimation of standard dose indices at an arbitrary age or weight. Error analysis suggested that weight was mildly better than age and that the best results were obtained with the bilinear function. Curve fitting of the relationship between CT dose indices and age or weight facilitates the determination of standard dose indices in pediatric brain CT at each facility and is expected to aid the establishment and application of the DRLs.

A systematic review of conversion factors between kerma-area product and effective/organ dose for cardiac interventional fluoroscopy procedures performed in adult and paediatric patients

The aim of this systematic review is to undertake a critical appraisal of the evidence in the published literature concerning the conversion factors between kerma-area product (P KA) and effective/organ dose (DCED_PKA, DCHT_PKA) for cardiac interventional fluoroscopy procedures performed in adults and paediatric patients and to propose reference conversion factors to help standardize dose calculations. A search strategy utilizing MeSH headings in three databases identified 59 (adult) and 37 (paediatric) papers deemed eligible for the review. Exclusion criteria were adopted to select data only from publications which established DCED_PKA in patients using the ICRP 103 tissue weighting factors. A time restriction from January 2007 was introduced in the search to capture the evolving trends of utilization of fluoroscopy-guided intervention technologies only in recent years. The suggested DCED_PKA and DCHT_PKA were synthesized by calculating the weighted averages of the values reported by the authors with weights corresponding to the study sample size. Eighteen studies for both adult (9) and paediatric (9) patients matching the search terms fulfilled the inclusion criteria. The suggested value for DCED_PKA in adult patients amounts to 0.24 mSv Gy−1cm−2. The suggested values for DCHT_PKA ranged from a minimum of 0.15 mSv Gy−1cm−2 for the female breast to a maximum of 0.97 mSv Gy−1cm−2 for the lungs. The suggested values for DCED_PKA in paediatric patients ranged from 3.45 mSv Gy−1cm−2 for the new-born to 0.49 mSv Gy−1cm−2 in the 15 years age class. The suggested values for DCHT_PKA ranged from a minimum of 0.33 mSv Gy−1cm−2 for bone marrow in the 15 years age class to a maximum of 11.49 mSv Gy−1cm−2 for the heart in the new-born. To conclude, values of DCED_PKA/DCHT_PKA were provided for calculating effective/organ doses in cardiac interventional procedures. They can be useful for standardizing dose calculations, hence for comparison of the radiation detriment from different imaging procedures and in the framework of epidemiologic studies.

Comparison of Radiation Exposure between Endoscopic Ultrasound-Guided Hepaticogastrostomy and Hepaticogastrostomy with Antegrade Stenting

Fluoroscopy forms an essential part of endoscopic ultrasound-guided hepaticogastrostomy (EUS-HGS) and hepaticogastrostomy with antegrade stenting (EUS-HGAS). To date, no study has assessed and compared radiation exposure between EUS-HGS and EUS-HGAS. This study aimed to compare the radiation exposure parameters between EUS-HGS and EUS-HGAS. This retrospective single-center cohort study included consecutive patients who underwent EUS-HGS or EUS-HGAS from October 2017 to March 2019. The air kerma (AK: mGy), kerma–area product (KAP: Gycm²), fluoroscopy time (FT: min), and procedure time (PT: min) were assessed and compared between the two procedures. Altogether, 45 and 24 patients underwent EUS-HGS and EUS-HGAS, respectively. The median AK, KAP, FT, and PT were higher in the EUS-HGAS group than in the EUS-HGS group. A comparison revealed no difference in the technical success rate, complications rate, adverse event occurrence rate, and re-intervention rate between both procedures. This is the first report in which radiation exposure was used as a comparative parameter between EUS-HGS and EUS-HGAS. This study revealed that radiation exposure is significantly higher in EUS-HGAS than in EUS-HGS. Increased awareness on radiation exposure is warranted among gastroenterologists so that they choose the procedure with lower radiation exposure in cases where both procedures are indicated.

Notifications and alerts in patient dose values for computed tomography and fluoroscopy-guided interventional procedures

The terms "notifications" and "alerts" for medical exposures are used by several national and international organisations. Recommendations for CT scanners have been published by the American Association of Physicists in Medicine. Some interventional radiology societies as well as national authorities have also published dose notifications for fluoroscopy-guided interventional procedures. Notifications and alerts may also be useful for optimisation and to avoid unintended and accidental exposures. The main interest in using these values for high-dose procedures (CT and interventional) is to optimise imaging procedures, reducing the probability of stochastic effects and avoiding tissue reactions. Alerts in X-ray systems may be considered before procedures (as in CT), during procedures (in some interventional radiology systems), and after procedures, when the patient radiation dose results are known and processed. This review summarises the different uses of notifications and alerts to help in optimisation for CT and for fluoroscopy-guided interventional procedures as well as in the analysis of unintended and accidental medical exposures. The paper also includes cautions in setting the alert values and discusses the benefits of using patient dose management systems for the alerts, their registry and follow-up, and the differences between notifications, alerts, and trigger levels for individual procedures and the terms used for the collective approach, such as diagnostic reference levels. KEY POINTS: • Notifications and alerts on patient dose values for computed tomography (CT) and fluoroscopy-guided interventional procedures (FGIP) allow to improve radiation safety and contribute to the avoidance of radiation injuries and unintended and accidental exposures. • Alerts may be established before the imaging procedures (as in CT) or during and after the procedures as for FGIP. • Dose management systems should include notifications and alerts and their registry for the hospital quality programmes.

National reference levels of CT procedures dedicated for treatment planning in radiation oncology

OBJECTIVE

To present results of the first national survey on reference levels of CT imaging performed for the treatment planning purposes in radiation oncology in Croatia.

METHODS

Data for CT protocols of five anatomical regions including head, head and neck, pelvis, breast, and thorax were collected at eight radiation oncology departments in Croatia. Data included volume CT dose index (CTDI_vol), dose-length product (DLP), scan length and set of acquisition and reconstruction parameters. Data on a total of 600 patients were collected. Median values of scan length, DLP and CTDI_vol were calculated for each acquisition protocol. Third quartiles of the median CTDI_vol and DLP values were proposed as the national radiotherapy planning reference levels (RPRL).

RESULTS

The largest CoV were assessed for RT Breast (63.8% for CTDI_vol), RT Thorax (79.7% for DLP) and RT H&N (21.2% for scan length). RT Head had the lowest CoV for CTDI_vol (1,9%) and DLP (17,2%), while RT Breast had the lowest coefficient of variation for scan length (12.8%). Proposed national RPRLs are: for RT Head CTDI_vol16cm = 62 mGy and DLP_16cm = 1738 mGy.cm; for RT H&N CTDI_vol16cm = 35 mGy and DLP_16cm = 1444 mGy.cm; for RT Breast CTDI_vol32cm = 16 mGy and DLP_32cm = 731 mGy.cm; for RT Thorax CTDI_vol32cm = 17 mGy and DLP_32cm = 865 mGy.cm; for RT Pelvis CTDI_vol32cm = 20 mGy and DLP_32cm = 1133 mGy.cm.

CONCLUSIONS

Results of this study show variations in CT imaging for treatment planning practice at the national level which call for optimization of procedures.

Cumulative Radiation Exposure in Covid-19 Patients Admitted to the Intensive Care Unit

Medical imaging plays a major role in coronavirus disease-2019 (COVID-19) patient diagnosis and management. However, the radiation dose received from medical procedures by these patients has been poorly investigated. We aimed to estimate the cumulative effective dose (CED) related to medical exposure in COVID-19 patients admitted to the intensive care unit (ICU) in comparison to the usual critically ill patients. We designed a descriptive cohort study including 90 successive ICU COVID-19 patients admitted between March and May 2020 and 90 successive non-COVID-19 patients admitted between March and May 2019. In this study, the CED resulting from all radiological examinations was calculated and clinical characteristics predictive of higher exposure risk identified. The number of radiological examinations was 12.0 (5.0–26.0) [median (interquartile range) in COVID-19 vs.4.0 (2.0–8.0) in non-COVID-19 patient (P < 0.001)]. The CED during a four-month period was 4.2 mSv (1.9–11.2) in the COVID-19 vs. 1.2 mSv (0.13–6.19) in the non-COVID-19 patients (P < 0.001). In the survivors, the CED in COVID-19 vs. non-COVID-19 patients was ≥100 mSv in 3% vs. 0%, 10–100 mSv in 23% vs. 15%, 1–10 mSv in 56% vs. 30% and <1 mSv in 18% vs. 55%. The CED (P < 0.001) and CED per ICU hospitalization day (P = 0.004) were significantly higher in COVID-19 than non-COVID-19 patients. The CED correlated significantly with the hospitalization duration (r = 0.45, P < 0.001) and the number of conventional radiological examinations (r = 0.8, P < 0.001). To conclude, more radiological examinations were performed in critically ill COVID-19 patients than non-COVID-19 patients resulting in higher CED. In COVID-19 patients, contribution of strategies to limit CED should be investigated in the future.

National diagnostic reference levels: What they are, why we need them and what's next

Diagnostic reference levels (DRLs) are an optimisation tool for medical imaging procedures using ionising radiation. They give an indication of the expected radiation dose received by an average-sized patient undergoing a given imaging procedure. Comparison of typical (median) exposure levels for common imaging procedures with DRLs helps imaging facilities identify procedures that may be amenable to further optimisation. Undertaking comparisons with published DRLs is a requirement for medical imaging facilities under the Code for Radiation Protection in Medical Exposure and for their access to Medicare rebates under the Diagnostic Imaging Accreditation Scheme (DIAS). The Australian Radiation Protection and Nuclear Safety Agency has created the National Diagnostic Reference Level Service to facilitate the collection of data for the establishment of national DRLs in Australia and to assist imaging facilities in comparing their typical doses with the national DRLs. National DRLs have been established in computed tomography, nuclear medicine, and for image-guided and interventional procedures. DRLs must be subject to ongoing review and revision by the national authority to ensure they reflect current practice. This ongoing cycle of assessment and review helps to ensure that the ratio of benefit to risk for patients is maximised.

Comparison of radiation exposure between endoscopic ultrasound-guided drainage and transpapillary drainage by endoscopic retrograde cholangiopancreatography for pancreatobiliary diseases

OBJECTIVES

The transpapillary drainage by endoscopic retrograde cholangiopancreatography (ERCP-D) cannot be performed without fluoroscopy, and there are many situations in which fluoroscopy is required even in endoscopic ultrasound-guided drainage (EUS-D). Previous studies have compared the efficacy, but not the radiation exposure of EUS-D and ERCP-D. While radiation exposure in ERCP-D has been previously evaluated, there is a paucity of information regarding radiation doses in EUS-D. This study aimed to assess radiation exposure in EUS-D compared with that in ERCP-D.

METHODS

This retrospective single-center cohort study included consecutive patients who underwent EUS-D and ERCP-D between October 2017 and March 2019. The air kerma (AK, mGy), kerma-area product (KAP, Gycm² ), fluoroscopy time (FT, min), and procedure time (PT, min) were assessed. The invasive probability weighting method was used to qualify the comparisons.

RESULTS

We enrolled 372 and 105 patients who underwent ERCP-D and EUS-D, respectively. The mean AK, KAP, and FT in the EUS-D group were higher by 53%, 28%, and 27%, respectively, than those in the ERCP-D group, whereas PT was shorter by approximately 11% (AK, 135.0 vs. 88.4; KAP, 28.1 vs. 21.9; FT, 20.4 vs. 16.0; PT, 38.7 vs. 43.5). The sub-analysis limited to biliary drainage cases showed the same trend (AK, 128.3 vs. 90.9; KAP, 27.0 vs. 22.2; FT, 16.4 vs. 16.1; PT, 32.5 vs. 44.4).

CONCLUSIONS

This is the first study to assess radiation exposure in EUS-D compared with that in ERCP-D. Radiation exposure was significantly higher in EUS-D than in ERCP-D, despite the shorter procedure time.

Establishment of national diagnostic reference levels for percutaneous coronary interventions (PCIs) in Thailand

PURPOSE

To establish national diagnostic reference levels (DRLs) for percutaneous coronary intervention (PCI) in Thailand for lesions of different complexity.

METHODS

Radiation dose quantity as kerma-area-product (KAP) and cumulative air-kerma at reference point (CAK) from 76 catheterization labs in 38 hospitals in PCI registry of Thailand was transferred online to central data management. Sixteen months data (May 2018 to August 2019) was analyzed. We also investigated role of different factors that influence radiation dose the most.

RESULTS

Analysis of 22,737 PCIs resulted in national DRLs for PCI of 91.3 Gy.cm² (KAP) and 1360 mGy (CAK). The NDRLs for KAP for type C, B2, B1 and A lesions were 106.8, 82.6, 67.9, and 45.3 Gy.cm² respectively and for CAK, 1705, 1247, 962, and 790 mGy respectively. Thus, as compared to lesion A, lesion C had more than double the dose and B2 had nearly 1.6 times and B1 had 1.2 times CAK. Our DRL values are lower than other Asian countries like Japan and Korea and are in the middle range of Western countries. University hospital had significantly higher dose than private or public hospital possibly because of higher load of complex procedures in university hospitals and trainees performing the procedures. Transradial approach showed lower doses than transfemoral approach.

CONCLUSIONS

This large multi-centric study established DRLs for PCIs which can act as reference for future studies. A hallmark of our study is establishment of reference levels for coronary lesions classified as per ACC/AHA and thus for different complexities.

LOCAL DIAGNOSTIC REFERENCE LEVELS FOR PEDIATRIC RETROGRADE WEDGE PORTOGRAPHY INTERVENTIONAL PROCEDURES USING A DOSE MONITORING SOFTWARE AT A TRANSPLANTATION INSTITUTE

The aim of this work was to establish local diagnostic reference levels (DRLs) for retrograde wedge portography (RWP) performed on pediatric patients assessing the usefulness of radiation dose monitoring software in the establishing process. Between September 2016 and April 2020, 66 consecutive RWP were performed at a transplantation institute and were included in our study. Patients were divided in three groups according to age: n = 25 infants, n = 20 middle childhood and n = 21 early adolescence. The third quartile of both Air Kerma at the reference point (Ka,r) and air kerma-area product (PKA) were evaluated to establish local DRLs (lDRLs). In addition, to control high Ka,r levels during procedures, the software notified to operators if Ka,r exceeded the dose 'alert' threshold set at 2 Gy. lDRLs were established for all three groups using PKA and Ka,r: infant group: 5.6 Gy.cm 2 and 0.034 Gy; middle childhood: 6.4 Gy.cm2 and 0.018 Gy and early adolescence: 12.8 Gy.cm2 and 0.059 Gy. The dose threshold 'alert' was never encountered (alert quota: 0%). The dose monitoring system supports the feasibility of accurate and easier lDRLs' establishment.

Radiation Dose and Fluoroscopy Time of Endovascular Coil Embolization in Patients with Carotid Cavernous Fistulas

Carotid cavernous fistulas (CCFs) are abnormal connections between the cavernous sinus and the internal and/or external carotid artery. Endovascular therapy is the gold standard treatment. In the current retrospective single-center study we report detailed dosimetrics of all patients with CCFs treated by endovascular coil embolization between January 2012 and August 2021. Procedural and dosimetric data were compared between direct and indirect fistulas according to Barrow et al., and different DSA protocol groups. The local diagnostic reference level (DRL) was defined as the 3rd quartile of the dose distribution. In total, thirty patients met the study criteria. The local DRL was 376.2 Gy cm². The procedural dose area product (DAP) (p = 0.03) and the number of implanted coils (p = 0.02) were significantly lower in direct fistulas. The median values for fluoroscopy time (FT) (p = 0.08) and number of DSA acquisitions (p = 0.84) were not significantly different between groups. There was a significantly positive correlation between DAP and FT (p = 0.003). The application of a dedicated low-dose protocol yielded a 32.6% DAP reduction. In conclusion, this study provides novel DRLs for endovascular CCF treatment using detachable coils. The data presented in this work might be used to establish new specific DRLs.

NATIONWIDE SURVEY OF RADIATION EXPOSURE FOR RADIOFREQUENCY CATHETER ABLATION FOR PULMONARY VEIN ISOLATION AND NONPULMONARY VEIN ISOLATION IN JAPAN

To propose typical values for the arrhythmia region between pulmonary vein isolation (PVI) and nonpulmonary vein isolation (non-PVI) in Japan. A nationwide questionnaire was posted to 343 facilities, to which 125 facilities (36.4%) responded. Results is the median for PVI and non-PVI were in terms of Ka,r (317 and 196 mGy), PKA (40.8 and 26.3 Gy.cm2), FT (43.0 and 27.3 min), and CI (326 and 102 images). When comparing PVI and non-PVI procedures, there were significant differences in Ka, r, PKA, FT, and CI (p < 0.05). In other words, by classifying into two types, PVI and non-PVI, we contributed to the establishment of typical values in Japan's RFCA.

Establishment of national diagnostic reference levels for computed tomography procedures in Sri Lanka: first nationwide dose survey

The main purpose of this study was to establish for the first time national diagnostic reference levels (NDRLs) for common computed tomography (CT) procedures in Sri Lanka. Patient morphometric data, exposure parameters and dose data such as volume CT dose index (CTDIvol) and dose-length product (DLP) were collected from 5666 patients who underwent 22 types of procedure. The extreme dose values were filtered before analysis to ensure that the data come from standard size patients. The median of the dose distribution was calculated for each institution, and the third quartile value of the median distribution was considered as the NDRL. Based on the inclusion and exclusion criteria, data from 4592 patients and 17 procedure types were considered for establishment of a NDRL, covering 41% of the country's CT machines. The proposed NDRLs based on CTDIvoland DLP were: non-contrast-enhanced (NC) head, 82.2 mGy/1556 mGy cm; contrast-enhanced (CE) head, 82.2 mGy/1546 mGy cm; chest NC, 7.4 mGy/350 mGy cm; chest CE, 8.3 mGy/464 mGy cm; abdomen NC, 10.5 mGy/721 mGy cm; abdomen arterial (A) phase, 13.4 mGy/398 mGy cm; abdomen venous (V) phase, 10.8 mGy/460 mGy cm; abdomen delay (D) phase, 12.6 mGy/487 mGy cm; sinus NC, 30.2 mGy/452 mGy cm; lumbar spine NC, 24.1 mGy/1123 mGy cm; neck NC, 27.5 mGy/670 mGy cm; high-resolution CT of chest, 10.3 mGy/341 mGy cm; kidneys ureters and bladder NC, 19.4 mGy/929 mGy cm; chest to pelvis (CAP) NC, 10.8 mGy/801 mGy cm; CAP A, 10.4 mGy/384 mGy cm; CAP V, 10.5 mGy/534 mGy cm; CAP D, 16.8 mGy/652 mGy cm. Although the proposed NDRLs are comparable with those of other countries, the observed broad dose distributions between the CT machines within Sri Lanka indicate that dose optimisation strategies for the country should be implemented for most of the CT facilities.

Statement of the Italian Association of Medical Physics (AIFM) task group on radiation dose monitoring systems

The evaluation of radiation burden in vivo is crucial in modern radiology as stated also in the European Directive 2013/59/Euratom—Basic Safety Standard. Although radiation dose monitoring can impact the justification and optimization of radiological procedure, as well as effective patient communication, standardization of radiation monitoring software is far to be achieved. Toward this goal, the Italian Association of Medical Physics (AIFM) published a report describing the state of the art and standard guidelines in radiation dose monitoring system quality assurance. This article reports the AIFM statement about radiation dose monitoring systems (RDMSs) summarizing the different critical points of the systems related to Medical Physicist Expert (MPE) activities before, during, and after their clinical implementation. In particular, the article describes the general aspects of radiation dose data management, radiation dose monitoring systems, data integrity, and data responsibilities. Furthermore, the acceptance tests that need to be implemented and the most relevant dosimetric data for each radiological modalities are reported under the MPE responsibility.

Radiation exposure in 101 non-coronary fluoroscopically guided interventional procedures: reference levels of air kerma at the reference point and air kerma area product

OBJECTIVES

To present the median value and 75th percentile of air kerma at the reference point (K_a,r), air kerma-area product (KAP), and fluoroscopic time for a large number of fluoroscopically guided interventional (FGI) procedures.

METHODS

This retrospective study included the consecutive non-coronary FGI procedures from a Radiology department between May 2016 and October 2018 at a large tertiary-care hospital in the U.S. An in-house developed, semi-automated software, integrated with a dictation system, was used to record patient examination information, including K_a,r, KAP and fluoroscopic time. The included patient procedures were categorized into procedure types. A software package R (v. 3.5.1, R Foundation) was used to calculate procedure-specific quartiles of radiation exposure.

RESULTS

Based on analysis of 24,911 FGI cases, median value and 75th percentile are presented for each of K_a,r, KAP and fluoroscopic time for 101 procedures that can act as benchmark for comparison for dose optimization studies.

CONCLUSION

This study provides reference levels ( 50th and 75th percentiles) for a comprehensive list of FGI procedures, reflecting an overall picture of the latest FGI studies for diagnosis, targeted minimally invasive intervention, and therapeutic treatment.

ADVANCES IN KNOWLEDGE

This study provides reference levels (50th and 75th percentiles) for the largest number of fluoroscopically guided interventional procedures reported to date (101 procedures), in terms of air kerma at the reference point, air kerma-area product, and fluoroscopic time, among which these quartiles for ≥50 procedures are presented for the first time.

Radiation exposure in the intra-arterial nimodipine therapy of subarachnoid hemorrhage related cerebral vasospasm

The selective intra-arterial nimodipine application for the treatment of cerebral vasospasm (CVS) in patients after spontaneous subarachnoid hemorrhage (sSAH) is widely employed. The purpose of this study is to examine the radiation exposure and to determine local diagnostic reference levels (DRLs) of intra-arterial nimodipine therapy. In a retrospective study design, DRLs and achievable dose (AD) were assessed for all patients undergoing (I) selective intra-arterial nimodipine application or (II) additional mechanical angioplasty for CVS treatment. Interventional procedures were differentiated according to the type of procedure and the number of probed vessels. Altogether 494 neurointerventional procedures of 121 patients with CVS due to sSAH could be included. The radiation exposure indices were distributed as follows: (I) DRL 74.3 Gy·cm², AD 59.8 Gy·cm²; (II) DRL 128.3 Gy·cm², AD 94.5 Gy·cm². Kruskal-Wallis test confirmed significant dose difference considering the number of probed vessels (p< 0.001). The mean cumulative dose per patient was 254.9 Gy·cm²(interquartile range 88.6-315.6 Gy·cm²). The DRLs of intra-arterial nimodipine therapy are substantially lower compared with DRLs proposed for other therapeutic interventions, such as thrombectomy or aneurysm coiling. However, repeated therapy sessions are often required, bearing the potential risk of a cumulatively higher radiation exposure.

Diagnostic reference levels in digital mammography: a systematic review

Diagnostic reference levels (DRLs) in digital mammography (DM) serve as a useful benchmark for dose monitoring and optimisation, allowing comparison amongst countries, institutions and mammography units. A systematic review of DRLs in DM, published in 2014, reported a lack of consistent and internationally accepted protocol in DRLs establishment, thereby resulting in wide variations in methodologies which complicates comparability between studies. In 2017, the International Commission of Radiation Protection (ICRP) published additional guidelines and recommendations to provide clarity in the protocol used in DRLs establishment. With the continuing evolvement of technology, optimisation of examinations and updates in guidelines and recommendations, DRLs should be revised at regular intervals. This systematic review aims to provide an update and identify a more consistent protocol in the methodologies used to establish DRLs. Searches were conducted through Web of Science, PubMed-MEDLINE, ScienceDirect, CINAHL and Google Scholar, which resulted in 766 articles, of which 19 articles were included after screening. Relevant data from the included studies were summarised and analysed. While the additional guidelines and recommendations have provided clarifications in the methodologies used in DRLs establishment, such as data source (i.e. the preference to use data derived from patient instead of phantoms to establish DRLs), protocol (i.e. stratification of DRLs by compressed breast thickness and detector technology, and the use of median value for DRLs quantity instead of mean) and percentiles used to establish DRLs (i.e. set at the 75th percentile with a minimum sample size of 50 patients), other differences such as the lack of a standard dose calculation method used to estimate mean glandular dose continues to complicate comparisons between studies and different DM systems. This systematic review update incorporated the updated guidelines and recommendations from ICRP which will serve as a useful resource for future research efforts related to DRLs, dose monitoring and optimisation.

First local diagnostic reference levels for fluoroscopically guided cardiac procedures in adult patients in Chile

The goal of this study was to generate the first values of local diagnostic reference levels for a range of fluoroscopically guided cardiac diagnostic and therapeutic procedures in adult patients in Chile and to compare radiation dose levels with others presented in the literature. The dosimetric data collection period was conducted over the whole of 2020. The local diagnostic reference levels were calculated as the 75th percentile of patient dose data distributions for kerma area-product values. The sample of collected clinical procedures (480) was divided into diagnostic and therapeutic procedures. The kerma area-product differences found between diagnostic and therapeutic procedures were statistically significant. The local diagnostic reference levels were 81.6 Gy cm2 and 166.9 Gycm2 for fluoroscopically guided cardiac diagnostic and therapeutic procedures, respectively. A comparison of our results with results found in the literature for the last 10 years, showed that there are no published papers for hospitals in Latin America and the Caribbean. It becomes urgent to be able to carry out more research of this type, given that the health reality between countries on different continents is very different. While in some the establishment of diagnostic reference levels is a legal obligation, in others it is a matter of good or bad will.

Estimation of radiation dose and establishment of local diagnostic reference levels for computed tomography of head in pediatric population

BACKGROUND

Pediatric population is more sensitive to the effects of radiation than adults. Establishing diagnostic reference level (DRL) is an efficient dose optimization technique implemented by many countries for reducing radiation dose during Computed Tomography (CT) examinations.

OBJECTIVES

To estimate radiation dose and establish a new local diagnostic reference level for CT head examination in the pediatric population.

MATERIALS AND METHODS

We prospectively recruited 143 pediatric patients referred for CT head examination with age ranging from 0-5 years old. All patients had undergone CT head examination using the standard pediatric head protocol. Volumetric CT dose index (CTDIvol) and dose length product (DLP) were recorded. The effective dose was first calculated. Then, 75th percentile of dose indices was calculated to establish DRLs.

RESULTS

DRLs in terms of CTDIvol and DLP are 23.84 mGy, 555.99 mGy.cm for patients <1 years old and 28.65 mGy, 794.99 mGy.cm for patients from 1-5 years old, respectively. Mean effective doses for <1 years old patients and 1-5 years old patients are 2.91 mSv and 2.78 mSv respectively.

CONCLUSION

The study concludes that DRL in terms of CTDIvol is lower but DRL in terms of DLP and the effective dose is higher compared to a few other studies which necessitate the need for dose optimization.

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.

Harmonisation of imaging protocols, radiation doses and image quality in gastrointestinal fluoroscopy examinations - multicentre study

BACKGROUND

Paediatric gastrointestinal fluoroscopy examinations can impart varying amounts of radiation for the same patient size and exam type.

OBJECTIVE

To investigate the variability of imaging protocol, radiation dose and image quality in paediatric fluoroscopy examinations in order to provide recommendations for the harmonisation and optimisation of local practices.

MATERIALS AND METHODS

Five paediatric radiology departments performing fluoroscopically-guided contrast enema, micturating cystourethrography and upper gastrointestinal tract examinations participated in this study. Information on imaging protocols and radiation doses was retrospectively collected for more than 2,400 examinations. Image quality was analysed on clinical and phantom images.

RESULTS

Patient doses showed great variability among centers with up to a factor of 5 for similar fluoroscopy times. The five departments had imaging protocols with major differences in fluoroscopy dose regulation curves and additional filtration. Image quality analysis on phantoms and patients images showed no major improvement in contrast, spatial resolution or noise when increasing the radiation dose. Age-based diagnostic reference levels using both dose area product and fluoroscopy time were proposed per procedure type.

CONCLUSION

Disparities between centers and no correlation of radiation dose with image quality criteria create margins for optimisation. These results highlight the need for guidelines on fluoroscopy image quality and dose reference levels in paediatric gastrointestinal examinations to harmonise practices and optimise patient dose.

RADIATION DOSE FOR PATIENTS WITH KAWASAKI DISEASE UNDERGOING FLUOROSCOPICALLY GUIDED CARDIAC CATHETERIZATION

The goal of the present study was to estimate the radiation dose for a group of 45 Kawasaki disease (KD) patients undergoing fluoroscopically guided cardiac catheterization. The sample of procedures corresponds to a single hospital and was collected in 10 years. Anthropometric characteristics and the quantities of air kerma-area product (PKA) among others were recorded for each procedure. Monte Carlo PCXMC 2.0 software was used to estimate organ and effective doses. The PKA value of 7.2 Gy cm2 was proposed as the local Diagnostic Reference Level for KD. For organ absorbed doses, median values for thyroid, heart, lungs, esophagus, skin, active bone and breast were 1.2; 2.2; 4.6; 2.7; 1.1; 1.2 and 2.7 mGy, respectively. For effective dose, the mean value was 2.7 ± 2.5 mSv. This paper presents the first patient dose values for the KD using catheterization techniques, in Latin America and the Caribbean Region.

STATISTICAL MODELING OF GLANDULARITY FROM MAMMOGRAPHY IMAGES

This study presents a methodology for estimation of breast glandularity, which is an important factor to assess radiological risk in mammography patients. The investigation took place in an institution located at department of Antioquia-Colombia, where 200 patients participated. The models were obtained using partial least squares regression, where Dance's model was used as reference; parameters of mammography images, equipment and patient were used as predicting variables (kV, mAs, patient's weight, breast area and mean gray value of breast images). Coefficients of correlation equal to 89 and 88 were obtained for training and validation respectively in mediolateral oblique (MLO) and 84 and 89 for craniocaudal (CC). These models were used to estimate the mean glandular dose for all patients and later to obtain the institutional reference levels, 0.87 and 0.96 mGy for CC and MLO, respectively, following the recommendations of the ICRP publication No. 135. This study suggests that glandularity could be estimated with few parameters from equipment and patient.

Patient exposure dose in interventional cardiology per clinical and technical complexity levels. Part 1: results of the VERIDIC project

BACKGROUND

Patients can be exposed to high skin doses during complex interventional cardiology (IC) procedures.

PURPOSE

To identify which clinical and technical parameters affect patient exposure and peak skin dose (PSD) and to establish dose reference levels (DRL) per clinical complexity level in IC procedures.

MATERIAL AND METHODS

Validation and Estimation of Radiation skin Dose in Interventional Cardiology (VERIDIC) project analyzed prospectively collected patient data from eight European countries and 12 hospitals where percutaneous coronary intervention (PCI), chronic total occlusion PCI (CTO), and transcatheter aortic valve implantation (TAVI) procedures were performed. A total of 62 clinical complexity parameters and 31 technical parameters were collected, univariate regressions were performed to identify those parameters affecting patient exposure and define DRL accordingly.

RESULTS

Patient exposure as well as clinical and technical parameters were collected for a total of 534 PCI, 219 CTO, and 209 TAVI. For PCI procedures, body mass index (BMI), number of stents ≥2, and total stent length >28 mm were the most prominent clinical parameters, which increased the PSD value. For CTO, these were total stent length >57 mm, BMI, and previous anterograde or retrograde technique that failed in the same session. For TAVI, these were male sex, BMI, and number of diseased vessels. DRL values for Kerma-area product (P_KA), air kerma at patient entrance reference point (K_a,r), fluoroscopy time (FT), and PSD were stratified, respectively, for 14 clinical parameters in PCI, 10 in CTO, and four in TAVI.

CONCLUSION

Prior knowledge of the key factors influencing the PSD will help optimize patient radiation protection in IC.

Radiation Exposure During Diagnostic and Therapeutic Angiography of Carotid-cavernous Fistula : A Retrospective Single Center Observational Study

Purpose

The aim of this study was to determine local diagnostic reference levels (DRLs) during endovascular diagnostics and therapy of carotid-cavernous fistulas (CCF).

Methods

In a retrospective study design, DRLs, achievable dose (AD) and mean values were assessed for all patients with CCF undergoing diagnostic angiography (I) or embolization (II). All procedures were performed with the flat-panel angiography system Allura Xper (Philips Healthcare). Interventional procedures were differentiated according to the type of CCF and the type of procedure.

Results

In total, 86 neurointerventional procedures of 48 patients with CCF were executed between February 2010 and July 2021. The following DRLs, AD and mean values could be determined: (I) DRL 215 Gy ∙ cm², AD 169 Gy ∙ cm², mean 165 Gy ∙ cm²; (II) DRL 350 Gy ∙ cm², AD 226 Gy ∙ cm², mean 266 Gy ∙ cm². Dose levels of embolization were significantly higher compared to diagnostic angiography (p < 0.001). No significant dose difference was observed with respect to the type of fistula or the embolization method.

Conclusion

This article reports on diagnostic and therapeutic DRLs in the management of CCF that could serve as a benchmark for the national radiation protection authorities. Differentiation by fistula type or embolization method does not seem to be useful.

PATIENT DOSES IN WHOLE-BODY PET/CT EXAMINATIONS IN THE LARGEST TERTIARY HOSPITAL IN GREECE

The purpose of this study was to determine the patient radiation dose in combined whole-body positron emission tomography/computed tomography (PET/CT) examinations performed in the largest tertiary hospital in Greece. Computed tomography dose index (CTDIvol), dose length product (DLP), weight, height and administered activity of 2-[18F] fluoro-2-deoxy-D-glucose values for PET/CT examinations were recorded in a sample of 1014 randomly selected patients. The mean (±standard deviation) and median (interquartile) CTDIvol values were equal to 5.5 ± 2.4 and 4.8 (2.5) mGy, respectively. The respective DLP values were 483.3 ± 212.4 and 426 (234.6) mGy·cm. For the administered activity, mean and median were equal to 363.9 ± 68.3 and 361.6 (85.6) MBq. The mean administered activity per body weight was 4.8 ± 0.6 and the median 4.8 (0.6) MBq/kg. The results of this survey are within the range of values reported in the literature and can be used as a standard of reference until national diagnostic reference levels are established for whole-body PET/CT procedures.

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.

Assessment of diagnostic reference levels awareness and knowledge amongst CT radiographers

Background

Reports indicated that numerous factors, including inadequate personnel knowledge, contributes to insufficient patient data for setting up diagnostic reference levels (DRLs) in developing countries. This study aims to evaluate the knowledge of DRLs as an optimisation tool amongst computed tomography (CT) radiographers in northern Nigeria. This is a quantitative cross-sectional study. A structured questionnaire was devised and distributed on site to sixty-two CT radiographers in northern Nigeria. A total of fifteen questions were included in the questionnaire focusing on DRLs, dose optimisation and dose descriptors generating quantitative data concerning overall CT radiographers’ perceived knowledge and awareness about DRLs.

Results

A response rate of 77.4% (48/62) was achieved. About 83.3% of the participants declare DRLs awareness, and 37.5% carried out a local dose survey. The percentage correctly perceived knowledge of concepts; DRLs was 45.8%, dose optimisation (42%) and CT dose descriptor (39%). Radiographers with work experience ranging from 4-10 years had the highest score.

Conclusion

In this survey, deficiencies were noted in radiographers’ knowledge about DRLs with precise knowledge gap in the implementation of local dose survey for DRLs and optimisation. There is a need for continuous radiographers’ training with greater emphasis on dose optimisation and institutional based dose evaluation.

Radiation exposures in pregnancy, health effects and risks to the embryo/foetus-information to inform the medical management of the pregnant patient

Generally, intentional exposure of pregnant women is avoided as far as possible in both medical and occupational situations. This paper aims to summarise available information on sources of radiation exposure of the embryo/foetus primarily in medical settings. Accidental and unintended exposure is also considered. Knowledge on the effects of radiation exposure on the developing embryo/foetus remains incomplete-drawn largely from animal studies and two human cohorts but a summary is provided in relation to the key health endpoints of concern, severe foetal malformations/death, future cancer risk, and future impact on cognitive function. Both the specific education and training and also the literature regarding medical management of pregnant females is in general sparse, and consequently the justification and optimisation approaches may need to be considered on a case by case basis. In collating and reviewing this information, several suggestions for future basic science research, education and training, and radiation protection practice are identified.

IMAGE QUALITY STUDY OF RADIATION-REDUCED COMBINED CHEST AND ABDOMEN/PELVIS CT COMPARED WITH A STANDARD PROTOCOL

The purpose of this study is to examine radiation doses and image quality of a low-dose (LD) protocol for chest and abdomen/pelvis (CAP) CT compared with a standard (STD) protocol. A total of 361 patients were included between October 2019 and April 2020; 104 patients with LD-protocol (100 kV, ref mAs 80 (chest)/145 (abdomen/pelvis)) and 257 patients with STD-protocol (100 kV, ref mAs 100 (chest)/180 (abdomen/pelvis)) at second-generation dual-source CT. Radiation doses for CTDIvol and DLP, and objective and subjective image qualities of 50 examinations from each group were evaluated. The LD-protocol applied significantly lower radiation doses compared with the STD-protocol (p < 0.001), achieving a dose reduction by 37% for the median DLP in chest, 19% in abdomen/pelvis and 22% in total. Median total DLP was 342 mGy·cm (LD) vs. 436 mGy·cm (STD). The LD-CAP CT protocol achieved a significant dose reduction far below national diagnostic reference levels, ensuring acceptable and good image quality.

UTERINE ARTERY EMBOLISATION: CONTINUOUS QUALITY IMPROVEMENT REDUCES RADIATION DOSE WHILE MAINTAINING IMAGE QUALITY

The purpose of this study was to introduce a continuous quality improvement (CQI) program for radiation dose optimisation during uterine artery embolisation (UAE) and assess its impact on dose reduction and image quality. The CQI program investigated the effects of optimising radiation dose parameters on the kerma-area product (KAP) and image quality when comparing a 'CQI intervention' group (n = 50) and 'Control' group (n = 50). Visual grading characteristics (VGC) analysis was used to assess image quality, using the 'Control' group as a reference. A significant reduction in KAP by 17% (P = 0.041, d = 0.2) and reference air kerma (Ka, r) by 20% (P = 0.027, d = 0.2) was shown between the two groups. The VGC analysis resulted in an area under the VGC curve (AUCVGC) of 0.54, indicating no significant difference in image quality between the two groups (P = 0.670). The implementation of the CQI program and optimisation of radiation dose parameters improved the UAE radiation dose practices at our centre. The dose reduction demonstrated no detrimental effects on image quality.

TYPICAL VALUES OF DOSIMETRIC DATA FOR CARDIAC FLUOROSCOPY-GUIDED PROCEDURES IN A SOUTH AFRICAN TEACHING HOSPITAL

Currently there are limited diagnostic reference level (DRL) data for South African (SA) public sector cardiac fluoroscopy-guided procedures (FGPs). A 4-y retrospective study of dosimetric data on 6265 patients determined typical values (50th percentile) of dosimetric data for the seven most frequent cardiac FGPs at a SA teaching hospital. Kerma-area-product (KAP), reference point air Kerma (Ka,r) and fluoroscopy time (FT) were, respectively, calculated for coronary angiography (CA) (n = 1935; 61Gy.cm2, 624 mGy, 5 min); CA with left ventriculography (n = 1687; 85Gy.cm2, 840 mGy, 3.9 min), valve screening (n = 129; 6Gy.cm2, 164 mGy, 2.3 min), percutaneous coronary intervention (n = 1922; 145Gy.cm2, 1569 mGy, 11.9 min), pacemaker implantation (n = 432; 9Gy.cm2, 100 mGy, 6.5 min), pericardial tap (n = 115; 1.9Gy.cm2, 18 mGy, 1.5 min) and transcatheter aortic valve implantation (n = 45; 65Gy.cm2, 658 mGy, 14.1 min). This work presents the largest SA public sector cardiac FGP dosimetric data to date and provides a key resource for future work in this domain.

NATIONAL DIAGNOSTIC REFERENCE LEVELS AND ACHIEVABLE DOSES FOR STANDARD CT EXAMINATIONS IN SUDAN

Radiation doses were determined to propose national diagnostic reference levels (NDRLs) and achievable doses (ADs) for computed tomography (CT) examinations in Sudan. Doses were estimated from retrospectively collected scan parameters for 1336 CT examinations of adult patients from 14 Sudanese hospitals using CT Expo 2.5 software. ADs and NDRLs were set at the 50th and 75th percentile of the hospital median dose distribution, respectively. The proposed CTDIvol (mGy) ADs ranged from: 10 (chest) to 64 (head), and that of the dose-length product (DLP; mGy.cm) ranged from 366 (chest) to 1225 (head). The proposed CTDIvol (mGy) NDRLs ranged from 15 kidney-ureter-bladder (KUB) to 79 (head), whereas that of the DLP (mGy.cm) ranged from 690 (chest) to 1490 (head). Current doses fell within the upper range of the doses presented in the literature emphasizing the need for implementation of the current ADs and NDRLs for CT to enhance patient protection and dose optimization in Sudan.