Radiation dose to the heart in paediatric interventional cardiology

Cumulative Radiation Dose from Medical Imaging in Children with Congenital Heart Disease: A Systematic Review

Children with congenital heart disease are exposed to repeated medical imaging throughout their lifetime. Although the imaging contributes to their care and treatment, exposure to ionising radiation is known to increase one's lifetime attributable risk of malignancy. A systematic search of multiple databases was performed. Inclusion and exclusion criteria were applied to all relevant papers and seven were deemed acceptable for quality assessment and risk of bias assessment. The cumulative effective dose (CED) varied widely across the patient cohorts, ranging from 0.96 mSv to 53.5 mSv. However, it was evident across many of the included studies that a significant number of patients were exposed to a CED >20 mSv, the current annual occupational exposure limit. Many factors affected the dose which patients received, including age and clinical demographics. The imaging modality which contributed the most radiation dose to patients was cardiology interventional procedures. Paediatric patients with congenital heart disease are at an increased risk of receiving an elevated cumulative radiation dose across their lifetime. Further research should focus on identifying risk factors for receiving higher radiation doses, keeping track of doses, and dose optimisation where possible.

Setting up regional diagnostic reference levels for pediatric interventional cardiology in Latin America and the Caribbean countries: preliminary results and identified challenges

The goal of the present study was to propose a set of preliminary regional diagnostic reference levels (DRLs) for pediatric interventional cardiology (IC) procedures in Latin America and the Caribbean countries, classified by age and weight groups. The study was conducted in the framework of the Optimization of Protection in Pediatric Interventional Radiology in Latin America and the Caribbean program coordinated by the World Health Organization and the Pan American Health Organization in cooperation with the International Atomic Energy Agency. The first step of the program was focused on pediatric IC. Dose data from diagnostic and therapeutic procedures were collected between December 2020 and December 2021. Regional DRLs were set as the third quartile of patient dose data (kerma area product) collected in 18 hospitals from 10 countries in an initial sample of 968 procedures. DRLs were set for four age bands and five weight ranges. The values obtained for the four age bands (<1 yr, 1 to <5 yr, 5 to <10 yr and 10 to <16 yr) were 2.9, 6.1, 8.8 and 14.4 Gy cm²for diagnostic procedures, and 4.0, 5.0, 10.0 and 38.1 Gy cm²for therapeutic procedures, respectively. The values obtained for the five weight bands (<5 kg, 5 to <15 kg, 15 to <30 kg, 30 to <50 kg and 50 to <80 kg) were 3.0, 4.5, 8.1, 9.2 and 26.8 Gy cm²for diagnostic procedures and 3.7, 4,3, 7.3, 16.1 and 53.4 Gy cm²for therapeutic procedures, respectively. While initial data were collected manually as patient dose management systems (DMSs) were not available in most of the hospitals involved in the program, a centralized automatic DMS for the collection and management of patient dose indicators has now been introduced and is envisaged to increase the sample size. The possibility of alerting on high dose values and introducing corrective actions will help in optimization.

Potential risks of cardiovascular and cerebrovascular disease and cancer due to cumulative doses received from diagnostic CT scans?

Potential risks from radiation exposure on the development of cardiovascular and cerebrovascular disease are indicated by epidemiological studies. Medical exposures give the largest dose to the population from artificial sources, with cumulative doses from multiple CT scans being significant. Data on doses from scans performed on 12 CT scanners in three hospitals over a period of 5½ years, derived using Radimetrics^TMsoftware, have been reviewed for 105 757 patients. Data have been downloaded for heart, brain, thyroid, and effective doses, and cumulative doses analysed using Excel^TMspreadsheets. 2.4% of patients having body CT scans received cumulative doses to the heart over 100 mSv, 9% of whom were under 50 years. 9.6% of patients having head CT scans received cumulative doses to the brain over 100 mSv with 0.08% over 500 mSv from whom 41% were under 50 years, but only 1.3% of patients scanned had thyroid/carotid artery doses over 100 mSv. An approximate evaluation of potential risks from exposures of the heart above 100 mSv and brain over 500 mSv for patients under 60 years would suggest that at most only one patient would demonstrate any excess risk from vascular disease resulting from the exposures. 0.67% of patients scanned received effective doses over 100 mSv, in line with results from European studies, with 8.4% being under 50 years. The application of age and sex specific risk coefficients relating to excess cancer incidence suggests that two or three patients with effective doses over 100 mSv and five patients with effective doses between 50 and 100 mSv, from those examined, might develop cancer as a result of exposure. However, this will be an overestimate, since it does not take patients' health into account. Exposure management software can aid in evaluating cumulative doses and identifying individual patients receiving substantial doses from repetitive imaging.

Organ and effective doses detriment to paediatric patients undergoing multiple interventional cardiology procedures

The aims of the present study were to present the frequency of multiple interventional cardiac procedures for a certain group of patients obtained at one of the largest paediatric hospitals in Chile. In addition it has been analysed cumulative kerma area product (KAP) and cumulative air kerma (CAK), and calculated organ doses for the patient groups undergoing 2, 3 and ≥ 4 procedures, using Monte Carlo software. Effective doses were also estimated for epidemiological purposes and to permit comparison with other imaging procedures. The sample used corresponds to the last 9 years and refers to a total of 1521 paediatric patients and 1824 interventional cardiac procedures. The results for frequency were: 13.7% of patients underwent 2 procedures, 4.1% underwent 3 procedures and 1.4% underwent 4 or more procedures. The median KAP and CAK values measured for the cumulative procedures in these three groups of patients were 3.7, 5.4 and 10.8 Gy·cm² and 59.9, 83.2 and 147.6 mGy, respectively. In terms of the most irradiated organs during interventional cardiac procedures, the highest median values (for the group of ≥4 procedures) were: active bone marrow 5.0 mGy, lungs 23.5 mGy, oesophagus 15.2 mGy, thyroid 7.8 mGy and breast 11.0 mGy. Median dose value to the heart (for the group of ≥4 procedures) was 12.7 mGy. Median values in terms of calculated effective dose for the three patient groups (with 2, 3 and ≥4 procedures) were 3.4, 5.9 and 8.7 mSv, respectively.

Towards the definition of Institutional diagnostic reference levels in paediatric interventional cardiology procedures in Greece

This study aimed to evaluate paediatric radiation doses in a dedicated cardiology hospital, with the objective of characterising patterns in dose variation. The ultimate purpose was to define Local (Institutional) Diagnostic Reference Levels (LDRLs) for different types of paediatric cardiac interventional procedures (IC), according to patient age. From a total of 710 cases performed during three consecutive years, by operators with more than 15 years of experience, the age was noted in only 477 IC procedures. The median values obtained for Fluoroscopy Time (FT), Number of Frames (N) and Kerma Area Product (P_KA) by age range were 5.8 min, 1322 and 2.0 Gy.cm² for <1 y; 6.5 min, 1403 and 3.0 Gy.cm² for 1 to <5 y; 5.9 min, 950 and 7.0 Gy.cm² for 5 to <10 y; 5.7 min, 940 and 14.0 Gy.cm² for 10 to <16 y, respectively. A large range of patient dose data is observed, depending greatly on procedure type and patient age. In all age groups the range of median FT, N and P_KA values was 3.1-15.8 min, 579-1779 and 1.0-20.8 Gy.cm² respectively. Consequently, the definition of LDRLs presents challenges mainly due to the multiple clinical and technical factors affecting the outcome. On the other hand the lack of paediatric IC DRLs makes the identification of good practices more difficult. A consensus is needed on IC procedures nomenclature and grouping in order to allow a common assessment and comparison of doses.

Paediatric interventional cardiology in Costa Rica: diagnostic reference levels and estimation of population dose

The goal of the present study was to propose a set of national diagnostic reference levels (DRLs) in Costa Rica for paediatric interventional cardiology (IC) procedures classified by age and weight and to estimate the collective dose of the paediatric population from these intervention practices. The data collection period was May 2016 to May 2017. The third quartile of patient dose data distributions for kerma-area product (KAP) values was set as the national DRLs. A sample of 154 paediatric IC procedures (collected in the national paediatric hospital with a single x-ray system) was used and divided into four age ranges and five weight ranges. The national DRLs obtained for KAPs by age range were 1.79 Gy cm² (<1 year) to 23.0 Gy cm² (10-15 years). The national DRLs obtained for KAPs by weight range were 1.0 Gy cm² (<10 kg) to 49.6 Gy cm² (50-79 kg). The contribution to the collective dose of the population of Costa Rica amounted to 0.78 person Sv.

The impact of iodinated contrast media on intravascular and extravascular absorbed doses in X-ray imaging: A microdosimetric analysis

Studies suggest iodinated contrast media (ICM) may increase organ dose and blood cell DNA damage for a given X-ray exposure. The impact of ICM on dose/damage to extravascular cells and cancer risks is unclear.

METHODS

We used Monte Carlo modelling to investigate the microscopic distribution of absorbed dose outside the lumen of arteries, capillaries and interstitial fluids containing blood and various concentrations of iodine. Models were irradiated with four X-ray spectra representing clinical procedures.

RESULTS

For the artery model, The average dose enhancement factors (DEF) to blood were 1.70, 2.38, 7.38, and 12.34 for mass concentrations of iodine in blood (ρiI) of 5, 10, 50 and 100 mg/ml, respectively, compared to 0 mg/ml. Average DEFs were reduced to 1.26, 1.51, 3.48 and 5.56, respectively, in the first micrometre of the vessel wall, falling to 1.01, 1.02, 1.06 and 1.09 at 40-50 μm from the lumen edge. For the capillary models, DEF for extravascular tissues was on average 48% lower than DEF for the whole model, including capillaries. A similar situation was observed for the interstitial model, with DEF to the cell nucleus being 35% lower than DEF for the whole model.

CONCLUSIONS

While ICM may modify the absorbed doses from diagnostic X-ray examinations, the effect is smaller than suggested by assays of circulating blood cells or blood dose enhancement. Conversely, the potentially large increase in dose to the endothelium of blood vessels means that macroscopic organ doses may underestimate the risk of radiation induced cardiovascular disease for ICM-enhanced exposures.

Enhanced radiation dose and DNA damage associated with iodinated contrast media in diagnostic X-ray imaging

A review was undertaken of studies reporting increased DNA damage in circulating blood cells and increased organ doses, for X-ray exposures enhanced by iodinated contrast media (ICM), compared to unenhanced imaging. This effect may be due to ICM molecules acting as a source of secondary radiation (Auger/photoelectrons, fluorescence X-rays) following absorption of primary X-ray photons. It is unclear if the reported increase in DNA damage to blood cells necessarily implies an increased risk of developing cancer. Upon ICM-enhancement, the attenuation properties of blood differ substantially from surrounding tissues. Increased energy deposition is likely to occur within very close proximity to ICM molecules (within a few tens of micrometres). Consequently, in many situations, damage and dose enhancement may be restricted to the blood and vessel wall only. Increased cancer risks may be possible, in cases where ICM molecules are given sufficient time to reach the capillary network and interstitial fluid at the time of exposure. In all situations, the extrapolation of blood cell damage to other tissues requires caution where contrast media are involved. Future research is needed to determine the impact of ICM on dose to cells outside the blood itself and vessel walls, and to determine the concentration of ICM in blood vessels and interstitial fluid at the time of exposure.

Organ and effective doses from paediatric interventional cardiology procedures in Chile

The aim of this study was to present the results of organ and effective doses for paediatric patients for different types of interventional cardiology procedures for age and weight groups, derived from a patient dosimetry pilot programme carried out in Chile, under the auspices of the International Atomic Energy Agency. Over seven years, a retrospective collection of demographic and patient dose data was obtained: age, gender, weight, height, number of cine series, total number of cine frames, fluoroscopy time, dose-area product (DAP) and cumulative dose at patient entrance reference point. Monte Carlo software was used to calculate organ and effective doses. 1506 procedures were divided into four age and seven weight groups. Organ doses (median values) for diagnostic and therapeutic procedures were: active bone marrow 0.90 and 0.64mGy; heart 1.99 and 1.46mGy; lungs 3.56 and 2.59mGy; thyroid 1.27 and 0.83; and breast (in the case of females) 1.78 and 1.36mGy. The ranges for effective doses (median values) and weight bands were 1.2-3.9mSv for diagnostic procedures and 1.0-2.5mSv for therapeutic procedures. The resulting conversion factors (median values) to estimate effective dose from DAP (in mSv/Gy.cm2) were: 1.70; 0.89; 0.58; and 0.40, for age groups of <1year, 1-<5years, 5-<10years and 10-<16years, respectively. The obtained set of dose values will enable comparisons with other imaging procedures (comparing the same age bands) for justification and optimization purposes.

Patient radiation doses in paediatric interventional cardiology procedures: a review

A large number of investigations into the radiation doses from x-ray guided interventional cardiology procedures in children have been carried out in recent years. A review was conducted of these studies, gathering data on kerma area product (P KA), fluoroscopic screening time (FT), air kerma, and estimates of effective dose and organ doses. The majority of studies focus on P KA and FT with no estimation of dose to the patient. A greater than ten-fold variation in average P KA was found between different studies, even where data were stratified by patient age or weight. Typical values of P KA were 0.6-10 Gy · cm2 (<1 year/10 kg), 1.5-30 Gy · cm2 (1-5 years), 2-40 Gy · cm2 (5-10 years), 5-100 Gy · cm2 (10-16 years) and 10-200 Gy · cm2 (>16 years). P KA was lowest for heart biopsy (0.3-10 Gy · cm2 for all ages combined) and atrial septostomy (0.4-4.0 Gy · cm2), and highest for pulmonary artery angioplasty (1.5-35 Gy · cm2) and right ventricular outflow tract dilatation (139 Gy · cm2). Most estimates of patient dose were in the form of effective dose (typically 3-15 mSv) which is of limited usefulness in individualised risk assessment. Few studies estimated organ doses. Despite advances in radiation protection, recent publications have reported surprisingly large doses, as represented by P KA and air kerma. There is little indication of a fall in these dose indicators over the last 15 years. Nor is there much suggestion of a fall in doses associated with the use of flat panel detectors, as opposed to image intensifiers. An assessment of the impact of radiation dose in the context of overall patient outcome is required.