Estimating brain and eye lens dose for the cardiologist in interventional cardiology-are the dose levels of concern?

OBJECTIVES: To establish conversion coefficients (CCs), between mean absorbed dose to the brain and eye lens of the cardiologist and the air kerma-area product, PKA, for a set of projections in cardiac interventional procedures. Furthermore, by taking clinical data into account, a method to estimate the doses per procedure, or annual dose, is presented. METHODS: Thermoluminescence dosimeters were used together with anthropomorphic phantoms, simulating a cardiologist performing an interventional cardiac procedure, to estimate the CCs for the brain and eye lens dose for nine standard projections, and change in patient size and x-ray spectrum. Additionally, a single CC has been estimated, accounting for each projections fraction of use in the clinic and associated PKA using clinical data from the dose monitoring system in our hospital. RESULTS: The maximum CCs for the eye lens and segment of the brain, is 5.47 µGy/Gycm2 (left eye lens) and 1.71 µGy/Gycm2 (left brain segment). The corresponding weighted CCs: are 3.39 µGy/Gycm2 and 0.89 µGy/Gycm2, respectively. CONCLUSIONS: Conversion coefficients have been established under actual scatter conditions, showing higher doses on the left side of the operator. Using modern interventional x-ray equipment, interventional cardiac procedures will not cause high radiation dose levels to the operator when a ceiling mounted shield is used, otherwise there is a risk that the threshold dose values for cataract will be reached. ADVANCE IN KNOWLEDGE: In addition to the CCs for the different projections, methods for deriving a single CC per cardiac interventional procedure and dose per year were introduced.

Age-specific and gender-specific radiation risks in paediatric angiography and interventional cardiology: conversion coefficients and risk reference values.

OBJECTIVES: To estimate risk for exposure-induced cancer death (REID), organ-specific risks of exposure-induced cancer death (REIDHT) and associated conversion coefficients (CCREID:KAP=REID/kerma-area product (KAP), CCREIDHT:KAP=REIDHT/KAP) in paediatric cardiac catheterizations using data from radiation dose structured reports (RDSR). A novel risk surveillance tool consisting of age-specific and gender-specific risk reference values (RRVs) related to population cancer risk is suggested. METHODS: The PCXMC v.2.0 code is used together with exposure-related information from RDSR from a cohort of 238 children to assess cancer risks and related conversion coefficients. The KAP corresponding to 1 in 1000 of increased REID is used to define age-specific and gender-specific KAP values to monitor risk in such patient cohorts, here denoted as RRVs. RESULTS: The REID estimates ranged from below 1 up to 300 in 100,000, and the RRVs for the different age groups and gender ranged from 0.77 Gycm2 and 2.1 Gycm2 for neonates (female, male) to 11 Gycm2 and 25 Gycm2 for 15-year-olds (female, male). The CCREID:KAP and CCREIDHT:KAP decreased biexponentially with increased age, being notably higher for female patients. CONCLUSIONS: Prominent risk contributing organs were the lungs and the (female) breast. The concept of age-specific and gender-specific RRVs related to population cancer risk is introduced and is intended to be used as a supporting tool for physicians performing such interventions. ADVANCES IN KNOWLEDGE: Age-related and gender-related conversion coefficients for radiation risk, CCREID:KAP and CCREIDHT:KAP, are introduced and a novel risk surveillance concept, the RRV, is suggested for paediatric cardiac catheterizations.

Calculating organ and effective doses in paediatric interventional cardiac radiology based on DICOM structured reports - Is detailed examination data critical to dose estimates?

PURPOSE: To estimate effective dose (E), equivalent organ doses (HT) and associated conversion coefficients (CCE:KAP = E/KAP, CCHT:KAP = HT/KAP; KAP = Kerma-area product) in paediatric cardiac interventions, using detailed exposure data from radiation dose structured reports (RDSR). These "RDSR dose estimations" have been compared with estimations performed using the approach currently implemented in the clinic that is based on a simplified assumptions method (SAM). METHODS: The Monte Carlo system PCXMC, incorporated into a previously developed framework, was used to calculate E and HT for 202 children. The calculations were performed with input values from RDSR, and also using simplified assumptions, including fixed nominal values for the focus-skin distance, collimated beam size, irradiation geometry and patient size (age, weight and height). RESULTS: Mean HT to critical organs were: 5-25 mSv (lungs), 5-8 mSv (breasts) and 5-22 mSv (heart), with the lower and upper end of the doses associated with the neonatal and 15 years group, respectively. The associated mean CCHT:KAP for the different age groups were: 9.4-1.6 mSv/Gycm2 (lungs), 8.9-0.54 mSv/Gycm2 (breasts) and 9.3-1.4 mSv/Gycm2 (heart). CONCLUSIONS: The extension of the concept of a conversion coefficient for HT is introduced and CCHT:KAP values for paediatric cardiac interventions divided in age groups are presented. This method of linking the KAP to HT is intended for use in epidemiological/cohort studies or in clinics that do not have access to RDSR. Further, the population-averaged conversion coefficients for the critical organs estimated from RDSR, displayed no statistically significant difference compared with the SAM approach.