Radiation doses and estimated risk from angiographic projections during coronary angiography performed using novel flat detector

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.

Combining Optimized Image Processing With Dual Axis Rotational Angiography: Toward Low-Dose Invasive Coronary Angiography

Background

Dual axis rotational coronary angiography (DARCA) reduces radiation exposure during coronary angiography on older x‐ray systems. The purpose of the current study is to quantify patient and staff radiation exposure using DARCA on a modality already equipped with dose‐reducing technology. Additionally, we assessed applicability of 1 dose area product to effective dose conversion factor for both DARCA and conventional coronary angiography (CCA) procedures.

Methods and Results

Twenty patients were examined using DARCA and were compared with 20 age‐, sex‐, and body mass index–matched patients selected from a prior study using CCA on the same x‐ray modality. All irradiation events are simulated using PCXMC (STUK, Finland) to determine organ and effective doses. Moreover, for DARCA each frame is simulated. Staff dose is measured using active personal dosimeters (DoseAware, Philips Healthcare, The Netherlands). With DARCA, median cumulative dose area product is reduced by 57% (ie, 7.41 versus 17.19 Gy·cm²). Effective dose conversion factors of CCA and DARCA are slightly different, yet this difference is not statistically significant. The occupational dose at physician's chest, leg, and collar level are reduced by 60%, 56%, and 16%, respectively, of which the first 2 reached statistical significance. Median effective dose is reduced from 4.75 mSv in CCA to 2.22 mSv in DARCA procedures, where the latter is further reduced to 1.79 mSv when excluding ventriculography.

Conclusions

During invasive coronary angiography, DARCA reduces radiation exposure even further toward low‐dose values on a system already equipped with advanced image processing and noise reduction algorithms. For both DARCA and CCA procedures, using 1 effective dose conversion factor of 0.30 mSv·Gy⁻¹·cm⁻² is feasible.

Radiation doses during cardiac catheterisation procedures in India: a multicentre study: Radiation dose study

AIMS

Established, evidence-based measures of radiation are required to minimise its hazards, while maintaining adequate image quality. The aim of this study is to evaluate radiation data and generate reference radiation levels for commonly performed coronary catheterisation procedures in India.

METHODS AND RESULTS

In this prospective, observational study, all procedures were performed in accordance with the established standards using Innova IGS 520/2100-IQ catheterisation laboratories. Demographic, procedural and radiation data were collected. Dose reference limits (DRL) were established as the 75th percentile of the total distribution. There were 2,906 coronary angiograms (CAG), 750 percutaneous coronary interventions (PCI) and 715 CAG+PCI. DRLs for dose area product were: 19.6 Gy·cm2 for CAG, 49.8 Gy·cm2 for PCI and 72.0 Gy·cm2 for CAG+PCI, respectively. Median cumulative air kerma levels were: 185 mGy for CAG, 533mGy for PCI, and 891 mGy for CAG+PCI. Male gender, higher BMI, combining CAG+PCI, fluoroscopy time, number of cine frames, and image acquisition settings were significant contributors to increased radiation dose.

CONCLUSIONS

This study established reference radiation dose levels for diagnostic and interventional coronary procedures in India, which were comparable to and in the lower range of international standards.

Radiation dose reference card for interventional radiology procedures: Experience in a tertiary referral centre

Background:

Fluoroscopy-guided interventions can potentially increase radiation risk to patients, if awareness on angiographic imaging technique and radiation dose is neglected.

Aim:

To develop patient radiation dose reference card from standardized imaging techniques for various radiology interventions performed using flat detector based angiography system.

Materials and Methods:

Real-time monitoring of angiographic exposure parameters and radiation dose were performed for 16 types of radiological interventions. Effective dose (ED) was estimated from dose area product (DAP) using PCXMC Monte Carlo simulation software. Radiation risk levels were estimated based on Biological Effects of Ionising radiation (BEIR) report VII predictive models for an Asian population.

Results:

Pulse rates of 7.5 pps and 0.6 mm Copper filtration during fluoroscopy and 4 frames per second (fps) and 0.1-0.3 mm Cu filtration during image acquisitions were found to reduce radiation dose. Owing to increased number of image acquisitions, DAP was highest during diagnostic spinal angiography 186.7 Gycm² (44.0–377.5). This resulted in highest ED of 59.4 mSv with moderate risk levels (1 in 1000 to 1 in 500). Most of the radiological interventions had low radiation risk levels (1 in 10,000 to 1 in 1000).

Conclusion:

The patient radiation dose reference card is valuable to the medical community and can aid in patient counselling on radiation induced risk from radiological interventions.

Retrospective study of patients radiation dose during cardiac catheterization procedures

OBJECTIVE

Cardiac catheterization procedures provide tremendous benefits to modern healthcare and the benefit derived by the patient should far outweigh the radiation risk associated with a properly optimized procedure. With increasing utilization of such procedures, there is growing concern regarding the magnitude and variations of dose to patients associated with procedure complexity and techniques parameters. Therefore, this study investigated radiation dose to patients from six cardiac catheterization procedures at our facility and suggest possible initial dose values for benchmark for patient radiation dose from these procedures. This initial benchmark data will be used for clinical radiation dose management which is essential for assessing the impact of any quality improvement initiatives in the cardiac catheterization laboratory.

METHODS

We retrospectively analyzed the dose parameters of 1000 patients who underwent various cardiac catheterization procedures: left heart catheterization (LH), percutaneous coronary intervention (PCI), complex PCI, LH with complex PCI, LH with PCI and cardiac resynchronization therapy (CRT) pacemaker in our cardiac catheterization laboratories. Patient's clinical radiation dose data [kerma-area-product (KAP) and air-kerma at the interventional reference point (Ka,r)] and technique parameters (fluoroscopy time, tube potential, current, pulse width and number of cine images) along with demographic information (age, height and weight) were collected from the hospital's RIS (Synapse), Sensis/Syngo Dynamics and Siemens Sensis Stats Manager electronic database. Statistical analysis was performed with the IBM SPSS Modeler v. 18.1 software.

RESULTS

The overall patient median age was 67.0 (range: 26.0-97.0) years and the median body mass index (BMI) was 28.8 (range: 15.9-61.7) kg/m2 . The median KAP for the LH, PCI, LH with complex PCI, complex PCI, LH with PCI and CRT-pacemaker procedures are 44.4 (4.1-203.2), 80.2 (18.9-208.5), 83.7 (48.0-246.1), 113.8 (60.9-284.5), 91.7 (6.0-426.0) and 51.1 (7.0-175.9) Gy-cm2 . The median Ka,r for the LH, PCI, LH with complex PCI, complex PCI, LH with PCI and CRT-pacemaker procedures are 701.0 (35.3-3794.0), 1384.7 (291.7-4021.8), 1607.0 (883.5-4448.3), 2260.2 (867.4-5311.9), 1589.3 (100.2-7237.4) and 463.8 (67.7-1695.9) mGy respectively.

CONCLUSION

We have analyzed patient radiation doses from six commonly used procedures in our cardiac catheterization laboratories and suggested possible initial values for benchmark from these procedures for the fluoroscopy time, KAP and air-kerma at the interventional reference point based on our current practices. Our data compare well with published values reported in the literature by investigators who have also studied patient doses and established benchmark dose levels for their facilities. Procedure-specific benchmark dose data for various groups of patients can provide the motivation for monitoring practices to promote improvements in patient radiation dose optimization in the cardiac catheterization laboratories.

ADVANCES IN KNOWLEDGE

We have investigated local patients' radiation doses and established benchmark radiation data which are essential for assessing the impact of any quality improvement initiatives for radiation dose optimization.

AN ASSESSMENT OF RADIATION EXPOSURE DOSES IN PATIENTS UNDERGOING PRIMARY PERCUTANEOUS CORONARY INTERVENTION BASED ON ANGIOGRAPHIC RECORDS

The stochastic and non-stochastic (deterministic) effects of radiation dose in patients undergoing primary percutaneous coronary intervention (PPCI) have been investigated using data recorded by an angiographic monitoring system. A total of 132 patients with acute myocardial infarction referred to the angiography department of Vali-Asr hospital, Fasa, Iran, during the second half of 2016 were recruited. Quantities like dose-area product (DAP), total air kerma (Ka,r) and fluoroscopy time (FT) were calculated and converted into effective dose (ED) and peak skin dose (PSD). The values for Ka,r, DAP and FT equaled 80 399.20 ± 63 312 mGy cm2, 1392.80 ± 1155.373 mGy and 524.11 ± 423.057 s, respectively, which were within the ranges reported in previous studies. After considering standard dose thresholds for Ka,r and PSD, it was revealed that only a small portion of patients had reached these thresholds and exceeded them (<3%). Moreover, ED < 20 mSv for the majority of patients was fairly consistent with results from a recent research in eight Belgian hospitals. It was shown that angiographic records are reliable for assessing radiation dose in patients.

Radiation dose from percutaneous transluminal coronary angioplasty procedure performed using a flat detector for different clinical angiographic projections

The radiation dose from complex cardiac procedures is of concern due to the lengthy fluoroscopic screening time and vessel complexities. This study intends to assess radiation dose based on angiographic projection and vessel complexities for clinical protocols used in the performance of percutaneous transluminal coronary angioplasty (PTCA). Dose-area product (DAP), reference air kerma (K _a,r) and real-time monitoring of tube potentials and tube current for each angiographic projection and dose setting were evaluated for 66 patients who underwent PTCA using a flat detector system. The mean DAP and cumulative K _a,r were 32.71 Gy cm² (0.57 Gy), 51.24 Gy cm² (0.9 Gy) and 102.03 Gy cm² (1.77 Gy) for single-, double- and triple-vessel PTCA, respectively. Among commonly used angiographic projections, left anterior oblique 45°-caudal 35° reached 2 Gy in 55 min using a low-dose fluoroscopy setting and 21 min for a medium-dose setting. Use of a low-dose setting for fluoroscopic screening showed a radiation dose reduction of 39% compared with a medium-dose setting.

Impact of the Ceiling-Mounted Radiation Shielding Position on the Physician's Dose from Scatter Radiation during Interventional Procedures

The effect of the ceiling-mounted radiation shielding on the amount of the scatter radiation was assessed under conditions simulating obese patients for clinically relevant exposure parameters. Measurements were performed in different projections and with different positions of the ceiling-mounted shielding: without shielding; shielding closest to the patient; and shielding closest to the physician performing the procedure. The protection provided by the shielding was assessed for cardiology when the femoral access is used and for radiology when the physician performs the procedure in the abdominal area. The results show that the use of the ceiling-mounted shielding can decrease the dose from the scatter radiation by 95% at the position of the performing physician. In cardiology, the impact is more pronounced when the left oblique projection is used. In radiology, a large decrease was observed for right oblique projections, compared to cardiology. The ceiling-mounted shielding should be placed as close to the physician as possible. The idea of creating the largest radiation shadow by placing the radiation shielding as close to the patient as possible does not provide as effective radiation protection of the operator as it might be thought.

Radiation dose and risk in children undergoing cardiac interventions performed using flat detector angiography systems

The purpose of the study was to measure radiation doses and estimate risk from various beam projections in children undergoing cardiac interventions. The dose area product (DAP) was measured for eleven patent ductus arteriosus device closures (PDA), four atrial septal defect device closures (ASD), and three balloon pulmonary valvuloplasty (BPV) interventions performed using a flat detector system. The total mean DAPs for PDA, ASD and BPV were 1.9 Gycm², 9.8 Gycm² and 6.2 Gycm² respectively. The fluoroscopic kerma dose rates increased by 10%, 33% and 92% when changing the projection from posterior-anterior to lateral projection for PDA interventions among infants, <5 yrs and >5 yrs respectively. The effective dose (ED) and organ doses were estimated from DAP using Monte Carlo software. Lungs received the highest organ dose of 7.4 mGy (PDA), 20.7 mGy (ASD) and 17.3 mGy (BPV) compared to other organs. The mean EDs from PDA, ASD and BPV were 2.5 mSv, 6.1 mSv and 4.9 mSv respectively. PDA intervention performed in infants had a radiation risk 66% higher than children aged between 3-10 years. Their lifetime attributable risk as per BEIR VII for cancer incidence was 1 in 907 males and 1 in 1047 females.

Conversion factors of effective and equivalent organ doses with the air kerma area product in patients undergoing coronary angiography and percutaneous coronary interventions

To derive effective dose (E), organ dose (H_T) and conversion factors with the air kerma area product (KAP) in coronary angiography (CA) and percutaneous coronary intervention (PCI) by the radial route, using the ICRP 103 tissue weighting factors. The study included 34 patients referred for CA and 31 for PCI. E and H_T were derived from in-the-field KAP measurements using Montecarlo methods. Median KAP of 23.2 and 56.8Gycm² and E of 6.9 and 20.0mSv were found for CA and PCI, respectively. Mean KAP and E were significantly higher in males than in females (52.4±40.0 vs 32.3±16.6Gycm²; p=0.02) and (16.8±13.6 vs 10.7±5.8mSv; p=0.04). KAP (r=0.39; p=0.001) and E (r=0.34; p=0.005) showed a significant correlation with the patient's weight. Conversion factors between KAP and E (E/KAP) were 0.30±0.04mSvGy^-1cm^-2 for CA and 0.33±0.05mSvGy^-1cm^-2 for PCI. No significant differences in the E/KAP between males and females were found (0.31±0.05 vs 0.33±0.05; p=0.08). Again, no significant correlation was found between E/KAP and patient's weight (r=0.23; p=0.07). The correlation between E and KAP was excellent for CA (r=0.99) and PCI (r=0.96). The correlation between H_T and KAP ranged from r=0.87 to r=1 and from r=0.71 to r=0.98 for CA and PCI, respectively. A single factor, the total KAP, could be used for a specific acquisition protocol to reliably estimate E and H_T without the need of a patient's specific analysis. Conversion factors might be installation, X-ray beam quality or protocol dependent.

Beam projections and radiation exposure in transradial and transfemoral approaches during coronary angiography

OBJECTIVE

We aimed to compare the operator and patient radiation exposure in standard projections during elective diagnostic coronary angiography procedures via transradial (TRA) versus transfemoral (TFA) approaches.

METHODS

In this analytical cross-sectional study, a total of 202 consecutive patients who were candidates for diagnostic coronary angiography were randomized to undergo the procedure via TFA or TRA approaches (101 in each group). Patients with abnormal Allen test and history of coronary artery bypass surgery, valvular heart disease, and unsuccessful coronary angiography were excluded from the study. A single operator performed all of the procedures using a single angiography system. Patient and operator radiation exposure were measured using diamentor and an electronic personal dosimeter, respectively. Each procedure comprised a standardized sequence of projections including four standard views for the left coronary system and two standard views for the right coronary system.

RESULTS

Left anterior oblique (LAO) caudal (50°/30°) and right anterior oblique RAO (30°) projections were associated with the highest and lowest patient radiation exposure, respectively. The operator received a significantly higher radiation exposure in the TRA approach for LAO cranial (for both left and right coronary systems) and LAO caudal (for left coronary system) projections during coronary angiography compared with the TFA approach.

CONCLUSION

Though a similar amount of patient radiation exposure in each projection was observed among TFA and TRA groups; LAO cranial and LAO caudal projections were associated with a significantly higher operator radiation exposure in the TRA group. These findings need to be considered when choosing the optimal arterial approach for patients scheduled for coronary angiography.