What are the clinical and technical factors that influence the kerma–area product in percutaneous coronary intervention?

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.

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.

MEASUREMENT OF PATIENT SKIN DOSE DISTRIBUTIONS IN THREE LEBANESE INTERVENTIONAL CARDIOLOGY SUITES

Using a mesh of 30 thermoluminescent dosemeters, adults' patient skin doses were measured for 99 coronary angiography (CA) and 89 percutaneous coronary interventions (PCI) performed in three Lebanese hospitals. Average peak skin dose (Dskin,max) were 152 mGy (range: 16-1144) for CAs and 576 mGy (range: 7-3361) for PCIs. While only four patients had a Dskin,max value exceeding the 2 Gy threshold for skin injuries, several patients had skin dose values above 1 Gy at several distinct locations proving that Dskin,max alone is not sufficient for repetitive procedures; 2D dose maps are required instead. Dskin,max correlated well with total air kerma-area product (PKA,T) for PCI in Hospitals 1 and 2 (R = 0.91 and 0.76, respectively) enabling the setup of an alert level at PKA,T = 240 and 210 Gy cm2, respectively, corresponding to a Dskin,max of 2 Gy. This was not possible for Hospital 3 due to weak correlations between Dskin,max and PKA,T.

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 StentBoost subtract imaging on patient radiation exposure during percutaneous coronary intervention

The purpose of this study was to assess the impact of StentBoost Subtract (SBS) imaging on patient radiation dose during percutaneous coronary intervention. Data were prospectively collected between February 2010 and November 2012 at a tertiary cardiac catheterization. All patients who had scheduled for coronary stent implantation performed by one expert interventional cardiologist with sufficient experience in SBS imaging and radiation protection, were included. The patients were divided into groups with or without SBS. A multiple linear regression analysis was used to determine the impact of SBS imaging on patient radiation dose. Of 712 patients screened, 414 patients were enrolled in the study (with SBS: n = 177, without SBS: n = 237). Although the DAP, fluoroscopy time and cine frames used in the group with SBS were significantly increased when compared with those used in the group without SBS (P < 0.05), multiple linear regression shows SBS imaging has no significant impact on patient radiation dose (P > 0.05). Multivariate predictors of patient radiation dose were the patients' BMI, B2/C lesions, number of stents placed and bifurcation stenting (P < 0.05). In selected patients, SBS imaging can be performed with comparable patient radiation dose, compared with plain fluoroscopic imaging. This may attribute to the operator's sufficient experience in SBS imaging and radiation protection.

Main clinical, therapeutic and technical factors related to patient's maximum skin dose in interventional cardiology procedures

OBJECTIVE

The study aimed to characterise the factors related to the X-ray dose delivered to the patient's skin during interventional cardiology procedures.

METHODS

We studied 177 coronary angiographies (CAs) and/or percutaneous transluminal coronary angioplasties (PTCAs) carried out in a French clinic on the same radiography table. The clinical and therapeutic characteristics, and the technical parameters of the procedures, were collected. The dose area product (DAP) and the maximum skin dose (MSD) were measured by an ionisation chamber (Diamentor; Philips, Amsterdam, The Netherlands) and radiosensitive film (Gafchromic; International Specialty Products Advanced Materials Group, Wayne, NJ). Multivariate analyses were used to assess the effects of the factors of interest on dose.

RESULTS

The mean MSD and DAP were respectively 389 mGy and 65 Gy cm(-2) for CAs, and 916 mGy and 69 Gy cm(-2) for PTCAs. For 8% of the procedures, the MSD exceeded 2 Gy. Although a linear relationship between the MSD and the DAP was observed for CAs (r=0.93), a simple extrapolation of such a model to PTCAs would lead to an inadequate assessment of the risk, especially for the highest dose values. For PTCAs, the body mass index, the therapeutic complexity, the fluoroscopy time and the number of cine frames were independent explanatory factors of the MSD, whoever the practitioner was. Moreover, the effect of technical factors such as collimation, cinematography settings and X-ray tube orientations on the DAP was shown.

CONCLUSION

Optimising the technical options for interventional procedures and training staff on radiation protection might notably reduce the dose and ultimately avoid patient skin lesions.

Clinical determinants of radiation dose in percutaneous coronary interventional procedures: influence of patient size, procedure complexity, and performing physician

OBJECTIVES

The objectives of this work were to establish the primary clinical determinants of patient radiation dose associated with percutaneous coronary interventional (PCI) and to identify opportunities for dose reduction.

BACKGROUND

Use of X-ray imaging and associated radiation dose is a necessary part of PCI. Potential adverse consequences of radiation dose include skin radiation injury and predicted increase in lifetime cancer risk.

METHODS

Cumulative skin dose (CSD) (measured in gray [Gy] units) was selected as a measurement of patient radiation burden. Several patient-, disease-, and treatment-related variables, including 15 performing physicians, were analyzed in a multiple linear regression statistical model with cumulative skin dose CSD as the primary end point. The model results provide an estimate of the relative CSD increase (decrease) attributable to each variable.

RESULTS

Percutaneous coronary interventions performed on 1,287 male and 540 female patients were included. Median patient age was 68.6 years, median body mass index was 29.7 kg/m(2), and median weight was 88 kg. Median CSD was 1.64 Gy per procedure for male and 1.15 Gy for female patients. Increasing body mass index, patient sex, lesion complexity, lesion location, and performing physician were significantly associated with CSD. Physicians who performed more procedures were associated with lower CSD.

CONCLUSIONS

Several primary determinants of patient radiation dose during PCI were identified. Along with physician development of radiation-sparing methods and skills, pre-procedure dose planning is proposed to help minimize radiation dose for PCI.

Does a flat panel detector reduce the patient radiation dose in interventional cardiology?

An internal audit has been performed to evaluate the patient radiation dose in the clinical use of X-ray cardiac flat panel detector (FPD) systems. Fluoroscopy and image acquisition (cine mode) programs are optimised for low-dose settings. The diagnostic and therapeutic interventional cardiac procedures are performed at 6 pulse s(-1) for fluoroscopy and 15 frames s(-1) for image acquisition. The FPD entrance dose is configured for 29 nGy pulse(-1) in the fluoroscopy mode and 0.10 microGy frame(-1) in the cine mode. From the data collected, the following local reference levels for coronary angiography and angioplasty have been obtained: kerma-area products 23 and 44 Gy cm(2), cumulative doses 376 and 776 mGy, fluoroscopy times 5 and 15.5 min and cine images 617 and 1163 images.