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.

Digital zoom is a useful, simple, and cost-effective method of reducing radiation exposure in percutaneous coronary intervention

Reducing radiation exposure is a very important issue in interventional cardiology techniques such as percutaneous coronary intervention. Although novel techniques to reduce radiation exposure are valuable, we should also reconsider older techniques. Digital zoom has been available in Japan from 2005. Digital zoom enlarges an 8-inch field of view (FOV) by 1.2 times, allowing visualization of a 6.7-inch FOV without FOV switching. We identified 2101 suitable cases of percutaneous intervention (PCI) and divided them into two groups according to the use of digital zoom; 1195 patients were included in the digital zoom group and 906 patients in the conventional group. We collected data regarding the reference air kerma (RAK) and dose-area product (DAP). We calculated RAK and DAP per minute fluoroscope time (RAK/min, DAP/min, respectively). There were intergroup differences in RAK, DAP, RAK/min, and DAP/min (digital zoom group vs conventional group; RAK, 1590 mGy [990-2410] vs 1850 [1220-2720], p < 0.01, RAK/min; 54.7 mGy/min [38.5-73.2] vs 71.2 [51.5-93.0], p < 0.01; DAP, 16,000 cGy × cm² [10,300-24,400] vs 20,700 [13,400-29,500], p < 0.001; DAP/min, 557 cGy × cm²/min [392-737] vs 782 [571-1010], p < 0.01, respectively). Because of baseline differences between the two groups, we performed propensity score matching. Even after score matching, there were intergroup differences in DAP, DAP/min, RAK, and RAK/min. Furthermore, the least squares method showed that digital zoom is a significant predictor of RAK (β = 0.14, p < 0.01) and DAP (β = 0.20, p < 0.01). Digital zoom is an older cost-effective technique that can significantly reduce radiation exposure in PCI.

Reduction of radiation exposure associated with renewal of the radiologic systems in coronary interventions

PURPOSE

Interventional coronary procedures are an important source of radiation. This study sought to evaluate the effect of the renewal of the radiologic system on patient exposure during diagnostic coronary angiography (DCA) and percutaneous coronary interventions (PCIs).

METHODS

DCA and PCIs were obtained from three centres, which renewed their radiologic systems during their participation in the multicentre prospective observational RAY'ACT-2 study. Data were analysed from the months before and after the radiologic system was changed. The primary outcomes were the dose reduction estimated by the kerma.area product (KAP in Gy·cm²) and the ratio of the KAP to fluoroscopy time (Gy·cm²·min^-1).

RESULTS

A total of 2148 patients underwent DCA (1575 before and 573 after the system change), and 1563 underwent PCI (1196 before and 367 after). A change in the radiologic system was associated with a KAP reduction of 43% for DCA (median [interquartile range]: 18.1Gy·cm² [10.2-34.0] versus 31.5 [19.0-49.0], P<0.0001), and 38% for PCI (42.2Gy·cm² [23.8-81.7] versus 70.1 [42.0-109.0], P<0.0001). Fluoroscopy time did not vary significantly, and the ratio KAP to fluoroscopy time significantly decreased by 54%. The dose reduction was homogeneous between the three centres and between different manufacturer's systems.

CONCLUSIONS

In this multicentre study, the renewal of the radiologic system was associated with a highly significant 40%-50% reduction in radiation dose, irrespective of the manufacturer. A close interaction between manufacturers and operators is needed to optimise the use of new equipment and the effectiveness of radiation reduction tools and techniques.

Scale-space for empty catheter segmentation in PCI fluoroscopic images

PURPOSE

In this article, we present a method for empty guiding catheter segmentation in fluoroscopic X-ray images. The guiding catheter, being a commonly visible landmark, its segmentation is an important and a difficult brick for Percutaneous Coronary Intervention (PCI) procedure modeling.

METHODS

In number of clinical situations, the catheter is empty and appears as a low contrasted structure with two parallel and partially disconnected edges. To segment it, we work on the level-set scale-space of image, the min tree, to extract curve blobs. We then propose a novel structural scale-space, a hierarchy built on these curve blobs. The deep connected component, i.e. the cluster of curve blobs on this hierarchy, that maximizes the likelihood to be an empty catheter is retained as final segmentation.

RESULTS

We evaluate the performance of the algorithm on a database of 1250 fluoroscopic images from 6 patients. As a result, we obtain very good qualitative and quantitative segmentation performance, with mean precision and recall of 80.48 and 63.04% respectively.

CONCLUSIONS

We develop a novel structural scale-space to segment a structured object, the empty catheter, in challenging situations where the information content is very sparse in the images. Fully-automatic empty catheter segmentation in X-ray fluoroscopic images is an important and preliminary step in PCI procedure modeling, as it aids in tagging the arrival and removal location of other interventional tools.

Radiation safety in the cardiac catheterization lab: A time series quality improvement initiative

BACKGROUND

Interventional cardiologists have one of the highest annual radiation exposures yet systems of care that promote radiation safety in cardiac catheterization labs are lacking. This study sought to reduce the frequency of radiation exposure, for PCI procedures, above 1.5Gy in labs utilizing a Phillips system at our local institution by 40%, over a 12-month period.

METHODS

We performed a time series study to assess the impact of different interventions on the frequency of radiation exposure above 1.5Gy. Process measures were percent of procedures where collimation and magnification were used and percent of completion of online educational modules. Balancing measures were the mean number of cases performed and mean fluoroscopy time.

INTERVENTIONS

Information sessions, online modules, policies and posters were implemented followed by the introduction of a new lab with a novel software (AlluraClarity©) to reduce radiation dose.

RESULTS

There was a significant reduction (91%, p<0.05) in the frequency of radiation exposure above 1.5Gy after utilizing a novel software (AlluraClarity©) in a new Phillips lab. Process measures of use of collimation (95.0% to 98.0%), use of magnification (20.0% to 14.0%) and completion of online modules (62%) helped track implementation. The mean number of cases performed and mean fluoroscopy time did not change significantly.

CONCLUSION

While educational strategies had limited impact on reducing radiation exposure, implementing a novel software system provided the most effective means of reducing radiation exposure.