Radiobiology in Cardiovascular Imaging

Practical guidance to reduce radiation exposure in electrophysiology applying ultra low-dose protocols: a European Heart Rhythm Association review

Interventional electrophysiology offers a great variety of treatment options to patients suffering from symptomatic cardiac arrhythmia. Catheter ablation of supraventricular and ventricular tachycardia has globally evolved a cornerstone in modern arrhythmia management. Complex interventional electrophysiological procedures engaging multiple ablation tools have been developed over the past decades. Fluoroscopy enabled interventional electrophysiologist throughout the years to gain profound knowledge on intracardiac anatomy and catheter movement inside the cardiac cavities and hence develop specific ablation approaches. However, the application of X-ray technologies imposes serious health risks to patients and operators. To reduce the use of fluoroscopy during interventional electrophysiological procedures to the possibly lowest degree and to establish an optimal protection of patients and operators in cases of fluoroscopy is the main goal of modern radiation management. The present manuscript gives an overview of possible strategies of fluoroscopy reduction and specific radiation protection strategies.

Safety and effectiveness of strategies to reduce radiation exposure to proceduralists performing cardiac catheterization procedures: a systematic review

OBJECTIVE

The objective of this systematic review was to synthesize the best available evidence on the effect of various radiation protection strategies on radiation dose received by proceduralists performing cardiac catheterization procedures involving fluoroscopy.

INTRODUCTION

Cardiac catheterization procedures under fluoroscopy are the gold standard diagnostic and treatment method for patients with coronary artery disease. The growing demand of procedures means that proceduralists are being exposed to increasing amounts of radiation, resulting in an increased risk of deterministic and stochastic effects. Standard protective strategies and equipment such as lead garments reduce radiation exposure; however, the evidence surrounding additional equipment is contradictory.

INCLUSION CRITERIA

Randomized controlled trials that compared the use of an additional radiation protection strategy with conventional radiation protection methods were considered for inclusion. The primary outcome of interest was the radiation dose received by the proceduralist during cardiac catheterization procedures.

METHODS

A three-step search was conducted in MEDLINE, CINAHL, Embase, and the Cochrane Library (CENTRAL). Trials published in the English language with adult participants were included. Trials published from database inception until July 2019 were eligible for inclusion. The methodological quality of the included studies was assessed using the JBI critical appraisal checklist for randomized controlled trials. Quantitative data were extracted from the included papers using the JBI data extraction tool. Results that could not be pooled in meta-analysis were reported in a narrative form.

RESULTS

Fifteen randomized controlled trials were included in the review. Six radiation protection strategies were assessed: leaded and unleaded pelvic or arm drapes, transradial protection board, remotely controlled mechanical contrast injector, extension tubing for contrast injection, real-time radiation monitor, and a reduction in frame rate to 7.5 frames per second. Pooled data from two trials demonstrated a statistically significant decrease in the mean radiation dose (P < 0.00001) received by proceduralists performing transfemoral cardiac catheterization on patients who received a leaded pelvic drape compared to standard protection. One trial that compared the use of unleaded pelvic drapes placed on patients compared to standard protection reported a statistically significant decrease (P = 0.004) in the mean radiation dose received by proceduralists.Compared to standard protection, two trials that used unleaded arm drapes for patients, one trial that used a remotely controlled mechanical contrast injector, and one trial that used a transradial protection board demonstrated a statistically significant reduction in the radiation dose received by proceduralists.Similarly, using a frame rate of 7.5 versus 15 frames per second and monitoring radiation dose in real-time radiation significantly lowered the radiation dose received by the proceduralist. One trial demonstrated no statistically significant difference in proceduralist radiation dose among those who used the extension tubing compared to standard protection (P = 1).

CONCLUSIONS

This review provides evidence to support the use of leaded pelvic drapes for patients as an additional radiation protection strategy for proceduralists performing transradial or transfemoral cardiac catheterization. Further studies on the effectiveness of using a lower fluoroscopy frame rate, real-time radiation monitor, and transradial protection board are needed.

Computed tomography coronary angiography - past, present and future

Computed tomography coronary angiography (CTCA) is a robust and reliable non-invasive alternative imaging modality to invasive coronary angiography, which is the reference standard in evaluating the degree of coronary artery stenosis. CTCA has high negative predictive value and can confidently exclude significant coronary artery disease (CAD) in low to intermediate risk patients. Over the years, substantial effort has been made to reduce the radiation dose and increase the cost efficiency of CTCA. In this review, we present the evolution of computed tomography scanners in the context of coronary artery imaging as well as its clinical applications and limitations. We also highlight the future directions of CTCA as a one-stop non-invasive imaging modality for anatomic and functional assessment of CAD.

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.

Effectiveness of protection strategies for reducing radiation exposure in proceduralists during cardiac catheterization procedures: a systematic review protocol

REVIEW QUESTION

What is the effectiveness of radiation protection strategies for reducing the radiation dose received by the proceduralist during cardiac catheterization procedures?

Comparison of sequential and high-pitch-spiral coronary CT-angiography: image quality and radiation exposure

New protocols for coronary computed tomography angiography (CCTA) could lower the radiation dose for patients but influence the image quality. To compare image quality and radiation exposure in step-and-shoot CCTA and high-pitch spiral CCTA. Fifty-nine pairs of patients matched for weight, height, sex and heart rate were included in this study (74 m, 44 f, average age 60 years, age range 29-94 years). Step-and-shoot CCTA and high-pitch spiral CCTA was performed on a third generation dual-source CT in equally sized patient groups. The signal-to-noise ratio (SNR) in the ascending aorta and the coronary arteries were determined for each dataset. Image quality was rated using a five-point scale. We used the t-test for paired samples to compare SNR and effective dose, and the Wilcoxon test to compare image quality scores. Mean effective dose for the step-and-shoot protocol (4.15 ± 3.07 mSv) was significantly higher in comparison to the high-pitch spiral protocol (1.2 ± 0.69 mSv; p < 0.0001). Mean SNR was higher with the step-and-shoot protocol compared to the high-pitch spiral protocol in the aorta, in the left main and peripheral coronary arteries (p < 0.01), in the proximal right coronary artery (p = 0.027). Image quality scores were significantly better for the step-and-shoot protocol (p = 0.0003). Step-and-shoot CCTA has significantly better SNR and overall image quality compared to high-pitch spiral CCTA, but with a mean effective dose more than thrice as high.

Myocardial perfusion imaging: Lessons learned and work to be done-update

As the second term of our commitment to Journal begins, we, the editors, would like to reflect on a few topics that have relevance today. These include prognostication and paradigm shifts; Serial testing: How to handle data? Is the change in perfusion predictive of outcome and which one? Ischemia-guided therapy: fractional flow reserve vs perfusion vs myocardial blood flow; positron emission tomography (PET) imaging using Rubidium-82 vs N-13 ammonia vs F-18 Flurpiridaz; How to differentiate microvascular disease from 3-vessel disease by PET? The imaging scene outside the United States, what are the differences and similarities? Radiation exposure; Special issues with the new cameras? Is attenuation correction needed? Are there normal databases and are these specific to each camera system? And finally, hybrid imaging with single-photon emission tomography or PET combined with computed tomography angiography or coronary calcium score. We hope these topics are of interest to our readers.