Abstract
Background
Transradial coronary angiography (TRA) has been associated with increased radiation doses. We hypothesized that contemporary image noise reduction technology would reduce radiation doses in the cardiac catheterization laboratory in a typical clinical setting.
Methods and results
We performed a single-center, retrospective analysis of 400 consecutive patients who underwent diagnostic and interventional cardiac catheterizations in a predominantly TRA laboratory with traditional fluoroscopy (N = 200) and a new image noise reduction fluoroscopy system (N = 200). The primary endpoint was radiation dose (mGy cm 2 ). Secondary endpoints were contrast dose, fluoroscopy times, number of cineangiograms, and radiation dose by operator between the two study periods. Radiation was reduced by 44.7% between the old and new cardiac catheterization laboratory (75.8 mGy cm 2 ± 74.0 vs. 41.9 mGy cm 2 ± 40.7, p < 0.0001). Radiation was reduced for both diagnostic procedures (45.9%, p < 0.0001) and interventional procedures (37.7%, p < 0.0001). There was no statistically significant difference in radiation dose between individual operators (p = 0.84). In multivariate analysis, radiation dose remained significantly decreased with the use of the new system (p < 0.0001) and was associated with weight (p < 0.0001), previous coronary artery bypass grafting (p < 0.0007) and greater than 3 stents used (p < 0.0004). TRA was used in 90% of all cases in both periods. Compared with a transfemoral approach (TFA), TRA was not associated with higher radiation doses (p = 0.20).
Conclusions
Image noise reduction technology significantly reduces radiation dose in a contemporary radial-first cardiac catheterization clinical practice.
Highlights
- •
Radial arterial access has been associated with higher doses compared to femoral access.
- •
In a radial-first cardiac catheterization laboratory (90% radial) we examined radiation doses reduction with a contemporary image-noise compared to a traditional x-ray system.
- •
Radial dose was reduced 45% in this all-comer population.
- •
The marked reduction in radiation doses with image noise reduction technology virtually eliminates the importance of small increases in radiation doses associated with radial access.
1
Introduction
Transradial approach (TRA) has become widely adopted in the last decade due to reduction in vascular access complications, improved patient comfort, and decreased recovery times and cost . Despite these benefits, there has been a small and statistically significant increase in radiation associated with TRA . Various techniques have been devised to reduce radiation associated with TRA such as radiation absorption drapes , radiation protection boards , real-time radiation monitoring and feedback , increasing operator experience , and reduction in fluoroscopy pulse rates .
In interventional cardiology, image processing can be challenging due to the movement of the heart. Image noise reduction technology has been shown to reduce radiation in experimental settings and with cardiac catheterization performed with a transfemoral approach (TFA) . Image noise reduction combines several novel features to improve real-time image quality. Spatial noise reduction filters out noise by averaging the pixel intensity with the surrounding pixels to distinguish an image from its surroundings. High-speed parallel computing capabilities enable visualization of clinically relevant structures at low levels of X-ray dose. Temporal noise reduction detects motion between frames to avoid the appearance of ghost images of moving objects. Motion compensation is applied to temporal filtering to further reduce image blur. This novel technology allows for more consecutive images to be averaged and thus significantly reduces noise . With image noise reduction technology, radiation dose is reduced with both fluoroscopy and cineangiography without loss of image quality. Large radiation reductions of up to 70% have been demonstrated in a variety of cardiology procedures .
In this single-center, retrospective study in a radial-first cardiac catheterization laboratory, we compared radiation dose in consecutive patients before and after introduction of a contemporary image noise reduction technology.
2
Methods
2.1
Radiographic equipment
At our institution, the cardiac catheterization laboratory was updated in 2015 to a new fluoroscopy system utilizing image noise reduction technology. The old laboratory was equipped with the Philips Allura Xper FD 20 (20-in. flat detector, year of manufacturing 2006, serial number 553803, Philips Medical Systems). The current cardiac catheterization laboratory is equipped with the Philips Allura Xper 8.1 Clarity FD 20 (year of manufacturing 2012, serial number 122448, Philips Medical Systems). The Clarity noise reduction system represents the distinguishing modification linked to radiation reduction between the two systems.
2.2
Cardiac catheterization and PCI
Our cardiac catheterization laboratory has used right TRA as a default arterial access since 2007. There were 3 principal interventional cardiologists during the study period, each with more than 5 years of TRA experience, approximately 600 diagnostic angiograms/year, and more than 150 percutaneous coronary interventions (PCIs)/year. These three operators performed 98% procedures during the study period (N = 391) and were included in the data analysis. Our institution is a cardiology fellowship teaching program and fellows with various levels of training participated in all procedures. Choice of access site (femoral/radial/ulnar/brachial and left/right) was at the discretion of the operator. Standard angulated projections for diagnostic angiography (3–5 for the left coronary and 1–3 for right coronary artery) and single plane ventriculography (right anterior oblique 30°) were used. The PCI views and angulations were performed at the operators’ discretion. For both the old and new system, the standard of care is a “low” fluoroscopy setting with 15 frames/s and cineangiography with 15 frames/s rates.
2.3
Sample size calculation
Assuming a 50% reduction in radiation with image noise reduction technology , the sample size required to detect the specified difference with 90% power and a 2-sided α level of 0.01 was 120 patients per group. We increased our patient size to 200 patients per group to allow for potentially lower observed differences.
2.4
Study design and patient cohort
We retrospectively reviewed 400 consecutive medical records, 200 with the old system and 200 with the new system. All consecutive cases in the cardiac catheterization laboratory were reviewed with no exclusions. The data collected consisted of patient demographics, including gender, age, height, and weight, comorbidities including diabetes mellitus, hypertension, hyperlipidemia, chronic renal insufficiency, coronary artery disease, cerebral vascular accidents, hemodialysis status, coronary artery bypass grafting (CABG), previous percutaneous coronary intervention (PCI), ejection fraction, and history of tobacco use, and procedural characteristics including indication for procedure, inpatient/outpatient status, diagnostic or PCI, access site, number of catheters used, number of stents used, number of cineangiography runs, fluoroscopy time, and radiation dose. The patient’s access site at the end of the procedure was the identified as the access site for the study.
2.5
Study endpoints
The primary endpoint for the study was radiation dose. The cumulative dose area product (DAP) measured in mGy cm 2 was used as the measure of radiation dose. Secondary endpoints were contrast dose, fluoroscopy times, number of cineangiograms, and radiation dose by operator between the two study periods.
2.6
Statistical analyses
The study population was separated into 2 groups, the old system and new system. Univariate analysis was initially performed to summarize the data. Continuous data are presented as a mean ± SD and t-test was used to determine statistical significance. Categorical variables are presented as category percentages and the Pearson χ 2 test was used to determine statistical significance. All tests were 2-tailed and a p value of less than 0.05 was considered significant for all tests. Multivariate linear regression analysis using the least square estimation method was conducted, with a p value of less than 0.05 considered statistically significant. The covariates for patient baseline characteristics, co-morbidities, and procedural characteristics, except for number of cineangiography runs, fluoroscopy time, and radiation dose, as described in the Study Design section were all included in multivariate linear regression analysis with the regression outcome being radiation dose. The number of cineangiography runs, fluoroscopy time, and radiation dose were not included in multivariate analysis as they are collinear with the radiation dose. All analyses were performed using the SAS statistical software version 9.2 (SAS Institute Inc., Cary, NC, USA).
This study has been approved by the University of Illinois at Chicago/Jesse Brown Veterans Affairs Institutional Review Board. The views expressed in this article are those of the authors and do not necessarily reflect the position or policy of the Department of Veterans Affairs or the US Government. The authors are solely responsible for the design and conduct of this study, all study analyses, and drafting and editing the paper. All authors have read and agreed to the manuscripts as written.
2
Methods
2.1
Radiographic equipment
At our institution, the cardiac catheterization laboratory was updated in 2015 to a new fluoroscopy system utilizing image noise reduction technology. The old laboratory was equipped with the Philips Allura Xper FD 20 (20-in. flat detector, year of manufacturing 2006, serial number 553803, Philips Medical Systems). The current cardiac catheterization laboratory is equipped with the Philips Allura Xper 8.1 Clarity FD 20 (year of manufacturing 2012, serial number 122448, Philips Medical Systems). The Clarity noise reduction system represents the distinguishing modification linked to radiation reduction between the two systems.
2.2
Cardiac catheterization and PCI
Our cardiac catheterization laboratory has used right TRA as a default arterial access since 2007. There were 3 principal interventional cardiologists during the study period, each with more than 5 years of TRA experience, approximately 600 diagnostic angiograms/year, and more than 150 percutaneous coronary interventions (PCIs)/year. These three operators performed 98% procedures during the study period (N = 391) and were included in the data analysis. Our institution is a cardiology fellowship teaching program and fellows with various levels of training participated in all procedures. Choice of access site (femoral/radial/ulnar/brachial and left/right) was at the discretion of the operator. Standard angulated projections for diagnostic angiography (3–5 for the left coronary and 1–3 for right coronary artery) and single plane ventriculography (right anterior oblique 30°) were used. The PCI views and angulations were performed at the operators’ discretion. For both the old and new system, the standard of care is a “low” fluoroscopy setting with 15 frames/s and cineangiography with 15 frames/s rates.
2.3
Sample size calculation
Assuming a 50% reduction in radiation with image noise reduction technology , the sample size required to detect the specified difference with 90% power and a 2-sided α level of 0.01 was 120 patients per group. We increased our patient size to 200 patients per group to allow for potentially lower observed differences.
2.4
Study design and patient cohort
We retrospectively reviewed 400 consecutive medical records, 200 with the old system and 200 with the new system. All consecutive cases in the cardiac catheterization laboratory were reviewed with no exclusions. The data collected consisted of patient demographics, including gender, age, height, and weight, comorbidities including diabetes mellitus, hypertension, hyperlipidemia, chronic renal insufficiency, coronary artery disease, cerebral vascular accidents, hemodialysis status, coronary artery bypass grafting (CABG), previous percutaneous coronary intervention (PCI), ejection fraction, and history of tobacco use, and procedural characteristics including indication for procedure, inpatient/outpatient status, diagnostic or PCI, access site, number of catheters used, number of stents used, number of cineangiography runs, fluoroscopy time, and radiation dose. The patient’s access site at the end of the procedure was the identified as the access site for the study.
2.5
Study endpoints
The primary endpoint for the study was radiation dose. The cumulative dose area product (DAP) measured in mGy cm 2 was used as the measure of radiation dose. Secondary endpoints were contrast dose, fluoroscopy times, number of cineangiograms, and radiation dose by operator between the two study periods.
2.6
Statistical analyses
The study population was separated into 2 groups, the old system and new system. Univariate analysis was initially performed to summarize the data. Continuous data are presented as a mean ± SD and t-test was used to determine statistical significance. Categorical variables are presented as category percentages and the Pearson χ 2 test was used to determine statistical significance. All tests were 2-tailed and a p value of less than 0.05 was considered significant for all tests. Multivariate linear regression analysis using the least square estimation method was conducted, with a p value of less than 0.05 considered statistically significant. The covariates for patient baseline characteristics, co-morbidities, and procedural characteristics, except for number of cineangiography runs, fluoroscopy time, and radiation dose, as described in the Study Design section were all included in multivariate linear regression analysis with the regression outcome being radiation dose. The number of cineangiography runs, fluoroscopy time, and radiation dose were not included in multivariate analysis as they are collinear with the radiation dose. All analyses were performed using the SAS statistical software version 9.2 (SAS Institute Inc., Cary, NC, USA).
This study has been approved by the University of Illinois at Chicago/Jesse Brown Veterans Affairs Institutional Review Board. The views expressed in this article are those of the authors and do not necessarily reflect the position or policy of the Department of Veterans Affairs or the US Government. The authors are solely responsible for the design and conduct of this study, all study analyses, and drafting and editing the paper. All authors have read and agreed to the manuscripts as written.
3
Results
3.1
Baseline patient characteristics
There were no differences in baseline patient characteristics between the two groups ( Table 1 ). Our population was fairly representative of a Veterans Affairs and major urban American hospital, with the majority of patients being male (94.5% vs. 98% in the old vs. new lab, p = 0.11), elderly (mean age of 65 years old in both groups, p = 0.92), African American (58.5% vs. 59.0%, p = 0.43) or Caucasian (35.5% vs. 34.5%, p = 0.43), and with extensive comorbidities including hypertension (90.0% vs. 91.0% in the old vs. new lab, p = 0.73), dyslipidemia (81.4% vs. 85.1%, p = 0.42), diabetes mellitus (39.4% vs. 49.0%, p = 0.07), cerebrovascular disease (12.1% vs. 16.0%, p = 0.31), congestive heart failure (33.7% vs. 37.0%, p = 0.53), and former or current tobacco abuse (75.6% vs. 85.2%, p = 0.03). More than a quarter of patients in both groups had prior PCI (28.5% vs. 27.5%), a tenth of patients had previous CABG (12.5% vs. 10.5% in the old vs. new lab, p = 0.53), and more than half of patients in both groups had multivessel CAD (>1 native vessel disease; 66.0% vs. 57.0%, p = 0.47).
| OLD LAB (n = 200) | NEW LAB (n = 200) | p-value | |
|---|---|---|---|
| Age, mean ± SD (y) | 65.7 ± 8.9 | 65.6 ± 9.2 | 0.63 |
| Men, % | 95.0 | 98.5 | 0.05 |
| Race, % | |||
| White | 35.5 | 34.5 | |
| Black | 58.5 | 59.0 | 0.44 |
| Other/Unknown | 6.0 | 6.5 | |
| Impatient Status, % | 48.5 | 41.5 | 0.15 |
| Medical History, % | |||
| Diabetes mellitus | 39.4 | 48.9 | 0.06 |
| Hypertension | 81.5 | 90.0 | 0.62 |
| CRI | 21.8 | 22.5 | 0.85 |
| Dyslipidemia | 81.4 | 84.5 | 0.41 |
| Hemodialysis | 5.0 | 3.0 | 0.30 |
| CAD | 12.2 | 19.0 | 0.43 |
| Smoker | |||
| Current | 41.9 | 39.6 | |
| Former | 33.7 | 45.6 | 0.25 |
| Never | 24.4 | 14.8 | |
| Myocardial Infarction | 27.0 | 27.8 | 0.86 |
| CHF | 33.7 | 37.0 | 0.49 |
| CVA | 12.2 | 16.0 | 0.27 |
| PVD | 22.5 | 15.08 | 0.06 |
| Previous CABG | 12.5 | 10.5 | 0.53 |
| Native Vessel Disease, % | |||
| No CAD | 43 | 34 | |
| 1-vessel | 19 | 22.5 | |
| 2-vessel | 16 | 19.5 | 0.47 |
| 3-vessel | 21.5 | 23.5 | |
| Left Main | 0.5 | 0.5 | |
| Ejection Fraction, % | 49 ± 20 | 47 ± 10 | 0.12 |
3.2
Procedural characteristics
The majority of procedures were elective (73.5% vs. 74.5%, p = 0.22), outpatient (51.5% vs. 58.5%, p = 0.16), and with the most common indication being chest pain (33.1% vs. 28.2%, p = 0.05), old vs. new laboratory, respectively. Almost a third of patients underwent PCI (27.5% vs. 28.5%, p = 0.82). ( Table 2 .) There were no statistically significant differences in radiation dose by individual operator (p = 0.84), number of catheters used (p = 0.36), number of stents placed (p = 0.25), cineangiography runs (p = 0.26), fluoroscopy times (p = 0.96), or contrast doses (p = 0.94) between the old and new laboratory, suggesting that the reduction in radiation dose was not attributable to any changes in these parameters ( Table 3 ). Additionally, there were no statistically significant differences in clinical practice between diagnostic and PCI procedures between the two time periods (p = 0.32).
| OLD LAB (n = 200) | NEW LAB (n = 200) | p-value | |
|---|---|---|---|
| PCI, % | 27.5 | 28.5 | 0.82 |
| Arterial Access | |||
| Right Radial, % | 75.5 | 80.0 | |
| Left Radial, % | 14.5 | 11.0 | |
| Femoral Access, % | 9.0 | 8.5 | 0.77 |
| Right Ulnar, % | 0.5 | 0.5 | |
| Right Brachial, % | 0.5 | 0.0 | |
| Indications for Procedure, % a | |||
| Acute Coronary Syndrome | 22.5 | 15.0 | |
| Ischemic Heart Disease | 18.5 | 17.0 | |
| Positive Functional Study | 32.0 | 27.0 | |
| Chest Pain | 45.5 | 37.5 | 0.048 |
| Valvular Heart Disease | 4.0 | 5.5 | |
| Heart Failure | 7.0 | 13.5 | |
| Cardiomyopathy | 7.5 | 13.5 | |
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
