Dual-source CT coronary angiography in patients with atrial fibrillation: Comparison with single-source CT
Introduction
Recent advances in multi-slice computed tomography (MSCT) technology have improved the quality of non-invasive coronary artery imaging. Investigators reported improved results in visualization of the coronary arteries and diagnosis of coronary artery disease in a selected population of patients [1], [2], [3], [4], [5], [6], [7]. One limitation of MSCT coronary angiography is that irregular heart rates prevent adequate visualization and evaluation of the coronary arteries, and patients with atrial fibrillation (AF) are usually excluded from scanning [1], [4], [6], [8], [9], [10].
Atrial fibrillation (AF) is the most common arrhythmia in elderly persons worldwide [11]. The prevalence of AF increases with age. In the Framingham study it’s prevalence doubles with each advancing decade of age, from 2% at age 60–69 years to almost 9% at age 80–89 years [12]. The most frequently associated cardiac conditions are hypertension (28.9%), atherosclerotic cardiovascular disease (24.7%) and rheumatic heart disease (17.5%) [13]. AF is a significant marker for both a higher incidence of stroke and death [14]. Non-rheumatic AF is associated with approximately a three to fivefold increase in risk for stroke after adjusting for other risk factors [15].
The recently introduced dual-source CT (DSCT) scanner is characterized by two x-ray tubes and two corresponding detectors mounted onto the rotating gantry with an angular offset of 90° [16] The new scanner system offers a high temporal resolution of 83 ms in a mono-segment reconstruction mode, which is a major difference from single-source CT (SSCT) systems that rely on multi-segment reconstruction techniques to improve temporal resolution [17]. However, the latter approach relies on a complete periodicity of heart motion, limiting its use in patients with variable heart rates.
A first feasibility study has shown promising results with DSCT in AF patients for coronary artery imaging [18]. Since AF patients are now included for CTA, it is the intend of the authors to assess the difference between SSCT and DSCT to find out if the differences in exclusion and inclusion are reasonable, as well as to find out what special implications it has to scan AF patients and to give a first hint what the best approach is to scan such patients, since there has been not much experience with AF patients due to the former exclusion. In addition to that, the purpose of this study is to explore the impact of patients’ heart rate (HR) on image quality (IQ) and reconstruction timing, so to find out what time window and HR are most suitable for these patients.
Section snippets
Patients
Between January 2007 and January 2008, 30 consecutive patients (11 male, 19 female; mean age 69.0 ± 9.2 years; age range 45–83 years) with suspected coronary artery disease and permanent AF underwent non-invasive DSCT coronary angiography. Exclusion criteria were allergic to iodine-containing contrast medium, renal insufficiency (serum creatinine > 1.5 mg/dl), pregnancy, respiratory impairment, unstable clinical status, marked heart failure, and previous bypass surgery. Patients were divided into
Results
The DSCT protocol was well tolerated by all patients, and all were able to hold their breath during data acquisition. IQ of the DSCT data was significantly better than that of the virtual SSCT data (mean score 1.33 ± 0.61 vs. 1.80 ± 1.02; Wilcoxon test Z = −8.755, P = 0.000). Of a total of 436 coronary segments that were present in our patients, 98.6% (430/436) of the segments shown in DSCT were diagnostic, compared with 89.9% (392/436) of the segments in virtual SSCT, χ2 = 32.595, P = 0.000 (see Table 1;
Discussion
Irregular heart rates are known as limitations of CT coronary angiography [20]. This is because at irregular heart rates, the temporal variability of the diastolic phase is increased between contiguous heart cycles, which create motion artifacts due to the inaccurate location of temporal windows, the lack of data, or both. This demands high temporal resolution of the CT scanner for accurate image reconstructions. Main purpose of this study is to evaluate the recent development of not excluding
Conclusion
In summary, due to its high temporal resolution, DSCT provides images of full diagnostic image quality in patients with AF, which otherwise would be excluded from CT examinations. The number of assessable segments for DSCT is still somewhat less than in non-AF patients, but in opposition to SSCT still valid for routine diagnostic imaging. Patients’ HR had impact on IQ and reconstruction timing.
Conflict of the interest statement
None.
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2013, Journal of Cardiovascular Computed TomographyCitation Excerpt :However, the evaluation that used all 4 reconstruction phases resulted in significantly higher number of diagnostic studies than the evaluation that used 3 or fewer reconstruction phases. The mean effective radiation dose was 6.5 ± 2.4 mSv (range, 3.0–10.5 mSv) in this study, notably lower than previous studies that evaluated radiation doses in coronary CT angiography,26 particularly for patients with AF in which the lowest reported dose was 8.7 ± 4.6 mSv (range, 6.3–13.5 mSv).8–11,20,21,27 Of additional note, given that examinations in the present study were performed for pulmonary vein evaluation, a longer scan range was routinely used to ensure capture of the superior pulmonary veins (average scan length, 17–21 cm); thus, dedicated coronary artery CT protocols that limit the scan range to the heart (average scan length, 12–15 cm) should result in even lower radiation doses.16,28
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Impact of heart rate and rhythm on radiation exposure in prospectively ECG triggered computed tomography
2012, European Journal of RadiologyCitation Excerpt :In addition to radiation exposure and scan time, image quality is important in evaluating the scanner performance for different types of arrhythmias. Nevertheless the impact on image quality can be assessed if the applied ECG-synchronized image acquisition was performed during the mid- or end- diastolic phase when taking into account the data that were published for retrospective ECG synchronized cardiac CT in patients with arrhythmias [10,17,18]. In prospectively ECG triggered CT, changes in heart rate and rhythm may have a significant impact on radiation exposure.
Coronary computed tomography angiography during arrhythmia: Radiation dose reduction with prospectively ECG-triggered axial and retrospectively ECG-gated helical 128-slice dual-source CT
2012, Journal of Cardiovascular Computed TomographyCitation Excerpt :Retrospective data acquisition acquires highly redundant z-axis coverage, thereby allowing preserved image quality at the expense of significantly higher radiation. Several studies have validated the diagnostic accuracy of retrospectively ECG-gated helical dual-source coronary CTA in patients with arrhythmia.7–10 However, the use of prospectively ECG-triggered axial acquisition with the use of dual-source CT (DSCT) in patients with arrhythmia has not been investigated.
256-slice CT coronary angiography in atrial fibrillation: The impact of mean heart rate and heart rate variability on image quality
2011, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated EquipmentQuality of coronary arterial 320-slice computed tomography images in subjects with chronic atrial fibrillation compared with normal sinus rhythm
2011, International Journal of Cardiology
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