Clinical utility of cardiac computed tomography

Association between metabolic syndrome, smoking status and coronary artery calcification

Coronary artery calcification (CAC), an indicator of coronary artery stenosis, is an independent risk factor of ischemic heart disease. Smoking increases the risk of metabolic syndrome (MS) and cardiovascular disease. Almost no previous studies have evaluated the combined effect of MS and smoking status on CAC. Therefore, in this study we examined the relationships between CAC, MS, and smoking. This study included 775 adult males without histories of cardiovascular disease who visited the Health Promotion Center at the University Hospital in Gyeonggi-do, Republic of Korea from January 2, 2010 to December 31, 2012. All subjects were screened for CAC by multi-detector computed tomography (MDCT). CAC increased significantly with age and body mass index (BMI). Among MS components, abdominal obesity and elevated fasting blood glucose were correlated with CAC. After adjusting for age and BMI, MS was associated with a 1.46-fold increase in CAC (95% CI:1.02-2.09), abdominal obesity was associated with a 1.45-fold increase (95% CI:1.04-2.04), elevated fasting blood glucose was associated with a 2-fold increase (95% CI:1.36-2.94), and MS and smoking combined were associated with 2.44-fold increase in CAC. Thus, the combination of smoking and MS had a greater impact on CAC than any single factor alone. MS is correlated with an increased risk of CAC, and a combination of MS and smoking is associated with even greater risk. These findings can be used to prevent cardiovascular disease in adults.

Quantitative assessment of image quality in 64-slice-computed tomography of coronary arteries in subjects undergoing screening for coronary artery disease

Accurate and consistent visualization of the entire coronary system with high-grade imaging quality is crucial for routine applications of multi-detector-computed tomography (MDCT) coronary angiography. To determine the imaging quality of 64-slice-MDCT coronary angiography, we respectively explored the quantitative parameters of imaging quality in 105 consecutive subjects (71 men, 34 women; aged 58.66 +/- 10.62 years) who underwent 64-slice-MDCT coronary angiography to screen for coronary disease. The interobserver agreement for semi-quantitative image quality, visible length, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the coronary arteries was good. The SNR and CNR of the proximal segments of the coronary arteries were superior to that of the distal segments of coronary arteries (p < 0.001). The visible length of the stenosed right coronary artery was significantly shorter than that of the non-stenosed right coronary artery (p = 0.03). The SNR and CNR of the stenosed and non-stenosed coronary arteries revealed no significant difference (p > 0.05). Body weight and body mass index were inversely related to the SNR and CNR of the aorta (p < 0.001). In conclusion, 64-slice-MDCT coronary angiography can provide excellent imaging quality of coronary arteries in subjects undergoing screening for coronary disease, although the SNR and CNR were relatively low at the distal segments of coronary arteries.

Recent developments in wide-detector cardiac computed tomography

Multidetector computed tomography (MDCT) using 64 detectors is widely used for cardiac imaging in the clinical setting. Despite promising results, 64-slice MDCT has important limitations for cardiac applications related to detector coverage, which leads to longer scan times, image artifacts, increased radiation and the need for higher contrast doses. The advent of wide or full cardiac coverage with 256- or 320-slice MDCT provides important advantages that can potentially improve the status of these limitations and expand the utility of cardiac MDCT imaging beyond coronary imaging. Additionally, the combination of wide-detectors and multi-energy acquisitions offer interesting possibilities of improved coverage and temporal resolution that may improve plaque characterization as well as viability and perfusion imaging. In this review we will discuss the current status of wide-detector MDCT scanners and their advantages for clinical coronary and ventricular imaging. We will also review examples of wide detector coronary angiography imaging and discuss emerging complementary non-coronary applications that have been enabled by wide-detector MDCT imaging.

Initial evaluation of coronary images from 320-detector row computed tomography

PURPOSE

To evaluate image quality and contrast opacification from coronary images acquired from 320-detector row computed tomography (CT). Patient dose is estimated for prospective and retrospective ECG-gating; initial correlation between 320-slice CT and coronary catheterization is illustrated.

METHODS

Retrospective image evaluation from forty consecutive patients included subjective assessment of image quality and contrast opacification (80 ml iopamidol 370 mg I/ml followed by 40 ml saline). Region of interest opacification measurements at the ostium and at 2.5 mm diameter were used to determine the gradient of contrast opacification (defined as the proximal minus distal HU measurements) in coronary arteries imaged in a single heartbeat. Estimated effective dose was compared for prospective versus retrospective ECG-gating, two body mass index categories (30 kg/m(2) cutoff), and single versus two heartbeat acquisition. When available, CT findings were correlated with those from coronary catheterization.

RESULTS

Over 89% of arterial segments (15 segment model) had excellent image quality. The most common reason for image degradation was cardiac motion. One segment in one patient was considered unevaluable. Contrast opacification was almost universally considered excellent. The mean Hounsfield units (HU) was greater than 350; the coronary contrast opacification gradient was 30-50 HU. Patient doses were greater for retrospective ECG-gating, larger patients, and those imaged with two heartbeats. For the most common (n=25) protocol (120 kV, 400 mA, prospective ECG-gating, 60-100% phase window, 16 cm craniocaudal coverage, single heartbeat), the mean dose was 6.8+/-1.4 mSv. All CT findings were confirmed in the four patients who underwent coronary catheterization.

CONCLUSION

Initial 320-detector row coronary CT images have consistently excellent quality and iodinated contrast opacification. These patients were scanned with conservative protocols with respect to iodine load, prospective ECG-gating phase window, and craniocaudal coverage. Future work will focus on lowering contrast and radiation dose while maintaining image quality.