Coronary Ct Angiography Intern

Coronary CT Angiography Intern 柳復威

Udo Hoffmann, Maros Ferencik, Ricardo C. Cury, and Antonio J. Pena Coronary CT Angiography J Nucl Med May 1 2006 47: 797-806.

 64-slice

coronary CT angiography is highly accurate for the exclusion of significant coronary artery stenosis (>50% luminal narrowing)  with negative predictive values of 97%– 100%, in comparison with invasive selective coronary angiography.

INTRODUCTION  patient

preparation  image acquisition  evaluation techniques

patient preparation Image quality improved at low heart rates (<65 beats per minute) 1. the inspirational breath hold (-6beats/min) 2. oral ß-blocker (50—100mg oral or 5–20 mg i.v. metoprolol) 3. combination (-11beats/min) 4. short-acting nitroglycerin (selective coronary angiography )

Supine position Sedation

image acquisition A

low-energy topogram

determination of the adequate initiation of the coronary CTA image acquisition to ensure homogeneous contrast enhancement of the entire coronary artery tree

 Two

techniques:

1. the timing bolus technique 2. the bolus tracking technique  CT

volume dataset

The minimal equipment requirement for state-of-the-art coronary CTA is a 16-slice scanner. However, 40- or 64slice MDCT scanners are recommended, as they increasethe volume coverage and permit reduction of the scan time and the amount of contrast agent.

Radiation exposure  64-slice

MDCT:11~22mSv (ECG-controlled dose modulation is 7– 11mSv)  invasive selective coronary angiography: 2.5–5mSv,  nuclear perfusion imaging with SPECT: 15~20mSv

Image evaluation  multiplanar

reformatted (MPR) images

For the confirmation of pathologic findings in the long and short axes of the vessel.  sliding

thin-slab MIP (STS-MIP) images

enhance the visualization of coronary artery stenosis in a long-axis view of the vessel if narrowing is caused by noncalcified atherosclerotic plaque

Artifact  Motion

Artifacts ： occur at high rates and most

often in the midsegment of the right coronary artery

 Misalignment

and Slab Artifacts ： high

heart rates, heart rate variability, and the presence of irregular or ectopic heart beats (e.g. PVC)

 Blooming

Artifacts ： High-attenuation

structures, such as calcified plaques or stents, appear enlarged (or bloomed) because of partial volume averaging effects and obscure the adjacent coronary lumen, the main cause of false-positive results in coronary CTA because of overestimation of the degree of stenosis

FINDINGS AND POTENTIAL CLINICAL APPLICATIONS  Detection

Stenosis

of Significant Coronary Artery

moderate sensitivity (about 80%) and excellent specificity (about 90%)

 Detection

and Characterization of Coronary Atherosclerotic Plaque

1. detects calcified or mixed plaque with sensitivities and specificities above 90%. 2. the detection of noncalcified plaques, with sensitivities and specificities ranging from 60% to 85%, but has the potential to further stratify noncalcified plaque into fibrous plaque and lipid-rich plaque 3. smaller plaques ( ＜ 0.5 mm) are not detected

Potential Clinical Applications limitation  

Data based on single-center, multicenter trials and studies with intermediate-risk populations are warranted a very specific subset of symptomatic middle-aged white men who had a high prevalence of CAD

Other potential applications    

coronary CTA is to improve the triage and management of patients with acute chest pain. preoperative risk patency of stents placed in the left main coronary artery bypass patency

CONCLUSION  



Severe coronary calcification remains the major limiting factor in coronary CTA. The high negative predictive value of 64-slice MDCT, relative to invasive selective coronary angiography, can rule out the presence of hemodynamically significant CAD. Although data on clinical utility, cost, and costeffectiveness are not yet available, coronary CTA may improve the management of patients with an intermediate probability of CAD and patients with acute chest pain.

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