Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Saturated fat and cardiovascular disease wikipedia , lookup
Electrocardiography wikipedia , lookup
Echocardiography wikipedia , lookup
Quantium Medical Cardiac Output wikipedia , lookup
Cardiac surgery wikipedia , lookup
Dextro-Transposition of the great arteries wikipedia , lookup
History of invasive and interventional cardiology wikipedia , lookup
Pitfalls in 16Detector Row CT of the Coronary Arteries Presented by Intern 許碩修 Introduction • Conventional coronary angiography requires admission and cause discomfort • Current 16-detector row CT enables visualization of the coronary arteries by contrast enhancement • The pitfalls of CT coronary angiography are closely related to limiting factors and postprocessing methods Techniques • Retrospective ECG-gated scans with 16detector-row CT (0.42-second rotation time) • 12 inner detector rings (standard protocol: pitch=0.31; HR <50 bpm: pitch=0.29) • 100 ml of iopamidol (300 or 370 mg/ml of iodine) followed by 40 ml of saline with power injector at 4 ml/sec Techniques (2) • Triggering scanning on 100-HU attenuation in the ascending aorta • Section thickness of 0.75 mm with 0.5-mm overlap, 18-cm field of view, acquisition matrix of 512*512 • Isotropic voxel of 0.4*0.4*0.6 mm Preparation • HR >65 bpm: 40-60 mg of single oral metoprolol 1 hour before examination • Sublingual nitroglycerin (0.3 mg) to dilate the coronary arteries • HR <68 bpm: temporal resolution of 210 msec • HR >68 bpm: multiplanar reformation was performed, resultant temporal resolution is 105-210 msec Performance • Initially, the reformation window starts at 400 msec prior to the next R wave • If motion artifacts exist, repeat with offset 20 ms toward the beginning and end of the cardiac cycle – Until no artifacts or 10 data sets are gained Requirements • Consistency of data sets as well as motion-free images of the heart can be easily evaluated by MPR • Various image degradation factors cause – Nonassessable segments – Pseudostenosis Artifacts at Coronary CT Angiography • • • • • • • • Pulsation Rhythm disorders Respiratory issues Partial volume averaging effect High-attenuation entities Inappropriate scan pitch Contrast material enhancement Patient body habitus Pulsation • Most common and important factors • Motion-free imaging requires a temporal resolution of 50 msec • Less movement during the filling phase is needed for the least amount of blurring • The RCA and LCX are closer to the atria than LAD, thus they are more affected by atrial contraction Pulsation (2) • Multiphase reformation and the selection of optimal reformation windows are required for different coronary arteries • The proportion of diastole depends on the heart rate • Nonexistent vascular discontinuity or wall irregularity may appear 400 msec prior to next R Apparent section gaps 200 msec prior to next R Pseudostenosis Rhythm Disorders • Reliable imaging only in patients with normal sinus rhythm • Slightly different cardiac cycle leads to a section gap and pseudostenosis • The association of section gaps and heart rate increase is recognized Rhythm Disorders (2) • Apparent multiple section gaps are called banding artifacts • The most frequent causes are arrhythmia, no breath, and alterations in heart rate • Long acquisition time is associated with increased frequency of alteration in heart rate • In a patient with Af Respiratory Issues • Breath-hold instructions and patient cooperation are essential • Banding artifacts due to alterations in heart rate or by incomplete breath holding is hard to tell apart Partial Volume Averaging Effect • The assessability of vessel diameter depends on spatial resolution along the z axis (greater than 1.5 mm) • The blooming effect on the coronary lumen due to calcification or intracoronary stent • The plaque attenuation depends on imaging plane or section thickness Streak Artifacts from High-Attenuation Entities • Streak artifacts are generated by highattenuation entities, high-contrast interfaces and cardiac motion • Highly concentrated contrast medium in the SVC can interfere the RCA – Decrease with appropriate scan timing and administration of saline Streak Artifacts from High-Attenuation Entities • Dense and extensive calcification causes streak artifacts and partial volume averaging effect • The artifacts depend largely on the stent material – Stent of gold cause the most severe artifacts Inappropriate Scan Pitch • The pitch is limited by patient’s R-R interval – Standard is used with HR >50 bpm – Low pitch is needed to completely cover the coronary arteries with long R-R interval • Shortage of data with unpredictable brachycardia may exist • Blurred image and pseudostenosis are found Contrast Material Enhancement • Excellent enhancement of the coronary arteries and minimal of the coronary veins by – Autodetection of contrast material – Adequate amount and rate of injection Patient Body Habitus • Image quality in very obese patients is poor due to a low signal-to-noise ratio – A section thickness of 1 mm instead of 0.75 mm is applied • To maintain the balance, it is necessary to increase the radiation dose or the section thickness Postprocessing Pitfalls • The potimal setting should be strictly applied at volume-rendered images Postprocessing Pitfalls • Postprocessed images such as VR and MIP do not show inner lumina • MPR and curved planar reformation can demonstrate portions of the inner lumen • Virtual endoscopy allows evaluation of the lumina from the inside but cannot provide quantitative information Anatomy of the Coronary Arteries • Knowledge of the anatomy of the coronary arteries is required for correct interpretation • The left main coronary artery divides into the LAD and the circumflex artery • In about 10% of cases, LCX continues as the posterior descending artery, which is referred to as left dominant Anatomy of the Coronary Arteries • Myocardial bridges may simulate stenosis of the proximal LAD artery when images are reformed during systole • In rare instances, a coronary artery may have an anomalous origin and course Improving the Diagnostic Accuracy • Excellent structural consistency and no motion artifacts • The reformation window settings and the effects of the heart rate has been focused • Most important limiting factors – Heavy calcification – Motion artifacts – A vessel lumen diameter less than 1.5 mm Conclusion • The advantages and disadvantages of each post-processing method should be clarified • Familiarity with these common pitfalls, coupled with the knowledge of normal anatomy and anatomical variant Conclusion • Optimal work flow should be determined Thanks for Your Attention!