Conclusion

Many quantitative analysis techniques have been developed for more accurate evaluation of cardiac wall motion and ventricular function from dynamic cardiac images. Most conventional techniques are usually based on global or regional evaluation of differences between end-diastolic and end-systolic frames. Such methods do not depict differences in timing of wall motion along different segments of the ventricle. Several studies have already demonstrated the importance of temporal evaluation of regional myocardial wall motion and the usefulness of the assessment of alterations in contraction and relaxation patterns and rates. The so-called "phase analysis" technique based on a pixel-by-pixel measurement of the phase and amplitude of the fundamental Fourier frequency in the time-activity curve of each pixel is commonly used for the evaluation of regional asynchrony of wall motion from radionuclide angiograms [47,66]. This technique has been extensively evaluated in clinical studies and was found to be very sensitive for the detection of ischemic alterations in regional wall motion [67]. It was found to be adequate for the detection of subtle abnormalities in the diastolic phase that usually occur in stress-induced ischemia. It is therefore often used to differentiate ischemic from nonischemic wall motion alterations during exercise radionuclide ventriculograms.

Similar techniques were successfully transposed to X-ray contrast angiograms and dynamic MRI imaging modalities [68].

Accurate edge detection of ventricular cavities remains a critical step for any quantitative evaluation of ventricular function. Most techniques reported in the literature based on differentiation of cardiac structures using differences of gray levels suffer from inaccuracies in edge detection when significant changes in tissue intensity occur. New image processing techniques and refined image acquisition systems are constantly improving the ability to automate the task of outlining anatomical structures for quantitative analysis of cardiac function and ventricular wall motion. Furthermore, the ability to analyze the intracardiac blood flow using Doppler echocardiography or flow-sensitive cine-MRI sequences permits a more comprehensive evaluation of the hemodynamic function of the heart.

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