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Homework answers / question archive / Write a 2500 word paper answering; Each read gradient-echo corresponds to one k-space with the positive and negative angles changing the direction of the read line

Write a 2500 word paper answering; Each read gradient-echo corresponds to one k-space with the positive and negative angles changing the direction of the read line

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Write a 2500 word paper answering; Each read gradient-echo corresponds to one k-space with the positive and negative angles changing the direction of the read line. The changing direction of the line read results in a phase ‘blip’ causing a shift in Ky, and this method of phase encoding is referred to as blip EPI.

Characteristics of EPI:EPI has three distinct characteristics in terms of speed, the variety of contrast, and flexibility in available resolution for small imaging structures like the pituitary gland. EPI offers higher rates (6 to 10 times) of imaging of short temporal events under motion. It provides high image quality by collecting more averages with increased slice frequency per TR. The signal to noise ratio of the images is high, and the resolution is also high. Its usefulness depends on the MR system used, and the efficiency is determined by the ability to perform 1282 or 2562 in a short time to avoid sizeable off-resonance artifacts. It means that high-quality images of moving patients can be obtained by using the speed of EPI.

A variety of tissue contrasts (T1, T2, and T2*) are allowed by EPI for image acquisition, and small structures are imaged using the flexibility in resolution where the field view can be reduced, the echo train length can be increased, or geometric distortions can be reduced to increase the resolution. Also, just half of the image data can be gathered that can be further synthesized through conjugation to obtain the remaining data. In contrast, flexibility can be used to produce an image similar in standards to that of an SE image with the same TE and TR by using an excitation pulse in the front part followed by an 1800 pulse (T2* dephasing) to create the first echo.

EPI compared to conventional fast imaging methods:EPI uses the Blip EP method of phase encoding, where each phase blip between echoes causes a shift in the k-spaceline. The gradient contributes to each k-space line refocused echo and is either read positively or negatively through the gradient change. The quickly switching angles that produce the echo train are responsible for the odd and even echoes. When the lines are read, the reversed read lines are reordered before constructing the image. Also, the rf pulse is not used to create multiple echoes as in conventional FSE.

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