# HW7_solutions - ECE 380 Biomedical Imaging Spring 2010...

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1 ECE 380 Biomedical Imaging Spring 2010 Homework 7 Solutions 1) The hydrogen nuclei in the body are found mainly in fat and water. The T 2 value of fat was measured to be 100 ms and that of water to be 500 ms. In a spin-echo experiment, calculate the delay between the 90 o pulse and the 180 o that maximizes the difference in signal intensities between the fat and water. (30 points) 12 2 2 2 2 // 1 / 2 2 2 2 / / / ( , , ) ( , )(1 ) As TR and T are constant in this problem, we have By maximizing the distance between T of water (T ) and T of fat (T ) ( ) =0 () W F TR T TE T TE T WF TE T TE T TE T I x y z x y e e Ie d ee d TE e   2 2 2 / 22 / 2 / 2 /100 /500 oo 0 100 500 By solving for TE we have TE=201.125 ms and the distance between 90 and 180 the pulses would be TE/2=100.56 ms W F F W TE T FW TE T F TE T W TE TE e TT T e T e e e  2) Suppose that two samples are located in a magnetic field at y=0 cm and y=10 cm. Calculate the phase acquired by the sample located at y=10 cm ? Assume that a 1 G/cm phase encoding gradient is applied in the +y-direction for 20 ms. (15 points)

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HW7_solutions - ECE 380 Biomedical Imaging Spring 2010...

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