A series of four sets of images (13 15 slices for each set) were obtained using echo times (TEs) of 20, 40, 60, and 80 ms and a repetition time (TR) of 3,000 ms. The images were produced using 32 mm field of view (FOV), 1-mm slice thickness, 256 × 256 matrix, and number of excitation (NEX) of 2. MR images were used to determine the tumor size and detect signs of necrosis.
AEC uses an adaptive filter identifying the echo path to obtain an echo replica that then is subtracted from the microphone signal [1 7].
Blood oxygen level dependent (BOLD) contrast was obtained with gradient echo echo-planar imaging (EPI) sequence (TR, 1000; TE, 30; flip angle, 90°; field of view, 24×24 cmatrixtrix size, 80×80).
The relations between the characteristics of the obtained impact-echo signal and the mechanical properties of concrete subjected to high temperature were presented as regression curves.
The resting-state functional images were obtained with echo-planar imaging (EPI) (30 continuous slices with a slice thickness = 5 mm, TR = 2000 ms, TE = 30 ms, flip angle = 90°, FOV = 240 mm × 240 mm, matrix = 64 × 64).
Functional images were acquired with a Magnetom Vision MRI scanner (Siemens, Erlangen, Germany) operating at 3T. Blood oxygenation level dependent (BOLD) contrast was obtained using echo-planar T2* weighted imaging (EPI).
In short, the first 30 time points were used to calculate the temporal signal-to-noise ratio for every voxel, needed to obtain the echo specific weighting factors for the echo combination.
For the human being detection, we select the signals from the 200th echo to the 300th echo and obtain one test echo signal from the average of every ten echoes.
Blood oxygenation level dependent (BOLD) contrast was obtained with gradient-echo echo-planar imaging (EPI) sequence (TR = 3000 ms, TE = 55/35, flip angle = 90°, field of view 24×24 cm2).
In all cases students were able to obtain adequate echo windows.
Therefore, a method to reduce the interchannel coherence must be introduced in order to obtain good echo cancelation performance providing the slightest alteration of the sound perception [1, 13].
