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Echo-planar imaging is able to generate images in less than 80 ms; however, images have poor quality since they have an intrinsic poor signal-to-noise ratio. Filtering techniques such as the Fourier transform can be applied to enhance the image quality. Another natural tool is the so-called wavelet transform, this is an analytical tool capable of generating an analysis in time and frequency simultaneously. The two-dimensional wavelet transform is applied to blood flow maps produced with a flow encoding echo-planar imaging sequence to improve the image signal-to-noise ratio. Enhanced flow maps and contour maps are presented. The wavelet transform shows that flow magnetic resonance images can be improved without detriment of the spatial resolution and unmasking the relevant anatomical and physiological information.

The coil separation of phased-array coils is an important issue if a wide area of interest is to be imaged. An equivalent circuit of two circular-shaped coils was used to compute the optimal distance in a two phased-array coil. This circuit included the mutual inductance of two circular coils. An expression for the mutual inductance was derived and the resulting values included in the circuit. With all these elements an equivalent circuit of two overlapped circular coils was built to simulate a phased-array coil. To find a solution to this circuit, specifically written programmes in Spice Opus Light were used. Optimal separations were calculated from separation-vs-attenuation for different coil radii. Results compare very well with those reported in the literature.