Acquiring a k-space line

[AndrewBworth]

The intensity of the different parts of k-space vary a great deal. So the parts of k-space that have the greatest intensity, make the largest contribution to the overall contrast. In general, the center of k-space contains most of the information about the INTENSITY of the information in the picture, while the whole of the k-space determines it's distribution. Fine details can't be discerned until they separate in k-space - so the outer edges of k-space contain the information about finer details.
The general intensity of a point in k-space is given by a function called a sinc function, sin(x)/(x), with the center of k-space given the value kx, ky = 0, where the value is greatest. (For 2D, the envelope of k-space would be given by a sinc function on the x dimension multiplied by a sinc function on the y, for 3D, three sinc functions). You'll see this function drops off quite rapidly from 0.
Sometimes a method known as keyhole imaging is done, where an entire image is acquired, but then only the center of the k-space is replaced - this is useful for dynamic imaging.