Examination of sensitivity distribution characteristics depending on the position of the array coil

The opposite-type array coil is useful because it is easy to attach in magnetic resonance imaging (MRI) examinations away from the center area. It is not well understood that sensitivity characteristics change when coil elements shift. We studied the effect when both coil elements (17 x 14 cm) shifted to the opposite side; we examined a hand including the wrist. The signal-to-noise ratio (SNR) of the axial image by the subtraction map declined 2.6%/cm. The profile of the sagittal and coronal view by the SNR map shows that the greater the distance between the center of the upper and lower coil elements, the lower the SNR is on the center of the examination area and the higher the SNR is on the edge of the examination area. In removing 10 cm from each of the coil elements, the profile became wide and linear. In the case of removing more than 7.5 cm, the wide area of uniformity was shown in the center of the images of sensitivity distribution. Uniformity by the segment method increased more than 10 cm. Use of the opposite-type array coil when shifting both coil elements to the opposite side may extend the examination area. (author)