"If the slices obtained at different disk spaces are not parallel, they may overlap. If two levels are acquired at the same time, e.g. L4-L5 and L5-S1, the level acquired second will include spins that have already been saturated. This causes a horizontal band of signal loss crossing the image, usually most pronounced posteriorly. The dark horizontal band at the bottom of the following axial image through the lumbar spine demonstrates this artifact."
"If the slices obtained at different disk spaces are not parallel, they may overlap. If two levels are acquired at the same time, e.g. L4-L5 and L5-S1, the level acquired second will include spins that have already been saturated. This causes a horizontal band of signal loss crossing the image, usually most pronounced posteriorly. The dark horizontal band at the bottom of the following axial image through the lumbar spine demonstrates this artifact."
"The slice-overlap artifact, also known as cross-talk artifact, is a type of MRI artifact, namely, the loss of signal seen in an image from a multi-angle, multi-slice acquisition, as is obtained commonly in the lumbar spine. It should not be confused with cross excitation which although similar in causation, is not due to angled images."