Quick Overview

The slice overlap artifact is another name for crosstalk artifact. If slices of multislice acquisitions are overlapping, the spinning nuclei belonging to more than one slice getting multiple times saturated, which leads to signal loss in this areas.

This problem occurs often in cervical or lumbar spine MRI, when scanning each disc with multi angle oblique technique. If prevention of overlapping is not possible, try to position the saturated region posterior to the spinal canal, outside the region of interest.

See also Crosstalk (Crosstalk), and Multiple Slice Imaging.

(3D MRA) The 3D angiography technique can be applied to focus on fast flowing (arterial) blood and to visualize small tortuous vessels. 3D TOF images are less sensitive to turbulent flow artifacts. The advantage of this approach is that the signal, acquired from the entire volume has an increased signal to noise ratio. Slices are defined by a second phase encoded axis, which divides the volume into 'partitions'. 3D TOF MRA is acquired with 3D FT slabs or multiple overlapping thin 3D FT slabs (MOTSA) depending on the coverage required and the range of flow-velocities under examination.
Such 3D techniques can provide equal spatial resolution along all three axes, i.e. be 'isotropic', or the partition thickness can be greater or less than the in plane spatial resolution in which case can be said to be 'anisotropic'. The circle of Willis, anatomy as well as its fast arterial flow, lends itself well to both 3D TOF and 2D or 3D phase contrast angiography.

(M2DMRA) The M2D technique can be used to image both fast and slow flow, due to good refreshment of flowing blood. Using overlapping slices can reduce staircase artifacts, which might be seen in projection of the slice thickness.

See also Time of Flight Angiography.

(MOTSA) This technique combines the best features of 2D time of flight angiography (2D TOF) and 3D TOF MRA. The MOTSA technique consists of multiple 2 cm thick 3D TOF slabs (which minimize saturation effects for through plane flow) combine to provide unlimited coverage similar to multiple 2D TOF slices. High resolution imaging of the carotid arteries is possible when image quality is of greater concern than acquisition time. Images with 1 mm (or less) spatial resolution in all three planes are required. The slabs typically overlap 25-40 to minimize the venetian blind artifact venetian blind artifact due to minimal saturation effects. MOTSA is an useful technique for the evaluation of vertebrobasilar ischemia and aneurysm scanning from the foramen magnum through the circle of Willis.

Quick Overview

Staircase artifacts might be seen in projection of the slice thickness in case of MIP or MPR reconstructions.

Use overlapping slices to reduce this artifact by changing the slice gap to a negative value. In most cases, a negative value of 20-30% is sufficient.