• Object ID: 00000018WIA30E66970GYZ
  • Topic ID: id_40021664 Version: 1.3
  • Date: May 10, 2022 4:18:53 AM

SAT Gap

Spatial saturation (often referred to as SAT) pulses suppress the signal from fat. SAT Gap allows you to adjust the gap between the SAT pulse and the excited slice to maximize Fat SAT effectiveness. By taking advantage of the chemical shift properties inherent to the SAT pulse and its relative position, the fat is suppressed.

Figure 1. The very narrow bandwidth and chemical shift between fat/water causes a spatial shift of the FAT SAT portion of the SAT pulse to cover the excited slice.
Table 1. SAT gap image legend
NumberDescription
1Fat SAT component
2Excited slice
3Single SAT pulse
4Water SAT component
5Desired flow
6Undesired flow
710 mm SAT gap
  • Increase the SAT Gap as the area to be scanned gets farther away from the heart. A 10 mm SAT Gap is typically used for carotid and iliac vessel exams and a 20 mm SAT Gap is typically used for distal femoral and popliteal vessel exams.
  • The effectiveness of the fat saturation is maximized at a 10 mm SAT gap. As the SAT Gap increases, the fat suppression becomes less effective.
  • In regions of highly pulsatile flow (e.g., popliteal, iliac), a narrow SAT Gap can result in pulsatile artifacts due to saturation of retrograde flow. To reduce the artifact, increase the SAT Gap, which moves the SAT pulse farther away from the slice. As the SAT Gap increases, the ghosting from retrograde flow decreases, but so do the fat suppression effects.