Potential pitfalls of functional MRI using conventional gradient‐recalled echo techniques

The conventional gradient‐recalled echo technique, FLASH, has widely been used for functional MRI. FLASH results at 4 T with short TEs of 10–20 ms mimic those at 1.5 T with TEs of 25–50 ms or longer. Under these conditions, large venous vessels dominate the activated area; however, the use of longer TEs at 4 T reveals activation in gray matter areas as well as large vessels. Inflow effects of large vessels can be greatly reduced with centric‐reordering of phase‐encoding steps and inter‐image delay. Finger and toe movement paradigms show that functional activation maps are consistent with classical somatotopic maps, and are specific to the tasks. Navigator‐based motion correction generates functional maps with larger activation areas by reducing physiological noise.