Regional perfusion imaging using pTILT

Purpose To demonstrate the feasibility that the pseudo-continuous transfer insensitive labeling technique (pTILT) sequence can be modified to achieve regional perfusion imaging by either vessel-encoded or vessel-selective pTILT, similar to the regional perfusion imaging sequences using pseudo-continuous arterial spin labeling (pCASL). Materials and Methods Static phantom experiments were carried out to investigate the selectivity and efficiency of region-specific labeling by pTILT. The ability of the modified pTILT sequences to separate perfusion territories was also examined at two levels of the arterial tree on four healthy subjects: (i) the left and right internal carotid arteries (ICAs) and (ii) individual vascular territories of arteries above the circle of Willis (anterior cerebral artery [ACA], left and right middle cerebral arteries [MCAs]). Results In the phantom study, compared with non-region-specific pTILT, a labeling efficiency of 0.92 and 0.88 was measured at the target vessels using vessel-encoded and vessel-selective pTILT, respectively. In human studies, the perfusion territories of ACA, left and right MCA branches with estimated CBF of 74.5 ± 26.1, 65.9 ± 7.2, and 72.3 ± 14.5 mL/100 g/min, respectively, as well as more general left/right end territories (76.8 ± 12.7 and 72.8 ± 7.2 mL/100 g/min), were clearly delineated by the modified pTILT sequences for regional perfusion imaging. Conclusion Two regional perfusion imaging modules (vessel-encoded and vessel-selective) used in pCASL can also be adapted into the pTILT sequence, and our results confirmed that the region-specific pTILT sequence is capable of regional perfusion imaging to separate perfusion territories of major cerebral arteries.