Purpose Velocity-selective arterial spin labeling (VSASL) has been proposed for renal perfusion imaging to mitigate planning challenges and effects of arterial transit time (ATT) uncertainties. In... Show morePurpose Velocity-selective arterial spin labeling (VSASL) has been proposed for renal perfusion imaging to mitigate planning challenges and effects of arterial transit time (ATT) uncertainties. In VSASL, label generation may shift in the vascular tree as a function of cutoff velocity. Here, we investigate label dynamics and especially the ATT of renal VSASL and compared it with a spatially selective pulsed arterial spin labeling technique, flow alternating inversion recovery (FAIR).Methods Arterial spin labeling data were acquired in 7 subjects, using free-breathing dual VSASL and FAIR with five postlabeling delays: 400, 800, 1200, 2000, and 2600 ms. The VSASL measurements were acquired with cutoff velocities of 5, 10, and 15 cm/s, with anterior-posterior velocity-encoding direction. Cortical perfusion-weighted signal, temporal SNR, quantified renal blood flow, and arterial transit time were reported.Results In contrast to FAIR, renal VSASL already showed fairly high signal at the earliest postlabeling delays, for all cutoff velocities. The highest VSASL signal and temporal SNR was obtained with a cutoff velocity of 10 cm/s at postlabeling delay = 800 ms, which was earlier than for FAIR at 1200 ms. Fitted ATT on VSASL was <= 0 ms, indicating ATT insensitivity, which was shorter than for FAIR (189 +/- 79 ms, P < .05). Finally, the average cortical renal blood flow measured with cutoff velocities of 5 cm/s (398 +/- 84 mL/min/100 g) and 10 cm/s (472 +/- 160 mL/min/100 g) were similar to renal blood flow measured with FAIR (441 +/- 84 mL/min/100 g) (P > .05) with good correlations on subject level.Conclusion Velocity-selective arterial spin labeling in the kidney reduces ATT sensitivity compared with the recommended pulsed arterial spin labeling method, as well as if cutoff velocity is increased to reduce spurious labeling due to motion. Thus, VSASL has potential as a method for time-efficient, single-time-point, free-breathing renal perfusion measurements, despite lower tSNR than FAIR. Show less
Purpose Arterial transit time uncertainties and challenges during planning are potential issues for renal perfusion measurement using spatially selective arterial spin labeling techniques. To... Show morePurpose Arterial transit time uncertainties and challenges during planning are potential issues for renal perfusion measurement using spatially selective arterial spin labeling techniques. To mitigate these potential issues, a spatially non-selective technique, such as velocity-selective arterial spin labeling (VSASL), could be an alternative. This article explores the influence of VSASL sequence parameters and respiratory induced motion on VS-label generation. Methods VSASL data were acquired in human subjects (n= 15), with both single and dual labeling, during paced-breathing, while essential sequence parameters were systematically varied; (1) cutoff velocity, (2) labeling gradient orientation and (3) post-labeling delay (PLD). Pseudo-continuous ASL was acquired as a spatially selective reference. In an additional free-breathing single VSASL experiment (n= 9) we investigated respiratory motion influence on VS-labeling. Absolute renal blood flow (RBF), perfusion weighted signal (PWS), and temporal signal-to-noise ratio (tSNR) were determined. Results (1) With decreasing cutoff velocity, tSNR and PWS increased. However, undesired tissue labeling occurred at low cutoff velocities (<= 5.4 cm/s). (2) Labeling gradient orientation had little effect on tSNR and PWS. (3) For single VSASL high signal appeared in the kidney pedicle at PLD < 800 ms, and tSNR and PWS decreased with increasing PLD. For dual VSASL, maximum tSNR occurred at PLD = 1200 ms. Average cortical RBF measured with dual VSASL (264 +/- 34 mL/min/100 g) at a cutoff velocity of 5.4 cm/s, and feet-head labeling was slightly lower than with pseudo-continuous ASL (283 +/- 55 mL/min/100 g). Conclusion With well-chosen sequence parameters, tissue labeling induced by respiratory motion can be minimized, allowing to obtain good quality RBF maps using planning-free labeling with dual VSASL. Show less
Escoffre, J.M.; Derieppe, M.; Lammertink, B.; Bos, C.; Moonen, C. 2017
