OBJECT: While pseudo-continuous arterial spin labeling (pCASL) is a promising imaging technique to visualize cerebral blood flow, it is also (acoustically) very loud during labeling. In this paper, we reduced the labeling loudness on our scanner by increasing the interval between the RF pulses from the literature standard of 1.0 ms. We also propose recommendations to reduce the loudness on scanners of the same type at other sites.
MATERIALS AND METHODS: First, the sound pressure level (SPL) was both simulated and measured as a function of the labeling interval (1.0-1.8 ms) and longitudinal position in the scanner (-10 to +10 cm, relative to isocenter). Subsequently, we selected the labeling interval with the lowest overall SPL for the "SPL-optimized" pCASL sequence. Nine volunteers were scanned to compare raw signal intensity, temporal signal-to-noise ratio (tSNR) and labeling efficiency between the SPL-optimized and the standard PCASL sequence.
RESULTS: Sound pressure level measurements on our scanner showed that loudness was reduced by 6.5 dB at the approximate location of the ear by adjusting the labeling interval to 1.4 ms. Furthermore, image quality was not affected, since no significant differences in signal intensity, tSNR and labeling efficiency were observed.
CONCLUSION: By increasing the pCASL labeling interval, acoustic noise in the pCASL sequence was reduced with 6.5 dB, while image quality was preserved.