Multi-delay pseudo-continuous arterial spin labeling to measure blood flow in the head and neck.

Perfusion MRI is promising for the assessment, prediction, and monitoring of radiation toxicity in organs at risk in head and neck cancer. Arterial spin labeling (ASL) may be an attractive alternative for conventional perfusion MRI, that does not require administration of contrast agents. However, currently, little is known about the characteristics and performance of ASL in healthy tissues in the head and neck region. Therefore, the purpose of this study was to optimize and evaluate multi-delay pseudo-continuous ASL (pCASL) for the head and neck region and to explore nominal values and measurement repeatability for the blood flow (BF), and transit time and T1 values needed for BF quantification in healthy tissues. Twenty healthy volunteers underwent a scan session containing 4 repeats of multi-delay pCASL (Post-label delays (PLDs): 1000, 1632, 2479 ms). ROIs were defined in the parotid glands, submandibular glands, tonsils, and cerebellum (as reference). Nominal values of BF were calculated as the average over 4 repeats per volunteer. The repeatability coefficient and within subject coefficient of repeatability (wCV) of BF were calculated. The effect of T1 (map versus cohort average) and transit time correction on BF was investigated. The mean BF (±SE) was 55.7±3.1 ml/100 g/min for the parotid glands, 41.2±2.8 ml/100 g/min for the submandibular glands, and 32.3±2.2 ml/100 g/min for the tonsils. The best repeatability was found in the parotid glands (wCV = 13.3%-16.1%), followed by the submandibular glands and tonsils (wCV=20.0-24.6%). On average the effect of T1 and transit time correction on BF was limited, although substantial bias occurred in individual acquisitions. In conclusion, we demonstrated the feasibility of BF measurements in the head and neck region using multi-delay pCASL and reported on nominal BF values, BF repeatability, the effect of T1, and transit time in various tissues in the head and neck region.