Quantification of the salivary volume flow rate in the parotid duct using the time-spatial labeling inversion pulse (Time-SLIP) technique at MRI: A feasibility study.

BACKGROUND: We developed a method to quantify the volume flow rate (VFR) using the time-spatial labeling inversion pulse (Time-SLIP) technique to evaluate salivary function. PURPOSE/HYPOTHESIS: To investigate the accuracy of quantification of the salivary VFR using the Time-SLIP technique in phantoms and to examine the feasibility of its use in human subjects. STUDY TYPE: This was a prospective phantom and volunteer study. POPULATION/SUBJECTS/PHANTOM/SPECIMEN/ANIMAL MODEL: A phantom and 23 normal volunteers who fasted at least 2 hours study was performed. FIELD STRENGTH/SEQUENCE: Flow images of the phantom and the parotid duct of 23 volunteers were acquired on a 3T-MRI scanner using the Time-SLIP technique. ASSESSMENT: Hypothesizing that flow aggregates in the conducting duct, we measured the VFR on flow images. In the phantom study, the actual VFR (slow, medium, fast flow) was controlled by an automatic pump system and the measured VFR was compared with the actual VFR on flow images. In the human study we injected citric acid into the mouth of healthy volunteers to stimulate saliva secretion and recorded the VFR. STATISTICAL TESTS: As this study was a feasibility study, statistical tests were not performed. RESULTS: In the phantom study, the VFR at slow, medium, and fast flow was 5.7 ± 0.4 (SD), 8.4 ± 0.3, and 12.2 ± 1.1 mm3 /sec, respectively. The error between the measured and actual VFR values was 2.8-3.7%. Salivary flow in the parotid duct was visualized in 22 of the 23 volunteers. The mean VFR was 8760 mm3 /10 min. DATA CONCLUSION: When salivary flow was stimulated with citric acid in normal volunteers, the salivary VFR could be obtained using the Time-SLIP technique. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:928-935.

Evaluation of the degenerative pattern of PCL in osteoarthritis patients using UTE-T2 mapping.

BACKGROUND: The posterior cruciate ligament (PCL) is one of the essential stabilizers of the knee joint and it was demonstrated that its degenerative change related to the knee osteoarthritis (OA). We aimed to evaluate signal of the PCL in OA patients in comparison with healthy young and elderly volunteers using the ultra-short echo timeenhanced (UTE)-T2∗ mapping, and to validate these findings with histology. METHODS: Thirty asymptomatic volunteers, 13 young people (younger group) and 17 elderly people (elder group), and 27 patients who had undergone total knee arthroplasty (OA group) were enrolled in this study. UTE-T2∗ maps of PCL were obtained from all participants. The PCL was divided into proximal, middle, and distal parts and the UTET2∗ values obtained from each part were compared among the groups. In OA group, the sacrificed PCLs were evaluated histologically in each part corresponding to the part of UTE-T2∗ maps and compared. RESULTS: The UTE-T2∗ values in OA group were significantly higher than those in other groups except in distal part. In elder group, the UTE-T2∗ values were significantly higher than those in younger group only in the proximal part. Moreover, in OA group, the UTE-T2∗ values in proximal and middle parts were significantly higher than those in distal part. There was a moderate correlation between the UTE-T2∗ values and histological scores. CONCLUSIONS: The specific signal intensity pattern of the PCL in patients with OA was demonstrated using UTE-T2∗ mapping, and these findings were related to histological degenerated status of the PCL.