CSF Pulsation Artifacts on ADC Maps Obtained with Readout-segmented EPI.

PURPOSE: Diffusion-weighted imaging (DWI) using readout-segmented EPI (rs-EPI) can minimize distortion and blurring artifacts; however, we sometimes encounter cerebrospinal fluid (CSF) pulsation artifacts on apparent diffusion coefficient (ADC) maps, especially when the number of readout segments (NRS) is increased. The purpose of this study was to evaluate the effect of the NRS on the CSF pulsation artifacts in the ADC maps of healthy volunteers. METHODS: In 10 healthy volunteers, we obtained DWI from rs-EPI with a b-value of 0 and 1000 s/mm2. The NRS was set to 5, 7, or 9. An ADC map was generated from the trace image and the b = 0 image. Each scan was performed twice. A circular region of interest (ROI) was drawn in the pons and bilateral thalami. The standard deviation (SD) of the ROI was measured to assess the artifacts. Bilateral SD values were averaged for the ROIs in the thalami. The SD values from two successive scans of each NRS were averaged for the pons and thalami, respectively. For the qualitative analysis, the CSF pulsation artifacts on each ADC map were graded by two observers independently as 0, no artifact; 1, mild artifact; 2, moderate artifact; or 3, severe artifact. RESULTS: In the quantitative analysis, the SD values tend to increase with the increasing of NRS in both thalami and pons; however, the difference in the SD values from each NRS did not reach a statistically significant level. In the qualitative analysis, there was a statistically significant difference in the scores between 5 and 9 segments and between 7 and 9 segments with both the observers, respectively (P < 0.05). CONCLUSION: The CSF pulsation artifacts on ADC maps obtained with rs-EPI are affected by the NRS.

Simple Estimation of the Endolymphatic Volume Ratio after Intravenous Administration of a Single-dose of Gadolinium Contrast.

PURPOSE: To evaluate the feasibility of a simple estimation for the endolymphatic volume ratio (endolymph volume/total lymph volume = %ELvolume) from an area ratio obtained from only one slice (%EL1slice) or from three slices (%EL3slices). The %ELvolume, calculated from a time-consuming measurement on all magnetic resonance (MR) slices, was compared to the %EL1slice and the %EL3slices. METHODS: In 40 ears of 20 patients with a clinical suspicion of endolymphatic hydrops, MR imaging was performed 4 hours after intravenous administration of a single dose of gadolinium-based contrast material (IV-SD-GBCM). Using previously reported HYDROPS2-Mi2 MR imaging, the %ELvolume values in the cochlea and the vestibule were measured separately by two observers. The correlations between the %EL1slice or the %EL3slices and the %ELvolume values were evaluated. RESULTS: A strong linear correlation was observed between the %ELvolume and the %EL3slices or the %EL1slice in the cochlea. The Pearson correlation coefficient (r) was 0.968 (3 slices) and 0.965 (1 slice) for observer A, and 0.968 (3 slices) and 0.964 (1 slice) for observer B (P < 0.001, for all). A strong linear correlation was also observed between the %ELvolume and the %EL3slices or the %EL1slice in the vestibule. The Pearson correlation coefficient (r) was 0.980 (3 slices) and 0.953 (1 slice) for observer A, and 0.979 (3 slices) and 0.952 (1 slice) for observer B (P < 0.001, for all). The high intra-class correlation coefficients (0.991-0.997) between the endolymph volume ratios by two observers were observed in both the cochlea and the vestibule for values of the %ELvolume, the %EL3slices and the %EL1slice. CONCLUSION: The %ELvolume might be easily estimated from the %EL3slices or the %EL1slice.

Volume Quantification of Endolymph after Intravenous Administration of a Single Dose of Gadolinium Contrast Agent: Comparison of 18- versus 8-minute Imaging Protocols.

PURPOSE: We measured the volume of the endolymphatic space by extending a previously proposed less observer-dependent method of area quantification and compared volume measurements obtained using long (18 min, Image A) and short (8 min, Image B) scan times. METHODS: We performed MR imaging of 40 ears in 20 patients with clinically suspected endolymphatic hydrops 4 hours after intravenous administration of single-dose gadolinium-based contrast material (IV-SD-GBCM). Two observers separately measured the ratio of the volume of the endolymph to that of total lymph in the cochlea and vestibule by extending the area ratio measurement method previously reported (Image A and B). The correlation between the values by Image A and B was calculated. RESULTS: We observed a strong linear correlation between Images A and B in the cochlear images; the Pearson's correlation coefficient (r) was 0.928 for Observer A and 0.926 for Observer B (P < 0.001, for all). A strong linear correlation was also observed in the vestibular images; the Pearson's correlation coefficient (r) was 0.962 for Observer A and 0.968 for Observer B (P < 0.001, for all). CONCLUSION: Measurement of endolymphatic volume after IV-SD-GBCM may be feasible using an MR imaging protocol with a reduced scan time of 8 min. This method might facilitate greater use of endolymphatic hydrops imaging in clinical applications.