A new pulse sequence to visualize slow flow

Abstract

The purpose of this paper is to present a new pulse sequence for visualizing slow flow. The new sequence consists of an initial Stejskal-Tanner flow sensitization part followed by a DEFT pulse and a spoiler gradient. A single-shot TSE readout train is then applied to sample the NMR signal. The sequence was initially tested using a simple flow phantom. To verify potential clinical use, both flow-sensitive MRCP and cerebrospinal fluid (CSF) images were produced. The phantom study proved the sequence sensitivity to flow in the range 0-1 cm/s. bVE-factors 1.5, 3, 6 and 12 were chosen. Within this flow velocity range, the signal dropped as predicted theoretically. This indicates that the method can be used to quantify flow. All anatomical features seen in a standard MRCP sequence were identified and the methods sensitivity to CSF flow was demonstrated by sagital images of the head. A new pulse sequence sensitive to slow flow has been developed.

The Secretory Flow of Pancreatic Juice in the Main Pancreatic Duct: Visualization by Means of MRCP with Spatially Selective Inversion-Recovery Pulse

“…Additionally, this technique is not physiologic because it requires the injection of secretin. Other reports have suggested that pancreatic juice fl ow could be detected by using a single-shot turbo spin-echo sequence based on a diffusion-weighted MR imaging technique (18)(19)(20). In this approach, the stationary pancreatic fl uid appears bright, while the moving pancreatic fl uid loses signal intensity as the b value used increases and appears as a fl ow void.…”

Magnetic resonance-assisted imaging of slow flow in the pancreatic and common bile duct in healthy volunteers

“…The pulse sequence used in this study to visualize changes in slow flow in the PD has been presented previously (5). Initial tests in an experimental study showed that semi-quantitative evaluation of flow was possible (6).…”

“…The study shows that changes in the slow flow of the PD can be detected, but the method is very sensitive to bowel movement artifacts, and thereby probably any movement during scanning, including any physiological flow within the PD. Signal fluctuation, which occurs earlier with increasing b factor, is also suspected to effect the visibility score (5).…”

“…The MRI sequences have been presented previously (Fig. 1) (5,6). A Phillips Gyroscan ACS-NT (1.5T; Best, The Netherlands) with Powertrack 6000 gradient system was used.…”

“…However, phase-contrast angiography does not allow for flow settings below approximately 1 cm/ s. Flow in the CBD and PD in the steady state is below 1 cm/s. We have previously published a pulse sequence to visualize slow flow, using a single-shot turbo spin-echo (SS-TSE) sequence based on diffusion-weighted (DW) MRI techniques (5). Application of this MRI technique in an experimental in vivo study in swine showed that semi-quantitative evaluation of flow was possible in the range of 0.0-1.32 cm/s (6).…”