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Published on: October 9, 2017
MRI of slow flow in artificial duct in swine
Johan Castberg Hellund1, Knut Jørgen Labori, Bjørn Atle Bjørnbeth
1Department of Radiology, Ullevaal University Hospital, 0407 Oslo, Norway. j.c.hellund@ioks.uio.no
Abstract:
Our aim was to evaluate whether it is possible to visualize slow flow within a small catheter placed inside a living animal. We used a flow-sensitive, single-shot turbo spin-echo (SS-TSE) MRI sequence, developed in house, based on diffusion-weighted (DW) techniques. Four anesthetized pigs were used as models. A plastic catheter was surgically placed within the common bile duct (CBD). To mimic flow, the catheter was filled with Ringer's acetate and connected to a pump. b factors (s/m(2)) of 0, 6, and 12, with flow velocities raging from 0 to 1.32 cm/s, were used. A total of 375 images were obtained and examined. After correction for bowel movement artifacts, all images displayed the catheter on zero flow. With a flow of 0.66 cm/s or higher, no images displayed the catheter with a b factor of 6 or 12. On the slower flow velocities, it was variable whether the catheter was visible or not, but at b=6 and flow 0.17 cm/s all catheters were viewable. This method made it possible to perform a semiquantitative evaluation of flow velocities in vivo, dividing flow into three groups.
Insights
This study demonstrates that a specialized MRI technique can visualize slow fluid flow in animal models. The diffusion-weighted MRI method successfully detected flow within a catheter, enabling semi-quantitative assessment.
Area of Science:
- Medical Imaging
- Biomedical Engineering
- Fluid Dynamics
Background:
- Visualizing slow fluid flow in small vessels is challenging.
- Existing MRI techniques may lack sensitivity for detecting subtle flow dynamics.
Purpose of the Study:
- To assess the feasibility of visualizing slow flow within a small catheter in vivo.
- To evaluate a novel flow-sensitive, single-shot turbo spin-echo (SS-TSE) MRI sequence for this purpose.
Main Methods:
- Utilized a custom-developed, diffusion-weighted (DW) SS-TSE MRI sequence.
- Employed four anesthetized pigs with a catheter placed in the common bile duct (CBD).
- Mimicked flow using Ringer's acetate at velocities from 0 to 1.32 cm/s with varying b-factors (0, 6, 12 s/m²).
Main Results:
- Catheters were visible at zero flow across all b-factors.
- Flow velocities of 0.66 cm/s or higher obscured the catheter at b-factors of 6 and 12 s/m².
- Flow at 0.17 cm/s with a b-factor of 6 s/m² allowed consistent catheter visualization.
Conclusions:
- The developed MRI sequence enables visualization of slow flow in small animal model catheters.
- This technique offers potential for semi-quantitative assessment of in vivo flow velocities.
- The method allows for categorizing flow into distinct groups based on velocity.
