IADR Abstract Archives
MRI of Fluid Flow Inside Teeth at Anatomic Velocities
Objectives: Accuracy of current methods to assess pulpal status of teeth, such as temperature and electricity, is lacking due to variation in patient response and clinician interpretation. In this project, magnetic resonance image (MRI) is investigated as a potential means to bring objectivity to diagnostic testing of pulp vitality by directly visualizing blood flow in teeth. Previous results demonstrated that MRI can detect fluid flow within the pulp space of an extracted tooth. This research is a refinement that builds on our previous work.
Methods: A modeled condition was prepared by 0.256 mm polytetrafluoroethylene micro tubing inserted in U-shape inside extracted teeth. 0.9% saline was pumped at controlled speed through the tubing, modeling bulk pulpal blood flow. 4T MRI interfaced to Agilent DirectDrive console with the intraoral dental coil was utilized. SWeep Imaging with Fourier Transformation (SWIFT) images were acquired in flow and no-flow states at different velocities and variable flip angles: 5, 10, and 15 degrees. Subtraction images of the flow and no-flow images were calculated to visualize and quantify fluid movement visibility using ImageJ.
Results: Decreasing flow velocities from at 20 cm/s to 1.5 cm/s, which is the approximate speed of physiologic blood flow in teeth, resulted in visible fluid flow with a mean SNR of 5.1. Both 5 and 15 degree flip angle images demonstrated minimal artifact while a 10 degree flip angle demonstrated visibly apparent susceptibility artifacts.
Conclusions: SWIFT with variable flip angles appears to successfully demonstrate fluid flow in an extracted tooth to 1.5 cm/s or at the approximate speed of physiologic pulpal blood flow. A 5 or 15 degree flip angle appears to be more optimal in maximizing signal of flow within teeth while minimizing artifacts. Additional efforts on translation to an in vivo model are ongoing.
Methods: A modeled condition was prepared by 0.256 mm polytetrafluoroethylene micro tubing inserted in U-shape inside extracted teeth. 0.9% saline was pumped at controlled speed through the tubing, modeling bulk pulpal blood flow. 4T MRI interfaced to Agilent DirectDrive console with the intraoral dental coil was utilized. SWeep Imaging with Fourier Transformation (SWIFT) images were acquired in flow and no-flow states at different velocities and variable flip angles: 5, 10, and 15 degrees. Subtraction images of the flow and no-flow images were calculated to visualize and quantify fluid movement visibility using ImageJ.
Results: Decreasing flow velocities from at 20 cm/s to 1.5 cm/s, which is the approximate speed of physiologic blood flow in teeth, resulted in visible fluid flow with a mean SNR of 5.1. Both 5 and 15 degree flip angle images demonstrated minimal artifact while a 10 degree flip angle demonstrated visibly apparent susceptibility artifacts.
Conclusions: SWIFT with variable flip angles appears to successfully demonstrate fluid flow in an extracted tooth to 1.5 cm/s or at the approximate speed of physiologic pulpal blood flow. A 5 or 15 degree flip angle appears to be more optimal in maximizing signal of flow within teeth while minimizing artifacts. Additional efforts on translation to an in vivo model are ongoing.
