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Simultaneous steering and imaging of magnetic particles using MRI toward delivery of therapeutics

View Article: PubMed Central - PubMed

ABSTRACT

Magnetic resonance navigation (MRN) offers the potential for real-time steering of drug particles and cells to targets throughout the body. In this technique, the magnetic gradients of an MRI scanner perform image-based steering of magnetically-labelled therapeutics through the vasculature and into tumours. A major challenge of current techniques for MRN is that they alternate between pulse sequences for particle imaging and propulsion. Since no propulsion occurs while imaging the particles, this results in a significant reduction in imaging frequency and propulsive force. We report a new approach in which an imaging sequence is designed to simultaneously image and propel particles. This sequence provides a tradeoff between maximum propulsive force and imaging frequency. In our reported example, the sequence can image at 27 Hz while still generating 95% of the force produced by a purely propulsive pulse sequence. We implemented our pulse sequence on a standard clinical scanner using millimetre-scale particles and demonstrated high-speed (74 mm/s) navigation of a multi-branched vascular network phantom. Our study suggests that the magnetic gradient magnitudes previously demonstrated to be sufficient for pure propulsion of micron-scale therapeutics in magnetic resonance targeting (MRT) could also be sufficient for real-time steering of these particles.

No MeSH data available.


Particle displacement versus time for motion between waypoints 9, 10, 11, 12 and 13.(a) Displacement along channel. (b) Displacement perpendicular to channel.
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f6: Particle displacement versus time for motion between waypoints 9, 10, 11, 12 and 13.(a) Displacement along channel. (b) Displacement perpendicular to channel.

Mentions: Figure 6 illustrates video camera and MRI displacement data for the particle trajectory connecting waypoints 9, 10, 11, 12, and 13. Since the proposed MRI sequence only measures position in the direction of propulsion, the two dimensional motion of the particle is plotted along axes parallel and perpendicular to the channel segments connecting adjacent waypoints. Particle motion parallel to the channel reaches an average velocity of about 74 mm/s (peak velocity is about 110 mm/s). For these segments, MRI position error relative to the camera was 7 mm ± 14.76 mm. Motion perpendicular to the channel is measured only by the video camera and is shown in Fig. 6(b). This plot shows that the particle experiences small-amplitude damped oscillations about the centre of each channel. Note that since the axis of motion is redefined as the particle reaches each waypoint, there are discontinuities in the plot at these times.


Simultaneous steering and imaging of magnetic particles using MRI toward delivery of therapeutics
Particle displacement versus time for motion between waypoints 9, 10, 11, 12 and 13.(a) Displacement along channel. (b) Displacement perpendicular to channel.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5036040&req=5

f6: Particle displacement versus time for motion between waypoints 9, 10, 11, 12 and 13.(a) Displacement along channel. (b) Displacement perpendicular to channel.
Mentions: Figure 6 illustrates video camera and MRI displacement data for the particle trajectory connecting waypoints 9, 10, 11, 12, and 13. Since the proposed MRI sequence only measures position in the direction of propulsion, the two dimensional motion of the particle is plotted along axes parallel and perpendicular to the channel segments connecting adjacent waypoints. Particle motion parallel to the channel reaches an average velocity of about 74 mm/s (peak velocity is about 110 mm/s). For these segments, MRI position error relative to the camera was 7 mm ± 14.76 mm. Motion perpendicular to the channel is measured only by the video camera and is shown in Fig. 6(b). This plot shows that the particle experiences small-amplitude damped oscillations about the centre of each channel. Note that since the axis of motion is redefined as the particle reaches each waypoint, there are discontinuities in the plot at these times.

View Article: PubMed Central - PubMed

ABSTRACT

Magnetic resonance navigation (MRN) offers the potential for real-time steering of drug particles and cells to targets throughout the body. In this technique, the magnetic gradients of an MRI scanner perform image-based steering of magnetically-labelled therapeutics through the vasculature and into tumours. A major challenge of current techniques for MRN is that they alternate between pulse sequences for particle imaging and propulsion. Since no propulsion occurs while imaging the particles, this results in a significant reduction in imaging frequency and propulsive force. We report a new approach in which an imaging sequence is designed to simultaneously image and propel particles. This sequence provides a tradeoff between maximum propulsive force and imaging frequency. In our reported example, the sequence can image at 27 Hz while still generating 95% of the force produced by a purely propulsive pulse sequence. We implemented our pulse sequence on a standard clinical scanner using millimetre-scale particles and demonstrated high-speed (74 mm/s) navigation of a multi-branched vascular network phantom. Our study suggests that the magnetic gradient magnitudes previously demonstrated to be sufficient for pure propulsion of micron-scale therapeutics in magnetic resonance targeting (MRT) could also be sufficient for real-time steering of these particles.

No MeSH data available.