Multiple field of view MR fluoroscopy

Abstract

This work describes a real-time imaging and visualization technique that allows multiple field of view (FOV) imaging. A stream of images from a single receiver channel can be reconstructed at multiple FOVs within each image frame. Alternately, or in addition, when multiple receiver channels are available, image streams from each channel can be independently reconstructed at multiple FOVs. The implementation described here provides for real-time visualization of the placement of guidewires and catheters on a dynamic roadmap during interventional procedures. The loopless catheter antenna, an electrically active intravascular probe, was used for MR signal reception. In 2D projection images, the catheter and surrounding structures within its diameter of sensitivity appear as bright signal. The simplicity of the resulting images allows very-narrow-FOV imaging to decrease imaging time. Very-narrow-FOV images are acquired on MR receiver channels that collect guidewire or catheter data. These very-narrow-FOV images provide very high frame rate continuous, real-time imaging of the interventional devices (25 fps). Large-FOV images are formed from receiver channels that collect anatomical data from standard imaging surface coils, and simultaneously provide a dynamic, frequently updated roadmap. These multiple-

Interventional cardiovascular procedures guided by real‐time MR imaging: An interactive interface using multiple slices, adaptive projection modes and live 3D renderings

“…Multiple parallel or oblique slices may be imaged in rapid succession to provide more complete views of a tortuous blood vessel or other anatomical structure, and these slices can be displayed together in a three‐dimensional (3D) rendering (7–9). Receiver coils embedded in interventional devices can be used for device tracking (10, 11), near‐field imaging (12, 13), or the coil locations may be visualized by colorizing the images reconstructed from the device coil signals and blending them with grayscale images produced from surface coil signals (7, 8, 14, 15). The color‐highlighted images indicate the positions of invasive devices with anatomical context.…”

Scan time reduction with an adaptive field of view

“…In this case, the entire volume would be covered in the first scan aiding the planning of subsequent dynamics. A recent technique proposed for magnetic resonance fluoroscopy [7] uses multiple channels, as in parallel imaging, with varying FOV to cover the region of interest. The method described here could be adapted to acquire successive images with a different FOV in a similar manner for use in interventions where scan time reduction is critical.…”

Real-Time MR Imaging–guided Laser Atrial Septal Puncture in Swine

“…Using 3/4; partial phase k-space coverage and echo-sharing, an imaging rate of 8 frames/sec was achieved with an acquisition-to-display latency of approximately 250 ms. Images reconstructed from active device signals were color highlighted and blended with surface coil images to highlight catheter position in relation to soft tissue anatomy (17) When required, catheters could be visualized even when outside of selected scanning slabs by selecting (X-ray-like device-only) projection mode MRI, which displays only the active catheters in a very thick slice. Saturation pre-pulses were toggled on/off during real-time imaging to suppress background tissue when gadolinium contrast enhancement was desired.…”