Real-time volume rendered MRI for interventional guidance

Abstract

Volume renderings from magnetic resonance imaging data can be created and displayed in real-time with user interactivity. This can provide continuous 3D feedback to assist in guiding an interventional procedure. A system is presented which can produce real-time volume renderings from 2D multi-slice or 3D MR pulse sequences. Imaging frame rates up to 30 per second have been demonstrated with a latency of approximately one-third of a second, depending on the image matrix size. Several interactive capabilities have been implemented to enhance visualization such as cut planes, individual channel scaling and color highlighting, view sharing, saturation preparation, complex subtraction, gating control, and choice of alpha blending or MIP rendering. The system is described and some interventional application examples are shown. To view movies of some of the examples, enter the following address into a web browser: http://nhlbi.nih.gov/labs/papers/lce/guttman/rtvolmri/index/htm.

Figures

Figure 1

Configuration of MRI system for producing real-time volume renderings.

Figure 2

Usage of the real-time volume rendering system in an intervention experiment. Two monitors were used, displaying a replication of the scanner console on the right, and the real-time volume rendering on the left.

Figure 3

Trans-thoracic myocardial injection of Gd-DTPA. Background suppression was enabled in these FGRE images. The needle is visible penetrating the chest wall in slice 2 (arrow). The bolus of Gd-DTPA is visible injected into the LV myocardium in slices 3 (arrow) and 4.

Figure 4

Volume renderings of myocardial injection. MIP was used to highlight the injection of Gd-DTPA (arrow). (a) Axial slice view. (b) Volume was rotated to view from a different angle. (c) Chest wall was removed using cut planes to enable an unobstructed view of the injection site.

Figure 5

Images from a 3-slice renal angiography example. Background suppression was activated at time b. A Gd-DTPA injection is visible entering the kidney via the renal artery at time c in slice 1. The kidney is enhanced at time d. At time e, contrast agent is visible exiting the kidney via the renal vein (slice 1) and inferior vena cava (slices 2 and 3).

Figure 6

Volume renderings of the renal angiography example using MIP. Time frames a–e are the same as in Fig. 5. Renal artery, kidney, renal vein, aorta, and vena cava are all visible in the renderings.

Figure 7

A passive guiding catheter in the LV creates a visible signal void. (a) Three slices with different portions of the catheter visible in each slice. Only the tip is visible in slice 1, and a portion is missing in slice 2 (circled) which is seen in slice 3. (b) Volume rendering of the same with alpha blending. The entire portion of the catheter around the aortic arch into the LV cavity is visible. (c) The catheter is also visible in reverse-video, through which an MIP is shown.

Figure 8

MR-guided myocardial injection. (a) Three slices shown without color enhancement. Signal from active guiding catheter is amplified and combined with surface coil signals. (b) Same slices shown with color enhancement. Injection catheter tip is apparently in slice 2 and the distal portion of the guiding catheter in the LV is seen most clearly in slice 3. (c) With background suppression enabled, the endomyocardial injection (arrow) is actually seen in slice 1, not where tip was observed. (d, e) Entire length of guiding catheter, tip of injection catheter (with alpha blending) and injection site (with background suppression and MIP, arrow) are seen in the volume rendering.