Browse Prior Art Database

CONTINUOUS LIVER TRACKING DURING FREE BREATHING MAGNETIC RESONANCE IMAGING GUIDED FOCUSED ULTRASOUND

IP.com Disclosure Number: IPCOM000241265D
Publication Date: 2015-Apr-10
Document File: 4 page(s) / 104K

Publishing Venue

The IP.com Prior Art Database

Abstract

The disclosed invention proposes a tracking technique based on liver blood vessels. The tracking is applied using a restricted FOV (rFOV) single shot gradient echo planar imaging (EPI) sequence. During FUS heating, echo-planar-imaging (EPI) sequence is applied continuously. Due to short time between images (TR), blood vessels of the liver appear bright and therefore they are used as landmarks that track liver motion. Landmarks locations are calculated continuously and the movement of any arbitrary point in the liver is determined by two dimensional (2D) interpolation of the locations. The technique includes landmark selection, tracking and target point interpolation. Initially the landmarks are assigned to the blood vessels. The landmarks are then tracked during heating. The location of the target point is found by 2D interpolation of the landmarks coordinates.

This text was extracted from a Microsoft Word document.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 49% of the total text.

CONTINUOUS LIVER TRACKING DURING FREE BREATHING MAGNETIC RESONANCE IMAGING GUIDED FOCUSED ULTRASOUND

BACKGROUND

The present invention relates generally to magnetic resonance imaging (MRI) guided focused ultrasound and more particularly to a tracking technique based on liver blood vessels.

Magnetic resonance imaging (MRI) guided focused ultrasound (FUS) tissue ablation of liver during free breathing requires continuous tracking of every target point to be treated throughout the treatment so that FUS transducer can deliver energy to a right position.

A conventional technique includes using navigator echoes at diaphragm.

Another conventional technique includes motion vector calculation taken before treatment and compared during treatment using an image registration algorithm.

One other conventional technique includes uses displacement field obtained to correct on-line motion artifacts on temperature maps and to adjust position of focal point emitted by a phased array transducer in order to track a target following a periodical displacement using an anticipation process. Processing of an image must is done in an interval of time between two successive acquisitions to ensure on-line monitoring of temperature evolution.

However, the above mentioned conventional techniques do not provide continuous tracking of liver during free breathing MRI guided focused ultrasound (FUS).

 It would be desirable to have an efficient technique to continuously track liver during free breathing MRI guided focused ultrasound (FUS).

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 depicts a reference image where red circles represent landmarks over blood vessels.

Figure 2 depicts an image from a series of images during tracking.

DETAILED DESCRIPTION

The disclosed invention proposes a tracking technique based on liver blood vessels. The tracking is applied using a restricted FOV (rFOV) single shot gradient echo planar imaging (EPI) sequence with imaging speed of up to 25 images/sec. Such speed is suitable for temperature measurement using proton resonance shift (PRS) technique.

During FUS heating, the EPI sequence is applied continuously. Due to short time between images (TR), blood vessels of the liver appear bright and therefore they are used as landmarks that track liver motion. Landmarks locations are calculated continuously and the movement of any arbitrary point in the liver is determined by two dimensional (2D) interpolation of the locations. Tracking is done by initially using one of the first EPI images as a reference image. The landmarks are set automatically on certain of the blood vessels that are suitable for tracking. Figure 1 depicts the reference image where red circles represent the landmarks over the blood vessels.

Figure 1

Then target points that are to be treated is set on the reference image. The location of the target point is derived from a high resolution planning image acquired shortly before the reference image. Finally, during FUS heating, the landmarks...