Computer graphics processing and selective visual display system – Computer graphics processing – Three-dimension
Reexamination Certificate
2000-02-11
2003-02-04
Nguyen, Phu (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics processing
Three-dimension
Reexamination Certificate
active
06515657
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to ultrasonic imaging. More particularly, the present invention relates to creating sectional views from volumetric ultrasound data and superimposing positional data for an interventional device, such as a catheter.
2. Background of the Invention
Many medical procedures involve inserting a catheter, or other interventional device, into a patient for a variety of purposes. One such procedure is cardiac catheterization for an angiogram.
To observe the condition of blood vessels within the heart, radio-opaque dye is injected into the bloodstream through the catheter and an x-ray image is taken. Typically, this procedure involves inserting a catheter into an artery in the patient's groin area and guiding the catheter through the arterial system and the aorta to the heart. In order to position the catheter and monitor its location within the patient, one or more x-ray images may be taken prior to injecting dye for the angiogram.
A catheter may be directly visible in an x-ray image, however, a heart typically is not. In order to determine the location of the catheter relative to the heart, dye may be injected through the catheter into the bloodstream. The dye acts as a contrasting agent allowing the heart to be located, by imaging the dye flowing through it. The image of the heart is then “frozen” at a point in time when the dye location (and concentration), provides the best image. Often, this snapshot image of the heart is traced on a transparent overlay which is then superimposed on a display monitor. After the dye concentration decreases, the overlay may be used to track the catheter location and movements relative to the heart, as indicated by the overlay. There are two disadvantages to this process. First, the image of the heart, made visible with the dye, is only temporary, requiring the overlay to track the catheter movement. Second, if the patient's position changes, the heart imaging must be repeated.
In addition to locating a catheter relative to a heart for an angiogram, there are many other medical procedures where an interventional device is inserted into a patient. In most, if not all, such procedures, locating and positioning the interventional device within a patient is extremely important.
Multiple views, or x-ray orientations, of a patient are often desirable to visualize objects and locations in three dimensions. Although there are many possible combinations of such views, some are favored by medical personnel for particular procedures. For cardiac imaging, the right anterior oblique (RAO) and the left anterior oblique (LAO) views are common.
FIG. 1
shows a schematic sectional depiction of a prone patient
10
and x-ray sources
12
and
14
. The RAO and LAO views are taken from the patient's right and left, respectively, of the anterior (front) of the heart. The oblique angle, shown as angles
16
and
18
, is the measure of how far off the vertical an x-ray source is oriented. The multiple views are often taken with a single x-ray source that is repositioned between positions
12
and
14
. An imaging system that readily presents RAO and LAO views allows medical personnel to view images in a familiar format, as this is what is presently standard in the art. Multiple preferred views for other procedures might similarly be pre-defined.
There are problems with present practices. First, x-rays and fluoroscopy produce radiation, and the effect of this radiation over the long term may be harmful. This is especially true for the medical personnel subjected to repeated radiation exposures over the course of an entire career.
In addition, the radio-opaque dye may harm the patient. For example, an angiogram is often performed on patients with serious heart problems. Injecting chemicals that may cause sensitivity, or an allergic reaction, directly into the heart of such a patient may cause a serious problem, and there is the possibility of kidney damage from the dye.
Finally, x-ray techniques require complex x-ray equipment and the costly overhead associated with such equipment. While this may not be a primary concern in a well equipped modem hospital, it is of concern in less developed or remote locations.
Ultrasound based imaging methods offer some potential advantages over x-ray based imaging methods. Ultrasound methods do not expose the patient or medical personnel to radiation and may reduce or eliminate the need for costly x-ray equipment. Also, the ability of ultrasound methods to directly image soft tissue and blood vessels, without the need for radio-opaque dye as a contrasting agent, eliminates the potential dye-related harms to a patient.
It would be desirable to have an imaging system that could eliminate, or serve as a partial substitution for, x-ray and fluoroscopy methods of imaging in procedures such as angiography and tissue biopsies. Preferably, such a system would present medical personnel with multiple views that are displayed simultaneously.
U.S. Pat. No. 4,173,228, issued to Steenwyk and Childress on Nov. 6, 1979, describes a catheter locating device (“the '228 patent”). The '228 patent uses an induction coil adjacent to the catheter tip, and a remote sensing device to monitor the amplitude and phase of signals induced in the coil, as a means of detecting the catheter location. However, an electrical signal from an induction coil is not well suited for detection by ultrasound imaging equipment. The '228 patent does teach one technique for locating a catheter, but it lacks the ability to directly map that location to a 3-D ultrasonic image of tissues within the body. Instead, such a device determines a catheter location relative to a position on the skin surface and a depth estimate, based on the magnitude of the signal received at the skin surface. It would be desirable to locate the catheter relative to internal body tissues, not the skin.
U.S. Pat. No. 5,515,853, issued to Smith, et al. on May 14, 1996, describes a 3-D ultrasound tracking system based on triangulation (“the '853 patent”). Using a network of at least four piezoelectric transducers exchanging signals, and an integrated personal computer (PC) as a digital controller, the '853 patent accurately measures the relative distances between the transducers. However, like the '228 patent discussed above, an apparatus based on the '853 patent lacks the ability to map the location of a catheter to a 3-D ultrasonic image of tissue within the body. Instead, the reference frame for catheter location information is the location of other piezoelectric transducers. For example, a series of transducers contained in a chest harness around a patient may be used to triangulate the position and orientation of a catheter relative to the chest harness, by measuring the distances to transducers mounted in the catheter. The '853 patent does briefly mention the possibility of “overlaying” transducer location information on a video loop, created from x-rays or ultrasound, to facilitate visualization of the catheter location. However, there is no teaching of how this overlay process might be performed. In contrast, an embodiment of the present invention is directed to describing the catheter location relative to tissue within the body in one or more 2-D views.
U.S. Pat. Nos. 5,817,022 and 5,868,673, (“the '022 and '673 patents”) issued to Vesely on Oct. 6, 1998, and on Feb. 9, 1999, respectively, are both, continuations-in-part from the application that became the '853 patent. Both also claim 3-D ultrasound tracking of interventional medical instruments by triangulating between a transducer attached to the medical instrument and a network of transducers either inside a patient's body or on the body surface. It would be desirable to simplify the apparatus so that a network of transducers is not required.
The '022 patent locates a medical instrument relative to the network of transducers in 3-D, and then displays a 2-D ultrasound image within the 3-D
Church Shirley L.
Feeney James F.
Nguyen Phu
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