Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2001-03-13
2003-06-10
Hook, James (Department: 3752)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S420000, C600S422000
Reexamination Certificate
active
06577887
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to an apparatus and method for improving diagnoses. Particularly, the present invention relates to an apparatus and method for altering the intravenous delivery of pharmaceuticals to improve therapy and diagnosis. Even more particularly, the present invention relates to an apparatus and method for altering the intravenous delivery of pharmaceuticals to improve therapy and diagnosis using contrast agents that enhance nuclear magnetic resonance signals.
2. Description of the Related Art
Arterial diseases and injuries are common and sometimes have severe consequences including death. Imaging arteries serves to screen, detect and characterize arterial disease before these consequences occur. It also serves to define anatomic features that may provide assistance when planning surgery or vascular intervention.
In the practice of clinical medicine, numerous pharmaceutical products are administered intravenously. Some of these pharmaceuticals are used for diagnostic purposes and include contrast agents such as iodinated contrast-media used in x-ray angiography (XRA) and Computed Tomography Angiography (CTA), gadolinium chelates used in Magnetic Resonance Angiography (MRA) and radioactive agents used in nuclear medicine such as 99m-Tc-labeled Sestamibi or 201-Thallium. Some pharmaceuticals are administered intravenously for therapeutic purposes, for example, I-131 Sodium Iodide for thyroid cancer and perhaps in the future, pharmaceuticals for gene-therapy. All of these intravenously administered agents have in common the fact that they are distributed throughout the body by way of the blood stream.
One of the advantages of the x-ray techniques is that image data can be acquired at a high rate so that a sequence of images may be acquired during injection of the contrast agent. Such dynamic studies enable one to select the image in which the bolus of contrast agent is flowing through the vasculature of interest. Images showing circulation of blood in the arteries and veins of the kidneys, the neck and head, the extremities and other organs have immense diagnostic utility. Unfortunately, these x-ray methods subject the patient to potentially harmful ionization radiation and often require the use of an invasive catheter to inject a contrast agent into the vasculature to be imaged.
MRA uses the nuclear magnetic resonance (NMR) phenomenon to produce images of the human vasculature. When a substance such as human tissue is subjected to a uniform magnetic field, the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field. A signal is emitted by the excited spins, and after the excitation signal is terminated, this signal may be received and processed to form an image. When utilizing these signals to produce images, magnetic field gradients are employed. Typically, the region to be imaged is scanned by a sequence of measurement cycles in which these gradients vary according to the particular localization method being used. The resulting set of received NMR signals are digitized and processed to reconstruct the image using one of many well-known reconstruction techniques.
To enhance the diagnostic capability of MRA, a contrast agent such as gadolinium can be injected into the patient prior to the MRA scan. Excellent diagnostic images may be acquired using contrast-enhanced MRA if the data acquisition is properly timed with the bolus passage. The non-invasiveness of MRA makes it a valuable screening tool for cardiovascular diseases. Screening typically requires imaging vessels in a large volume. This is particularly true for diseases in the runoff vessels of the lower extremity.
In MRA, contrast material injected into a vein in the upper extremity travels by vein to the right atrium of the heart. From there it travels to the right ventricle, then to the lungs where it is oxygenated. It returns to the left atrium of the heart, then to the left ventricle, the aorta, the common iliac artery, the internal and external iliac, the common femoral, and then throughout the smaller arteries of the thigh and leg. As the arterial blood passes through the lower extremities, it enters the capillaries of the muscles and then returns to the heart via the venous system. MRA of the lower extremities is done to visualize the vascular structures to determine the extent that some of the arteries (or veins) of the leg may be narrowed or partially blocked. Effective images can be made only while there is contrast material in the blood vessel being imaged. There exists only a short window of opportunity, approximately 30 to 45 seconds, when the contrast material is in the iliac, femoral and lower leg arteries when these images can be obtained and before the contrast material has entered the venous phase.
U.S. Pat. No. 5,928,148 (1999, Wang et al.) discloses a method of performing magnetic resonance angiography over a large field of view using table stepping. The MRA data is acquired from a large region of interest by translating the patient to successive stations at which successive portions of the MRA data set are acquired. Patient movement is chosen to track a bolus of contrast agent as it passes through the region of interest to achieve maximum image contrast. In one embodiment, a stationary local coil is supported adjacent the patient to acquire the MRA data. In another embodiment, a multi-segment local coil moves with the patient and its segments are sequentially switched into operation.
U.S. Pat. No. 5,924,987 (1999, Meaney et al.) discloses a method and apparatus for magnetic resonance arteriography using contrast agents. Meaney et al. disclose a technique of and a system for imaging vascular anatomy over a distance considerably greater than the maximum practical field of view of a magnetic resonance imaging system while using substantially one contrast agent injection. A plurality of image volumes are acquired that are representative of different portion's of the patient's body.
U.S. Pat. No. 5,553,619 (1996, Prince) discloses a method and apparatus for administration of contrast agents for use in magnetic resonance arteriography. The method and apparatus adapts the timing of a maximum or substantially elevated rate of infusion to correlate with the collection of image data corresponding to the center of k-space. Adapting the timing of a maximum or substantially elevated rate of infusion to correlate with the collection of image data corresponding to the center of k-space provides a period of a maximum or substantially elevated contrast concentration in the artery of interest relative to adjacent veins during collection of at least a portion of the image data corresponding to the center of k-space.
U.S. Pat. No. 5,417,213 (1995, Prince) discloses a method of imaging arteries distinctly from veins using nuclear magnetic resonance imaging in combination with intravenous administration of a magnetic resonance contrast agent. The contrast agent is injected in such a way that the arterial contrast concentration is substantially higher than the venous and background tissue concentration for a sufficiently long period of time to acquire the magnetic resonance image. The injection site of the contrast agent is chosen such that it is in a vein that is remote from the artery of interest.
U.S. Pat. No. 6,037,771 (2000, Liu et al.) discloses a sliding thin-slab method of acquiring three-dimensional MRA data. Liu et al. discloses the use of a 3DFT gradient-recalled echo pulse sequence to acquire NMR data from which an MR angiogram is produced. A thin slab excitation is employed and this thin slab is incremented in slice-thickness steps through the volume of interest as the NMR data is acquired. Navigator echoes are acquired at each thin slab location to correct the NMR data for phase errors produced by the sliding slab technique.
A disadvantage presented by the prior art is that the amount of imaging time required to make high-quality images is long compared to the amount of time
Wolff Floyd
Wolff Steven
Deleault, Esq. Robert R.
Hook James
Mesmer & Deleault, PLLC
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