Bridges – Transportable
Reexamination Certificate
1999-05-07
2001-10-02
Walberg, Teresa (Department: 3742)
Bridges
Transportable
Reexamination Certificate
active
06295680
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates generally to a method and apparatus for use in detecting focal accumulation of radiopharmaceutical agents within an arterial lumen. More particularly, the present invention provides a miniaturized fiber optic-coupled scintillator attached to an external image processing unit for detecting accumulated radiopharmaceutical agents within a blood vessel. Optionally, the apparatus may be fitted with a system for minimizing the accumulated plaque.
2. Summary of Related Art
Atherosclerosis is one of a handful of conditions in which a thickening or hardening of the walls of arterial vessels occurs, the other conditions being Monckeberg's sclerosis (deposition of calcium salts in the muscular wall of arteries) and arteriolosclerosis (thickening of arterioles). Atherosclerosis is generally multifocal. The lesion or atherosclerotic plaque—comprises a mass of fatty material. This material is associated with fibrous connective tissue and frequently includes deposits of calcium salts and other residual material. These plaques initially begin in the intima of the affected vessel but may eventually extend into the media of the vessel.
In developed countries, atherosclerosis is frequently seen in all but the youngest of people, although genetic predispositions play an important role in the course of the disease. The damage caused by atherosclerosis varies. If a medium-sized blood vessel such as a coronary artery is involved, the plaque build-up may restrict blood flow or may stop it altogether in more extreme cases. Thrombus formation may also result on the roughened area which results from the built-up plaques. Of considerable concern is the possibility of the soft lipid portion of the plaque breaking away and being deposited in a narrow vessel, frequently resulting in a stroke. Relief of focal high-grade obstruction may control symptoms, but the patient usually is left with numerous nonobstructive plaques prone to later rupture and infarction.
While conventional imaging and detection of coronary atherosclerosis by contrast angiography or intravascular ultrasonography provides valuable anatomic detail, it does not characterize the underlying biological processes which may lead to plaque expansion or rupture with attendant acute coronary syndromes. In particular, available imaging and detection modalities have limited ability to predict the site of future myocardial infarction and have demonstrated an inability to differentiate between active (unstable) and inactive (stable) plaque sites. While percutaneous coronary revascularization provides excellent symptom relief in selected patients with obstructive coronary artery disease, it has been difficult to demonstrate that percutaneous revascularization reduces the incidence of future myocardial infarction.
While all plaque build-up on vessel walls is to be of concern, it is impractical to resolve each plaque site throughout the affected individual's vascular system. Atherosclerotic plaques are characterized by mural inflammatory infiltrates which may contribute to their instability. Noninvasive imaging and detection of mural inflammation in atherosclerotic arteries is hampered by small tissue mass, high background activity from visceral and blood pool radiotracer, poor spatial resolution, poor correlation with local anatomy, and, in coronary arteries, by cardiac motion artifact. It is accordingly desirable to treat the most potentially dangerous plaques, or the so-called “active” plaques which are metabolically active. It is this form of plaque that cause the most trouble to the body in the form of coronary artery disease and atherosclerosis because of their tendency to let loose some of the lipid material from the site causing thrombosis. If loosened, this material could travel through the vascular system causing a coronary attack if in the region of the heart, a stroke if in the region of the brain, or an occlusion of a vessel if in the leg. The difficulty is in identifying the stable plaque from the unstable plaque and providing a method of treatment.
Accordingly, a method to identify the active, unstable, or “vulnerable” coronary atherosclerotic plaques might have broad clinical utility and remains wanting in the art.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide a method and apparatus capable of differentiating active (or unstable) plaque from inactive (or stable) plaque.
It is a further object of the present invention to provide such a method and apparatus which is minimally invasive.
Yet a further object of the present invention is to provide such a method and apparatus which may optionally treat the identified and affected site.
Still a further object of the present invention is to provide such a method and apparatus which treats the affected site by expansion through the use of a balloon or a stent.
An additional object of the present invention is to provide such a method and apparatus which treats the affected site by mechanical means such as ablation through mechanical cutting or laser cutting.
A further object of the present invention is to provide such a method and apparatus which treats the affected site by treatment directed at altering metabolic activity.
These objects are accomplished through the provision of a miniaturized radiation detector for local radioactivity imaging and detection applied directly within the arterial lumen. Local imaging and detection isolates a small volume of interest from a larger pool of background radioactivity. Furthermore, a suitable intravascular device may be insensitive to cardiac motion, have a clinically-useful spatial resolution using several available clinical radionuclides, and may correlate images in real-time with conventional coronary or peripheral cineangiograms.
The apparatus and method of the present invention may be widely applicable in the study, diagnosis, and management of coronary and non-coronary atherosclerosis by tracing in vivo biochemical processes using radioactive tags. The method and apparatus of the present invention may be used to detect processes not otherwise amenable to study using conventional techniques including contrast angiography and intravascular ultrasound. The local-imaging and detection approach is superior to conventional radiopharmaceutical imaging and detection with external gamma or positron tomography systems.
The method and apparatus of the present invention overcomes many of the problems generally associated with external imaging and detection strategies which are limited by the low volume of pathological tissue, low signal-to-noise ratios from low lesion radioactivity and high background activity from blood pool and viscera. External imaging and detection is also limited by poor spatial resolution, poor correlation with local anatomy, and cardiac motion artifact. Conversely, the present method and apparatus provides a miniaturized radiation detector which identifies local radioactivity imaging and detection directly within the coronary artery lumen. Local imaging and detection isolates a small volume of interest from a larger pool of background radioactivity. In addition, the apparatus of the present invention is sensitive to cardiac motion, demonstrates clinically-useful spatial resolution using most clinical radionuclides, and is able to correlate images in real-time with conventional cineangiograms. Furthermore, the radiation detector material is especially suited for detecting beta particles (electrons and positrons, which have tissue penetrance limited to several millimeters), making this device particularly suitable for intravascular applications.
More particularly, the apparatus of the present invention is an ultraminiaturized device which embodies the properties of intracoronary devices including flexibility (the ability to travel around a bend with a narrow radius), softness (the ability to travel around a bend without straightening a vessel and without damaging its endoluminal surface), traceability (the ability
Lederman Robert J.
Wahl Richard L.
Harness & Dickey & Pierce P.L.C.
Robinson Daniel
The Regents of the University of Michigan
Walberg Teresa
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