Media and methods for enhanced medical imaging

Details Media and methods for enhanced medical imaging Media and methods for enhanced medical imaging

2002-03-08

2004-11-16

Park, Hankyel T. (Department: 1648)

Drug, bio-affecting and body treating compositions

Radionuclide or intended radionuclide containing; adjuvant...

C424S001170, C424S001450, C424S009400

Reexamination Certificate

active

06818199

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates generally to enhance medical imaging. More particularly, the present invention relates to metal particle agents and the methods of their use in medical imaging.
The practice of medicine was revolutionized by the discovery of x-rays by Roentgen in 1895. Today, over 300 million diagnostic x-ray examinations are performed each year in the United States. Even with the rapid growth of Magnetic Resonance Imaging (MRI), 75 to 80% of all diagnostic imaging utilize X-rays.
X-rays show bone structure well, but for better delineation of soft tissue structures, including vasculature, the alimentary canal (digestive tract), and bladder, contrast agents are required to enhance image contrast. Sodium iodide was first used in 1923 to opacify the bladder, and shortly afterwards the intravenously administered agent sodium 5-iodo-2-pyridone-N-acetate (Uroselectan) was introduced for imaging the urinary tract. Water soluble, ionic, triiodobenzene contrast agents were then developed for intra vascular use, such as diatrizoate and ioxaglate. These, however, unpredictably and occasionally caused moderate to severe anaphylactic, cardiovascular and pain reactions. Part of this toxicity was later found to be a result of the high osmolality, so agents that were non-ionic with lower osmolality were developed, such as the monomeric iohexol (also called by the trade names Omnipaque and Exypaque), based on German patent 2,726,196, corresponding to U.S. Pat. No. 4,250,113, and a dimeric version with even lower osmolality, iodixanol (trade names Accupaque and Visipaque), described in European patent 108,638.
Currently there are two types of X-ray image contrast enhancing agents approved for human use: a) aromatic iodinated compounds that are water soluble, and b) barium sulfate suspensions, used only for gastrointestinal tract imaging.
The development of the above-mentioned contrasting agents notwithstanding, several serious medical problems persist that affect millions of individuals which could be addressed using even better contrast agents. One such problem is the large number of sudden unexpected heart attacks and deaths that occur. Each year in the U.S. 1,100,000 new and recurrent heart attacks occur, resulting in 500,000 deaths per year. It is the number one killer. Heart attacks often occur suddenly without warning, when a coronary artery with plaque buildup (atherosclerosis) breaks loose, initiating a clot that blocks the artery (myocardial infarction). Heart muscle dies due to lack of oxygen, the heart pumps insufficiently, brain function is destroyed, and the victim commonly may die before adequate treatment is obtained.
Plaque buildup and narrowing of the coronary arteries occurs over a period of years, but few people know the condition of their coronary arteries and the risk and danger thereof. If the condition of the coronary arteries was known, treatments could be administered before the cataclysmic event occurred, and many sudden fatal heart attacks could be avoided. The reason that routine checks of the coronary arteries are not done with annual physicals, or for persons over a certain age or believed to be at risk is that the current best test, coronary angiography, which images the coronary arteries directly and permits visualization of constrictions, is itself an expensive, complicated, time-consuming, and risky procedure. This test involves piercing a leg or arm artery (which is under high pressure) with a needle, snaking a catheter through the arteries to the heart, and watching coronary arterial blood flow in real-time using X-ray fluoroscopy. A very concentrated iodine dye is injected, which, for a few seconds, provides sufficient contrast to allow the coronary arteries to be imaged. This procedure requires the services of a skilled cardiologist and operating team. A number of possibly fatal events could be initiated by the procedure such as blood clots in major, vital arteries (caused by the catheter dislodging pieces of plaque from the artery wall) resulting in stroke, massive reaction to the dye, cardiac arrhythmia, damage or puncture of arteries, infection, hemorrhage, and heart attack.
Coronary angiography carries with it these major complication rates—death (0.12-0.20%), cerebrovascular accident (0.03-0.20%), myocardial infarction (0.0-0.25%); and minor complication and local infection (0.57-1.6%) or arrhythmia (0.30-0.63%). Total risk of serious complications is 1.7%. About one out of every 600 persons subjected to such trans-arterial coronary angiography die from the procedure alone. Due to the high level of invasiveness and risk, it is not recommended for routine use and especially not for the elderly and those in poor health, namely those who need it most. Yet, about 1,250,000 cardiac catheterizations for coronary angiography are performed annually in the United States at a cost of $5,000 to $6,000 per procedure. The high cost of the procedure and associated risk therefore make routine coronary angiography inappropriate for use as a screening test.
The ability to perform non-invasive coronary angiography would represent a major improvement in patient care. Information regarding coronary anatomy could then be acquired with minimal risk, even for patients in whom coronary angiography is contraindicated due to severe allergic history to current radiographic contrast agents, fever with documented infection, bleeding diatheses, recent gastrointestinal bleeding, or cerebrovascular accident. Follow-up angiographic information in patients undergoing revascularization procedures could also be more readily obtained.
Echocardiography and Doppler techniques use ultrasound, and can be done in a doctor's office, with no risk. These techniques provide information about the size of the heart chambers, the pumping function, valve function, and blood volume. However, they are not suitable for anatomic evaluation of the coronary arteries Since 1973, Computed Tomography (CT) has grown to become one of the most important radiological examination processes in the industrialized world. CT delineates organs in a new way by producing digitally reconstructed images of cross-sections of a patient. In this way, it achieves a higher than normal sensitivity to improve the natural radiological contrasts between organs. It is exceptionally sensitive to contrast media, moreover, and can detect disease-related abnormalities from the distribution of an intravenous dose of a contrast medium.
Consequently, 60-80% of all CT examinations involve the use of a contrast medium. The primary uses for CT include brain and spine investigations, abdominal and urological studies, and approximately 20% of all CT procedures are performed to investigate the liver. An advanced CT technique, called spiral or helical CT, has been developed which achieves the resolution of normal CT but with shorter examination times and a lower x-ray dose. Multi-slice CT (MSCT) is another improvement, with typically 2 or 4 source/detector pairs operating simultaneously, which can improve the resolution and acquisition time.
Electron Beam Computed Tomography (EBCT), or Ultrafast CT, uses a rapid x-ray scanner, which can freeze the heart beating motion, to visualize calcification in the coronary arteries without use of dyes or catheterization.
Electron Beam Tomography (EBT) scanner is different from conventional (mechanical) CT scanners, focusing an electron beam onto tungsten target rings positioned around the patient. Each sweep of the electron beam produces a continuous 30 degree fan beam of x-rays that pass through the patient to a stationary array of detectors which generates cross-sectional images, with scan times of 50 milliseconds. Exposures can be triggered from an electrocardiogram (ECG or EKG) to visualize a specific part of the beating heart cycle and to reduce overall dose.
Intra vascular ultrasound (IVUS) is an invasive technique, where the sound equipment is on the catheter snaked into the artery. This technique allows the architecture of the wall, its components, size, shape,

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