Intravascular ultrasound
Encyclopedia
Intravascular ultrasound (IVUS) is a medical imaging
methodology using a specially designed catheter
with a miniaturized ultrasound
probe attached to the distal end of the catheter. The proximal end of the catheter
is attached to computerized ultrasound
equipment. It allows the application of ultrasound
technology to see from inside blood vessel
s out through the surrounding blood
column, visualizing the endothelium
(inner wall) of blood vessel
s in living individuals.
The arteries
of the heart
(the coronary arteries
) are the most frequent imaging target for IVUS. IVUS is used in the coronary arteries to determine the amount of atheromatous plaque
built up at any particular point in the epicardial coronary artery. The progressive accumulation of plaque within the artery wall over decades is the setup for vulnerable plaque
which, in turn, leads to heart attack
and stenosis
(narrowing) of the artery (known as coronary artery lesions). IVUS is of use to determine both plaque volume within the wall of the artery and/or the degree of stenosis of the artery lumen
. It can be especially useful in situations in which angiographic imaging is considered unreliable; such as for the lumen of ostial lesions or where angiographic images do not visualize lumen segments adequately, such as regions with multiple overlapping arterial segments. It is also used to assess the effects of treatments of stenosis such as with hydraulic angioplasty expansion of the artery, with or without stents, and the results of medical therapy over time.
process in living people. Based on the angiographic view and long popular medical beliefs, it had long been assumed that areas of high grade stenosis
(narrowing) of the lumen
(opening) within the coronary arteries
, visible by angiography, were the likely points at which most myocardial infarctions (heart attacks) would occur. Research using IVUS has helped to reveal the fallacy (in most instances) of this belief.
IVUS enables accurately visualizing not only the lumen of the coronary arteries but also the atheroma
(membrane/cholesterol loaded white blood cells) "hidden" within the wall. IVUS has thus enabled advances in clinical research providing a more thorough perspective and better understanding.
In the early 1990s, IVUS research on the re-stenosis problem after angioplasty
lead to recognition that most of the re-stenosis problem (as visualized by an angiography examination) was not true re-stenosis. Instead it was simply a remodeling of the atheromatous plaque, which was still protruding into the lumen of the artery after completion of angioplasty; the stenosis only appearing to be reduced because blood and contrast could now flow around and through some of the plaque. The angiographic dye column appeared widened adequately; yet considerable plaque was within the newly widened lumen and the lumen remained partially obstructed. This recognition promoted more frequent use of stent
s to hold the plaque outward against the inner artery walls, out of the lumen.
Additionally, IVUS examinations, as they were done more frequently, served to reveal and confirm the autopsy research findings of the late 1980s, showing that atheromatous plaque tends to cause expansion of the internal elastic lamina, causing the degree of plaque burden to be greatly underestimated by angiography. Angiography only reveals the edge of the atheroma that protrudes into the lumen.
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Perhaps the greatest contribution to understanding, so far, was achieved by clinical research trials completed in the United States in the late 1990s, using combined angiography and IVUS examination, to study which coronary lesions most commonly result in a myocardial infarction. The studies revealed that most myocardial infarctions occur at areas with extensive atheroma within the artery wall, however very little stenosis of the artery opening. The range of lumen stenosis locations at which myocardial infarctions occurred ranged from areas of mild dilatation all the way to areas of greater than 95% stenosis. However the average or typical stenosis at which myocardial infarctions occurred were found to be less than 50%, describing plaques long considered insignificant by many. Only 14% of heart attack
s occurred at locations with 75% or more stenosis, the severe stenoses previously thought by many to present the greatest danger to the individual. This research has changed the primary focus for heart attack
prevention from severe narrowing
to vulnerable plaque
.
Current clinical uses of IVUS technology include checking how to treat complex lesions before angioplasty
and checking how well an intracoronary stent has been deployed within a coronary artery after angioplasty
. If a stent is not expanded flush against the wall of the vessel, turbulent flow may occur between the stent and the wall of the vessel; some fear this might create a nidus for acute thrombosis
of the artery.
The computerized IVUS echocardiographic imaging systems list for $120,000, US, 2007 for a cart based system and ~$70,000 for an installed or integrated solution. The disposable catheters used to do each examination typically cost ~$600, US, 2007. In many hospitals, the IVUS system is placed as part of a bundle deal based on minimum disposable sales volumes. In other words, the cost of the console is paid for by rebates from other purchased products including IVUS catheters. Because no standard exists, IVUS catheters cannot be interchanged between different manufacturers.
Additionally, IVUS adds significant additional examination time and some increased risk to the patient beyond performing a standard diagnostic angiographic examination. This increase is significantly less when IVUS is part of a percutaneous coronary intervention
, since much of the setup is the same for the intervention as for the IVUS imaging.
IVUS continues to improve and some manufacturers have proposed building IVUS technology into angioplasty
and stent
balloon catheters, a potential major advance, but limited by complexity, cost and increased bulk of the catheters.
or vein
, angiographic techniques are used and the physician positions the tip of a guidewire, usually 0.36 mm (0.014") diameter with a very soft and pliable tip and about 200 cm long. The physician steers the guidewire from outside the body, through angiography catheters and into the blood vessel branch to be imaged.
The ultrasound catheter tip is slid in over the guidewire and positioned, using angiography techniques so that the tip is at the farthest away position to be imaged. The sound waves are emitted from the catheter tip, are usually in the 20-40 MHz range, and the catheter also receives and conducts the return echo information out to the external computerized ultrasound equipment which constructs and displays a real time ultrasound image of a thin section of the blood vessel currently surrounding the catheter tip, usually displayed at 30 frames/second image.
The guide wire is kept stationary and the ultrasound catheter tip is slid backwards, usually under motorized control at a pullback speed of 0.5 mm/s. (The motorized pullback tends to be smoother than hand movement by the physician.)
The (a) blood vessel wall inner lining
, (b) atheromatous disease within the wall and (c) connective tissues covering the outer surface of the blood vessel are echogenic, i.e. they return echoes making them visible on the ultrasound display.
By contrast, the blood itself and the healthy muscular tissue portion of the blood vessel wall is relatively echolucent, just black circular spaces, in the images.
Heavy calcium deposits
in the blood vessel wall both heavily reflect sound, i.e. are very echogenic, but are also distinguishable by shadowing. Heavy calcification blocks sound transmission beyond and so, in the echo images, are seen as both very bright areas but with black shadows behind (from the vantage point of the catheter tip emitting the ultrasound waves).
wall in living animals and humans. It has led to an explosion of better understanding and research on both (a) the behavior of the atherosclerosis
process and (b) the effects of different treatment strategies for changing the evolution of the atherosclerosis disease process. This has been important given that atherosclerosis is the single most frequent disease process for the greatest percentage of individuals living in first world countries.
While the routine use of IVUS during percutaneous coronary intervention
does not improve short term outcomes, there are a number of situations in which IVUS is of particular use in the treatment of coronary artery disease of the heart
. In particular in cases when the degree of stenosis of a coronary artery is unclear, IVUS can directly quantify the percentage of stenosis and give insight into the anatomy of the plaque.
One particular use of IVUS in the coronary anatomy is in the quantification of left main disease in cases where routine coronary angiography gives equivocal results. Many studies in the past have shown that significant left main disease can increase mortality
, and that intervention (either coronary artery bypass graft surgery or percutaneous coronary intervention
) to reduce mortality is necessary when the left main stenosis is significant.
When using IVUS to determine whether an individual's left main disease is clinically significant, in terms of the desirability of physical intervention, the two most widely used parameters are the degree of stenosis and the minimal lumen area. A cross sectional area of ≤7 mm² in a symptomatic individual or ≤6 mm² in an asymptomatic individual is considered to be clinically significant and warrants intervention to improve one-year mortality. However, these exact cutoffs are up for debate and different cutoff cross-sectional areas may be used in practice depending on differing interpretations of the trial data.
s, torcetrapib
and other approaches.
Medical imaging
Medical imaging is the technique and process used to create images of the human body for clinical purposes or medical science...
methodology using a specially designed catheter
Catheter
In medicine, a catheter is a tube that can be inserted into a body cavity, duct, or vessel. Catheters thereby allow drainage, administration of fluids or gases, or access by surgical instruments. The process of inserting a catheter is catheterization...
with a miniaturized ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
probe attached to the distal end of the catheter. The proximal end of the catheter
Catheter
In medicine, a catheter is a tube that can be inserted into a body cavity, duct, or vessel. Catheters thereby allow drainage, administration of fluids or gases, or access by surgical instruments. The process of inserting a catheter is catheterization...
is attached to computerized ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
equipment. It allows the application of ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
technology to see from inside blood vessel
Blood vessel
The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...
s out through the surrounding blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
column, visualizing the endothelium
Endothelium
The endothelium is the thin layer of cells that lines the interior surface of blood vessels, forming an interface between circulating blood in the lumen and the rest of the vessel wall. These cells are called endothelial cells. Endothelial cells line the entire circulatory system, from the heart...
(inner wall) of blood vessel
Blood vessel
The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...
s in living individuals.
The arteries
Artery
Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....
of the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
(the coronary arteries
Coronary circulation
Coronary circulation is the circulation of blood in the blood vessels of the heart muscle . The vessels that deliver oxygen-rich blood to the myocardium are known as coronary arteries...
) are the most frequent imaging target for IVUS. IVUS is used in the coronary arteries to determine the amount of atheromatous plaque
Atheroma
In pathology, an atheroma is an accumulation and swelling in artery walls that is made up of macrophage cells, or debris, that contain lipids , calcium and a variable amount of fibrous connective tissue...
built up at any particular point in the epicardial coronary artery. The progressive accumulation of plaque within the artery wall over decades is the setup for vulnerable plaque
Vulnerable plaque
A vulnerable plaque is a kind of atheromatous plaque – a collection of white blood cells and lipids in the wall of an artery - that is particularly unstable and prone to produce sudden major problems, such as a heart attack or stroke.In many cases, a vulnerable plaque has a thin fibrous cap and a...
which, in turn, leads to heart attack
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...
and stenosis
Stenosis
A stenosis is an abnormal narrowing in a blood vessel or other tubular organ or structure.It is also sometimes called a stricture ....
(narrowing) of the artery (known as coronary artery lesions). IVUS is of use to determine both plaque volume within the wall of the artery and/or the degree of stenosis of the artery lumen
Lumen (anatomy)
A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...
. It can be especially useful in situations in which angiographic imaging is considered unreliable; such as for the lumen of ostial lesions or where angiographic images do not visualize lumen segments adequately, such as regions with multiple overlapping arterial segments. It is also used to assess the effects of treatments of stenosis such as with hydraulic angioplasty expansion of the artery, with or without stents, and the results of medical therapy over time.
Advantages over angiography
Arguably the most valuable use of IVUS is to visualize plaque, which cannot be seen by angiography. It has been increasingly used in research to better understand the behavior of the atherosclerosisAtherosclerosis
Atherosclerosis is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol...
process in living people. Based on the angiographic view and long popular medical beliefs, it had long been assumed that areas of high grade stenosis
Stenosis
A stenosis is an abnormal narrowing in a blood vessel or other tubular organ or structure.It is also sometimes called a stricture ....
(narrowing) of the lumen
Lumen (anatomy)
A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...
(opening) within the coronary arteries
Coronary circulation
Coronary circulation is the circulation of blood in the blood vessels of the heart muscle . The vessels that deliver oxygen-rich blood to the myocardium are known as coronary arteries...
, visible by angiography, were the likely points at which most myocardial infarctions (heart attacks) would occur. Research using IVUS has helped to reveal the fallacy (in most instances) of this belief.
IVUS enables accurately visualizing not only the lumen of the coronary arteries but also the atheroma
Atheroma
In pathology, an atheroma is an accumulation and swelling in artery walls that is made up of macrophage cells, or debris, that contain lipids , calcium and a variable amount of fibrous connective tissue...
(membrane/cholesterol loaded white blood cells) "hidden" within the wall. IVUS has thus enabled advances in clinical research providing a more thorough perspective and better understanding.
In the early 1990s, IVUS research on the re-stenosis problem after angioplasty
Angioplasty
Angioplasty is the technique of mechanically widening a narrowed or obstructed blood vessel, the latter typically being a result of atherosclerosis. An empty and collapsed balloon on a guide wire, known as a balloon catheter, is passed into the narrowed locations and then inflated to a fixed size...
lead to recognition that most of the re-stenosis problem (as visualized by an angiography examination) was not true re-stenosis. Instead it was simply a remodeling of the atheromatous plaque, which was still protruding into the lumen of the artery after completion of angioplasty; the stenosis only appearing to be reduced because blood and contrast could now flow around and through some of the plaque. The angiographic dye column appeared widened adequately; yet considerable plaque was within the newly widened lumen and the lumen remained partially obstructed. This recognition promoted more frequent use of stent
Stent
In the technical vocabulary of medicine, a stent is an artificial 'tube' inserted into a natural passage/conduit in the body to prevent, or counteract, a disease-induced, localized flow constriction. The term may also refer to a tube used to temporarily hold such a natural conduit open to allow...
s to hold the plaque outward against the inner artery walls, out of the lumen.
Additionally, IVUS examinations, as they were done more frequently, served to reveal and confirm the autopsy research findings of the late 1980s, showing that atheromatous plaque tends to cause expansion of the internal elastic lamina, causing the degree of plaque burden to be greatly underestimated by angiography. Angiography only reveals the edge of the atheroma that protrudes into the lumen.
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...
s occurred at locations with 75% or more stenosis, the severe stenoses previously thought by many to present the greatest danger to the individual. This research has changed the primary focus for heart attack
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...
prevention from severe narrowing
Stenosis
A stenosis is an abnormal narrowing in a blood vessel or other tubular organ or structure.It is also sometimes called a stricture ....
to vulnerable plaque
Vulnerable plaque
A vulnerable plaque is a kind of atheromatous plaque – a collection of white blood cells and lipids in the wall of an artery - that is particularly unstable and prone to produce sudden major problems, such as a heart attack or stroke.In many cases, a vulnerable plaque has a thin fibrous cap and a...
.
Current clinical uses of IVUS technology include checking how to treat complex lesions before angioplasty
Angioplasty
Angioplasty is the technique of mechanically widening a narrowed or obstructed blood vessel, the latter typically being a result of atherosclerosis. An empty and collapsed balloon on a guide wire, known as a balloon catheter, is passed into the narrowed locations and then inflated to a fixed size...
and checking how well an intracoronary stent has been deployed within a coronary artery after angioplasty
Angioplasty
Angioplasty is the technique of mechanically widening a narrowed or obstructed blood vessel, the latter typically being a result of atherosclerosis. An empty and collapsed balloon on a guide wire, known as a balloon catheter, is passed into the narrowed locations and then inflated to a fixed size...
. If a stent is not expanded flush against the wall of the vessel, turbulent flow may occur between the stent and the wall of the vessel; some fear this might create a nidus for acute thrombosis
Thrombosis
Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...
of the artery.
Disadvantages versus angiography
The primary disadvantages of IVUS being used routinely in a cardiac catheterization laboratory are its expense, the increase in the time of the procedure, and the fact that it is considered an interventional procedure, and should only be performed by angiographers that are trained in interventional cardiology techniques. In addition, there may be additional risk imposed by the use of the IVUS catheter.The computerized IVUS echocardiographic imaging systems list for $120,000, US, 2007 for a cart based system and ~$70,000 for an installed or integrated solution. The disposable catheters used to do each examination typically cost ~$600, US, 2007. In many hospitals, the IVUS system is placed as part of a bundle deal based on minimum disposable sales volumes. In other words, the cost of the console is paid for by rebates from other purchased products including IVUS catheters. Because no standard exists, IVUS catheters cannot be interchanged between different manufacturers.
Additionally, IVUS adds significant additional examination time and some increased risk to the patient beyond performing a standard diagnostic angiographic examination. This increase is significantly less when IVUS is part of a percutaneous coronary intervention
Percutaneous coronary intervention
Percutaneous coronary intervention , commonly known as coronary angioplasty or simply angioplasty, is one therapeutic procedure used to treat the stenotic coronary arteries of the heart found in coronary heart disease. These stenotic segments are due to the build up of cholesterol-laden plaques...
, since much of the setup is the same for the intervention as for the IVUS imaging.
IVUS continues to improve and some manufacturers have proposed building IVUS technology into angioplasty
Angioplasty
Angioplasty is the technique of mechanically widening a narrowed or obstructed blood vessel, the latter typically being a result of atherosclerosis. An empty and collapsed balloon on a guide wire, known as a balloon catheter, is passed into the narrowed locations and then inflated to a fixed size...
and stent
Stent
In the technical vocabulary of medicine, a stent is an artificial 'tube' inserted into a natural passage/conduit in the body to prevent, or counteract, a disease-induced, localized flow constriction. The term may also refer to a tube used to temporarily hold such a natural conduit open to allow...
balloon catheters, a potential major advance, but limited by complexity, cost and increased bulk of the catheters.
Method
To visualize an arteryArtery
Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....
or vein
Vein
In the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...
, angiographic techniques are used and the physician positions the tip of a guidewire, usually 0.36 mm (0.014") diameter with a very soft and pliable tip and about 200 cm long. The physician steers the guidewire from outside the body, through angiography catheters and into the blood vessel branch to be imaged.
The ultrasound catheter tip is slid in over the guidewire and positioned, using angiography techniques so that the tip is at the farthest away position to be imaged. The sound waves are emitted from the catheter tip, are usually in the 20-40 MHz range, and the catheter also receives and conducts the return echo information out to the external computerized ultrasound equipment which constructs and displays a real time ultrasound image of a thin section of the blood vessel currently surrounding the catheter tip, usually displayed at 30 frames/second image.
The guide wire is kept stationary and the ultrasound catheter tip is slid backwards, usually under motorized control at a pullback speed of 0.5 mm/s. (The motorized pullback tends to be smoother than hand movement by the physician.)
The (a) blood vessel wall inner lining
Endothelium
The endothelium is the thin layer of cells that lines the interior surface of blood vessels, forming an interface between circulating blood in the lumen and the rest of the vessel wall. These cells are called endothelial cells. Endothelial cells line the entire circulatory system, from the heart...
, (b) atheromatous disease within the wall and (c) connective tissues covering the outer surface of the blood vessel are echogenic, i.e. they return echoes making them visible on the ultrasound display.
By contrast, the blood itself and the healthy muscular tissue portion of the blood vessel wall is relatively echolucent, just black circular spaces, in the images.
Heavy calcium deposits
Calcification
Calcification is the process in which calcium salts build up in soft tissue, causing it to harden. Calcifications may be classified on whether there is mineral balance or not, and the location of the calcification.-Causes:...
in the blood vessel wall both heavily reflect sound, i.e. are very echogenic, but are also distinguishable by shadowing. Heavy calcification blocks sound transmission beyond and so, in the echo images, are seen as both very bright areas but with black shadows behind (from the vantage point of the catheter tip emitting the ultrasound waves).
Uses
IVUS, as outlined above, has been the best technology, so far, to demonstrate the anatomy of the arteryArtery
Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....
wall in living animals and humans. It has led to an explosion of better understanding and research on both (a) the behavior of the atherosclerosis
Atherosclerosis
Atherosclerosis is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol...
process and (b) the effects of different treatment strategies for changing the evolution of the atherosclerosis disease process. This has been important given that atherosclerosis is the single most frequent disease process for the greatest percentage of individuals living in first world countries.
Intravascular ultrasound in the coronary anatomy
Percutaneous coronary intervention
Percutaneous coronary intervention , commonly known as coronary angioplasty or simply angioplasty, is one therapeutic procedure used to treat the stenotic coronary arteries of the heart found in coronary heart disease. These stenotic segments are due to the build up of cholesterol-laden plaques...
does not improve short term outcomes, there are a number of situations in which IVUS is of particular use in the treatment of coronary artery disease of the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
. In particular in cases when the degree of stenosis of a coronary artery is unclear, IVUS can directly quantify the percentage of stenosis and give insight into the anatomy of the plaque.
One particular use of IVUS in the coronary anatomy is in the quantification of left main disease in cases where routine coronary angiography gives equivocal results. Many studies in the past have shown that significant left main disease can increase mortality
Death
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....
, and that intervention (either coronary artery bypass graft surgery or percutaneous coronary intervention
Percutaneous coronary intervention
Percutaneous coronary intervention , commonly known as coronary angioplasty or simply angioplasty, is one therapeutic procedure used to treat the stenotic coronary arteries of the heart found in coronary heart disease. These stenotic segments are due to the build up of cholesterol-laden plaques...
) to reduce mortality is necessary when the left main stenosis is significant.
When using IVUS to determine whether an individual's left main disease is clinically significant, in terms of the desirability of physical intervention, the two most widely used parameters are the degree of stenosis and the minimal lumen area. A cross sectional area of ≤7 mm² in a symptomatic individual or ≤6 mm² in an asymptomatic individual is considered to be clinically significant and warrants intervention to improve one-year mortality. However, these exact cutoffs are up for debate and different cutoff cross-sectional areas may be used in practice depending on differing interpretations of the trial data.
Validating the efficacy of new treatments
Because IVUS is widely available in coronary catheterization labs worldwide and can accurately quantify arterial plaque, especially within the coronary arteries, it is increasingly being used to evaluate newer and evolving strategies for the treatment of coronary artery disease, including the statinStatin
Statins are a class of drugs used to lower cholesterol levels by inhibiting the enzyme HMG-CoA reductase, which plays a central role in the production of cholesterol in the liver. Increased cholesterol levels have been associated with cardiovascular diseases, and statins are therefore used in the...
s, torcetrapib
Torcetrapib
Torcetrapib was a drug being developed to treat hypercholesterolemia and prevent cardiovascular disease...
and other approaches.
External links
- Intravascular Ultrasound Center from Angioplasty.Org
- Reprint of ASTEROID Study, JAMA 2006;295:1556-65: This trial relies on IVUS for assessment of medical treatment.
- iLab Ultrasound Imaging System from Boston Scientific
- LipiScan IVUS Imaging System from InfraReDx, Inc.