Medical Ultrasound Imaging
Thursday, 21 November 2024
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Ultrasound technology with its advancements is vital for delivering high-quality patient care. Innovations including high-frequency ultrasound, 3D//4D imaging, contrast enhanced ultrasound, elastography, and point-of-care ultrasound, have expanded the capabilities of ultrasound imaging and improved diagnostic accuracy. B-Mode imaging, also known as brightness mode, is the fundamental technique in ultrasound imaging. It produces two-dimensional images based on the echoes received from tissues and organs. Understanding the principles of B-Mode imaging, such as gain adjustment, depth control, and image optimization, is crucial for obtaining diagnostically valuable images. M-Mode imaging, on the other hand, allows for the visualization of motion over time, enabling assessment of cardiac structures and function, as well as fetal heart rate. High-frequency ultrasound refers to the use of ultrasound waves with frequencies greater than 10 MHz. This technology enables improved resolution, allowing for detailed imaging of superficial structures like skin, tendons, and small organs. High-frequency ultrasound has found applications in dermatology, ophthalmology, and musculoskeletal imaging. Traditional 2D ultrasound has been augmented by the advent of 3D ultrasound technology. By acquiring multiple 2D images from different angles, this technique construct a volumetric representation of the imaged area. The addition of 4D ultrasound in real-time motion adds further value by capturing dynamic processes. Doppler imaging employs the Doppler effect to evaluate blood flow within vessels and assess hemodynamics. Color Doppler assigns color to different blood flow velocities, providing a visual representation of blood flow direction and speed. Spectral Doppler displays blood flow velocities as a waveform, allowing for detailed analysis of flow patterns, resistance, and stenosis. Contrast enhanced ultrasound employs microbubble contrast agents to enhance the visualization of blood flow and tissue perfusion. By injecting these agents intravenously, sonographers can differentiate between vascular structures and lesions. Elastography is a technique that measures tissue elasticity or stiffness. It assists in differentiating between normal and abnormal tissues, aiding in the diagnosis of various conditions such as liver fibrosis, breast lesions, and thyroid nodules. Fusion imaging combines ultrasound with other imaging modalities, such as computed tomography (CT), magnetic resonance imaging (MRI), or positron emission tomography (PET). By overlaying or merging ultrasound images with those obtained from other modalities, the user can precisely locate and characterize abnormalities, guide interventions, and improve diagnostic accuracy. Fusion imaging has proven particularly useful in areas such as interventional radiology, oncology, and urology. See also Equipment Preparation, Environmental Protection, Handheld Ultrasound, Portable Ultrasound and Ultrasound Accessories and Supplies. •
(CEUS) Contrast agents increase the reflection of ultrasonic energy, improve the signal to noise ratio and caused by that the detection of abnormal microvascular and macrovascular disorders. Contrast enhanced ultrasound is used in abdominal ultrasound (liver sonography) as well as in cerebrovascular examinations e.g., for an accurate grading of carotid stenosis. The used contrast agents are safe and well tolerated. The quality of the enhancement depends on:
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the concentration of the contrast agent;
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the type of injection, flow rate;
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the patient characteristics;
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the microbubble quality and properties of the filling gas and the shell.
The additional use of ultrasound contrast agents (USCAs) may overcome typical limitations like poor contrast of B-mode imaging or limited sensitivity of Doppler techniques. The development of new ultrasound applications (e.g., blood flow imaging, perfusion quantification) depends also from the development of pulse sequences for bubble specific imaging. In addition, contrast enhanced ultrasound improves the monitoring of ultrasound guided interventions like RF thermal ablation. See also Contrast Enhanced Doppler Imaging, Contrast Harmonic Imaging, Contrast Imaging Techniques and Contrast Pulse Sequencing.  Further Reading: News & More:
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(UCA / USCA) Ultrasonography is the most commonly performed diagnostic imaging procedure. The introduction of sonographic contrast media into routine practice modifies the use of ultrasound in a variety of clinical applications. USCAs consist of microbubbles filled with air or gases and can be classified according to their pharmacokinetics. Among the blood pool agents, transpulmonary ultrasound contrast agents offer higher diagnostic potential compared to agents that cannot pass the pulmonary capillary bed after a peripheral intravenous injection. In addition to their vascular phase, some USCAs can exhibit a tissue- or organ-specific phase. The sonogram image quality is improved either by decreasing the reflectivity of the undesired interfaces or by increasing the backscattered echoes from the desired regions. Different types of ultrasound contrast agents: Ultrasound contrast agents act as echo-enhancers, because of the high different acoustic impedance at the interface between gas and blood. The enhanced echo intensity is proportional to the change in acoustical impedance as the sound beam crosses from the blood to the gas in the bubbles. The ideal qualities of an ultrasound contrast agent:
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high echogenicity;
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low attenuation;
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low blood solubility;
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low diffusivity;
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ability to pass through the pulmonary capillary bed;
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lack of biological effects with repeat doses.
A typical ultrasound contrast agent consists of a thin flexible or rigid shell composed of albumin, lipid, or polymer confining a gas such as nitrogen, or a perfluorocarbon. The choice of the microbubble shell and gas has an important influence on the properties of the agent. Current generations of microbubbles have a diameter from 1 μm to 5 μm. The success of these agents is mostly dependent on the small size and on the stability of their shell, which allows passage of the microbubbles through the pulmonary circulation. Microbubbles must be made smaller than the diameter of capillaries or they would embolize and be ineffective and perhaps even dangerous. The reflectivity of these microbubbles is proportional to the fourth power of a particle diameter but also directly proportional to the concentration of the contrast agent particles themselves. Ultrasound contrast agents produce unique acoustic signatures that allow to separate their signal from tissue echoes and to depict whether they are moving or stationary. This enables the detection of capillary flow and of targeted microbubbles that are retained in tissues such as normal liver. The new generation of contrast media is characterized by prolonged persistence in the vascular bed which provides consistent enhancement of the arterial Doppler signal. Contrast agents make it also possible to perform dynamic and perfusion studies. Targeted contrast imaging agents are for example taken up by the phagocytic cell systems and thus have liver/spleen specific effects. See also Ultrasound Contrast Agent Safety, Adverse Reaction, Tissue-Specific Ultrasound Contrast Agent, and Bubble Specific Imaging. Further Reading: Basics:
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[This entry is marked for removal.] From Acusphere Inc AI-700 (trade name Imagify™) is an US contrast agent, usable for myocardial perfusion undergoing regulatory FDA approval. The synthetic polymers used in AI-700 (perflubutane polymer microspheres) do not break during the ultrasound imaging procedure. The used perfluorocarbon filling gas is less soluble in water and therefore has the propensity to stay inside the contrast agent particles. As a result, a higher concentration of gas is delivered to the myocardium over a longer period of time, thereby enabling AI-700 to target the broader application of myocardial perfusion assessment. Imagify is a dry powder consisting of small, porous microparticles filled with perfluoropropane. These microparticles are made of a synthetic biodegradable polymer, called poly (D, L-lactide co-glycolide), or PLGA, that has been used in other drug delivery systems approved by the FDA. The composition and structure of the phospholipid containing microparticles and the properties of the perfluorocarbon gas slow the rate at which the gas dissolves and prevent the microparticles from being quickly broken down. The powder is to suspend in sterile water and injected by a single intravenous injection prior to ultrasound imaging. In 2009, Acusphere Inc received feedback from the Food and Drug Administration (FDA) to their New Drug Application (NDA) stating that another clinical trial would be required for U.S. approval, this one demonstrating that Imagify with ultrasound is superior to ultrasound without Imagify. In June 2004, Acusphere entered into a Collaboration, License and Supply Agreement with Nycomed Danmark APS for the European development and marketing rights to Acusphere's lead product candidate AI-700. Acusphere's focus will be on preparing the Marketing Authorization Application (MAA) for filing in Q4 2010, building upon the work that the previous partner, Nycomed, had done, in concert with the NDA. In 2008 the FDA panel rejected the regulatory application for AI-700 (Imagify™) because of safety concerns. Further Reading: News & More:
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[This entry is marked for removal.] From POINT Biomedical Corp CARDIOsphere® is an ultrasound contrast agent for assessment of myocardial perfusion in patients with coronary artery disease composed of highly echogenic bispheres. PB127 is a new developed microbubble with a bilayer polymer/albumin shell filled with nitrogen gas that has ideal characteristics for power harmonic Doppler. They can be destroyed by high power ultrasound, and spectral decorrelation between ultrasound pulses is maximized by rapid dissolution of the released nitrogen gas. POINT Biomedical Corp. announced (March 01, 2004) that it has completed two Phase 3 trials of CARDIOsphere®. The Phase 3 trials were designed to evaluate the performance of CARDIOsphere® imaging relative to radionuclide imaging for detecting obstructive coronary artery disease and identifying the anatomic location of perfusion defects.
Drug Information and Specification
RESEARCH NAME
PB 127
DEVELOPER
INDICATION -
DEVELOPMENT STAGE Myocardial perfusion -
Phase 3 completed APPLICATION
Infusion
TYPE
Microbubble
Polylactide/Albumin
CHARGE
Slight Negative
Nitrogen
PREPARATION
Reconstitute with 2ml H2O per vial and dilute with 150 ml DSW
DO NOT RELY ON THE INFORMATION PROVIDED HERE, THEY ARE
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