Elastography is any of a class of medical imaging modalities that map the elastic properties and stiffness of soft tissue . The main idea is that whether the tissue is hard or soft will give diagnostic information about the presence or status of disease . For example, cancerous tumours will often be harder than the surrounding tissue, and diseased livers are stiffer than healthy ones.
79-686: The most prominent techniques use ultrasound or magnetic resonance imaging (MRI) to make both the stiffness map and an anatomical image for comparison. Palpation is the practice of feeling the stiffness of a person's or animal's tissues with the health practitioner's hands. Manual palpation dates back at least to 1500 BC, with the Egyptian Ebers Papyrus and Edwin Smith Papyrus both giving instructions on diagnosis with palpation. In ancient Greece , Hippocrates gave instructions on many forms of diagnosis using palpation, including palpation of
158-438: A false negative misdiagnosis. Naturally, elastography sees use for organs and diseases where manual palpation was already widespread. Elastography is used for detection and diagnosis of breast , thyroid , and prostate cancers. Certain types of elastography are also suitable for musculoskeletal imaging, and they can determine the mechanical properties and state of muscles and tendons . Because elastography does not have
237-424: A probe . The ultrasound pulses echo off tissues with different reflection properties and are returned to the probe which records and displays them as an image. A general-purpose ultrasonic transducer may be used for most imaging purposes but some situations may require the use of a specialized transducer. Most ultrasound examination is done using a transducer on the surface of the body, but improved visualization
316-583: A 'push' inside the tissue using the acoustic radiation force from a focused ultrasound beam. The amount the tissue along the axis of the beam is pushed down is reflective of tissue stiffness; softer tissue is more easily pushed than stiffer tissue. ARFI shows a qualitative stiffness value along the axis of the pushing beam. By pushing in many different places, a map of the tissue stiffness is built up. Virtual Touch imaging quantification (VTIQ) has been successfully used to identify malignant cervical lymph nodes. In shear-wave elasticity imaging (SWEI), similar to ARFI,
395-400: A 'push' is induced deep in the tissue by acoustic radiation force . The disturbance created by this push travels sideways through the tissue as a shear wave . By using an image modality like ultrasound or MRI to see how fast the wave gets to different lateral positions, the stiffness of the intervening tissue is inferred. Since the terms "elasticity imaging" and "elastography" are synonyms,
474-498: A 2-D stiffness map. No shear waves are involved in ARFI and no axial elasticity assessment is involved in SWEI. SWEI is implemented in supersonic shear imaging (SSI). Supersonic shear imaging (SSI) gives a quantitative, real-time two-dimensional map of tissue stiffness. SSI is based on SWEI: it uses acoustic radiation force to induce a 'push' inside the tissue of interest generating shear waves and
553-400: A distortion to observe. These are: The primary way elastographic techniques are categorized is by what imaging modality (type) they use to observe the response. Elastographic techniques use ultrasound , magnetic resonance imaging (MRI) and pressure/stress sensors in tactile imaging (TI) using tactile sensor (s). There are a handful of other methods that exist as well. The observation of
632-419: A great many ultrasound elastographic techniques. The most prominent are highlighted below. Quasistatic elastography (sometimes called simply 'elastography' for historical reasons) is one of the earliest elastography techniques. In this technique, an external compression is applied to tissue, and the ultrasound images before and after the compression are compared. The areas of the image that are least deformed are
711-536: A method of signal generation and processing that results in a specific application. Most imaging techniques are operating in B-mode. Therapeutic ultrasound aimed at a specific tumor or calculus is not an imaging mode. However, for positioning a treatment probe to focus on a specific region of interest, A-mode and B-mode are typically used, often during treatment. Compared to other medical imaging modalities, ultrasound has several advantages. It provides images in real-time,
790-489: A price of deeper tissue penetration. In anesthesiology , ultrasound is commonly used to guide the placement of needles when injecting local anesthetic solutions in the proximity of nerves identified within the ultrasound image (nerve block). It is also used for vascular access such as cannulation of large central veins and for difficult arterial cannulation . Transcranial Doppler is frequently used by neuro-anesthesiologists for obtaining information about flow-velocity in
869-407: A single-cell resolution. When using these imaging modalities, quasi-static compression may be induced in the tissue sample by a micro-indentation device, such as a microtweezer. The resultant deformation can be measured from the microscopy images using image-based nodal tracking algorithms, and mechanical properties can be discerned using finite element method (FEM) analyses. Elastography is used for
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#1732858656699948-405: A useful hint to treat patients with symptoms related to pelvic prolapse, double incontinence and obstructed defecation. It is also used to diagnose and, at higher frequencies, to treat (break up) kidney stones or kidney crystals ( nephrolithiasis ). Scrotal ultrasonography is used in the evaluation of testicular pain , and can help identify solid masses. Ultrasound is an excellent method for
1027-421: Is portable , and can consequently be brought to the bedside. It is substantially lower in cost than other imaging strategies. Drawbacks include various limits on its field of view, the need for patient cooperation, dependence on patient physique, difficulty imaging structures obscured by bone , air or gases, and the necessity of a skilled operator, usually with professional training. Sonography (ultrasonography)
1106-456: Is a common medical procedure. The need for intravenous access occurs in the outpatient laboratory, in the inpatient hospital units, and most critically in the Emergency Room and Intensive Care Unit. In many situations, intravenous access may be required repeatedly or over a significant time period. In these latter circumstances, a needle with an overlying catheter is introduced into the vein and
1185-408: Is an emerging technique that that utilizes optical microscopy to obtain tissue images. The most common form of optical elastography, optical coherence elastography (OCE), is based on optical coherence tomography (OCT), which combines interferometry with lateral beam scanning for rapid 3D image acquisition and achieves spatial resolutions of 5-15 μm. For OCE, a mechanical load is applied to the tissue and
1264-421: Is an essential tool in cardiology , assisting in evaluation of heart valve function, such as stenosis or insufficiency , strength of cardiac muscle contraction, and hypertrophy or dilatation of the main chambers. ( ventricle and atrium ) Point of care ultrasound has many applications in emergency medicine . These include differentiating cardiac from pulmonary causes of acute breathlessness , and
1343-545: Is called obstetric ultrasonography , and was an early development of clinical ultrasonography. The machine used is called an ultrasound machine , a sonograph or an echograph . The visual image formed using this technique is called an ultrasonogram , a sonogram or an echogram . Ultrasound is composed of sound waves with frequencies greater than 20,000 Hz, which is the approximate upper threshold of human hearing. Ultrasonic images, also known as sonograms, are created by sending pulses of ultrasound into tissue using
1422-440: Is curable but must be treated to preserve health and fertility. There are two methods of performing pelvic sonography – externally or internally. The internal pelvic sonogram is performed either trans vaginally (in a woman) or transrectally (in a man). Sonographic imaging of the pelvic floor can produce important diagnostic information regarding the precise relationship of abnormal structures with other pelvic organs and it represents
1501-470: Is implemented in a device which can also assess the controlled attenuation parameter (CAP) which is good surrogate marker of liver steatosis . Magnetic resonance elastography (MRE) was introduced in the mid-1990s, and multiple clinical applications have been investigated. In MRE, a mechanical vibrator is used on the surface of the patient's body; this creates shear waves that travel into the patient's deeper tissues. An imaging acquisition sequence that measures
1580-440: Is moved through the medium at a supersonic speed. Second, the generated shear wave is visualized by using ultrafast imaging technique. Using inversion algorithms, the shear elasticity of medium is mapped quantitatively from the wave propagation movie. SSI is the first ultrasonic imaging technology able to reach more than 10,000 frames per second of deep-seated organs. SSI provides a set of quantitative and in vivo parameters describing
1659-459: Is often possible if a transducer can be placed inside the body. For this purpose, special-use transducers, including transvaginal , endorectal, and transesophageal transducers are commonly employed. At the extreme, very small transducers can be mounted on small diameter catheters and placed within blood vessels to image the walls and disease of those vessels. The imaging mode refers to probe and machine settings that result in specific dimensions of
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#17328586566991738-620: Is often used as image guidance for renal interventions. Furthermore, novel applications in renal US have been introduced with contrast-enhanced ultrasound (CEUS), elastography and fusion imaging. However, renal US has certain limitations, and other modalities, such as CT (CECT) and MRI, should be considered for supplementary imaging in assessing renal disease. Intravenous access, for the collection of blood samples to assist in diagnosis or laboratory investigation including blood culture, or for administration of intravenous fluids for fluid maintenance of replacement or blood transfusion in sicker patients,
1817-499: Is routinely used in urology to determine the amount of fluid retained in a patient's bladder. In a pelvic sonogram, images include the uterus and ovaries or urinary bladder in females. In males, a sonogram will provide information about the bladder, prostate , or testicles (for example to urgently distinguish epididymitis from testicular torsion ). In young males, it is used to distinguish more benign testicular masses ( varicocele or hydrocele ) from testicular cancer , which
1896-419: Is that they create a distortion in the tissue, observe and process the tissue response to infer the mechanical properties of the tissue, and then display the results to the operator, usually as an image. Each elastographic method is characterized by the way it does each of these things. To image the mechanical properties of tissue, we need to see how it behaves when deformed. There are three main ways of inducing
1975-548: Is the initial imaging choice, avoiding radiation if possible, although it frequently needs to be followed by other imaging methods such as CT . Endoanal ultrasound is used particularly in the investigation of anorectal symptoms such as fecal incontinence or obstructed defecation . It images the immediate perianal anatomy and is able to detect occult defects such as tearing of the anal sphincter . Ultrasonography of liver tumors allows for both detection and characterization. Ultrasound imaging studies are often obtained during
2054-399: Is the separation of shear waves and compression waves. The technique can be implemented in 1D and 2D which required the development of an ultrafast ultrasound scanner. Transient elastography gives a quantitative one-dimensional (i.e. a line) image of "tissue" stiffness. It functions by vibrating the skin with a motor to create a passing distortion in the tissue (a shear wave ), and imaging
2133-448: Is used at the bedside or examination table to evaluate a number of different lung abnormalities as well as to guide procedures such as thoracentesis , (drainage of pleural fluid (effusion)), needle aspiration biopsy, and catheter placement. Although air present in the lungs does not allow good penetration of ultrasound waves, interpretation of specific artifacts created on the lung surface can be used to detect abnormalities. Ultrasound
2212-488: Is used for imaging flow in the intracerebral arteries. Intravascular ultrasound ( IVUS ) uses a specially designed catheter with a miniaturized ultrasound probe attached to its distal end, which is then threaded inside a blood vessel. The proximal end of the catheter is attached to computerized ultrasound equipment and allows the application of ultrasound technology, such as a piezoelectric transducer or capacitive micromachined ultrasonic transducer , to visualize
2291-437: Is used to create an image of internal body structures such as tendons , muscles , joints, blood vessels, and internal organs, to measure some characteristics (e.g., distances and velocities) or to generate an informative audible sound. The usage of ultrasound to produce visual images for medicine is called medical ultrasonography or simply sonography , or echography . The practice of examining pregnant women using ultrasound
2370-485: Is widely used in medicine . It is possible to perform both diagnosis and therapeutic procedures , using ultrasound to guide interventional procedures such as biopsies or to drain collections of fluid, which can be both diagnostic and therapeutic. Sonographers are medical professionals who perform scans which are traditionally interpreted by radiologists, physicians who specialize in the application and interpretation of medical imaging modalities, or by cardiologists in
2449-632: The Focused Assessment with Sonography for Trauma (FAST) exam , extended to include assessment for significant hemoperitoneum or pericardial tamponade after trauma ( EFAST ). Other uses include assisting with differentiating causes of abdominal pain such as gallstones and kidney stones . Emergency Medicine Residency Programs have a substantial history of promoting the use of bedside ultrasound during physician training. Both abdominal and endoanal ultrasound are frequently used in gastroenterology and colorectal surgery . In abdominal sonography,
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2528-425: The endothelium of blood vessels in living individuals. In the case of the common and potentially, serious problem of blood clots in the deep veins of the leg, ultrasound plays a key diagnostic role, while ultrasonography of chronic venous insufficiency of the legs focuses on more superficial veins to assist with planning of suitable interventions to relieve symptoms or improve cosmetics. Echocardiography
2607-440: The transducer at the desired frequency. The frequencies can vary between 1 and 18 MHz , though frequencies up to 50–100 megahertz have been used experimentally in a technique known as biomicroscopy in special regions, such as the anterior chamber of the eye. Older technology transducers focused their beam with physical lenses. Contemporary technology transducers use digital antenna array techniques (piezoelectric elements in
2686-571: The 90s , 2.5% of 4,000 people born in 1991 and 1992 were found by ultrasound scanning at the age of 18 to have non-alcoholic fatty liver disease; five years later transient elastography found over 20% to have the fatty deposits on the liver of steatosis, indicating non-alcoholic fatty liver disease; half of those were classified as severe. The scans also found that 2.4% had the liver scarring of fibrosis , which can lead to cirrhosis . Other techniques include elastography with optical coherence tomography (i.e. light). Tactile imaging involves translating
2765-769: The absence of sonography. It is currently believed that the risk of delayed diagnosis is greater than the small risk, if any, associated with undergoing an ultrasound scan. However, its use for non-medical purposes such as fetal "keepsake" videos and photos is discouraged. Obstetric ultrasound is primarily used to: According to the European Committee of Medical Ultrasound Safety (ECMUS) Ultrasonic examinations should only be performed by competent personnel who are trained and updated in safety matters. Ultrasound produces heating, pressure changes and mechanical disturbances in tissue. Diagnostic levels of ultrasound can produce temperature rises that are hazardous to sensitive organs and
2844-424: The basal cerebral vessels . In angiology or vascular medicine, duplex ultrasound (B Mode imaging combined with Doppler flow measurement) is used to diagnose arterial and venous disease. This is particularly important in potential neurologic problems , where carotid ultrasound is commonly used for assessing blood flow and potential or suspected stenosis in the carotid arteries , while transcranial Doppler
2923-513: The brain. It also has the advantage of being more uniform across operators and less dependent on operator skill than most methods of ultrasound elastography. MR elastography has made significant advances over the past few years with acquisition times down to a minute or less and has been used in a variety of medical applications including cardiology research on living human hearts. MR elastography's short acquisition time also makes it competitive with other elastography techniques. Optical elastography
3002-407: The breasts, wounds, bowels, ulcers, uterus, skin, and tumours. In the modern Western world, palpation became considered a respectable method of diagnosis in the 1930s. Since then, the practice of palpation has become widespread, and it is considered an effective method of detecting tumours and other pathologies. Manual palpation has several important limitations: it is limited to tissues accessible to
3081-510: The case of cardiac ultrasonography ( echocardiography ). Sonography is effective for imaging soft tissues of the body. Superficial structures such as muscle , tendon , testis , breast , thyroid and parathyroid glands, and the neonatal brain are imaged at higher frequencies (7–18 MHz), which provide better linear (axial) and horizontal (lateral) resolution . Deeper structures such as liver and kidney are imaged at lower frequencies (1–6 MHz) with lower axial and lateral resolution as
3160-578: The catheter is then inserted securely into the vein while the needle is withdrawn. The chosen veins are most frequently selected from the arm, but in challenging situations, a deeper vein from the neck ( external jugular vein ) or upper arm ( subclavian vein ) may need to be used. There are many reasons why the selection of a suitable vein may be problematic. These include, but are not limited to, obesity, previous injury to veins from inflammatory reaction to previous 'blood draws', previous injury to veins from recreational drug use. In these challenging situations,
3239-415: The chosen vein. Ultrasound training for intravenous cannulation is offered in most ultrasound training programs. The creation of an image from sound has three steps – transmitting a sound wave , receiving echoes , and interpreting those echoes. A sound wave is typically produced by a piezoelectric transducer encased in a plastic housing. Strong, short electrical pulses from the ultrasound machine drive
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3318-399: The embryo/fetus. Biological effects of non-thermal origin have been reported in animals but, to date, no such effects have been demonstrated in humans, except when a micro-bubble contrast agent is present. Nonetheless, care should be taken to use low power settings and avoid pulsed wave scanning of the fetal brain unless specifically indicated in high risk pregnancies. Figures released for
3397-464: The evaluation process of Fatty liver disease . Ultrasonography reveals a "bright" liver with increased echogenicity. Pocket-sized ultrasound devices might be used as point-of-care screening tools to diagnose liver steatosis. Gynecologic ultrasonography examines female pelvic organs (specifically the uterus , ovaries , and fallopian tubes ) as well as the bladder , adnexa , and pouch of Douglas . It uses transducers designed for approaches through
3476-415: The head and neck can be differentiated, evaluated, and managed with the help of diagnostic ultrasound and ultrasound-guided procedures. In neonatology , transcranial Doppler can be used for basic assessment of intracerebral structural abnormalities, suspected hemorrhage, ventriculomegaly or hydrocephalus and anoxic insults ( periventricular leukomalacia ). It can be performed through the soft spots in
3555-449: The image. Additionally, under compression, objects can move into or out of the image or around in the image, causing problems with interpretation. Another limit of this technique is that like manual palpation, it has difficulty with organs or tissues that are not close to the surface or easily compressed. Acoustic radiation force impulse imaging (ARFI) uses ultrasound to create a qualitative 2-D map of tissue stiffness. It does so by creating
3634-407: The insertion of a catheter into a vein has been greatly assisted by the use of ultrasound. The ultrasound unit may be 'cart-based' or 'handheld' using a linear transducer with a frequency of 10 to 15 megahertz . In most circumstances, choice of vein will be limited by the requirement that the vein is within 1.5 cms. from the skin surface. The transducer may be placed longitudinally or transversely over
3713-422: The interpretation of standard B-mode and Color mode ultrasound images. In the food industry, low-intensity ultrasonics has already been used since the 1980s to provide information about the concentration, structure, and physical state of components in foods such as vegetables, meats, and dairy products and also for quality control, for example to evaluate the rheological qualities of cheese. Transient elastography
3792-408: The investigation of many disease conditions in many organs. It can be used for additional diagnostic information compared to a mere anatomical image, and it can be used to guide biopsies or, increasingly, replace them entirely. Biopsies are invasive and painful, presenting a risk of hemorrhage or infection, whereas elastography is completely noninvasive. Elastography is used to investigate disease in
3871-423: The kidneys is essential in the diagnosis and management of kidney-related diseases. The kidneys are easily examined, and most pathological changes are distinguishable with ultrasound. It is an accessible, versatile, relatively economic, and fast aid for decision-making in patients with renal symptoms and for guidance in renal intervention. Using B-mode imaging , assessment of renal anatomy is easily performed, and US
3950-461: The lateral resolution decreases. Therefore, the wider the transducer width and the higher the frequency of ultrasound, the longer the Fresnel zone, and the lateral resolution can be maintained at a greater depth from the transducer. Ultrasound waves travel in pulses. Therefore, a shorter pulse length requires higher bandwidth (greater number of frequencies) to constitute the ultrasound pulse. As stated,
4029-443: The layers between different tissues or scattered from smaller structures. Specifically, sound is reflected anywhere where there are acoustic impedance changes in the body: e.g. blood cells in blood plasma , small structures in organs, etc. Some of the reflections return to the transducer. The return of the sound wave to the transducer results in the same process as sending the sound wave, in reverse. The returned sound wave vibrates
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#17328586566994108-421: The liver. Liver stiffness is usually indicative of fibrosis or steatosis ( fatty liver disease ), which are in turn indicative of numerous disease conditions, including cirrhosis and hepatitis . Elastography is particularly advantageous in this case because when fibrosis is diffuse (spread around in clumps rather than continuous scarring), a biopsy can easily miss sampling the diseased tissue, which results in
4187-474: The lower abdominal wall, curvilinear and sector, and specialty transducers such as transvaginal ultrasound . Obstetrical sonography was originally developed in the late 1950s and 1960s by Sir Ian Donald and is commonly used during pregnancy to check the development and presentation of the fetus . It can be used to identify many conditions that could be potentially harmful to the mother and/or baby possibly remaining undiagnosed or with delayed diagnosis in
4266-399: The major organs of the abdomen such as the pancreas , aorta , inferior vena cava , liver , gall bladder , bile ducts , kidneys , and spleen may be imaged. However, sound waves may be blocked by gas in the bowel and attenuated to differing degrees by fat, sometimes limiting diagnostic capabilities. The appendix can sometimes be seen when inflamed (e.g.: appendicitis ) and ultrasound
4345-499: The microscale between cells and whole tissues. OCT relies on longer wavelengths, of 850 - 1050 nm, and therefore provides a lower optical resolution compared to common light microscopy, which uses visible wavelengths of 400-700 nm, and provides lateral spatial resolutions of <1 μm. Examples of higher resolution analysis include the use of confocal and light-sheet microscopy respectively for mechanical characterization of multicellular spheroids and for structural analysis of 3D organoids at
4424-602: The motion of that distortion as it passes deeper into the body using a 1D ultrasound beam. It then displays a quantitative line of tissue stiffness data (the Young's modulus ). This technique is used mainly by the Fibroscan system, which is used for liver assessment, for example, to diagnose cirrhosis . A specific implementation of 1D transient elastography called VCTE has been developed to assess average liver stiffness which correlates to liver fibrosis assessed by liver biopsy. This technique
4503-437: The neck, including the thyroid and parathyroid glands , lymph nodes , and salivary glands , are well-visualized by high-frequency ultrasound with exceptional anatomic detail. Ultrasound is the preferred imaging modality for thyroid tumors and lesions, and its use is important in the evaluation, preoperative planning, and postoperative surveillance of patients with thyroid cancer . Many other benign and malignant conditions in
4582-524: The newborn, respiratory distress syndrome, congenital pneumonia, meconium aspiration syndrome, and pneumothorax. A neonatal lung ultrasound score, first described by Brat et al., has been found to highly correlate with oxygenation in the newborn. In ophthalmology and optometry , there are two major forms of eye exam using ultrasound: Ultrasound is used to assess the lungs in a variety of settings including critical care, emergency medicine, trauma surgery, as well as general medicine. This imaging modality
4661-441: The ones that are the stiffest, while the most deformed areas are the least stiff. Generally, what is displayed to the operator is an image of the relative distortions ( strains ), which is often of clinical utility. From the relative distortion image, however, making a quantitative stiffness map is often desired. To do this requires that assumptions be made about the nature of the soft tissue being imaged and about tissue outside of
4740-434: The original term SWEI denoting the technology for elasticity mapping using shear waves is often replaced by SWE. The principal difference between SWEI and ARFI is that SWEI is based on the use of shear waves propagating laterally from the beam axis and creating elasticity map by measuring shear wave propagation parameters whereas ARFI gets elasticity information from the axis of the pushing beam and uses multiple pushes to create
4819-675: The period 2005–2006 by the UK Government (Department of Health) show that non-obstetric ultrasound examinations constituted more than 65% of the total number of ultrasound scans conducted. Blood velocity can be measured in various blood vessels, such as middle cerebral artery or descending aorta , by relatively inexpensive and low risk ultrasound Doppler probes attached to portable monitors. These provide non-invasive or transcutaneous (non-piercing) minimal invasive blood flow assessment. Common examples are transcranial Doppler , esophageal Doppler and suprasternal Doppler . Most structures of
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#17328586566994898-405: The physician's hand, it is distorted by any intervening tissue, and it is qualitative but not quantitative . Elastography, the measurement of tissue stiffness, seeks to address these challenges. There are numerous elastographic techniques, in development stages from early research to extensive clinical application. Each of these techniques works in a different way. What all methods have in common
4977-446: The resultant deformation is measured using speckle tracking or phase sensitive detection. Early implementations of OCE involved applying a quasi-static compression to the tissue, though more recently dynamic loading has been achieved through the application of a sinusoidal modulation via a contact transducer or acoustic wave. Other imaging modalities with greater optical resolution have also been introduced for optical elastography to probe
5056-483: The results of a digital "touch" into an image. Many physical principles have been explored for the realization of tactile sensors : resistive, inductive, capacitive, optoelectric, magnetic, piezoelectric, and electroacoustic principles, in a variety of configurations. Medical ultrasonography Medical ultrasound includes diagnostic techniques (mainly imaging techniques) using ultrasound , as well as therapeutic applications of ultrasound. In diagnosis, it
5135-548: The same limitations as manual palpation, it is being investigated in some areas for which there is no history of diagnosis with manual palpation. For example, magnetic resonance elastography is capable of assessing the stiffness of the brain , and there is a growing body of scientific literature on elastography in healthy and diseased brains. In 2015, preliminary reports on elastography used on transplanted kidneys to evaluate cortical fibrosis have been published showing promising results. In Bristol University 's study Children of
5214-451: The skull of a newborn infant ( Fontanelle ) until these completely close at about 1 year of age by which time they have formed a virtually impenetrable acoustic barrier to ultrasound. The most common site for cranial ultrasound is the anterior fontanelle. The smaller the fontanelle, the more the image is compromised. Lung ultrasound has been found to be useful in diagnosing common neonatal respiratory diseases such as transient tachypnea of
5293-413: The sound is focused either by the shape of the transducer, a lens in front of the transducer, or a complex set of control pulses from the ultrasound scanner, in the beamforming or spatial filtering technique. This focusing produces an arc-shaped sound wave from the face of the transducer. The wave travels into the body and comes into focus at a desired depth. Materials on the face of the transducer enable
5372-408: The sound to be transmitted efficiently into the body (often a rubbery coating, a form of impedance matching ). In addition, a water-based gel is placed between the patient's skin and the probe to facilitate ultrasound transmission into the body. This is because air causes total reflection of ultrasound; impeding the transmission of ultrasound into the body. The sound wave is partially reflected from
5451-488: The stiffness can be calculated from it. Most elastography techniques find the stiffness of tissue based on one of two main principles: Some techniques will simply display the distortion and/or response, or the wave speed to the operator, while others will compute the stiffness (specifically the Young's modulus or similar shear modulus ) and display that instead. Some techniques present results quantitatively, while others only present qualitative (relative) results. There are
5530-409: The study of the penis , such as indicated in trauma, priapism, erectile dysfunction or suspected Peyronie's disease . Musculoskeletal ultrasound is used to examine tendons, muscles, nerves, ligaments, soft tissue masses, and bone surfaces. It is helpful in diagnosing ligament sprains, muscles strains and joint pathology. It is an alternative or supplement to x-ray imaging in detecting fractures of
5609-472: The tissue mechanical properties: Young's modulus, viscosity, anisotropy. This approach demonstrated clinical benefit in breast, thyroid, liver, prostate, and musculoskeletal imaging. SSI is used for breast examination with a number of high-resolution linear transducers. A large multi-center breast imaging study has demonstrated both reproducibility and significant improvement in the classification of breast lesions when shear wave elastography images are added to
5688-411: The tissue response can take many forms. In terms of the image obtained, it can be 1-D (i.e. a line), 2-D (a plane), 3-D (a volume), or 0-D (a single value), and it can be a video or a single image. In most cases, the result is displayed to the operator along with a conventional image of the tissue, which shows where in the tissue the different stiffness values occur. Once the response has been observed,
5767-454: The tissue's stiffness is computed from how fast the resulting shear wave travels through the tissue. Local tissue velocity maps are obtained with a conventional speckle tracking technique and provide a full movie of the shear wave propagation through the tissue. There are two principal innovations implemented in SSI. First, by using many near-simultaneous pushes, SSI creates a source of shear waves which
5846-491: The transducer and the transducer turns the vibrations into electrical pulses that travel to the ultrasonic scanner where they are processed and transformed into a digital image. To make an image, the ultrasound scanner must determine two characteristics from each received echo: Acoustic radiation force Too Many Requests If you report this error to the Wikimedia System Administrators, please include
5925-449: The transducer produce echoes at different times) to enable the ultrasound machine to change the direction and depth of focus. Near the transducer, the width of the ultrasound beam almost equals to the width of the transducer, after reaching a distance from the transducer (near zone length or Fresnel zone ), the beam width narrows to half of the transducer width, and after that the width increases (far zone length or Fraunhofer's zone ), where
6004-532: The ultrasound image. Several modes of ultrasound are used in medical imaging: Most machines convert two-way time to imaging depth using as assumed speed of sound of 1540 m/s. As the actual speed of sound varies greatly in different tissue types, an ultrasound image is therefore not a true tomographic representation of the body. Three-dimensional imaging is done by combining B-mode images, using dedicated rotating or stationary probes. This has also been referred to as C-mode . An imaging technique refers to
6083-413: The velocity of the waves is used, and this is used to infer the tissue's stiffness (the shear modulus ). The result of an MRE scan is a quantitative 3-D map of the tissue stiffness, as well as a conventional 3-D MRI image. One strength of MRE is the resulting 3-D elasticity map, which can cover an entire organ. Because MRI is not limited by air or bone, it can access some tissues ultrasound cannot, notably
6162-487: The wrist, elbow and shoulder for patients up to 12 years ( Fracture sonography ). Quantitative ultrasound is an adjunct musculoskeletal test for myopathic disease in children; estimates of lean body mass in adults; proxy measures of muscle quality (i.e., tissue composition) in older adults with sarcopenia Ultrasound can also be used for needle guidance in muscle or joint injections , as in ultrasound-guided hip joint injection . In nephrology , ultrasonography of
6241-564: Was initially called time-resolved pulse elastography when it was introduced in the late 1990s. The technique relies on a transient mechanical vibration which is used to induce a shear wave into the tissue. The propagation of the shear wave is tracked using ultrasound in order to assess the shear wave speed from which the Young's modulus is deduced under hypothesis of homogeneity, isotropy and pure elasticity (E=3ρV²). An important advantage of transient elastography compared to harmonic elastography techniques
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