(black butterfly-like shape) and hyperplastic
prostate (BPH) visualized by medical ultrasound Sonography (ultrasonography) 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 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 a price of deeper tissue penetration.
Anesthesiology 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 the basal
cerebral vessels.
Angiology (vascular) 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 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 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.
Cardiology (heart) showing the four chambers and mitral and
tricuspid valves
Echocardiography 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)
Emergency medicine Point of care ultrasound has many applications in
emergency medicine. These include differentiating cardiac from pulmonary causes of
acute breathlessness, and 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.
Gastroenterology/Colorectal surgery Both
abdominal and
endoanal ultrasound are frequently used in
gastroenterology and
colorectal surgery. In abdominal sonography, 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 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.
Hepatology Ultrasonography of liver tumors allows for both detection and characterization. Ultrasound imaging studies are often obtained during 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.
Gynecology and obstetrics 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 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
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 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: • Date the pregnancy (
gestational age) • Confirm fetal viability • Determine location of
fetus, intrauterine vs
ectopic • Check the location of the placenta in relation to the cervix • Check for the number of fetuses (
multiple pregnancy) • Check for major physical abnormalities. • Assess fetal growth (for evidence of
intrauterine growth restriction (IUGR)) • Check for fetal movement and heartbeat. • Determine the sex of the baby According to the European Committee of Medical Ultrasound Safety (ECMUS) 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 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.
Hemodynamics (blood circulation) 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.
Otolaryngology (head and neck) Most structures of 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 the head and neck can be differentiated, evaluated, and managed with the help of diagnostic ultrasound and ultrasound-guided procedures.
Neonatology 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 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 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.
Ophthalmology () In
ophthalmology and
optometry, there are two major forms of eye exam using ultrasound: •
A-scan ultrasound biometry, is commonly referred to as an
A-scan (
amplitude scan).
A-mode provides data on the length of the
eye, which is a major determinant in
common sight disorders, especially for determining the power of an intraocular lens after cataract extraction. •
B-scan ultrasonography, or
B-scan-Brightness scan, is a
B-mode scan that produces a cross-sectional view of the
eye and the
orbit. It is an essential tool in ophthalmology for diagnosing and managing a wide array of conditions affecting the posterior segment of the eye.It is non invasive and uses frequency 10–15 MHz. It is often used in conjunction with other imaging techniques (like OCT or fluorescein angiography) for a more comprehensive evaluation of ocular conditions.
Pulmonology (lungs) Ultrasound is used to assess the
lungs in a variety of settings including critical care, emergency medicine, trauma surgery, as well as general medicine and nursing. This imaging modality is used at the bedside or examination table to evaluate a number of different lung abnormalities as to guide
respiratory therapy and
mechanical ventilation, and 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. Lung, or pulmonary ultrasound does not visualise the lung itself, but the tissue-air-interface at the pleural line. The fact that artefact interpretation is essential sets lung ultrasound apart from modalities aimed at imaging an actual organ. This distinction has mechanical implications that are important when trying to interpret artifactual patterns. Where modern sonography is aided by software filters and acoustic harmonics to enhance visualisation of organs such as the heart or liver, they corrupt the specific patterns sought in lung ultrasound. Therefore, a software preset void of imaging filters, harmonic imaging, and beam compounding, is preferred.
Lung ultrasound basics •
The Normal Lung Surface: The lung surface is composed of visceral and parietal
pleura. These two surfaces are typically pushed together and make up the pleural line, which is the basis of lung (or pleural) ultrasound. This line is visible less than a centimeter below the rib line in most adults. On ultrasound, it is visualized as a
hyperechoic (bright white) horizontal line if the ultrasound probe is applied perpendicularly to the skin. •
Artifacts: Lung ultrasound relies on artifacts, which would otherwise be considered a hindrance in imaging. Air blocks the ultrasound beam and thus visualizing healthy lung tissue itself with this mode of imaging is not practical. Consequently, physicians and sonographers have learned to recognize patterns that ultrasound beams create when imaging healthy versus diseased lung tissue. Three commonly seen and utilized artifacts in lung ultrasound include lung sliding, A-lines, and B-lines. • §
Lung Sliding: The presence of lung sliding, which indicates the shimmering of the pleural line that occurs with movement of the visceral and parietal pleura against one another with respiration (sometimes described as 'ants marching'), is the most important finding in normal aerated lung. Lung sliding indicates both that the lung is present at the chest wall and that the lung is functioning. Additionally, it is important to note that there are multiple types of interactions between the pleural surface and the ultrasound wave that can generate artifacts with some similarity to B-lines but which do not have pathologic significance. •
Atelectasis: Consolidations are, as opposed to artifactual patterns, directly visualised on lung ultrasound. Differentiation of consolidations within the lung can be made with qualitative methods such as the presence of dynamic, or static air bronchograms, being air trapped within smaller airways inside of consolidations. Pathognomic changes in resorptive and
compressive atelectasis, respectively can thus be distinguished. •
Pneumothorax: In clinical settings when pneumothorax is suspected, lung ultrasound can aid in diagnosis. In pneumothorax, air is present between the two layers of the pleura and lung sliding on ultrasound is therefore absent. The
negative predictive value for lung sliding on ultrasound is reported as 99.2–100% – briefly, if lung sliding is present, a pneumothorax is effectively ruled out. Pleural effusions on ultrasound appear as structural images within the thorax rather than an artifact. They will typically have four distinct borders including the pleural line, two rib shadows, and a deep border. •
COVID-19: Lung ultrasound has proved useful in the diagnosis of COVID-19 especially in cases where other investigations are not available.
Urinary tract (black butterfly-like shape) and hyperplastic
prostate (
BPH) visualized by medical sonographic technique Ultrasound 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 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 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).
Penis and scrotum Scrotal ultrasonography is used in the evaluation of
testicular pain, and can help identify solid masses. Ultrasound is an excellent method for the study of the
penis, such as indicated in trauma, priapism, erectile dysfunction or suspected
Peyronie's disease.
Musculoskeletal 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 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.
Kidneys In
nephrology, ultrasonography of 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 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.
Venous access 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, 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 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, 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 the chosen vein. Ultrasound training for intravenous cannulation is offered in most ultrasound training programs. == Mechanism ==