Editing Medical ultrasound (section)

==Uses==
[[File:UltrasoundBPH.jpg|thumb|[[Urinary bladder]] (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 [[medical diagnosis|diagnosis]] and [[Therapeutic ultrasound|therapeutic procedures]], using [[ultrasound]] to guide interventional procedures such as [[biopsy|biopsies]] or to drain collections of fluid, which can be both diagnostic and therapeutic. [[Sonographer]]s 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.<ref>{{cite journal |last1=Izadifar |first1=Zahra |last2=Babyn |first2=Paul |last3=Chapman |first3=Dean |title=Mechanical and Biological Effects of Ultrasound: A Review of Present Knowledge |journal=Ultrasound in Medicine & Biology |date=June 2017 |volume=43 |issue=6 |pages=1085–1104 |doi=10.1016/j.ultrasmedbio.2017.01.023|pmid=28342566 |s2cid=3687095 |doi-access=free }}</ref> Superficial structures such as [[muscle]], [[tendon]], [[testes|testis]], [[breast]], [[thyroid]] and parathyroid glands, and the [[neonatal]] brain are imaged at higher [[frequency|frequencies]] (7–18&nbsp;MHz), which provide better linear (axial) and horizontal (lateral) [[Angular resolution|resolution]]. Deeper structures such as liver and kidney are imaged at lower frequencies (1–6&nbsp;MHz) with lower axial and lateral resolution as a price of deeper tissue penetration.{{citation needed|date=July 2024}}

=== Anesthesiology ===
In [[anesthesiology]], ultrasound is commonly used to guide the placement of needles when injecting local anesthetic solutions in the proximity of [[nerve]]s 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 circulation|cerebral vessels]].{{citation needed|date=April 2022}}

=== Angiology (vascular) ===
[[Image:IVUS of CAD (1).png|right|thumb|Intravascular ultrasound image of a coronary artery (left), with color-coding on the right, delineating the lumen (yellow), external elastic membrane (blue) and the atherosclerotic plaque burden (green)]]
{{Further|Doppler ultrasonography|Intravascular ultrasound}}
In [[angiology]] or [[Blood vessel|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 [[neurology|potential neurologic problems]], where [[Carotid ultrasonography|carotid ultrasound]] is commonly used for assessing blood flow and potential or suspected stenosis in the [[carotid artery|carotid arteries]], while [[transcranial Doppler]] is used for imaging flow in the intracerebral arteries.{{citation needed|date=April 2022}}

[[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 vessel]]s in living individuals.<ref name="pmid21327914">{{cite journal | vauthors = Garcìa-Garcìa HM, Gogas BD, Serruys PW, Bruining N | title = IVUS-based imaging modalities for tissue characterization: similarities and differences | journal = Int J Cardiovasc Imaging | volume = 27 | issue = 2 | pages = 215–24 | date = February 2011 | pmid = 21327914 | pmc = 3078312 | doi = 10.1007/s10554-010-9789-7 }}</ref>

In the case of the common and potentially, serious problem of blood clots in the deep veins of the leg, [[ultrasonography of deep venous thrombosis|ultrasound]] plays a key diagnostic role, while [[ultrasonography of chronic venous insufficiency of the legs]] focuses on more [[superficial vein]]s to assist with planning of suitable interventions to relieve symptoms or improve cosmetics.{{citation needed|date=August 2022}}

=== Cardiology (heart) ===
{{Main|Echocardiography}}
[[File:Ultrasound of human heart apical 4-cahmber view.gif|thumb|Ultrasound of human [[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 [[Mitral valve stenosis|stenosis]] or [[Aortic valve insufficiency|insufficiency]], strength of [[cardiac muscle]] contraction, and [[Ventricular hypertrophy|hypertrophy]] or [[Ventricular dilation|dilatation]] of the main chambers. ([[Ventricle (heart)|ventricle]] and [[Atrium (heart)|atrium]]){{citation needed|date=April 2022}}

=== Emergency medicine ===
{{Main|Emergency ultrasound}}
[[Point-of-care ultrasound|Point of care]] ultrasound has many applications in [[emergency medicine]].<ref>{{cite journal |title=Ultrasound Guidelines: Emergency, Point-of-Care and Clinical Ultrasound Guidelines in Medicine |journal=Annals of Emergency Medicine |date=May 2017 |volume=69 |issue=5 |pages=e27–e54 |doi=10.1016/j.annemergmed.2016.08.457|pmid=28442101 |s2cid=42739523 }}</ref> These include differentiating cardiac from pulmonary causes of [[Pulmonary edema|acute breathlessness]], and the [[Focused assessment with sonography for trauma|Focused Assessment with Sonography for Trauma (FAST) exam]], extended to include assessment for significant [[hemoperitoneum]] or [[pericardial tamponade]] after [[Physical trauma|trauma]] ([[EFAST]]). Other uses include assisting with differentiating causes of abdominal pain such as [[gallstone]]s and [[Kidney Stones|kidney stones]]. Emergency Medicine Residency Programs have a substantial history of promoting the use of bedside ultrasound during physician training.{{citation needed|date=August 2022}}

=== Gastroenterology/Colorectal surgery ===
{{Further|Abdominal ultrasonography|Endoanal ultrasound}}

Both [[abdominal ultrasonography|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 duct]]s, [[kidney]]s, and [[spleen]] may be imaged. However, sound waves may be blocked by gas in the [[Gastrointestinal tract|bowel]] and attenuated to differing degrees by fat, sometimes limiting diagnostic capabilities. The [[Vermiform appendix|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 [[computerised tomography|CT]]. [[Endoanal ultrasound]] is used particularly in the investigation of anorectal symptoms such as [[fecal incontinence]] or [[obstructed defecation]].{{citation needed|date=July 2021}} It images the immediate [[perianal]] anatomy and is able to detect occult defects such as tearing of the [[Anal sphincterotomy|anal sphincter]].

=== Hepatology ===

[[Ultrasonography of liver tumors]] allows for both detection and characterization.<ref>{{cite journal |last1=Harvey |first1=Christopher J. |last2=Albrecht |first2=Thomas |title=Ultrasound of focal liver lesions |journal=European Radiology |date=September 2001 |volume=11 |issue=9 |pages=1578–1593 |doi=10.1007/s003300101002|pmid=11511877 |s2cid=20513478 }}</ref>
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.<ref>Miles DA, Levi CS, Uhanova J, Cuvelier S, Hawkins K, Minuk GY. Pocket-Sized Versus Conventional Ultrasound for Detecting Fatty Infiltration of the Liver. Dig Dis Sci. 2020 Jan;65(1):82-85. doi: 10.1007/s10620-019-05752-x. Epub 2019 Aug 2. PMID 31376083.</ref><ref>Costantino A, Piagnani A, Caccia R, Sorge A, Maggioni M, Perbellini R, Donato F, D'Ambrosio R, Sed NPO, Valenti L, Prati D, Vecchi M, Lampertico P, Fraquelli M. Reproducibility and accuracy of a pocket-size ultrasound device in assessing liver steatosis. Dig Liver Dis. 2024 Jun;56(6):1032-1038. {{doi|10.1016/j.dld.2023.11.014}}. Epub 2023 Nov 27. PMID 38016894.</ref>

=== Gynecology and obstetrics ===
{{Main|Gynecologic ultrasonography|Obstetric ultrasonography}}

[[File:Head-3D.jpg|thumb|right|Orthogonal planes of a three-dimensional sonographic volume with transverse and coronal measurements for estimating fetal cranial volume<ref>{{cite journal |doi=10.1177/875647938500100504 |title=Fetal Biometry: Vertical Calvarial Diameter and Calvarial Volume |year=1985 |last1=Dubose |first1=T. J. |journal=[[Journal of Diagnostic Medical Sonography]] |volume=1 |issue=5 |pages=205–217|s2cid=73129628 }}</ref><ref>{{cite web|url=http://hcp.obgyn.net/ultrasound/content/article/1760982/1906113|title=3D BPD Correction|last=Dubose|first=Terry|date=July 14, 2011|archive-url=https://web.archive.org/web/20160303035029/http://www.obgyn.net/articles/3d-bpd-correction|archive-date=March 3, 2016|url-status=dead|access-date=2015-01-14}}</ref>]]
[[Gynecologic ultrasonography]] examines female pelvic organs (specifically the [[uterus]], [[ovaries]], and [[fallopian tubes]]) as well as the [[Urinary bladder|bladder]], [[Adnexa of uterus|adnexa]], and [[pouch of Douglas]]. It uses transducers designed for approaches through the lower abdominal wall, curvilinear and sector, and specialty transducers such as [[Vaginal ultrasonography|transvaginal ultrasound]].<ref>{{Cite web |url=https://www.bmus.org/for-patients/what-to-expect-from-different-types-of-ultrasound-examination/pelvic-gynaecology-ultrasound-including-transvaginal/ |title=Pelvic / Gynaecology Ultrasound (including transvaginal) |access-date=2023-12-20 |website=The British Medical Ultrasound Society}}</ref>

[[Obstetrical ultrasonography|Obstetrical sonography]] was originally developed in the late 1950s and 1960s by Sir [[Ian Donald]]<ref>{{cite journal |last1=Hellman |first1=LouisM. |last2=Duffus |first2=GillianM. |last3=Donald |first3=Ian |last4=Sundén |first4=Bertil |title=Safety of Diagnostic Ultrasound in Obstetrics |journal=The Lancet |date=May 1970 |volume=295 |issue=7657 |pages=1133–1135 |doi=10.1016/s0140-6736(70)91212-2|pmid=4192094 }}</ref><ref>{{cite journal |last1=Campbell |first1=S |title=A short history of sonography in obstetrics and gynaecology. |journal=Facts, Views & Vision in ObGyn |date=2013 |volume=5 |issue=3 |pages=213–29 |pmid=24753947|pmc=3987368 }}</ref> 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.<ref name="keepsake">{{cite web|url=https://www.fda.gov/ForConsumers/ConsumerUpdates/ucm095508.htm|title=Avoid Fetal "Keepsake" Images, Heartbeat Monitors|website=U.S. food and Drug Administration|publisher=U.S. Government|archive-url=https://web.archive.org/web/20190423055443/https://www.fda.gov/ForConsumers/ConsumerUpdates/ucm095508.htm|archive-date=April 23, 2019|url-status=dead|access-date=11 September 2017}}</ref>

Obstetric ultrasound is primarily used to:{{citation needed|date=July 2024}}
* Date the pregnancy ([[Gestational age (obstetrics)|gestational age]])
* Confirm fetal viability
* Determine location of [[fetus]], intrauterine vs [[Ectopic pregnancy|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)<ref>[http://www.efsumb.org/ecmus/ecmus-ss-uk.asp Clinical Safety Statements] {{webarchive|url=https://web.archive.org/web/20120626122956/http://www.efsumb.org/ecmus/ecmus-ss-uk.asp |date=2012-06-26 }}. Efsumb.org. Retrieved on 2011-11-13.</ref>
{{blockquote|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 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.{{citation needed|date=August 2022}}

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.<ref>{{Cite web | url=https://www.uscom.com.au/products/uscom1a/applications/ |title = Applications » Uscom}}</ref> These provide non-invasive or transcutaneous (non-piercing) minimal invasive blood flow assessment. Common examples are [[transcranial Doppler]], [[Esophogeal doppler|esophageal Doppler]] and [[Transthoracic echocardiogram|suprasternal Doppler]].{{citation needed|date=April 2022}}

=== Otolaryngology (head and neck) ===
{{Anchor|Head ultrasonography|Neck ultrasonography|Thyroid ultrasonography}}
[[File:Neck ultrasound.jpg|thumb|Neck ultrasound]]
Most structures of the neck, including the [[thyroid]] and [[parathyroid gland]]s,<ref>Ghervan C. Thyroid and parathyroid ultrasound. Med Ultrason. 2011 Mar;13(1):80-4. PMID 21390348.</ref> [[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.{{citation needed|date=August 2022}}

=== 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.<ref>{{cite journal |last1=Yoshida |first1=Hiroko |last2=Yasuhara |first2=Akihiro |last3=Kobayashi |first3=Yohnosuke |title=Transcranial Doppler sonographic studies of cerebral blood flow velocity in neonates |journal=Pediatric Neurology |date=March 1991 |volume=7 |issue=2 |pages=105–110 |doi=10.1016/0887-8994(91)90005-6|pmid=2059249 }}</ref> The most common site for [[cranial ultrasound]] is the anterior fontanelle. The smaller the fontanelle, the more the image is compromised.{{citation needed|date=July 2024}}

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.<ref>{{Cite journal |last1=Singh |first1=Yogen |last2=Tissot |first2=Cecile |last3=Fraga |first3=María V. |last4=Yousef |first4=Nadya |last5=Cortes |first5=Rafael Gonzalez |last6=Lopez |first6=Jorge |last7=Sanchez-de-Toledo |first7=Joan |last8=Brierley |first8=Joe |last9=Colunga |first9=Juan Mayordomo |last10=Raffaj |first10=Dusan |last11=Da Cruz |first11=Eduardo |last12=Durand |first12=Philippe |last13=Kenderessy |first13=Peter |last14=Lang |first14=Hans-Joerg |last15=Nishisaki |first15=Akira |date=2020-02-24 |title=International evidence-based guidelines on Point of Care Ultrasound (POCUS) for critically ill neonates and children issued by the POCUS Working Group of the European Society of Paediatric and Neonatal Intensive Care (ESPNIC) |journal=Critical Care |volume=24 |issue=1 |pages=65 |doi=10.1186/s13054-020-2787-9 |doi-access=free |issn=1466-609X |pmc=7041196 |pmid=32093763}}</ref> A neonatal lung ultrasound score, first described by Brat et al., has been found to highly correlate with oxygenation in the newborn.<ref>{{Cite journal |last1=Brat |first1=Roselyne |last2=Yousef |first2=Nadya |last3=Klifa |first3=Roman |last4=Reynaud |first4=Stephanie |last5=Shankar Aguilera |first5=Shivani |last6=De Luca |first6=Daniele |date=August 2015 |title=Lung Ultrasonography Score to Evaluate Oxygenation and Surfactant Need in Neonates Treated With Continuous Positive Airway Pressure |url=https://pubmed.ncbi.nlm.nih.gov/26237465 |journal=JAMA Pediatrics |volume=169 |issue=8 |pages=e151797 |doi=10.1001/jamapediatrics.2015.1797 |issn=2168-6211 |pmid=26237465}}</ref><ref>{{Cite journal |last1=Kelner |first1=Jacob |last2=Moote |first2=Douglas |last3=Shah |first3=Rahul |last4=Anuar |first4=Amirul |last5=Golioto |first5=Annmarie |date=2024-08-09 |title=Lung Ultrasound Score for Prediction of Surfactant Administration in Preterm Infants with Respiratory Failure |url=https://pubmed.ncbi.nlm.nih.gov/39122885 |journal=Journal of Perinatology|volume=44 |issue=9 |pages=1258–1263 |doi=10.1038/s41372-024-02090-3 |issn=1476-5543 |pmid=39122885}}</ref>

=== Ophthalmology ({{visible anchor|eyes}}) ===
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''). [[#Modes|A-mode]] provides data on the length of the [[human eye|eye]], which is a major determinant in [[eye disease|common sight disorders]], especially for determining the power of an intraocular lens after cataract extraction.{{citation needed|date=April 2022}}
* ''B-scan ultrasonography'', or ''B-scan-Brightness scan'', is a [[#Modes|B-mode]] scan that produces a cross-sectional view of the [[human eye|eye]] and the [[orbit (anatomy)|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&nbsp;MHz. It is often used in conjunction with other imaging techniques (like OCT or fluorescein angiography) for a more comprehensive evaluation of ocular conditions.

=== {{anchor|Pulmonology (lungs)}}Pulmonology (lungs) ===
Ultrasound is used to assess the [[lung]]s in a variety of settings including critical care, emergency medicine, trauma surgery, as well as general medicine. This imaging modality 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.<ref>{{Cite web|url=https://www.uptodate.com/contents/bedside-pleural-ultrasonography-equipment-technique-and-the-identification-of-pleural-effusion-and-pneumothorax|title=UpToDate|website=www.uptodate.com|access-date=2019-07-23}}</ref> 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.<ref>{{Cite web|url=https://lus.mstech.eu|title=Lung Ultrasound Simulator|access-date=2021-09-30}}</ref>

==== Lung ultrasound basics ====
* '''The Normal Lung Surface:''' The lung surface is composed of visceral and parietal [[Pulmonary pleurae|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 [[Echogenicity|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.<ref name=":0">{{Cite book|title=Lung Ultrasound in the Critically Ill: The BLUE Protocol|last=Lichtenstein|first=Daniel|publisher=Springer|year=2016|isbn=978-3-319-15370-4}}</ref>
** §&nbsp; '''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.<ref name=":1">{{cite journal |last1=Husain |first1=LubnaF |last2=Hagopian |first2=Laura |last3=Wayman |first3=Derek |last4=Baker |first4=WilliamE |last5=Carmody |first5=KristinA |title=Sonographic diagnosis of pneumothorax |journal=Journal of Emergencies, Trauma, and Shock |date=2012 |volume=5 |issue=1 |pages=76–81 |doi=10.4103/0974-2700.93116 |pmid=22416161 |pmc=3299161 |doi-access=free }}</ref> Lung sliding indicates both that the lung is present at the chest wall and that the lung is functioning.<ref name=":0" />
** §&nbsp; '''A-lines:''' When the ultrasound beam makes contact with the [[Pulmonary pleurae|pleural line]], it is reflected back creating a bright white horizontal line. The subsequent reverberation artifacts that appear as equally spaced horizontal lines deep to the pleura are A-lines. Ultimately, A-lines are a reflection of the ultrasound beam from the pleura with the space between A-lines corresponding to the distance between the parietal pleura and the skin surface.<ref name=":0" /> A-lines indicate the presence of air, which means that these artifacts can be present in normal healthy lung (and also in patients with pneumothorax).<ref name=":1" />
** §&nbsp; '''B-lines:''' B-lines are also reverberation artifacts. They are visualized as [[Echogenicity|hyperechoic]] vertical lines extending from the pleura to the edge of the ultrasound screen. These lines are sharply defined and laser-like and typically do not fade as they progress down the screen.<ref name=":0" /> A few B-lines that move along with the sliding pleura can be seen in normal lung due to acoustic impedance differences between water and air. However, excessive B-lines (three or more) are abnormal and are typically indicative of underlying lung pathology.<ref name=":1" />

==== Lung pathology assessed with ultrasound ====
* '''[[Pulmonary edema]]''': Lung ultrasound has been shown to be very sensitive for the detection of pulmonary edema. It allows for improvement in diagnosis and management of critically ill patients, particularly when used in combination with echocardiography. The sonographic feature that is present in pulmonary edema is multiple B-lines. B-lines can occur in a healthy lung; however, the presence of 3 or more in the anterior or lateral lung regions is always abnormal. In pulmonary edema, B-lines indicate an increase in the amount of water contained in the lungs outside of the pulmonary vasculature. B-lines can also be present in a number of other conditions including pneumonia, pulmonary contusion, and lung infarction.<ref>{{Cite journal|last1=Blanco|first1=Pablo A.|last2=Cianciulli|first2=Tomás F.|date=2016|title=Pulmonary Edema Assessed by Ultrasound: Impact in Cardiology and Intensive Care Practice|journal=Echocardiography|language=en|volume=33|issue=5|pages=778–787|doi=10.1111/echo.13182|pmid=26841270|s2cid=37476194}}</ref> 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.<ref>{{cite journal |last1=Soldati |first1=Gino |last2=Demi |first2=Marcello |title=The use of lung ultrasound images for the differential diagnosis of pulmonary and cardiac interstitial pathology |journal=Journal of Ultrasound |date=June 2017 |volume=20 |issue=2 |pages=91–96 |doi=10.1007/s40477-017-0244-7 |pmid=28592998 |pmc=5440336 }}</ref>
* '''[[Pneumothorax]]''': In clinical settings when pneumothorax is suspected, lung ultrasound can aid in diagnosis.<ref>{{cite journal |last1=Volpicelli |first1=Giovanni |last2=Elbarbary |first2=Mahmoud |last3=Blaivas |first3=Michael |last4=Lichtenstein |first4=Daniel A. |last5=Mathis |first5=Gebhard |last6=Kirkpatrick |first6=Andrew W. |last7=Melniker |first7=Lawrence |last8=Gargani |first8=Luna |last9=Noble |first9=Vicki E. |last10=Via |first10=Gabriele |last11=Dean |first11=Anthony |last12=Tsung |first12=James W. |last13=Soldati |first13=Gino |last14=Copetti |first14=Roberto |last15=Bouhemad |first15=Belaid |last16=Reissig |first16=Angelika |last17=Agricola |first17=Eustachio |last18=Rouby |first18=Jean-Jacques |last19=Arbelot |first19=Charlotte |last20=Liteplo |first20=Andrew |last21=Sargsyan |first21=Ashot |last22=Silva |first22=Fernando |last23=Hoppmann |first23=Richard |last24=Breitkreutz |first24=Raoul |last25=Seibel |first25=Armin |last26=Neri |first26=Luca |last27=Storti |first27=Enrico |last28=Petrovic |first28=Tomislav |title=International evidence-based recommendations for point-of-care lung ultrasound |journal=Intensive Care Medicine |date=April 2012 |volume=38 |issue=4 |pages=577–591 |doi=10.1007/s00134-012-2513-4 |pmid=22392031 |doi-access=free }}</ref> In pneumothorax, air is present between the two layers of the pleura and lung sliding on ultrasound is therefore absent. The [[Positive and negative predictive values|negative predictive value]] for lung sliding on ultrasound is reported as 99.2–100%&nbsp;– briefly, if lung sliding is present, a pneumothorax is effectively ruled out.<ref name=":1" /> The absence of lung sliding, however, is not necessarily specific for pneumothorax as there are other conditions that also cause this finding including [[acute respiratory distress syndrome]], [[Pulmonary consolidation|lung consolidations]], pleural adhesions, and [[pulmonary fibrosis]].<ref name=":1" />
* '''[[Pleural effusion]]''': Lung ultrasound is a cost-effective, safe, and non-invasive imaging method that can aid in the prompt visualization and diagnosis of pleural effusions. Effusions can be diagnosed by a combination of physical exam, percussion, and [[auscultation]] of the chest. However, these exam techniques can be complicated by a variety of factors including the presence of [[mechanical ventilation]], obesity, or patient positioning, all of which reduce the sensitivity of the physical exam. Consequently, lung ultrasound can be an additional tool to augment plain [[Chest radiograph|chest Xray]] and [[CT scan|chest CT]].<ref name=":2">{{cite journal |last1=Brogi |first1=E. |last2=Gargani |first2=L. |last3=Bignami |first3=E. |last4=Barbariol |first4=F. |last5=Marra |first5=A. |last6=Forfori |first6=F. |last7=Vetrugno |first7=L. |title=Thoracic ultrasound for pleural effusion in the intensive care unit: a narrative review from diagnosis to treatment |journal=Critical Care |date=December 2017 |volume=21 |issue=1 |page=325 |doi=10.1186/s13054-017-1897-5 |pmid=29282107 |pmc=5745967 |doi-access=free }}</ref> 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.<ref name=":0" /> In critically ill patients with pleural effusion, ultrasound may guide procedures including needle insertion, [[thoracentesis]], and [[Chest tube|chest-tube insertion]].<ref name=":2" />
* '''[[Lung cancer]] staging:''' In [[pulmonology]], endobronchial ultrasound (EBUS) probes are applied to standard flexible endoscopic probes and used by pulmonologists to allow for direct visualization of endobronchial lesions and lymph nodes prior to transbronchial needle aspiration.  Among its many uses, EBUS aids in lung cancer staging by allowing for lymph node sampling without the need for major surgery.<ref>{{cite journal |doi=10.1136/thx.2005.047829 |title=Real-time endobronchial ultrasound guided transbronchial needle aspiration for sampling mediastinal lymph nodes |year=2006 |last1=Herth |first1=F J F |last2=Eberhardt |first2=R |last3=Vilmann |first3=P |last4=Krasnik |first4=M |last5=Ernst |first5=A |journal=Thorax |volume=61 |issue=9 |pages=795–8 |pmid=16738038 |pmc=2117082}}</ref>
* '''[[COVID-19]]''': Lung ultrasound has proved useful in the diagnosis of COVID-19 especially in cases where other investigations are not available.<ref>{{cite journal |last1=Lesser |first1=FD |last2=Smallwood |first2=N |last3=Dachsel |first3=M |title=Point-of-care lung ultrasound during and after the COVID-19 pandemic |journal=Ultrasound |date=1 August 2021 |volume=29 |issue=3 |pages=140 |pmid=34567225|  doi=10.1177/1742271X211033737| pmc=8366220 |s2cid=236980540 |doi-access=free }}</ref><ref>{{cite journal |last1=Knight |first1=T. |last2=Parulekar |first2=P. |last3=Rudge |first3=G. |last4=Lesser |first4=F. |last5=Dachsel |first5=M. |last6=Aujayeb |first6=A. |last7=Lasserson |first7=D. |last8=Smallwood |first8=N. |title=S68 National COVID point of care lung ultrasound evaluation (society for acute medicine with the intensive care society) |journal=Thorax |date=1 November 2021 |volume=76 |issue=Suppl 2 |pages=A44–A45 |doi=10.1136/thorax-2021-BTSabstracts.74|s2cid=243885812 |doi-access=free }}</ref><ref>{{cite journal |last1=Lesser |first1=FD |last2=Dachsel |first2=M |last3=Smallwood |first3=N |title=The Diagnostic Accuracy and Prognostic Value of Lung ultrasound in Suspected COVID-19 a retrospective service evaluation. |journal=Acute Medicine |date=2022 |volume=21 |issue=1 |pages=56–58 |doi=10.52964/AMJA.0895 |pmid=35342913|s2cid=247762623 |doi-access=free }}</ref>

=== Urinary tract ===
{{main|Urinary tract ultrasound}}
[[File:UltrasoundBPH.jpg|thumb|right|[[Urinary bladder]] (black butterfly-like shape) and hyperplastic [[prostate]] ([[Benign prostatic hyperplasia|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 [[ovary|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[[vagina]]lly (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.{{Citation needed|date=July 2021}} It is also used to diagnose and, at higher frequencies, to treat (break up) kidney stones or kidney crystals ([[nephrolithiasis]]).<ref>{{cite journal |url=http://www.pelviperineology.org/practical/sonography_female_pelvic_floor_clinical_indications_and_techniques.html |title=Sonography of the female pelvic floor:clinical indications and techniques |first1=Vittorio Luigi |last1=Piloni |first2=Liana |last2=Spazzafumo |journal=Pelviperineology |volume=26 |issue=2 |date=June 2007 |pages=59–65 |access-date=August 7, 2007 |archive-date=January 31, 2009 |archive-url=https://web.archive.org/web/20090131101200/http://pelviperineology.org/practical/sonography_female_pelvic_floor_clinical_indications_and_techniques.html |url-status=dead }}</ref>

=== Penis and scrotum ===
{{Main|Scrotal ultrasound|Penile ultrasonography}}
[[Scrotal ultrasound|Scrotal ultrasonography]] is used in the evaluation of [[testicular pain]], and can help identify solid masses.<ref name="GrahamKeane2009">{{cite book|first1=Sam D.|last1=Graham|author2=Thomas E Keane|title=Glenn's Urologic Surgery|url=https://books.google.com/books?id=GahMzaKgMKAC&pg=PA433|access-date=1 July 2011|date=25 September 2009|publisher=Lippincott Williams & Wilkins|isbn=978-0-7817-9141-0|pages=433–}}</ref>

Ultrasound is an excellent method for the study of the [[penis]], such as indicated in trauma, priapism, erectile dysfunction or suspected [[Peyronie's disease]].<ref name="FernandesSouza2018">{{cite journal |last1=Fernandes |first1=Maitê Aline Vieira |last2=Souza |first2=Luis Ronan Marquez Ferreira de |last3=Cartafina |first3=Luciano Pousa |title=Ultrasound evaluation of the penis |journal=Radiologia Brasileira |date=23 July 2018 |volume=51 |issue=4 |pages=257–261 |doi=10.1590/0100-3984.2016.0152 |pmid=30202130 |pmc=6124582 }}</ref>

=== Musculoskeletal ===
[[Musculoskeletal]] ultrasound is used to examine tendons, muscles, nerves, ligaments, soft tissue masses, and bone surfaces.<ref>Arend CF. Ultrasound of the Shoulder. Porto Alegre: Master Medical Books; 2013. (Free access at [https://web.archive.org/web/20171224065120/http://www.shoulderus.com/sample-chapters/ultrasound-of-the-shoulder-book ShoulderUS.com]){{page needed|date=November 2013}}</ref>
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<ref>{{cite journal |last1=Hübner |first1=U. |last2=Schlicht |first2=W. |last3=Outzen |first3=S. |last4=Barthel |first4=M. |last5=Halsband |first5=H. |title=Ultrasound in the diagnosis of fractures in children |journal=The Journal of Bone and Joint Surgery. British Volume |date=November 2000 |volume=82-B |issue=8 |pages=1170–1173 |doi=10.1302/0301-620x.82b8.10087|pmid=11132281 }}</ref> ([[Fracture sonography]]).

Quantitative ultrasound is an adjunct musculoskeletal test for myopathic disease in children;<ref>{{Cite journal|last1=Zaidman|first1=Craig M.|last2=van Alfen|first2=Nens|date=2016-04-01|title=Ultrasound in the Assessment of Myopathic Disorders|journal=Journal of Clinical Neurophysiology|volume=33|issue=2|pages=103–111|doi=10.1097/WNP.0000000000000245|pmid=27035250|s2cid=35805733}}</ref><ref>{{Cite journal|last1=Harris-Love|first1=Michael O.|last2=Monfaredi|first2=Reza|last3=Ismail|first3=Catheeja|last4=Blackman|first4=Marc R.|last5=Cleary|first5=Kevin|date=2014-01-01|title=Quantitative ultrasound: measurement considerations for the assessment of muscular dystrophy and sarcopenia|journal=Frontiers in Aging Neuroscience|volume=6|pages=172|doi=10.3389/fnagi.2014.00172|pmc=4094839|pmid=25071570|doi-access=free}}</ref> estimates of lean body mass in adults;<ref>{{Cite journal|last1=Abe|first1=Takashi|last2=Loene|first2=Jeremy P.|last3=Young|first3=Kaelin C.|last4=Thiebaud|first4=Robert S.|last5=Nahar|first5=Vinayak K.|last6=Hollaway|first6=Kaitlyn M.|last7=Stover|first7=Caitlin D.|last8=Ford|first8=M. Allison|last9=Bass|first9=Martha A.|date=2015-02-01|title=Validity of ultrasound prediction equations for total and regional muscularity in middle-aged and older men and women|journal=Ultrasound in Medicine & Biology|volume=41|issue=2|pages=557–564|doi=10.1016/j.ultrasmedbio.2014.09.007|pmid=25444689}}</ref> proxy measures of muscle quality (i.e., tissue composition)<ref>{{Cite journal|last1=McGregor|first1=Robin A.|last2=Cameron-Smith|first2=David|last3=Poppitt|first3=Sally D.|date=2014-01-01|title=It is not just muscle mass: a review of muscle quality, composition and metabolism during ageing as determinants of muscle function and mobility in later life|journal=Longevity & Healthspan|volume=3|issue=1|pages=9|doi=10.1186/2046-2395-3-9|pmc=4268803|pmid=25520782 |doi-access=free }}</ref> in older adults with [[sarcopenia]]<ref>{{Cite journal|last1=Watanabe|first1=Yuya|last2=Yamada|first2=Yosuke|last3=Fukumoto|first3=Yoshihiro|last4=Ishihara|first4=Tatsuro|last5=Yokoyama|first5=Keiichi|last6=Yoshida|first6=Tsukasa|last7=Miyake|first7=Motoko|last8=Yamagata|first8=Emi|last9=Kimura|first9=Misaka|date=2013-01-01|title=Echo intensity obtained from ultrasonography images reflecting muscle strength in elderly men|journal=Clinical Interventions in Aging|volume=8|pages=993–998|doi=10.2147/CIA.S47263|pmc=3732157|pmid=23926426 |doi-access=free }}</ref><ref>{{Cite journal|last1=Ismail|first1=Catheeja|last2=Zabal|first2=Johannah|last3=Hernandez|first3=Haniel J.|last4=Woletz|first4=Paula|last5=Manning|first5=Heather|last6=Teixeira|first6=Carla|last7=DiPietro|first7=Loretta|last8=Blackman|first8=Marc R.|last9=Harris-Love|first9=Michael O.|date=2015-01-01|title=Diagnostic ultrasound estimates of muscle mass and muscle quality discriminate between women with and without sarcopenia|journal=Frontiers in Physiology|volume=6|pages=302|doi=10.3389/fphys.2015.00302|pmc=4625057|pmid=26578974|doi-access=free}}</ref>

Ultrasound can also be used for needle guidance in muscle or [[joint injection]]s, as in [[ultrasound-guided hip joint injection]].{{citation needed|date=July 2024}}

=== Kidneys ===
{{Main|Renal ultrasonography}}
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.<ref name=Hansen2015>{{cite journal |last1=Hansen |first1=Kristoffer |last2=Nielsen |first2=Michael |last3=Ewertsen |first3=Caroline |title=Ultrasonography of the Kidney: A Pictorial Review |journal=Diagnostics |date=23 December 2015 |volume=6 |issue=1 |pages=2 |doi=10.3390/diagnostics6010002 |pmid=26838799 |pmc=4808817 |doi-access=free }} [https://creativecommons.org/licenses/by/4.0/ (CC-BY 4.0)]</ref> 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.<ref name=Hansen2015/>

=== 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.{{citation needed|date=August 2022}}

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 [[Hertz|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.{{citation needed|date=August 2022}}