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Ultrasound (Sonography)

Ultrasonography is an imaging technique used in medicine for the imaging of subcutaneous body structures, blood vessels, joints, and internal organs to exclude structural pathologies. This technique is based on the utilization of ultrasound (or high-frequency, inaudible sound waves). In medical imaging, the sound waves have a frequency of 2–18 megahertz (MHz). The equipment utilizes a transducer acting as the emitter and receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors of sound waves, and a central computer processes the electrical signals to generate the image. The general advantages of this type of imaging is its low cost, availability, and safety. Some specialties that rely heavily on ultrasound examination are cardiology, nephrology, general surgery, gastroenterology, emergency medicine, and obstetrics.

Last updated: 6 May, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Terminology and Technical Aspects

Definitions

  • Ultrasound: inaudible sound waves with a frequency of 2–18 megahertz (MHz) when used for medical imaging
  • Ultrasound imaging: the use of ultrasound to generate anatomical images

Core components of an ultrasound machine

  • Transducer (or probe):
    • A device placed on the patient’s body to visualize a target 
    • Acts as an emitter and receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors of sound waves
    • Contains piezoelectric crystals that convert electrical signals into sound waves
    • The reflected sound waves (echoes) travel back to the probe and are converted to electrical signals.
    • Types:
      • Convex (used in fetal imaging)
      • Micro-convex (used in gynecologic imaging)
      • Linear (used in vascular imaging)
      • Phased array (used in thoracic imaging)
    • Frequency is inversely related to wavelength and depth of tissue penetration Penetration X-rays.
    • Higher frequencies →  detailed image
  • Central processing unit (CPU): processes electrical signals to generate an image
  • Console: 

Generation of images with ultrasound

The main principle behind ultrasound imaging is the transmission and reflection of sound waves through the tissues.

  1. Sound waves are emitted by the transducer.
  2. Sound waves penetrate the tissues in the form of a beam.
  3. As the beam travels, it is reflected by structures in the tissues (or echoes) back to the transducer, with some energy being absorbed by the tissues.
    • The amplitude of the echoes depends on the degree of energy absorption Absorption Absorption involves the uptake of nutrient molecules and their transfer from the lumen of the GI tract across the enterocytes and into the interstitial space, where they can be taken up in the venous or lymphatic circulation. Digestion and Absorption of the emitted beam.
    • Absorbed energy from the beam is later released as heat Heat Inflammation.
  4. The echoes return to the transducer.
  5. The sound waves are turned into electrical signals and then amplified in the console. The signals are assigned a shade of gray depending on the amplitude of the echo produced by the tissue after interacting with the piezoelectric crystals.
    • Higher amplitudes are assigned shades closer to white.
    • Lower amplitudes are assigned shades closer to black.
  6. The CPU processes the electrical signals into images that can be seen on the monitor.
Interaction between ultrasound waves and the tissues (sonography)

Ultrasound waves and the tissues:
The diagram shows that as the ultrasound wave beam (blue horizontal bar) penetrates the tissues, a percentage is reflected back (left arrows) toward the transducer while another continues to go deeper into the tissues (right arrow), losing some energy to the parenchyma as it goes.

Image by Lecturio.

Images

Imaging planes:

Types of images:

  • Static images (photographs)
  • Cine images: captured during real-time scanning

Image definition or sharpness of the image generated can be characterized in terms of:

  • Axial Axial Computed Tomography (CT) definition: 
    • Differentiation of 2 objects close to each other, parallel to the beam
    • Determines the depth of the ultrasound beam; quality Quality Activities and programs intended to assure or improve the quality of care in either a defined medical setting or a program. The concept includes the assessment or evaluation of the quality of care; identification of problems or shortcomings in the delivery of care; designing activities to overcome these deficiencies; and follow-up monitoring to ensure effectiveness of corrective steps. Quality Measurement and Improvement impacted by beam penetration Penetration X-rays
  • Lateral definition: 
    • Differentiation of 2 objects on a plane perpendicular to the beam
    • Determines the ability of the probe to distinguish structures perpendicular to the beam
    • Primarily determined by the beam width

Image definition is also determined by how close objects are to the transducer; according to their frequencies, probes have a near and a far field of “ vision Vision Ophthalmic Exam”:

  • Near field: the focal point of the probe with the greatest lateral definition
  • Far field: greater axial Axial Computed Tomography (CT) definition at the expense of lateral definition

Doppler ultrasound

Doppler ultrasound (or just “Doppler”) is a widely used ultrasound method based on the principle of sound-wave compression Compression Blunt Chest Trauma and dilation relative to the receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors. Doppler ultrasound is most commonly used to visualize blood flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure.

  • When the ultrasound beam comes into contact with the blood, its frequency is shifted, either becoming:
    • Compressed (frequency is increased) by a flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure that is coming toward the transducer
    • Dilated (frequency is decreased) by a flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure away from the transducer
  • There are different Doppler methods:
    • Spectral Doppler: demonstrates the direction and waveform of flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure
    • Power Power The probability that a test will correctly reject a false null hypothesis. Statistical Tests and Data Representation Doppler: a single color is assigned to all areas of flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure, which has increased sensitivity Sensitivity Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Blotting Techniques to detect slow/lower flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure
    • Continuous-wave Doppler: used for measuring high-velocity flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure
    • Pulse-wave Doppler: makes measurements on a small segment of the ultrasound beam

Interpretation

The interpretation of ultrasound images is done in real time, while the examination is being performed.

Ultrasound evaluation

  • The sonographer needs to be well familiarized with the presentation Presentation The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck. Normal and Abnormal Labor of the anatomy in the particular ultrasound method they employ.
  • The sequence of evaluation also depends on its purpose, for example:
    • FAST follows a specific sequence of anatomical landmarks within the abdomen and thorax very quickly in the emergency setting.
    • A biophysical profile Biophysical Profile Obstetric Imaging is performed in fetuses with suspected growth restriction by measuring their biometric parameters and checking where they lie in the growth curves Growth Curves Short Stature in Children

Terminology

  • Hyperechoic (e.g., surface of bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types, urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy calculi, fat-containing lesions): a structure that produces a high-amplitude echo (lighter grays and white)
  • Hypoechoic (e.g., abscesses without gas, solid tumors without calcifications or fat): a structure that produces a low-amplitude echo (darker grays)
  • Anechoic (e.g., simple cysts Cysts Any fluid-filled closed cavity or sac that is lined by an epithelium. Cysts can be of normal, abnormal, non-neoplastic, or neoplastic tissues. Fibrocystic Change): a structure that produces no echo at all (looks completely black)
  • Isoechoic: a structure that produces an echo of a very similar amplitude to its environment and is very difficult to distinguish

Doppler ultrasound

By convention, in color Doppler:

  • Blood flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure that is coming toward the probe (compressed sound waves) is depicted in red.
  • Blood flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure away from the probe (dilated sound waves) is depicted as blue.

Artifacts

Artifacts are artificial objects produced by the equipment’s misinterpretation of sound-wave data coming back from the tissues that do not represent actual structures. 

Some examples of artifacts are:

  • Enhancement: Echoes from structures behind hypoechoic/anechoic objects appear brighter.
  • Shadowing: Echoes from structures behind denser objects appear darker or are not visualized at all. 
  • Reverberation: Echos are trapped between two hyperechoic objects and bounce back and forth several times.
Ultrasound (sonography) of acute cholecystitis

Ultrasound from a patient with acute cholecystitis Acute cholecystitis Acute inflammation of the gallbladder wall. It is characterized by the presence of abdominal pain; fever; and leukocytosis. Gallstone obstruction of the cystic duct is present in approximately 90% of the cases. Cholecystitis:
Multiple gallstones Gallstones Cholelithiasis (gallstones) is the presence of stones in the gallbladder. Most gallstones are cholesterol stones, while the rest are composed of bilirubin (pigment stones) and other mixed components. Patients are commonly asymptomatic but may present with biliary colic (intermittent pain in the right upper quadrant). Cholelithiasis are visualized within the gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract: Anatomy lumen with gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract: Anatomy wall thickening and pericholecystic fluid Pericholecystic Fluid Imaging of the Liver and Biliary Tract. Shadowing can be seen behind the gallstone.

Image: “Ultrasound of a patient with acute cholecystitis Acute cholecystitis Acute inflammation of the gallbladder wall. It is characterized by the presence of abdominal pain; fever; and leukocytosis. Gallstone obstruction of the cystic duct is present in approximately 90% of the cases. Cholecystitis” by Spangler R et al AL Amyloidosis. License: CC BY 4.0

Applications of Ultrasound

Pros and cons CoNS Staphylococcus of ultrasound imaging

Table: Pros and cons CoNS Staphylococcus of ultrasound imaging
Pros Cons CoNS Staphylococcus
  • No radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma (safest imaging method)
  • Portability
  • Can be used in multiple settings
  • Relatively low cost
  • Visualization of soft tissues
  • Can differentiate cystic Cystic Fibrocystic Change from solid lesions
  • Can assess moving structures (e.g., heart)
  • Patient comfort during test
  • Dependent on operator training
  • Difficulty in evaluating deep tissues (e.g., retroperitoneal Retroperitoneal Peritoneum: Anatomy vessels)
  • Gas collections (e.g., in the bowels) interfere with visualization.
  • Sound waves cannot penetrate bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types and metal.

Indications and contraindications Contraindications A condition or factor associated with a recipient that makes the use of a drug, procedure, or physical agent improper or inadvisable. Contraindications may be absolute (life threatening) or relative (higher risk of complications in which benefits may outweigh risks). Noninvasive Ventilation

Indications:

  • Trauma patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship
    • FAST
    • Point-of-care ultrasound Point-Of-Care Ultrasound Focused Assessment with Sonography for Trauma (FAST) ( POCUS POCUS Focused Assessment with Sonography for Trauma (FAST))
    • Rapid ultrasound in shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock ( RUSH RUSH Abdominal and cardiac evaluation with sonography in shock (ACES) and rapid ultrasound for shock and hypotension (RUSH) are point-of-care ultrasound (POCUS) examinations indicated in cases of nontraumatic, undifferentiated hypotension, or shock. ACES and RUSH: Resuscitation Ultrasound Protocols)
    • Abdominal and cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) evaluation with sonography Sonography The visualization of deep structures of the body by recording the reflections or echoes of ultrasonic pulses directed into the tissues. Use of ultrasound for imaging or diagnostic purposes employs frequencies ranging from 1. 6 to 10 megahertz. Diagnostic Procedures in Gynecology in shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock ( ACES ACES Abdominal and cardiac evaluation with sonography in shock (ACES) and rapid ultrasound for shock and hypotension (RUSH) are point-of-care ultrasound (POCUS) examinations indicated in cases of nontraumatic, undifferentiated hypotension, or shock. ACES and RUSH: Resuscitation Ultrasound Protocols)
  • Gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract: Anatomy and biliary system:
    • Acute cholecystitis Acute cholecystitis Acute inflammation of the gallbladder wall. It is characterized by the presence of abdominal pain; fever; and leukocytosis. Gallstone obstruction of the cystic duct is present in approximately 90% of the cases. Cholecystitis
    • Cholelithiasis Cholelithiasis Cholelithiasis (gallstones) is the presence of stones in the gallbladder. Most gallstones are cholesterol stones, while the rest are composed of bilirubin (pigment stones) and other mixed components. Patients are commonly asymptomatic but may present with biliary colic (intermittent pain in the right upper quadrant). Cholelithiasis
  • GI system: appendicitis Appendicitis Appendicitis is the acute inflammation of the vermiform appendix and the most common abdominal surgical emergency globally. The condition has a lifetime risk of 8%. Characteristic features include periumbilical abdominal pain that migrates to the right lower quadrant, fever, anorexia, nausea, and vomiting. Appendicitis
  • Kidney: hydronephrosis Hydronephrosis Hydronephrosis is dilation of the renal collecting system as a result of the obstruction of urine outflow. Hydronephrosis can be unilateral or bilateral. Nephrolithiasis is the most common cause of hydronephrosis in young adults, while prostatic hyperplasia and neoplasm are seen in older patients. Hydronephrosis
  • Scrotum Scrotum A cutaneous pouch of skin containing the testicles and spermatic cords. Testicles: Anatomy:
    • Testicular torsion Testicular torsion Testicular torsion is the sudden rotation of the testicle, specifically the spermatic cord, around its axis in the inguinal canal or below. The acute rotation results in compromised blood flow to and from the testicle, which puts the testicle at risk for necrosis. Testicular Torsion
    • Testicular cancer Testicular cancer Testicular cancer is the most common solid malignancy affecting men 15-35 years of age. Most of the testicular cancers are of the germ cell tumor type, and they can be classified as seminomas and nonseminomas. The most common presentation of testicular cancer is a painless testicular mass. Testicular Cancer
  • Gynecologic imaging:
    • Ectopic pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care
    • Polycystic ovarian syndrome Polycystic ovarian syndrome Polycystic ovarian syndrome (PCOS) is the most common endocrine disorder of reproductive-age women, affecting nearly 5%-10% of women in the age group. It is characterized by hyperandrogenism, chronic anovulation leading to oligomenorrhea (or amenorrhea), and metabolic dysfunction. Polycystic Ovarian Syndrome
  • Pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care assessment:
    • Diagnosis
    • Fetal growth monitoring
    • Placenta Placenta A highly vascularized mammalian fetal-maternal organ and major site of transport of oxygen, nutrients, and fetal waste products. It includes a fetal portion (chorionic villi) derived from trophoblasts and a maternal portion (decidua) derived from the uterine endometrium. The placenta produces an array of steroid, protein and peptide hormones (placental hormones). Placenta, Umbilical Cord, and Amniotic Cavity previa 
  • Cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) and pulmonary:
    • Congestive heart failure Congestive heart failure Congestive heart failure refers to the inability of the heart to supply the body with normal cardiac output to meet metabolic needs. Echocardiography can confirm the diagnosis and give information about the ejection fraction. Congestive Heart Failure
    • Pleural effusion Pleural Effusion Pleural effusion refers to the accumulation of fluid between the layers of the parietal and visceral pleura. Common causes of this condition include infection, malignancy, autoimmune disorders, or volume overload. Clinical manifestations include chest pain, cough, and dyspnea. Pleural Effusion
  • Blood vessels:
    • Carotid artery stenosis Carotid artery stenosis Carotid artery stenosis is a chronic atherosclerotic disease resulting in narrowing of the common and internal carotid arteries. Common risk factors include family history, advanced age, hyperlipidemia, smoking, and diabetes mellitus. Patients may present with or without symptoms of decreased cerebral perfusion. Carotid Artery Stenosis
    • Deep vein thrombosis Thrombosis Formation and development of a thrombus or blood clot in the blood vessel. Epidemic Typhus

There are no contraindications Contraindications A condition or factor associated with a recipient that makes the use of a drug, procedure, or physical agent improper or inadvisable. Contraindications may be absolute (life threatening) or relative (higher risk of complications in which benefits may outweigh risks). Noninvasive Ventilation for ultrasound imaging.

Other Imaging Methods

Comparison with other imaging methods

Table: Comparison of imaging methods
Radiography CT Ultrasound MRI
Mechanism of acquisition Ionizing radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma Ionizing radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma Acoustic energy Ferromagnetic pulses
Relative cost Inexpensive Expensive Inexpensive Very expensive
Portable Yes No Yes No
Length of exam Seconds < 1 minute Seconds Approximately 1 hour
Contrast No May be needed May be needed May be needed

Imaging method options by system

  • Imaging of the CNS ( brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification, spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord: Anatomy, and vertebral column Vertebral column The human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum. Vertebral Column: Anatomy): 
    • Radiography is often used to evaluate for fractures of the vertebral column Vertebral column The human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum. Vertebral Column: Anatomy
    • CT is a good choice for head trauma Head trauma Head trauma occurs when external forces are directed to the skull and brain structures, resulting in damage to the skull, brain, and intracranial structures. Head injuries can be classified as open (penetrating) or closed (blunt), and primary (from the initial trauma) or secondary (indirect brain injury), and range from mild to severe and life-threatening. Head Trauma and to exclude intracranial hemorrhage Intracranial hemorrhage Subarachnoid hemorrhage (SAH) is a type of cerebrovascular accident (stroke) resulting from intracranial hemorrhage into the subarachnoid space between the arachnoid and the pia mater layers of the meninges surrounding the brain. Most sahs originate from a saccular aneurysm in the circle of willis but may also occur as a result of trauma, uncontrolled hypertension, vasculitis, anticoagulant use, or stimulant use. Subarachnoid Hemorrhage
    • MRI provides more detailed images of the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification and spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord: Anatomy, allowing identification Identification Defense Mechanisms of infarction, tumors, disc herniation Herniation Omphalocele, and demyelinating disease.
  • Pulmonary radiology Pulmonary Radiology Pulmonary, or chest, imaging includes imaging of the lungs and surrounding structures in the thorax. Imaging of the chest represents a substantial portion of the imaging tests that are routinely performed. Common imaging methods include X-ray, CT, MRI, and ultrasonography (US). Imaging of the Lungs and Pleura and imaging of the mediastinum Mediastinum The mediastinum is the thoracic area between the 2 pleural cavities. The mediastinum contains vital structures of the circulatory, respiratory, digestive, and nervous systems including the heart and esophagus, and major thoracic vessels. Mediastinum and Great Vessels: Anatomy
    • Radiography is the preferred initial imaging study for viewing lung pathology. 
    • CT provides more detailed views of the lung parenchyma, mediastinal structures, and vasculature. 
    • MRI is not often used, but may be employed for evaluating malignancies and cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) disease. 
    • Ultrasonography can be used for rapid bedside trauma assessment and for guiding procedures such as thoracentesis Thoracentesis Aspiration of fluid or air from the thoracic cavity. It is coupled sometimes with the administration of drugs into the pleural cavity. Thoracic Surgery.
  • Breast imaging Breast Imaging Female breasts, made of glandular, adipose, and connective tissue, are hormone-sensitive organs that undergo changes along with the menstrual cycle and during pregnancy. Breasts may be affected by various diseases, in which different imaging methods are important to arrive at the correct diagnosis and management. Mammography is used for breast cancer screening and diagnostic evaluation of various breast-related symptoms. Imaging of the Breast
    • Mammography Mammography Radiographic examination of the breast. Breast Cancer Screening is often the initial choice for breast cancer screening Breast cancer screening Breast cancer is the most common cancer in women and the 2nd-leading cause of cancer-related deaths in women in the United States. Early detection and improved pathology-specific treatments have resulted in a decrease in death rates. Breast Cancer Screening
    • MRI may be used to further evaluate and stage breast cancer Breast cancer Breast cancer is a disease characterized by malignant transformation of the epithelial cells of the breast. Breast cancer is the most common form of cancer and 2nd most common cause of cancer-related death among women. Breast Cancer
    • Ultrasonography is helpful for evaluating lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs nodes and to guide biopsy Biopsy Removal and pathologic examination of specimens from the living body. Ewing Sarcoma.
  • Imaging of the abdomen and renal imaging Renal imaging The renal system is composed of 2 kidneys, 2 ureters, a bladder, and a urethra. Varying conditions such as infections, cysts, solid masses, ischemia, and mechanical obstruction can affect the renal system. Evaluation of diseases rely on imaging methods such as radiography, ultrasonography, CT, and MRI. Some of these are also used to guide tissue sampling (e.g., renal biopsy). Imaging of the Urinary System
    • Radiography is often used to evaluate for kidney stones Kidney stones Nephrolithiasis is the formation of a stone, or calculus, anywhere along the urinary tract caused by precipitations of solutes in the urine. The most common type of kidney stone is the calcium oxalate stone, but other types include calcium phosphate, struvite (ammonium magnesium phosphate), uric acid, and cystine stones. Nephrolithiasis, bowel obstruction Bowel obstruction Any impairment, arrest, or reversal of the normal flow of intestinal contents toward the anal canal. Ascaris/Ascariasis, and pneumoperitoneum Pneumoperitoneum A condition with trapped gas or air in the peritoneal cavity, usually secondary to perforation of the internal organs such as the lung and the gastrointestinal tract, or to recent surgery. Pneumoperitoneum may be purposely introduced to aid radiological examination. Perforated Viscus. In addition, barium may be used to assess swallowing Swallowing The act of taking solids and liquids into the gastrointestinal tract through the mouth and throat. Gastrointestinal Motility and bowel function. 
    • CT and MRI provide more detailed assessments of the abdominal viscera and vasculature. 
    • Nuclear medicine Nuclear medicine A specialty field of radiology concerned with diagnostic, therapeutic, and investigative use of radioactive compounds. Nuclear Imaging can be used to assess gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract: Anatomy function and gastric emptying Gastric emptying The evacuation of food from the stomach into the duodenum. Gastrointestinal Motility and for GI bleeding.
  • Imaging of the uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Uterus, Cervix, and Fallopian Tubes: Anatomy and ovaries Ovaries Ovaries are the paired gonads of the female reproductive system that contain haploid gametes known as oocytes. The ovaries are located intraperitoneally in the pelvis, just posterior to the broad ligament, and are connected to the pelvic sidewall and to the uterus by ligaments. These organs function to secrete hormones (estrogen and progesterone) and to produce the female germ cells (oocytes). Ovaries: Anatomy
    • Ultrasonography is the most commonly used method to evaluate the ovaries Ovaries Ovaries are the paired gonads of the female reproductive system that contain haploid gametes known as oocytes. The ovaries are located intraperitoneally in the pelvis, just posterior to the broad ligament, and are connected to the pelvic sidewall and to the uterus by ligaments. These organs function to secrete hormones (estrogen and progesterone) and to produce the female germ cells (oocytes). Ovaries: Anatomy and uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Uterus, Cervix, and Fallopian Tubes: Anatomy, including assessing pregnancies and the causes of abnormal uterine bleeding Abnormal Uterine Bleeding Abnormal uterine bleeding is the medical term for abnormalities in the frequency, volume, duration, and regularity of the menstrual cycle. Abnormal uterine bleeding is classified using the acronym PALM-COEIN, with PALM representing the structural causes and COEIN indicating the non-structural causes. Abnormal Uterine Bleeding
    • CT and MRI provide more detailed views and are often useful in assessing cysts Cysts Any fluid-filled closed cavity or sac that is lined by an epithelium. Cysts can be of normal, abnormal, non-neoplastic, or neoplastic tissues. Fibrocystic Change, malignancies, and benign Benign Fibroadenoma masses.
  • Imaging of the musculoskeletal system: 
    • Radiography is often used to exclude fractures. 
    • CT is more sensitive to bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types pathology, including osteomyelitis Osteomyelitis Osteomyelitis is an infection of the bone that results from the spread of microorganisms from the blood (hematogenous), nearby infected tissue, or open wounds (non-hematogenous). Infections are most commonly caused by Staphylococcus aureus. Osteomyelitis
    • MRI is preferred for a soft tissue Soft Tissue Soft Tissue Abscess evaluation, such as assessing for malignancy Malignancy Hemothorax and myositis. 
    • Bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types scanning can be useful in finding occult fractures, osteomyelitis Osteomyelitis Osteomyelitis is an infection of the bone that results from the spread of microorganisms from the blood (hematogenous), nearby infected tissue, or open wounds (non-hematogenous). Infections are most commonly caused by Staphylococcus aureus. Osteomyelitis, and metabolic bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types disease.

References

  1. Chen MM, Whitlow CT. (2011). Chapter 1. Scope of diagnostic imaging. In Chen MM, Pope TL, Ott DJ (Eds.). Basic Radiology, 2nd ed., Chapter 1. McGraw-Hill. https://accessmedicine-mhmedical-com.ezproxy.unbosque.edu.co/content.aspx?bookid=360&sectionid=39669007
  2. Zaer NF, Amini B, Elsayes KM. (2014). Overview of diagnostic modalities and contrast agents. In Elsayes KM, Oldham SA (Eds.). Introduction to Diagnostic Radiology. McGraw-Hill. https://accessmedicine-mhmedical-com.ezproxy.unbosque.edu.co/content.aspx?bookid=1562&sectionid=95875179

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