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Ultrasound
Medical ultrasonography uses ultrasound (high-frequency sound waves) to
visualize soft tissue structures in the body in real time. No ionizing radiation
is involved, but the quality of the images obtained using ultrasound is highly
dependent on the skill of the person (ultrasonographer) performing the exam.
Ultrasound is also limited by its inability to image through air (lungs, bowel
loops) or bone. The use of ultrasound in medical imaging has developed mostly
within the last 30 years. The first ultrasound images were static and two
dimensional (2D), but with modern-day ultrasonography 3D reconstructions can be
observed in real-time; effectively becoming 4D.
Because ultrasound does not utilize ionizing radiation, unlike radiography, CT
scans, and nuclear medicine imaging techniques, it is generally considered
safer. For this reason, this modality plays a vital role in obstetrical imaging.
Fetal anatomic development can be thoroughly evaluated allowing early diagnosis
of many fetal anomalies. Growth can be assessed over time, important in patients
with chronic disease or gestation-induced disease, and in multiple gestations
(twins, triplets etc.). Color-Flow Doppler Ultrasound measures the severity of
peripheral vascular disease and is used by Cardiology for dynamic evaluation of
the heart, heart valves and major vessels. Stenosis of the carotid arteries can
presage cerebral infarcts (strokes). DVT in the legs can be found via ultrasound
before it dislodges and travels to the lungs (pulmonary embolism), which can be
fatal if left untreated. Ultrasound is useful for image-guided interventions
like biopsies and drainages such as thoracentesis). It is also used in the
treatment of kidney stones (renal lithiasis) via lithotripsy. Small portable
ultrasound devices now replace peritoneal lavage in the triage of trauma victims
by directly assessing for the presence of hemorrhage in the peritoneum and the
integrity of the major viscera including the liver, spleen and kidneys.
Extensive hemoperitoneum (bleeding inside the body cavity) or injury to the
major organs may require emergent surgical exploration and repair.
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