Callen Ultrasonography In Obstetrics And Gynecology Free
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Sonography is a medical imaging technique using sound waves to create images of internal structures, such as the heart and abdominal organs. The images are created by the transmission and receipt of waves of ultrasound energy. Callen and Nicholson (2016) provide a useful summary of the key components of sonography as a diagnostic imaging technique.
The pulse is the high-energy acoustic wave generated by the ultrasound transducer. It is delivered repeatedly at a set frequency or cyclic rate, typically around 5 to 20 Hz. The transducer is scanned across the body to cover the region of interest. The timing of the pulse is determined by the distance of the transducer from the body and the ultrasound velocity in the tissue. A radiologist can therefore control the pulse to detect structures within the body, such as a fetal heart, placenta and fetal bones. This is one reason why sonography has become a standard investigative tool in obstetrics. This technique is also called real-time scanning.
Callen has written numerous books, monographs and scholarly articles on emergency medicine, radiology, medical education, public health and medical ethics. He is a frequent lecturer, keynote speaker and conference chair.
Reference: Michael E. Callen, MD, The Emergency Medicine Clinics of North America: a report of the American College of Emergency Physicians 2017 Winter Emergency Medicine Institute, Washington, D.C. February 15-20, 2017, 1. Available at: Emergency Medicine News and Education (EMN&E) .
Womb and fetus are the ones that are being observed, not the adult. The technique was apparently first used in obstetrics in the 1920s. Traditionally, the conditions that would require an obstetric ultrasound examination were placentation disorders, fetal trauma, and suspected anomalies.
Modern ultrasonography, she says, is a relatively new technology. It relies on ultrasound-induced tissue vibration, which can be detected as changes in the electrical impedance of tissues. The technique was first used by an Italian obstetrician, who noted the differences between the behavior of the amniotic fluid in the uterus as the fetus moved, and the compressibility of the amniotic fluid as the fetus moved.
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