39-6 Ultrasonography Ultrasonography is a method of imaging body parts by us- ing high-frequency sound (ultrasound)...

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39-6 Ultrasonography Ultrasonography is a method of imaging body parts by us- ing high-frequency sound (ultrasound) waves. Usually, a handheld wand that emits ultrasonic waves is placed against the patient's skin. The waves pass through different tissues at different speeds, and some waves are reflected back to the wand. Sensors in the wand detect the reflected ultrasound and relay the information to a computer capable of con- structing an image based on the reflections. The image pro- duced by this technique is called a sonogram (fig. 39.4). Ider An advantage of the technique is that ultrasound energy is not as dangerous as the radiation used in CT scans and regu- lar radiographs. This is one reason that it has become popular among obstetric physicians. Developing fetal tissue that could be harmed by x-rays is not harmed by ultrasound waves. Therefore, the development of an embryo or a fetus can be monitored by ultrasonography. (a) Sonograms can be used to determine whether there is a single fetus or multiple fetuses. Abnormally developed structures are sometimes visible. Late in development, male or female genitals can sometimes be seen. Occasionally, measurements of a fetus at various stages are made. The normal rate of development of organs can then be verified. Usually, the age of a fetus is given as the clinical age rather than the developmental age used earlier in this exercise. The clinical age is the time since the mother's last menstrual period, whereas the developmental age is the time since fertilization. (b) Figure 39.4 (a) This sonogram shows the outline of a fetal skull at 153 days (clinical age). Compare it with (b) the skull of the same fetus at 206 days. 1. The size of the skull has increased by what percentage during the 53 days between two sonograms shown in fig. 39.4? 2. Which structures in particular do you think are likely to show up well in a sonogram? 3. What other applications for ultrasonography can you think of? 4. What advantages do CT scans, MR images, and regular radiographs have over sonograms? 39-6 Ultrasonography Ultrasonography is a method of imaging body parts by us- ing high-frequency sound (ultrasound) waves. Usually, a handheld wand that emits ultrasonic waves is placed against the patient's skin. The waves pass through different tissues at different speeds, and some waves are reflected back to the wand. Sensors in the wand detect the reflected ultrasound and relay the information to a computer capable of con- structing an image based on the reflections. The image pro- duced by this technique is called a sonogram (fig. 39.4). Ider An advantage of the technique is that ultrasound energy is not as dangerous as the radiation used in CT scans and regu- lar radiographs. This is one reason that it has become popular among obstetric physicians. Developing fetal tissue that could be harmed by x-rays is not harmed by ultrasound waves. Therefore, the development of an embryo or a fetus can be monitored by ultrasonography. (a) Sonograms can be used to determine whether there is a single fetus or multiple fetuses. Abnormally developed structures are sometimes visible. Late in development, male or female genitals can sometimes be seen. Occasionally, measurements of a fetus at various stages are made. The normal rate of development of organs can then be verified. Usually, the age of a fetus is given as the clinical age rather than the developmental age used earlier in this exercise. The clinical age is the time since the mother's last menstrual period, whereas the developmental age is the time since fertilization. (b) Figure 39.4 (a) This sonogram shows the outline of a fetal skull at 153 days (clinical age). Compare it with (b) the skull of the same fetus at 206 days. 1. The size of the skull has increased by what percentage during the 53 days between two sonograms shown in fig. 39.4? 2. Which structures in particular do you think are likely to show up well in a sonogram? 3. What other applications for ultrasonography can you think of? 4. What advantages do CT scans, MR images, and regular radiographs have over sonograms?

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1 Since the USG has not given any information about the measurements solving the problem with gestational age Head circumference at birth is 35cm Duri... View the full answer