Ultrasonography is an imaging technology that uses high-frequency sound waves to characterize tissue. It is a useful and flexible modality in medical imaging, and often provides an additional or unique characterization of tissues, compared with other modalities such as conventional radiography or CT.
In an ultrasound exam, a hand-held transducer is placed against the skin or in a body cavity. The transducer sends out high frequency sound waves that reflect off of body structures. The returning sound waves, or echoes, are displayed as an image on a monitor.
The image is based on the frequency and strength (amplitude) of the sound signal and the time it takes to return from the patient to the transducer. Unlike with an x-ray, there is no ionizing radiation exposure with this test and the images are real-time, they can show movement of the body's internal organs as well as blood flowing through blood vessels.
There has been increasing use of ultrasonography in medical practice from the popular fetal assessment and study of internal organs to vascular studies, elastography, musculoskeletal studies and ultrasound guided biopsy.
Traditional ultrasound scanning is 2D, meaning it sends and receives ultrasound waves in just one plane. The reflected waves then provide a flat, black-and-white image of the fetus or structure through that plane.
Most of the detailed evaluation of fetal anatomy and morphology so far has been done using 2D ultrasound.
Further development of ultrasound technology led to the acquisition of volume data, i.e., slightly differing 2D images caused by reflected waves which are at slightly different angles to each other. These are then integrated by high-speed computing software to produce a 3-dimensional image. The technology behind 3D ultrasound thus has to deal with image volume data acquisition, volume data analysis and finally volume display.
3D imaging allows fetal structures and internal anatomy to be visualized as static 3D images. However, 4D ultrasound allows us to add live streaming video of the images e.g showing the motion of the fetus, it is thus 3D ultrasound in live motion.
4D ultrasound has the same advantages as 3D, while also allowing us to study the motion of various moving organs of the body.
Our GE Voluson E6 and Logiq S7 ultrasound machine gives good 2D images for optimized 3D and 4D studies with HD-live options.
Common uses of Ultrasonography?
How do I prepare for this investigation?
- Examining many of the body's internal organs, including the liver, gallbladder, spleen, pancreas, kidneys, bladder, uterus, and ovaries.
- Examination of a fetus while in the womb.
- Doppler studies to see blood flow.
- Ultrasound guided needle biopsies.
- Assessment of superficial structures, such as the thyroid gland and scrotum (testicles)
- Upper and lower extremity vascular ultrasound to evaluate for deep vein thrombosis (DVT).
Wear comfortable, loose-fitting clothing. Examinations of the kidneys, bladder, pelvis, uterus, ovaries, and for early pregnancy require well distended bladder. Drink about 1 liter of water 30-45 minutes before the exam, and refrain from urinating.
Examinations of the abdomen or of the abdominal aorta require that you have nothing to eat or drink for at least 6-8 hours prior to the exam to avoid contraction of the gall bladder and gas in the stomach and intestine. Medications can be taken with small amount of water when necessary.
What are the benefits?
What should I expect during this exam?
- Ultrasound studies are mostly noninvasive.
- Occasionally, an ultrasound exam may be temporarily uncomfortable, but it is almost never painful.
- Ultrasound uses non-ionizing sound waves and has not been associated with carcinogenesis. This is particularly important for the evaluation of fetal and gonadal tissue.
- Ultrasound scanning gives a clear picture of soft tissues that do not show up well on x-ray images.
- Ultrasound is the preferred imaging modality for the diagnosis and monitoring of pregnant women and their unborn babies.
- Ultrasound examination is less expensive to conduct than CT or MRI.
7. The real-time nature of ultrasound imaging is useful for the evaluation of physiology as well as anatomy (e.g. fetal heart rate), Doppler evaluation of organs and vessels adds a dimension of physiologic data, not available on some other modalities.
The overall objective is to obtain the best images to aid diagnosis. Most ultrasound exams are painless, you may feel pressure from the applied transducer during the procedure.
The physician/technologist will explain the investigation to you and take a short medical history after which you will be positioned on the table, a clear gel will be applied to the area under examination. This will help the transducer make contact with the skin. The transducer will be moved in various planes to image the area. The duration depends on the study being done but usually 10-15mins.
After the examination is complete and the gel has been wiped off, you may be asked to wait while the ultrasound images are reviewed by the radiologist.