Ultrasonography (USG) is a diagnostic technique of imaging by the means of ultrasonic, which is a sound wave with a frequency higher than human hearing ability. This technique is used to image internal organs and muscles, their sizes and structures. Generally, the purpose of USG is to help enforcing the diagnosis in various disorders of body organs.
USG test uses the sound waves with the frequencies of 1-10 MHz. The choice of frequency determines image resolution and penetration into the patient's body. The high frequency sound wave is generated from the crystals inside a tool called transducer/probe. The transformation resulted from mechanical force toward the crystals will generate electrical voltage this phenomenon is called Piezoelectric effect. The form of the crystals will also transform if it is affected by electrical field. The crystals will inflate and deflate according to the pattern of electrical field which goes through them so that a high frequency sound wave is generated.
One of the examples of ultrasonography is obstetric sonography used by obstetrician to predict the age of pregnancy, to estimate the date of confinement and to help finding disorders in the fetus.
Before performing USG test, the preparation steps the patient has to take are as follows:
- People suffering from obstipation should better be medicated by laxative in the previous evening.
- Test upon organs of upper abdominal cavity should be performed in the condition of fasting besides, in the morning, the patient is prohibited to eat and drink substances that may cause gas in stomach since the image of the organs being checked may be blurred.
- For gallbladder test, the patient is suggested to do fasting at least 6 hours before the test, thus maximal passive dilatation can be obtained.
- Obstetric and pelvic tests require the bladder to be full.