How does ultrasound work?
How does ultrasound work?
Ultrasonography or ultrasound scanning is an imaging technique that uses ultrasound to image the internal organs of the body. Ultrasound has very high frequency (above 20,000 Hz) and so is not audible to the human ear. Typically, ultrasound at frequencies ranging from 2 to 15 megahertz is used in ultrasound scanners. Using ultrasonography, it is possible to visualize muscles, tendons and many other internal organs of the body. Using ultrasound, it is also possible to monitor the development of the fetus in the womb.
Ultrasound scanning is performed with the help of a handheld transducer. A water based gel is applied to the skin and the transducer is moved over the region which is to be examined. The transducer contains a piezoelectric oscillator that generates ultrasound. It also contains a detector that detects reflected ultrasound waves. Ultrasound waves produced by the detector penetrate the body and get reflected back by the tissues. Different tissues reflect differently and based on this, the image is constructed. Usually, ultrasound frequencies between 7-15 megahertz are used to image superficial structure whereas, deeper structures like the liver are imaged using frequencies in the range of 1-6 megahertz.
Unlike other imaging techniques, ionizing radiation is not used in ultrasound scanning. This makes it a safe technique. Ultrasound also has other therapeutic applications. For example, ultrasound can be used in cancer treatment to destroy cancer cells by localized heating. Focused ultrasound can also be used to break up stones in the kidneys by lithotripsy.
However, there are certain limitations on the use of ultrasound scanning. Presence of gas in the gastrointestinal tract may yield poor results. Sonography of the brain is also very limited as ultrasound doesn’t penetrate the skull bones well. Similarly, ultrasound scanning will not yield valuable results if the patient is obese.
Related pages:
- Medical Imaging
- Electrocardiogram [ECG]
- Electroencephalogram [EEG]
- Ultrasound
- Computed tomography [CT Imaging]
- Magnetic resonance imaging [MRI]
- Positron emission tomography [PET]
- Commonly Used Radionuclides in Nuclear Medicine
