How Ultrasound Works: Mystery Revealed for Ordinary Mortals

FROM WAR TO WARD – the ultrasound machine has a very interesting history that spanned for more than fifty years. Developed by Ian Donald of the Royal Air Force, the National Health Service, together with his team at Glasgow University, who would have thought that a destructive technology can be used for a good cause?

Fast forward to the present times, the ultrasound machine has become a major imaging device used by healthcare professionals to view the internal organs of the body, from blood vessels to the kidneys, liver, and many more. Rapid technological advances provided further improvements to the machine, enhancing image quality from bistable to grayscale and now colored, and from still images to real-time moving images.

How Ultrasound Works

In the heart of the ultrasound imaging machine is the transducer which is consists of piezoelectric crystals. These crystals vibrate when electric signal is applied, producing high-frequency sound waves, which is called “ultrasound”. The transducer, so to speak, is the mouth and ears of the ultrasound machine. The sound waves travel outward. More importantly, this type of crystals also works in reverse. When pressure waves hit the piezoelectric crystals, they emit electrical currents. Thus, the same crystals can be used to send and receive sound waves.

When the transducer emits ultrasound waves into the body, they pass through the skin to the internal organs. As the waves encounter tissues with different characteristics and density, they produce “echoes” that reflect back to the piezoelectric crystals. This mechanism happens more than a thousand times per second. The returning echoes are converted to electric signals, which computer converts into points of reference on the image.  

Medical transducers contain a large array of crystals which create a series of image lines, that together, form a complete image frame called a “sonogram”. The entire process takes place 20 times per second. This allows real-time motion to be displayed in the ultrasound image.

Transducers come in many shapes and sizes. The shape of the transducer probe determines its field of view, and how frequent and deep the sound waves penetrate, as well as the resolution of the image. The probe can be moved along the surface of the body at different angles to obtain different views.

Uses of Ultrasound

Ultrasound imaging can be used for diagnostic, functional and therapeutic purposes.

Diagnostic ultrasound, such as the procedure used to monitor the growth and development of the fetus, produces either 2D or 3D ultrasound images, as well as the most recent 4D (which is basically 3D in motion). It can also be used to view the heart, eyes, thyroid, breast, abdominal organs, muscles, skin, and blood vessels.

Functional ultrasound, on the other hand, is specifically used to monitor and measure blood flow in vessels within the body to the heart. It can even measure the speed of the blood flow, along with its movement using color-coded maps called Doppler imaging. Functional ultrasound is also used to measure the relative stiffness of tissues, which is helpful in differentiating healthy tissues from tumors. Also known as “elastography”, this ultrasound technique is used to test for liver fibrosis – a condition characterized by excessive scar tissues in the liver.

More than its ability to diagnose, ultrasound machines can be used for therapy too. This particular technique, called “ultra therapy”, produces high levels of acoustic output to heat, ablate and break up diseased or abnormal tissues.

Ultrasound Gels for Accurate Readings

When using an ultrasound machine, it is a commonplace to apply a high quality specialized ultrasound gel which is made mostly of water. The thing is that ultrasound waves can’t travel through air effectively. The ultrasound gel serves as a “contact medium” from the transducer probe to the tissues inside the body. It allows the sound waves to travel back and forth the transducer without crossing air at any point. This drastically reduces the reflection that the air-tissue creates, allowing 500 times the number of electrical signals to reach the tissues to generate clear-cut images. Furthermore, the gel helps prevent the friction and damage to the skin.

It goes without saying that the use of ultrasound gel is imperative. However, some clinicians make use of coupling alternatives to cut costs. Unfortunately, these alternatives may not be safe for the machine. Some contains dye that can cause discoloration to the transducer, thus, affecting the image quality.

Machine Maintenance

Because ultrasound equipment is essential for a smoothly functioning medical laboratory, the care, prevention and maintenance of the machine should be strictly observed. Majority of clinics and hospitals get maintenance agreements from their original equipment manufacturer (OEM). While considered the safest, it is also the most expensive option to maintain medical equipment.

Nonetheless, healthcare professionals can keep their ultrasound machine in its best condition through preventive maintenance. This includes cleaning the machine regularly and ensuring that connections are plugged in properly, particularly the wiring, cables and transducers.

The transducer and the patient physiology cables should be wiped down clean. Medical-grade wipes are able to clean, disinfect and sanitize sensitive equipment without causing damage. They are also effective at cleaning the leftover gel from the transducer.


The ultrasound machine is no doubt one of the greatest medical inventions of all time. Unlike the X-ray, ultrasound does not produce radiation, which is known to cause harmful effects to the body. The ultrasound machine works by utilizing sound wave to capture images of the internal organs. Thanks to the piezoelectric crystals that send and receive electrical signals from the body. To maintain accuracy of images taken, the right ultrasound supplies should be used, from the coupling gel to the cleaning wipes. Maintaining the ultrasound machine is necessary for its continued and accurate use in patient diagnostic testing. Failure to implement proper care and preventive maintenance is one of the most common causes of faulty medical equipment.

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