An ultrasound image. Image credit: Flickr
An ultrasound image. Image credit: Flickr

Ultrasound, also called sonography, is a painless and safe imaging methodology that employs sound waves to create pictures depicting internals of a body. These waves originate from a scanning or ultrasound machine, through a corded, handheld probe called “transducer”. The sound waves enter the body and reflect back to the transducer whenever they hit a road block or come in contact with a body part or organ.

The reflections or echoes are picked up the transducer and transmitted real time as images on a computer screen. The sound waves or pulses are transmitted at a high-frequency of 1 to 5 megahertz, which makes them inaudible to the human ear. Several million sound pulses travel every second during the process. Since the images are live, organ movement and also blood flow via the blood vessels can be exhibited. 

The scan could be external (over the skin), internal (inside the body) or endoscopic (tube insertion). Generally, an ultrasound technician performs the test in a health center’s radiology department. Other healthcare professionals, such as physiotherapists or midwives with special training in ultrasound, may also take charge.

The Procedure

Live scan images presented on the computer screen. Image credit: Flickr
Live scan images presented on the computer screen. Image credit: Flickr

Typically, an ultrasound is done within 30 to 60 minutes. Anesthesia is not needed and the patient is awake during the exam. Patients could be asked to come in with an almost-full bladder, or not drink or eat 12 hours prior to the exam, etc. based on the type of exam. The clarity of the images produced depends on the equipment used and how effectively the sound waves enter the body.    

The transducer must be in direct contact with the skin; therefore, the body areas to be examined must be devoid of any form of clothing. For easy gliding across the skin or to eliminate air pockets between the skin and transducer, a water-based substance or gel is applied to the spot. Based on requirements, a hospital gown could be provided to the patient. Also, but rarely, an injection is given prior to the procedure as that may help produce clearer images.     

Post the scan, the patient can eat, drink, or drive as normal almost instantly. However, in case of an endoscopic scan wherein sedatives are administered to help relax the patient, a few hours of hospital stay is recommended. Also, for the next 24 hours, no driving, alcohol consumption, working with machinery, etc. is allowed.

Ultrasound Transducer

Transducer at work. Image credit: Flickr
Transducer at work. Image credit: Flickr

The transducer is a critical component of an ultrasound machine. It creates sound waves and receives echoes. The probe comprises single or multiple quartz crystals, known as piezoelectric crystals. When the machine is powered on, an electric current moves through these crystals, causing them to vibrate or alter shape rapidly. As a result, outward moving sound waves are created. When these crystals receive echoes, the sound pulses get processed and transmitted to the computer screen as images.       

The probe could also be moved along the surface to obtain various angles. Some probes are made to be placed inside the several body openings (rectum, vagina, esophagus, etc.) so that the body organs (prostate gland, uterus, stomach) can be examined even closer. For instance, in a transvaginal ultrasound, the transducer is inserted into a vagina to acquire improved images of the ovaries and uterus.


Ultrasounds are primarily used for medical purposes, such as during pregnancy and diagnosis of multiple health conditions that hurt the body’s soft tissues and organs (blood vessels and heart, gallbladder, spleen, liver, kidneys, pancreas, testicles, uterus, eyes, ovaries, etc.). It’s used in cancer detection, cardiology, gynecology, urology and obstetrics, to name a few.   

Ultrasounds are common during prenatal care. During pregnancy, the test helps:

  • Determine fetus size and presence of multiple fetuses.
  • Ascertain due dates.
  • Monitor and visualize fetus growth.
  • Check baby sex, provided the baby’s genital part can be viewed clearly.
  • Find breast and ovary tumors, etc.

Some health practitioners recommend pregnant women to undergo an ultrasound test, ideally between the 18th and 22nd week of pregnancy to check baby position, placenta, amount of fluid surrounding the baby, etc.

Ultrasound Benefits and Some Shortcomings

Ultrasound advantages are:

  • No pain – not needing injections, incisions, or needles.
  • Zero ionizing radiation exposure – making the procedure safer than CT scans and X-rays.
  • Zero-to-minimal reported side effects.
  • Less expensive and widespread technique.
  • Produces clearer images compared to an X-ray.

Ultrasounds are not the best when it comes to transmitting images of body parts holding gas or air – the bowel, for instance. Also, an ultrasound test helps detect abnormalities but doesn’t confirm the existence of a specific condition.

Fresh Technology

Ultrasound is an evolving field, like any other medical domain. The improvements have primarily been in the scanning techniques and resultant image quality. Easy handling and device mobility or wireless probing is also gaining traction. 3D ultrasound, 4D ultrasound, Doppler ultrasound, sonoelastography, contrast-enhanced ultrasound, etc. are techniques owing their birth to constant research and innovation.