Extending the Reach of Prenatal Ultrasound

Science Highlights
February 28, 2011

Ultrasound gives expectant parents and health care providers an unprecedented window into pregnancy. High-end systems now capture striking images of fetal facial expressions and activity such as finger movements. Basic systems allow trained providers to diagnose the most common pregnancy complications such as multiple births, breech births in which a baby’s buttocks or feet are born first, and placenta previa, a condition in which the placenta grows over the cervix and can cause severe bleeding.

However, one of the challenges facing patients in rural and underserved populations is access to prenatal ultrasound. Inexpensive, portable systems that require no special training could improve outcomes for women in these areas where the risk of death is much higher than for those who receive regular care. Recent studies have shown that women in parts of the United States are 10 times more likely to die from complications of pregnancy than women in parts of western Europe.[1] Low-cost ultrasound could detect placenta previa, of particular significance in Africa where this condition is responsible for more than 50,000 maternal deaths each year.

Costly Wands

To create novel ultrasound transducers, GE researchers use patterned ultraviolet light to expose a mixture of photosensitive material and piezoelectric powder. This approach eliminates expensive and lengthy cutting.
To create novel ultrasound transducers, GE researchers use patterned ultraviolet light to expose a mixture of photosensitive material and piezoelectric powder. This approach eliminates expensive and lengthy cutting.

Currently, one major obstacle to low-cost ultrasound systems is the price of the transducer, the wand that generates and receives sound waves. The transducer’s size and shape controls the kind of sound waves used to create an image as well as its clarity. While ultrasound equipment has come a long way in the last 30 years – moving from systems the size of washing machines to those the size of laptops and decreasing in overall system cost – the cost to produce the transducers remains high.

Recently, researchers at General Electric’s Global Research Center in Niskayuna, New York, began developing a low-cost method to fabricate ultrasound transducers. The team, led by GE physicist Scott Smith, has created an approach that aims to be faster and less costly than traditional approaches and allows for a range of transducer shapes and sizes. The new approach could make ultrasound available to patients who need it most.

No More Gluing and Cutting

Smith and his group use digital microprinting (DMP) to create the novel transducers. DMP, a fabrication method developed by Prabhjot Singh and the GE Manufacturing Technologies Laboratory, was initially used to fabricate structural ceramics for aerospace components. DMP’s simplicity and speed intrigued Smith, who teamed with Singh to adapt the process to work with the basic materials used to create transducers. With DMP, the researchers add special powders containing piezoelectric crystals (a stiff substance that gives off electrical charges when pressure is applied) and organic compounds to form a toothpaste-like mixture. The mixture is spread thin on a metal plate and then exposed to ultraviolet light. Any material that does not cure during exposure is rinsed off. The process is repeated until the transducer is the desired shape and size. The transducer then is heated at progressively higher temperatures until it hardens and becomes electronically active.

A key benefit to the new approach is that it eliminates the painstaking gluing and cutting normally associated with transducer fabrication. Using conventional techniques transducers are made by gluing piezoelectric material to acoustic matching layers. The acoustic layers make it easier to transfer energy into and out of the body. After joining these pieces, a dicing saw slowly cuts them in straight lines. Cutting time varies depending on the size and shape of the transducer. In the case of obstetrical transducers, which are several centimeters long and 1 to 2 cm wide, cutting can take several hours.

“One of the beauties of the fabrication technique,” says Smith, is that transducers can be made in any shape or size. This flexibility will come in handy for other applications, such as cardiology where the transducer has to be small enough to fit through the ribs.

Toward Smart Systems

With the novel fabrication method in place, Smith and GE Research are turning their efforts to simplifying the interface between operator and machine. They are creating a “smart” system that will automatically adjust the image quality so that an operator who may not have specialized obstetrical training can focus on diagnosis. As for image resolution or clarity, Smith says that, while the transducer may not provide images with the same clarity as high-end systems, they will be adequate to determine fetal number, orientation, and placenta location. “The goal with the resolution is to make it very comparable with what’s currently available,” says Smith.

While noting further technology development is required, Smith said systems with the new transducers could be in initial clinical evaluation within the year.

This work is funded in part by the National Institute of Biomedical Imaging and Bioengineering.

1 World Health Organization. Maternal Mortality in 2005: Estimates developed by WHO, UNICEF, UNFPA and the World Bank. Geneva, 2007.