For the development of shear wave elastography for precise, non-invasive cancer diagnosis

As is well known, there is a type of sound that we cannot hear: ultrasound. The history of ultrasound stretches back more than two centuries, beginning with the study of sound in nature. In 1794, the Italian scientist Lazzaro Spallanzani observed how bats navigate using sound waves, an early recognition of echolocation that planted the seed for future develop­ments. A century later, in 1880, Pierre and Jacques Curie discovered the piezoelectric effect – the ability of certain crystals to generate an electric charge when subjected to mechanical stress and vice versa. This breakthrough was essential because it allowed sound waves to be both generated and detected, paving the way for practical ultrasound technology.

The early 20th century saw sound waves applied in new ways, particularly during World War I when sonar (Sound Navigation and Ranging) was developed to detect submarines under water. This military innovation highlighted the potential of sound for imaging and inspired scientists to adapt the technology for medicine. By the late 1940s, Austrian neurologist Karl Dussik was among the first to use ultrasound in a medical setting, attempting to visualize the human brain.

In the 1950s, further progress was made by Scottish physician Ian Donald, who pioneered its application in obstetrics and gynecology, demonstrating the value of ultrasound for examining pregnancies.

The 1960s and 1970s marked the development of real-time imaging, in particular Doppler ultrasound and B scans, allowing moving images of blood flow and internal organs to be captured instead of static scans. This made ultrasound far more practical and reliable in clinical settings. From the 1980s onward, rapid advances in digital technology improved image quality, making ultrasound a standard diagnostic tool in fields ranging from prenatal care to cardiology and abdominal medicine.

However, the assessment and reliable, biopsy-free diagnosis of cancer in soft tissues remained a difficult undertaking. One possible solution for this task has been functional ultrasound imaging, in particular shear wave elastography (SWE). This is an imaging technique that measures tissue stiffness, particularly in organs such as the liver, breast, prostate, or thyroid, by determining the propagation velocity of transverse shear waves. Shear wave elastography is now routinely used for the early detection of tumors, fibrosis, or inflammation in soft tissue.

While conventional methods use individual focused pulses traveling into the body, being reflected at tissue inhomogenities and traveling back, the “Supersonic Shear Imaging” (SSI) method developed by the award winners uses clever phase control of the piezo transducers to form a transverse shock front that can be used to capture depth information precisely and quickly. Due to the extremely high frame rate (> 10,000 fps), the SSI method, unlike more traditional SWE methods, can display high-resolution, large-area 2D elastograms (2D color maps of elasticity) in real time.

The SSI process was developed and patented by the award winners. Through the start-up Supersonic Imagine, which they founded, it has been distributed worldwide since 2009, with approximately 3,000 Aixplorer systems installed by the end of 2020. Shear wave elastography is now used in a similar form in the ultrasound devices of almost all established manufacturers.

Univ.-Prof. Dr.-Ing. Dr. med. Dr. h. c. Steffen Leonhardt