On the Horizon: Three Imaging Technologies Head Toward the Clinic

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ARFI_Liver_Metastatic-Carcinoma.jpg - ARFI Liver
Figure 1. Metastatic mass appears stiffer (darker) than surrounding liver tissue. Patient with metastatic melanoma in liver, no known fibrosis.
Source: Kathryn Radabaugh Nightingale, PhD

In 2013, the National Institute of Biomedical Imaging and Bioengineering (NIBIB) celebrated its tenth year of operating as a focal point for advancing the development of technologies to improve the health of the U.S. population. Bill Gates once said: “We always overestimate the change that will occur in the next two years and underestimate the change that will occur in the next ten.” 1 Looking back over the past decade, we have seen a significant change in how radiology is practiced—but what research tools currently being developed might change radiology practice in the next decade?

Shortly before NIBIB was founded, Health Affairs published a physician survey asking about the most important medical innovations of the previous 25 years.  Doctors rated MRI and CT scanning as the most significant developments ahead of twenty-nine other innovations including statins, hip replacements and bone marrow transplants.

In 2014, it is estimated that more than 33 million MRI procedures will be performed in the U.S., up 40% from a decade earlier; there were 81 million CT procedures performed, up 52% over the same period. Ultrasound procedures have become equally as ubiquitous. It is clear that the ability to noninvasively see inside the body has revolutionized medicine; these technologies can now aid in early diagnosis as well as enable monitoring of both disease progress and treatment efficacy. There also is a growing demand for imaging procedures to be able to identify functional and molecular characteristics of abnormal pathology that inform treatment, in addition to simply identifying location.

There are many exciting, new imaging techniques that are continually being developed, with NIBIB receiving more than 850 applications in 2013 related to developing new technologies. As Gates once observed, after the discovery and demonstration of a new approach, we see a burst of enthusiasm for investigating this new, potentially game-changing technique. In practice, however, it often takes close to two decades before a technique is ready for wide adoption into clinical practice.

Maintaining momentum through this long translational process of optimizing and validating promising imaging solutions is challenging, and often relies on bringing together multidisciplinary teams that can pursue research questions, develop convincing evidence for safety and efficacy and design products that are attractive to end-users. Below are three areas in which NIBIB is funding technologies that may lead to new clinical procedures within the next decade.

Elastography

Palpation, employed by medical practitioners for millennia, is used to detect differences in the stiffness of tissues. It is considered an effective method for detecting pathologies, but is limited to tissues accessible to a physician’s hands and is qualitative in nature. To overcome these limitations, both ultrasound and magnetic resonance techniques have been developed. Ultrasound techniques have been available for more than two decades and several systems have been approved for use by the FDA in the past six years; however they are still considered experimental by many insurers. Magnetic resonance elastography (MRE) was developed in 1995 and offered improved image reconstruction, assessment of tissue anisotropy, access to organs like the brain that are not accessible by traditional ultrasound approaches and decreased operator dependency. However, long acquisition times are a disadvantage.

NIBIB has been actively funding research into removing some of the barriers to further clinical translation of ultrasound elastography. Several current projects study acoustic radiation force impulse imaging (ARFI) and shear wave elasticity imaging (SWEI), both of which are expected to be less operator-dependent. ARFI uses focused, high-intensity sound beams to produce “push-pulses” that generate shear waves (secondary waves that extend in a direction perpendicular to the direction of the push pulse) within tissue; and then monitors the tissue response with ultrasonic methods.

The tissue response is related to the stiffness properties and structure of the liver and is displayed as high resolution, qualitative elastographic images of the liver. The speed of the shear waves is proportional to the stiffness of tissue; thus ARFI can also produce quantitative stiffness measurements based on the speed of the shear waves. These measurements can then be used to quantitatively map tissue properties; for example, to