From a Mental Image to Imaging Function in 3D

I’m an engineer, and I work on developing ultrasound technology. When clinical colleagues describe how they use ultrasound to guide minimally invasive procedures, they will often reach a point in the explanation of the procedure when they say: “then I form a mental image of the anatomy.”

I recently attended a conference in Venice, Italy (the IEEE International Ultrasonics Symposium), where researchers have recently used sonar to map the ancient, now-submerged canal system of Venice, uncovering 2000-year-old roads. If we can traverse 2000-year-old Roman roads with sound, why can’t we do the same for minimally invasive procedures? How can we move beyond mental images to guide minimally invasive procedures with 3D images of both anatomy and functional information?

While more than 40 unique minimally invasive procedures are currently performed routinely, image guidance still relies heavily on forms of imaging that use ionizing radiation—for example, fluoroscopy or X-ray computed tomography (CT). For example, more than 1 million percutaneous coronary interventions are performed each year using fluoroscopy

If the technology that helps us explore underwater ruins or drive on the interstate could be integrated into the instruments that are inserted into the body during minimally invasive procedures, these procedures could then be performed without exposing the patient and staff to radiation. Catheters and guidewires could become devices to guide and monitor the procedure. With the right devices, ultrasound could perform several of these measurements, including 3D anatomical imaging, monitoring blood flow, stiffness, and perhaps even monitoring temperature or pressure. It’s easy to imagine a future in which interventions in cardiovascular diseases—the leading cause of death in the U.S.—are guided by ultrasound or other sensors integrated into the needles, guidewires, and in patches on the outside of the patient’s body.  

It’s an exciting time to work in ultrasound technology development because the spaces in which ultrasound can be applied are being stretched in ways that are not possible with other imaging modalities. However, it’s not quite as simple as adding all the sensors to existing devices. All fundamental physical limits on device performance in small spaces must be addressed. For example, an ultrasound transducer is several times less sensitive when sub-millimeter in size in comparison with transducers typically used for non-invasive imaging. Image quality and frame rates must be sufficiently high even with smaller devices.

Imagine if the catheter gives a 3D image of blood flow dynamics surrounding a stenosis, or the guidewire itself can image a chronic occlusion and allows the interventionalist to route the wire around it. Ultrasound-based monitoring patches on the outside of the patient’s body could be integrated with the sensors integrated into the instruments to provide a comprehensive view of the vitals and the instrument location. While imagination is required to envision the future we want, it would be better if we did not have to imagine the anatomy during the procedure. Partnerships between technology developers and clinical experts can enable a future with 3D ultrasound guidance of minimally invasive procedures.

Brooks Lindsey, PhD, is an Assistant Professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Institute of Technology and Emory University.