Ultrasound computed tomography (USCT) presents a safer alternative to imaging techniques like X-ray computed tomography (commonly known as CT or “CAT” scans) because it does not produce ionizing radiation. Exposure to ionizing radiation, particularly when repeated, poses risks of tissue damage. Moreover, traditional CT scanners are typically large, fixed units, requiring patients to be moved, regardless of their condition or any life-sustaining devices they may be connected to. Transporting patients, especially those with head or spinal injuries, can be hazardous. In contrast, USCT offers a portable imaging option that can be brought directly to the patient. However, achieving accurate medical images with USCT is difficult due to sensor position uncertainty, which can shift with the patient’s movement. Researchers have now addressed this issue in a breakthrough that could enable broader use of ultrasound imaging in emergency and critical care settings. This advance holds the potential to enhance patient care in intensive medical environments.

Scientists from Colorado State University (CSU, Fort Collins, CO, USA) and the University of São Paulo (São Paulo, Brazil) have been working on a bedside-compatible USCT imaging system. This would enable quicker diagnosis and treatment of critical conditions without subjecting patients to harmful radiation. In intensive care and emergency settings, using USCT requires sensors to be attached to the patient’s body to transmit ultrasound through it. The sensors are positioned on a belt worn around the patient’s torso. Unlike CT scanners, which operate within fixed parameters, USCT must adjust to the varying body shapes and sizes of different patients. Because patients naturally move, especially when breathing, the position of these sensors constantly changes. The research team has now applied a technique from seismology to address this problem and enhance the resolution of USCT images, particularly for monitoring the lungs.

Seismic imaging, which uses sound to map the Earth’s interior, inspired solving the sensor positioning issue. The researchers utilized a seismic tomography technique known as static correction, commonly used to determine earthquake locations and study subsurface structures by compensating for irregularities near the Earth’s surface. Static correction in seismology estimates how seismic waves are altered in speed and timing as they approach the sensor, influenced by factors like elevation, weathering, or local geological features. Similarly, in medical ultrasound imaging, the same technique can be used to identify and correct for shifts in sensor location. Applying these corrections improves imaging precision, allowing finer anatomical details to be observed.

The team also designed an algorithm to estimate ultrasound sensor positions with high accuracy and tested the approach in both simulations and experimental setups using torso replicas made from ballistic gel, a substance that mimics human tissue. They worked with healthcare professionals to ensure that the method would have practical value in clinical environments. In earlier studies, they had verified that the ultrasound amplitudes and frequencies used were within FDA safety limits and had successfully tested the method in animal models, specifically pigs. The technology is now approaching the stage of human testing. Their recent study, published in IEEE Transactions on Biomedical Engineering, demonstrated significant improvements in image resolution by solving the sensor positioning challenge. This progress brings USCT closer to becoming a widely adopted, low-cost, mobile alternative to imaging systems that emit radiation.

"With this solution, continuous lung monitoring at the bedside becomes more practical, helping physicians make more informed decisions about mechanical ventilation strategies and track lung health in conditions such as COVID-19,” said Roberto Ceccato, a Ph.D. candidate at the University of São Paulo.

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