Ultrasound tomography for lung imaging: an experimental phantom study

The ability to create real-time images of pulmonary function is highly desirable in many clinical situations. For example, information on air delivery is vital for patients in the intensive care unit (ICU) who are going through mechanical ventilation due to respiratory failure. The functional information obtained from imaging can be used to provide early warnings of developing pulmonary pathologies in real time, reducing complications and improving patient outcomes. Electrical impedance tomography (EIT) is an imaging system that has gone through clinical studies and provides such information. EIT has several drawbacks and the most important one is its limited spatial resolution and very low resolution in depth, which cannot be avoided by adding more electrodes. Therefore, it is possible to introduce ultrasound tomography (UST) as an imaging technique with the potential to provide real-time nonionizing pulmonary monitoring in lung imaging. In contrast, the UST can show significant resolution enhancement when more transducers are used. The central region of thorax can be detected with UST due to its enhanced resolution in the central area. In this work, we developed a realistic geometry thorax phantom and are focusing on the performances of 3-D UST for lung imaging applications. Results are validated using experimental thoracic phantoms representing the possible use of UST for lung imaging. The UST imaging is achieved by detecting and reconstructing the changes of sound velocity distribution resulting from pulmonary functions and conditions.