This Small Business Innovation Research (SBIR) Phase I project addresses the clinical need for an X-ray replacement technology that is portable, low-cost, and safe. X-ray is the dominant modality currently in use for diagnostic imaging of bone despite its many limitations: emission of radiation, bulky, and relatively expensive. The research objectives of this feasibility study include: 1) Design, integrate, and test a low-power consumption mechanically scanned ultrasound transducer; 2) Demonstrate a handheld ultrasound system with free-hand three-dimensional (3D) bone reconstruction in in vitro phantoms; and 3) Demonstrate a free-hand 3D bone imaging system in ex vivo whole porcine models. It is anticipated that the mechanically scanned ultrasound transducer will yield frame rates > 15 frames/s and resolution < 2.5 mm at imaging depths > 10 cm. In vitro phantom experiments will be performed using a computer aided design model of the human spine. Error between 3D ultrasound reconstructions and the computer model is anticipated to be < 2.5 mm. Finally, the proposed device is anticipated to yield > 0.90 correlation to CT reconstructions of whole porcine spinal bones. Overall, this project is anticipated to demonstrate feasibility of a handheld 3D ultrasound-based bone imaging technology with high correlation to CT.
The broader impact/commercial potential of this project includes safer, less expensive, and more accurate imaging of bone anatomy in medical imaging technology applications: spinal anesthesia, orthopedic, emergency medicine. In applications such as emergency care, the technology would enable patient-side imaging of bone anatomy, which is currently unavailable due to the bulkiness of X-ray machines. Additionally, the public would benefit by an overall reduction in ionizing radiation exposure from X-ray and a subsequent reduction in cancers. The estimated market potential for the proposed ultrasound-based bone imaging technology is estimated at approximately $580 M/yr in the United States. The primary target market for the technology is the lumbar spinal anesthesia market. Currently these procedures exhibit failure rates of 40% - 80% in the obese, which results in poor patient outcomes and higher costs for health care providers. The general scientific and technological understanding of acoustics will be enhanced through this project by a better understanding of ultrasound interactions with specular reflecting surfaces, such as bone.
This Small Business Innovation Research (SBIR) Phase I project addresses the clinical need for an X-ray replacement technology that is portable, low-cost, and safe. X-ray is currently the dominant modality for diagnostic imaging of bone despite its many limitations, which include: emission of radiation, bulkiness, and relatively high cost. The proposed solution that was investigated in this project is a handheld ultrasound system with new 3D ultrasound-based bone imaging technology. In Objective 1, a low power consumption mechanically scanned ultrasound transducer was integrated into a custom handheld ultrasound system. The investigators on this project have previously demonstrated the benefits of this type of transducer when imaging bone with ultrasound because it can mitigate particular sources of artifacts that are derived from the geometry of standard ultrasound transducers. The mechanically scanned transducer design also facilitates portability and provides greater flexibility for more involved signal processing, due to simplified electronics and lower channel counts. Results from Objective 1 demonstrated successful integration of the mechanically scanned ultrasound transducer. Resolution using a dynamic receive-only focusing approach was demonstrated to achieve our criteria of < 2 mm resolution over 10 cm of imaging depth. While providing real-time imaging up to 17 frames/s, the device also exhibited a 75-minute battery life under continuous imaging. In Objective 2, real-time 3D bone imaging was demonstrated successfully, for the first time, with a handheld ultrasound device in a tissue-mimicking phantom of the lumbar spine. Finally, Objective 3 validated these results in a more realistic imaging environment using whole pig models, which retained all tissue structures including skin, fat, and tendons. Real-time 3D reconstructions of the pig model using the custom handheld ultrasound system were compared to computed tomography (CT) gold standard reconstructions. Root mean squared (RMS) error between the ultrasound 3D bone reconstruction and CT was demonstrated to meet our criteria for acceptance of < 2.5 mm RMS error over 15 runs. Correlation coefficients between ultrasound 3D surface points and CT were excellent, with average coefficients > 0.99. While all criteria for acceptance were met, the performance of the proposed ultrasound system in the pig model was degraded compared with the tissue-mimicking phantom, as anticipated, due to additional noise sources. Successful achievement of the research objectives in Phase I establishes feasibility of the proposed handheld 3D bone imaging technology. With further research and development, this technology has potential to achieve a broader impact in medicine through commercialization of products that address the need for safe, low cost, and high performance bone imaging. This technology has potential use in medical imaging applications such as spinal anesthesia, orthopedics, and emergency medicine. In addition, the general scientific understanding of acoustics can be enhanced with further investigations into ultrasound interactions with specular reflecting surfaces, such as bone.
