Non-Invasive Monitoring of Intracranial Pressure with Volumetric Ophthalmic Ultrasound: Integration with NASA's Flexible Ultrasound System (FUS)

This project is the initial integration of the 3-D ophthalmic imaging capability onto NASA's next generation flexible ultrasound system (FUS). A separate National Space Biomedical Research Institute (NSBRI) project (SMST02803) led to the development of 3-D ophthalmic ultrasound imaging on the current operational ultrasound platform (GE Vivid q) on board the International Space Station (ISS). The FUS is a state-of-the-art software beamforming architecture based on the GE Vivid E95 cardiovascular system with enhanced imaging capabilities. The FUS is switchable between its two operating modes, a high-quality clinical imager and a configurable research system with full control of the ultrasound acquisition and processing. Mechanical 3-D probes, like the prototype ophthalmic probe previously developed, are not compatible with the FUS platform and the frequency range of the electronic 3-D probes supported by the FUS platform are not suitable for ophthalmic imaging. The hardware and software differences between the current ISS ultrasound system and the newer FUS platform required additional effort to enable the ophthalmic imaging capabilities on the FUS.

The goals for this project are to integrate the prototype 3-D ophthalmic probe onto the FUS for 2-D imaging and develop new hardware to connect the current volume acquisition hardware to the FUS for 3-D imaging. The approach seeks to minimize the hardware and software development through the reuse of existing components and implementation of the ultrasound imaging in the clinical mode of the FUS. The target outcome is preliminary lab testing of the 3-D imaging on the FUS. The scope of the project does not include fabrication of new volume acquisition hardware, exploring all of the advanced imaging on the FUS, acoustic safety testing, or integration with the FUS's acoustic output safety control for human scanning.

A commercially-available probe adapter was modified allowing connection of the prototype ophthalmic probe to the FUS, and the FUS software was modified to recognize the prototype probe. Several new ophthalmic imaging modes were implemented in the FUS's clinical software to enable 2-D imaging on the FUS. This implementation, as opposed to implementation in the research mode, leveraged the clinical image quality on the FUS and reduced the development time. Additionally, the initial integration utilized two of the FUS's advanced imaging modes which included true confocal imaging to improve image resolution and virtual apex for broader anatomical coverage. The probe adapter was further modified to interface the probe's control signals with the previously-developed volume acquisition hardware, and the probe adapter was connected to a breadboard-version of the volume acquisition hardware allowing initial testing of the 3-D acquisitions on the FUS.

The first 2-D images of an ultrasound phantom were acquired on the FUS and an initial integration test of the 3-D acquisition hardware on the FUS was completed. The 2-D imaging tests demonstrated improved depth of focus, higher spatial resolution, and larger anatomical coverage with the FUS. The 3-D integration testing revealed a hardware issue resulting in non-uniform rotation of the mechanical 3-D probe during the acquisitions and the source narrowed down to corruption of the control signals in the probe adapter box. Further effort is required to better isolate these signals in the probe adapter box and provide the uniform rotation of the ultrasound transducer array necessary for accurate reconstruction of the ultrasound data from the 3-D acquisition.

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