Since the Axiom lab opened in 2004, we have investigated a wide range of basic engineering, physics and pre-clinical questions.
One of the two founding projects investigated low-contrast imaging using flat-panel based C-arm CT, and was funded by an NIH grant R01 EB003524 from 2004 to 2008 title "Improved C-arm CT for Interventional Procedures" (PI Rebecca Fahrig). Work included development of new technologies for x-ray scatter correction, truncation correction, and lag correction, with the overall goal of achieving 10 HU contrast resolution in a 10 mm slice reconstructed from a 10 s scan. The ability to visualize fresh intracranial bleeds was demonstrated, and image quality and dose were evaluated.
The second founding project investigated data presentation and visualization modes in the interventional suite through the "Interactive Stereowall" (PI Sandy Napel). New technologies included the Rotational Roadmap (RoRo), the Stereo Roadmap and new approaches to 2D-3D registration. These early results were highlighted at the Stanford symposium "C-arm CT in the Interventional Suite, and Stereo Visualization".
First in-vivo results using ECG-gated C-arm CT came from the Axiom lab. The ability to visualize newly-created radiofrequency scars as well as infarct was then demonstrated using this new imaging approach. Algorithms to reduce noise, and motion-related artifact have been developed in collaboration with the University of Erlangen-Nurnberg. This work was supported by an ARRA NIH grant HL087917 "Cardiac C-arm CT" (PI Rebecca Fahrig).
Providing functional assessment in the interventional suite is now a major focus, with initial studies demonstrating the ability to provide quantitative assessment of cerebral blood flow. Perfusion blood volume and perfusion blood flow in healthy and embolized liver has also been demonstrated. These studies are strengthened by the ability to carry out same-day comparisons against standard imaging protocols using clinical CT.
One on-going major project investigates dual-energy imaging using interventional CT. Dual-energy imaging allows the differentiation of materials and tissue based on differential absorption of varying x-ray photon energies. For example, iodine, a commonly used vascular contrast agent, shows sharply decreasing attenuation with increasing x-ray energy. This spectral response is different than that of soft tissue which shows more constant attenuation.
The team explores fast kV-switching dual-energy imaging with an interventional angiography system using only one sweep of the C-arm. The system is equipped with one x-ray tube and can be used to generate images at different x-ray energies by switching the x-ray tube voltage rapidly from pulse to pulse. To date, there is no clinically available angiographic C-arm system available, allowing dual-energy imaging during a single rotational 3D acquisition.
Future work using the zeego@Stanford will continue to push the image quality of C-arm CT towards that of clinical CT, with a focus on exploiting the unique flexibility of the zeego system to achieve high resolution, high speed, and accurate CT reconstructions for translation into the interventional suite.