Omni-/Multi-Tomography – grand fusion of modalities
By Ge Wang on April 14, 2011
Updated July 23rd, 2011
The physiome concept was presented to the International Union of Physiological Sciences (IUPS) in 1993, and was designated as a strategic area by IUPS in 2001. A physiome describes physiological processes and their interactions from the scale of genome to organism in a systematic fashion. The IUPS Physiome Project supports a worldwide repository of models and datasets, and represents an integral component of systems biology and modern medicine.
In the medical imaging field, efforts are being made to link molecular assays with diagnostic imaging; however, the success to date has been rather limited. One reason is that medical imaging often times does not offer a sufficient spectrum of information. For example, current x-ray CT scanners only produce gray-scale images, while information from genetic and epigenetic profiling is huge. This imbalance between phenotype descriptions (e.g. CT images) and genome-level tests suggests more independent imaging features are demanded. Indeed, the medical imaging field is rapidly trending in this direction. X-ray CT is in transition from gray-scale to true-color images, thanks to the energy-sensitive photon-counting detection technology. Furthermore, x-ray phase-contrast and dark-field imaging systems are under development. Overall, imaging modalities and contrast agents are constantly being improved to generate more and more information on structural, functional, cellular and molecular characteristics of biological systems.
The holy grail of imaging for diagnosis and intervention would produce simultaneous and dynamic multimodal tomographic in vivo observations of highly complex and interconnected physiological and pathological phenomena. The modality fusion approach has been effective in partially meeting this challenge, as demonstrated by the popularity of PET/CT and other hybrid scanners. I envision that the next stage is to integrate more imaging modalities into a single system, or even perform a grand fusion of tomographic imaging modalities to include CT, MRI, PET, SPECT, US, optical and photoacoustic imaging, and more. However, given the physical size requirements of typical scanners, this grand fusion task appears impractical due to space conflict. We could line up the scanners of different types, but this sequential arrangement would make simultaneous capture impossible, especially when relatively slow modalities are involved (e.g. MRI, PET and SPECT).
Over the past several years, interior tomography has been studied for theoretically exact CT image reconstruction over an interior region of interest (ROI) from data associated only with x-rays through the ROI, which means that the imaging chain can be rather narrow. This approach has been extended for interior SPECT, and also achieved some success for interior MRI. To overcome the aforementioned space conflict for grand fusion, let us elevate interior tomography from a CT mode to a general guiding principle for the biomedical imaging field. In other words, we propose to transform each imaging modality into a slim imaging chain for ROI-targeted reconstruction instead of traditional global reconstruction. These compressed imaging chains can now be integrated into a single gantry for concurrent data acquisition and grand interior reconstruction in a unified framework regularized by prior knowledge from sparsity to atlases.
It is acknowledged that interior imaging may be more straightforward for some modalities than others. Taking MRI as a more demanding example, the grand fusion approach would ideally require a combination of a localized magnetic field, focused RF excitation, advanced data processing and reconstruction algorithms. While the technical challenges are nontrivial, we recognize clearly that the advance from modality fusion to grand fusion has enormous potential. We are working in this direction and welcome your input.
In the Second International Conference on Computational and Mathematical Biomedical Engineering, Dr. Peter Hunter presented the opening lecture entitled “A Bioengineer’s View of Recent Development in VPH/ Physiome Project”. After Dr. Hunter’s presentation, I gave a keynote speech on interior tomography, but changed the title from “Interior Tomography” to “Interior Tomographysiome”. In this talk, I stated “tomographysiome goes beyond the modality fusion approach and integrates as many as possible tomographic information sources for studies on systems biomedicine, preclinical and clinical applications. Interior tomographysiome targets most informative, localized tomographic sampling for biomedical investigations, sensitive yet specific diagnosis, as well as personalized and even preventive interventions.” Then, I coined the term tomogranphy from “tomography” and “grand fusion”, and presented this topic at the University of Virginia on April 1, 2011, and at CERN on April 5, 2011. The etymology has further evolved to simplify the conceptual meaning and accommodate integration of future modalities, hence omni-/multi-tomography.
Virginia Tech filed a provisional patent application entitled “Tomogranphy – Interior Tomographysiome” (VTIP 11-103, Application Number 61471245) on April 4, 2011.