The papers published in this special issue of Academic Radiology were contributed following the International Symposium on Metabolic Imaging and Spectroscopy, organized at the University of Pennsylvania to honor the 100th birthday of legendary scientist Professor Britton Chance. This event focused on scientific contributions and strategic reviews of methods to study cell and tissue function and metabolism, organized by Professors Lin Z. Li and Arjun Yodh. The papers contained in this issue were contributed to summarize results presented at the conference as well as extend the work in future directions. Each paper was submitted for peer review commensurate with standard practice at Academic Radiology, and the content focused on in vivo human applications, with either direct or potential for translation for eventual diagnostic use.
The first two articles present work on near-infrared spectral imaging of breast cancer, a topic that was a direct product of the pioneering efforts of Dr. Chance. Each paper examines a particular aspect of how near-infrared spectroscopy (NIRS) imaging can be accomplished and how the coupling of fibers to the breast affects the measurements. Mastanduno et al. report that a magnetic resonance imaging (MRI)-coupled fiberoptic array for imaging breast tissue with a range of breast sizes is possible, which is a critically important part of making this type of imaging available to all women. This is followed by the article by Busch et al , which quantifies the change in blood volume, oxygen saturation, and flow in response to typical mammographic compression forces. Understanding this dynamic of breast metabolism is critical in interpreting contrast-agent imaging and maximizing the diagnostic value of NIRS measurements and other vascular contrast imaging procedures in the breast.
Dr. Chance was keenly interested in optical measurements of brain injury and function. In the third article of this special issue, Lynch et al. compare noninvasive NIRS measurements of oxygen concentration in venous blood with invasive sampling. By adding venous oxygenation measurements to existing optical techniques to measure tissue and arterial oxygen concentration and blood flow, the work by Lynch et al. will improve quantification of tissue oxygen metabolism. Sun et al. quantify cerebral hemodynamic changes during hemorrhagic shock using NADH signals, one of the key optical markers of mitochondrial metabolism advanced by Dr. Chance’s studies. Understanding the origin of tissue injury postshock may suggest new avenues for therapeutic research. Kainerstorfer et al. describe a model to extract cerebral blood flow and oxygen metabolism from functional NIRS measurements, paving the way for NIRS future applications in both functional activation and autoregulation of the injured brain. Zirak et al. apply NIRS with diffuse correlation spectroscopy to measure vasoreactivity following ischemic stroke, suggesting a noninvasive technique to stratify risk of future strokes.
Nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) were also among the full spectrum of the biophysical techniques used by Dr. Chance to probe key biological questions. Notably he was one of the pioneers developing in vivo 31 P-NMR for studying metabolism. The following two review articles focus on the development of noninvasive NMR and EPR methods for clinical translations. Swartz et al. describe the first large-scale clinical EPR system for translational human applications such as measurement of tissue oxygen and radiation dosimetry in vivo. Wehrli et al. review the development of magnetic resonance susceptometry, which is based on the paramagnetic effects of deoxygenated hemoglobin. The technique has been applied to measure venous blood oxygen saturation and brain oxygen consumption rate in human subjects.
The ability to measure metabolism with MR spectroscopy was a keen interest of Dr. Chance, and related to this, the use of hyperpolarized MRS has exploded in recent years with new clinical trials happening frequently after a long development in preclinical models. Li et al. demonstrate new technique being prototypes to use hyperpolarized 13 C-pyruvate MRI to differentiate tumor malignancy quantitatively in two breast cancer mouse xenograft models, MCF-7 and MDA-MD-231, extending ratiometric methods to interpret the data for diagnostic value. Zhang et al. provide a review of the key developments of hyperpolarized 13 C MRI in assessing signaling pathways in cancer and propose a systems approach for integrating cancer genomics, human subjects/animal models, and hyperpolarized 13 C MRI to further explore key issues such as genomic-driven therapy, intratumoral heterogeneity, and drug resistance.
Tumor metabolic imaging for detection of lesions has become mainstream in the form of positron emission tomography (PET) imaging. Hess et al highlight the latest progress and the potential avenues of using PET computed tomography scanners for imaging with flourodeoxyglucose in understanding diseases and treatment responses.
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References
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