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Proceedings Paper

Radiofrequency time-domain EPR imaging: instrumentation development and recent results in functional physiological in vivo imaging
Author(s): Sankaran Subramanian; Nallathamby Devasahayam; M. C. Krishna
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Paper Abstract

Electron Paramagnetic Resonance is an emerging technique finding applications in functional physiological imaging. Traditionally EPR imaging developed as a CW (continuous wave) technique involving the measurement of free radical distribution in vivo using constant frequency and field-sweep modality almost identical to the early developments of MRI. As in CT and PET this involved the generation of projections in presence of gradients and the reconstruction of images via filtered back-projection. The large line-width and the concomitant short relaxation times posed a serious challenge for the development of time-domain methods akin to modern pulsed NMR & MRI. With the recent availability of narrow line stable non-toxic radicals based on triarylmethyl (TAM), ultra fast data acquisition systems (signal digitizer and summer), very fast electronic switches and low-noise amplifiers, we have developed time-domain imaging schemes in EPR operating in the radiofrequency region Using a novel pure-phase encoding scheme, we are able to generate 2 and 3 dimensional spatial images and spectral-spatial images that adds an additional functional dimension to these images. The special space-encoding scheme with fast gradient ramping allow rapid in vivo imaging of small animals with superior spatial and functional information with good temporal resolution that can provide valuable physiological and pharmacokinetic insight. Our main thrust has been in the investigation of tumor hypoxia and tumor reoxygenation for the purpose of minimizing the radiation dose for maximum tumor cell killing. These and some of the allied imaging methods, and results from tumor investigation will be presented.

Paper Details

Date Published: 19 February 2007
PDF: 17 pages
Proc. SPIE 6441, Imaging, Manipulation, and Analysis of Biomolecules, Cells, and Tissues V, 644106 (19 February 2007); doi: 10.1117/12.700928
Show Author Affiliations
Sankaran Subramanian, Ctr. for Cancer Research, National Cancer Institute (United States)
Nallathamby Devasahayam, Ctr. for Cancer Research, National Cancer Institute (United States)
M. C. Krishna, Ctr. for Cancer Research, National Cancer Institute (United States)


Published in SPIE Proceedings Vol. 6441:
Imaging, Manipulation, and Analysis of Biomolecules, Cells, and Tissues V
Daniel L. Farkas; Robert C. Leif; Dan V. Nicolau, Editor(s)

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