Sankaran Subramanian

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The absolute partial pressure of oxygen (pO(2)) in the mammary gland pad and femoral muscle of female mice was measured using EPR oximetry at 700 MHz. A small quantity of lithium phthalocyanine (LiPc) crystals was implanted in both mammary and femoral muscle tissue of female C3H mice. Subsequent EPR measurements were carried out 1-30 days after implantation(More)
Enhancement of image intensity, using the T1-weighted spoiled gradient-echo (SPGR) sequence, was measured in SCC tumor implanted in the flank of C3H mice while they were subjected to several types of oxygenation challenges inside a hyperbaric chamber designed and constructed to fit in an MRI resonator. The central portions of the tumor gave a positive(More)
Imaging of free radicals by electron paramagnetic resonance (EPR) spectroscopy using time domain acquisition as in nuclear magnetic resonance (NMR) has not been attempted because of the short spin-spin relaxation times, typically under 1 microsecond, of most biologically relevant paramagnetic species. Recent advances in radiofrequency (RF) electronics have(More)
A novel method, called relaxo-oximetry, for rapid spatially resolved in vivo measurements of oxygen concentration using time-domain radiofrequency (RF) electron paramagnetic resonance (EPR) is described. Time-domain data from triaryl methyl (TAM)-based single-electron contrast agents were processed by systematic deletion of the initial time points to arrive(More)
Proton nuclear magnetic resonance relaxation parameters (T1, T2) were measured for over 100 malignant and normal tissue samples of various organs of the human body. The purpose of this study was to estimate the reliability of the NMR technique in discriminating normal from malignant tissues. Breast and cervix samples were analyzed by using the malignancy(More)
In this study we report the application of continuous-wave (CW) electron paramagnetic resonance (EPR) constant-time spectral spatial imaging (CTSSI) for in vivo oxymetry. 2D and 3D SSI studies of a phantom and live mice were carried out using projection reconstruction (PR) and constant-time (CT) modalities using a CW-EPR spectrometer/imager operating at 300(More)
The performance of two electron paramagnetic resonance (EPR) spectrometers/imagers, one configured in pulsed mode and the other in continuous wave (CW) mode, at an operating frequency of 300 MHz is compared. Using the same resonator (except for altered Q-factors), identical samples and filling factors in the two techniques have been evaluated for their(More)
Imaging of stable paramagnetic spin probes in phantom objects and in vivo was evaluated using a RF time domain EPR spectrometer/imager operating at 300 MHz. Projections were collected using static magnetic field gradients and images were reconstructed using filtered back-projection techniques. Results from phantom objects containing approximately 10(17)(More)
Electron Paramagnetic Resonance (EPR) is a spectroscopic technique that detects and characterizes molecules with unpaired electrons (i.e., free radicals.) Unlike the closely related nuclear magnetic resonance (NMR) spectroscopy, EPR is still under development as an imaging modality. Athough a number of physical factors have hindered its development, EPR's(More)
Magnetic resonance imaging (MRI) provides high-resolution morphological images useful in diagnostic radiology to differentiate between normal and abnormal/pathological states in tissues. More recently, emerging developments in MRI have added a functional/physiological dimension to anatomical images. Electron paramagnetic resonance (EPR), a magnetic(More)