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Digital Imaging Analysis

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Imaging experiments were performed by using standard spin warp gradient echo sequence for MRI, except that each phase encoding step was preceded by an ESR saturation pulse to elicit the Overhauser enhancement. Fig.1 shows the pulse sequence started with the ramping of the B0 field to 7.53 mT for 14N labeled nitroxyl radical, followed by switching on the ESR irradiation. Then, the B0 was ramped up to 14.53 mT before the NMR pulse (617 KHz) and the associated field gradients were turned on. At the beginning or end of the cycle, a conventional (native) NMR signal intensity (with ESR OFF) was measured for computing the enhancement factors. A Hewlett-Packard PC (operating system, LINUX 5.2) was used for data acquisition. The images were reconstructed from the echoes by using standard software, and were stored in DICOM format (Digital Imaging and Communications in Medicine). MATLAB codes were used for the computation of DNP parameters and curve fitting. Typical scan conditions were as follows, repetition time (TR)/echo time (TE): 2000 ms/25 ms; ESR irradiation time (TESR): 50 ~ 800 ms, in steps of 50 or 100 ms; RF power, 90 W. The reproducibility of the data was confirmed with several experiments. The DNP parameters and enhancement factors were obtained from the data set with good correlation (R2 …show more content…

The phantom tubes were arranged as shown in Fig. 9a. Images were recorded for various RF power ranging from 6.7 W to 90.6 W. Typical scan conditions were as follows, repetition time (TR)/echo time (TE): 1100 ms/25 ms; ESR irradiation time (TESR): 500 ms, scanning time, 60 s; NMR frequency, 617 KHz; ESR irradiation frequency, 220.6 MHz. No. of averages, 10; slice thickness, 50 mm, image field of view, 40 x 40 mm; pixel size, 0.63 mm 0.63

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