Abstract. Diffusion-weighted magnetic resonance imaging (MRI) is frequently used clinically, and is available for the whole-body screening for tumors. The exact mechanism by which the apparent diffusion coefficient (ADC) value decreases in tumorous tissue remains unclear, although various theories have been proposed, including intracellular and extracellular factor theories. It is impossible to distinguish each factor in the intracellular and extracellular spaces as the source of MR signal generation by means of conventional comparison between MR images and pathological specimens. Other factors which have been reported to affect ADC include cellularity and cellular edema of human tissues, and temperature of phantoms at the time of measurement. We employed a new technique that enables cellular MR imaging using a newly developed bio-phantom containing a living culture tumor cell line, Jurkat-N1. We investigated possible reasons for observed decreases in ADC values for tumors, and we considered the contribution of both the intracellular and extracellular space to such a decrease. The ADC values of the bio-phantom increased with increasing heat exposure from 27 to 45˚C. ADC values also increased after the destruction by sonication of tumor cell membranes. ADC values decreased as cellularity increased in the bio-phantom. ADC values decreased due to cellular edema caused by a low salt concentration in the bio-phantom. Changes in pressure in the bio-phantom had no effect on the observed ADC values. We calculated both the intracellular ADC and extracellular ADC values using the ADC values, cellularity, and cellular volume of Jurkat-N1 cells in the bio-phantom. The extracellular ADC values in the bio-phantom were estimated to be lower than the ADC value of distilled water. These results indicate that not only intracellular ADC values, but also extracellular ADC values contribute to the determination of the ADC values of bio-phantoms. This is the first report to have examined the contribution of intracellular and extracellular space on the ADC values of bio-phantoms containing cultured tumor cells.
A different domain observation technique by modulation of a polarizing plane has been developed for Nd-Fe-B sintered magnets. A liquid crystal element inserted in a longitudinal Kerr microscope is used as an optical modulator to acquire a reference image needed to enhance Kerr contrast by image processing. Domain images of the Nd-Fe-B magnet can be clearly observed by this technique in a high magnetic field up to 4.4 kOe. It was found that polishing of the sintered magnet reduced its coercive force.
We propose and demonstrate a novel pH imaging sensor based on the CCD (Charge Coupled Device) technology. This device consists of pH sensing parts, which sense pH value and transform a pH value to electric charges, and conventional CCD parts, which transfer the electric charges to read out circuit. A thin Si3N4 film which acts as the hydrogen ion-sensitive membrane was used in the pH sensing film. The prototype devices were fabricated. The output signal fiom the imaging sensor was lineally changed from pH0 to 14, and successfully observed a pH image on a black & white TV monitor.
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