Various custom-made phantoms designed to optimize magnetic resonance imaging (MRI) sequences have been created and subsequently reported in JSRT. However, custom-made phantoms that correctly match the T1-value and T2-values of human brain tissue (gray matter and white matter) cannot be made easily or quickly. The aim of this project was to search for alternative materials, such as fruits and vegetables, for optimizing MRI sequences. The following eight fruits and vegetables were investigated: apple, tomato, melon, apple mango (Mangifera indica), banana, avocado, peach, and eggplant. Their potential was studied for use in modeling phantoms of normal human brain tissues. MRI (T1- and T2-weighted sequences) was performed on the human brain and the fruits and vegetables using various concentrations of contrast medium (gadolinium) in the same size tubes as the custom-made phantom. The authors compared the signal intensity (SI) in human brain tissue (gray matter and white matter) with that of the fruits and the custom-made phantom. The T1 and T2 values were measured for banana tissue and compared with those for human brain tissue in the literature. Our results indicated that banana tissue is similar to human brain tissue (both gray matter and white matter). Banana tissue can thus be employed as an alternative phantom for the human brain for the purpose of MRI.

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Silicon wet etching with surfactant-added TMAH solution has been investigated to achieve 45° micromirrors on a silicon concave structure used for a hot-embossing mold. The concentrations of TMAH solution and etching temperatures are important etching parameters that affect the surface morphology of both the (100) bottom plane and (110) inclined side walls. In this study, the concentrations of 10, 20, and 25% were used in an etching process at temperatures of 60, 65, 70, and 75 °C. In terms of the optical performance of the fabricated micromirror, the 25% TMAH solution was most effective at achieving a flat and smooth 45° micromirror. A silicon mold etched with Triton-X-added TMAH solution at 65 °C was used for fabricating a polymer microstructure with a 45°-inclined micromirror. The results of the reflection experiment revealed that the reflectivity of the Al-deposited polymer mirror improved as the concentration of TMAH solution used for silicon mold etching increased.

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