Development of Nondestructive ESR Technology Toward Noninvasive Measurement of Skin Melanin Radicals

Abstract

In this study, investigation was performed on improving the X-band (9 GHz) electron spin resonance (ESR) imaging to detect and analyze melanin radicals contained in melanoma, a skin cancer. A new detector for non-invasive measurement was developed and a foothold was established for non-invasive measurement of melanin radicals inherent in skin diseases. As a result, it was found that pheomelanin (radical) is involved in malignant melanoma, and that the image intensity increases with the increasing stage of the melanoma. The pheomelanin radical was determined based on the hyperfine coupling constant. Furthermore, it was newly found that in other skin diseases in which melanin is involved, there is a good correlation between the degree of blackness of the skin disease and the ESR intensity, except for melanoma. In the case of melanoma, this correlation deviated from this correlation because eumelanin and pheomelanin radicals contributed to produce a stronger ESR signal. The main reason for this is thought to be that melanoma contains eumelanin and pheomelanin radicals. In this study, the sensitivity of the newly developed dielectric detector was significantly increased, and it was confirmed from the spectrum obtained by a single sweep that there was a pheomelanin radical in the melanoma sample.