In vivo proton relaxation times analysis of the skin layers by magnetic resonance imaging.

If in vivo magnetic resonance imaging is nowadays a powerful non-invasive method in medical diagnosis, its application in order to study the skin in vivo is not yet in common use because skin imaging requires a high resolution, at least in the direction perpendicular to the skin surface. We have therefore designed a specific imaging module, which, connected to a standard whole-body imager at 1.5 Tesla, allows us to obtain in vivo magnetic resonance images of skin on most parts of the body. With a depth resolution of about 70 microns, we are able to differentiate the skin layers: epidermis, dermis, subcutaneous fat, and even a thickened stratum corneum on palm as well as on heel. This paper reports the T1 and T2 water proton relaxation times of the different skin layers, in vivo, which are magnetic resonance parameters extracted from the images. Results show that skin layers are characterized by shorter T2 relaxation times than other biologic soft tissues. On the contrary, the measured T1 values are in the same range as in other tissues. These short T2 values may be assigned to the fibrous protein content of the skin and particularly of the dermis. This study on normal skin is the precursor of further works such as the influence of aging. As regards skin pathologies, it will be a powerful tool to follow the evolution of skin diseases under treatment.