Fabrication of Realistic and Dynamic Human Head Phantoms.

Abstract

Optical tomography will be a new modality of non-invasive diagnosis in medicine and biology, and is expected to image the distribution of optical properties in human bodies by measuring transmitted light at skin surfaces. In the process of developing optical tomographic imaging systems for diagnosis of disease and study of brain functions of human heads, we need realistic optical phantoms which anatomically and optically simulate human heads with complicated and multi-layered structures. In this study, we have fabricated optical phantoms based on MRI images of a human head. The phantoms had a multi-layered structure with different optical properties at five layers; i.e., skin, skull, cerebrospinal fluid layer, gray matter and white matter. Also the phantoms which were mainly made of solid resin had dynamic parts to simulate the temporal variation of physiological functions in brain. The optical properties of the liquid circulating through the dynamic part can be changed to simulate the change in oxygenation states. The material of the skin layer was a soft rubber in order to achieve a good contact with optical fibers. The fabricated optical head phantom was checked by X-ray CT to see whether air bubbles were trapped or not, and to measure the size and cavity in the phantom.