In-Vivo Bone Mineral Density and Structures in Humans: From Isotom Over Densiscan to Xtreme-CT

In the early s, Prof. Ruegsegger, Institute forMedical Technology andMedical Informatics, Eidg. Technische Hochschule (ETH) and University in Zurich, was asked by the NASA to develop a device cable of quantifying bone loss in astronauts and people working or training under conditions of weightlessness (micro-gravity). The result was the Isotom, a small tomograph for peripheral quantitative computed tomography (pQCT), which allowed us in these early days to perform measurements of the trabecular compartment of the bone only, as the cortical part of the bone was not yet accessible (Fig. ; Ruegsegger et al. , ). Our first step was to perform “bed-rest studies” in male volunteers in . After  weeks of immobilization, trabecular bone loss exceeded 15% in the radius, a tremendously high bone loss as compared with the approximately 1% of yearly trabecular bone loss in perimenopausal women. Having completed these studies, the device was transferred back to Zurich and we decided to adapt it in order to match the specific needs of our patients with osteoporosis.This laid the basis forGeneration , i. e. theDensiscan ,manufactured by