T-2 vertebral bone marrow changes after space flight

Bone biopsies indicate that during immobilization bone marrow adipose tissu e increases while the functional cellular fraction decreases. One objective of our Spacelab flight experiment was to determine, using in vivo volume-l ocalized magnetic resonance spectroscopy (VLMRS), whether bone marrow compo sition was altered by space flight. Four crew members of a 17 day Spacelab mission participated in the experiment. The apparent cellular fraction and transverse relaxation time (T-2) were determined twice before launch and at several times after flight. Immediately after flight, no significant chang e in the cellular fraction was found. However, the T-2 Of the cellular, but not the fat component increased following flight, although to a variable e xtent, in all crew members with a time course for return to baseline lastin g several months. The T-2 Of seven control subjects showed no significant c hange. Although these observations may have several explanations, it is spe culated that the observed T-2 changes might reflect increased marrow osteob lastic activity during recovery from space flight. Magn Reson Med 41:495-49 8, 1999. (C) 1999 Wiley-Liss, Inc.