Radiology, Vol 169, 105-107, Copyright © 1988 by Radiological Society of North America
The spine: changes in T2 relaxation times from disuse
AD LeBlanc, E Schonfeld, VS Schneider, HJ Evans and KH Taber
Department of Nuclear Medicine, Methodist Hospital, Houston, TX 77030.
Magnetic resonance imaging of the spine was performed in six healthy male
volunteers before and after 5 weeks of continuous bed rest. Imaging studies
consisted of a single 1-cm sagittal section obtained with a spin-echo
technique through the center of the spinal column. The T2s of the lumbar
vertebral body and nucleus pulposus and the area of the latter were
measured. In both vertebrae and disks, there was a significant decrease in
T2 after bed rest. The nucleus pulposus also decreased in size with bed
rest. The decrease in relaxation time of the lumbar vertebrae could be
explained by the replacement of hematopoietic marrow by fatty marrow, a
known consequence of paralytic immobilization. The decreases in size and T2
of the disks probably represent loss of water. The significance of these
changes to the mechanical integrity of these structures after
immobilization or space flight is not known but will depend in part on
whether changes are progressive with increasing length of immobilization
and on the rate and extent that they are reversed after reambulation. These
results indicate that relaxation times can be altered by simple disuse,
which often accompanies the underlying disease.
