ABSTRACT
Muscle activation produces increases in magnetic resonance (T
2) signal intensity leading to recruitment images that demonstrate spatial patterns
and intensity of muscle activation. These T
2 activation maps are useful for visualizing and quantifying various aspects of muscle
function. Activity-dependent changes in T
2 result from an increase in the T
2 relaxation time of muscle water. The current state of investigation indicates that
the mechanism of increased T
2 results from osmotically driven shifts of muscle water that increase the volume of
the intracellular space and from intracellular acidification resulting from the end
products of metabolism. Although the spatial resolution of magnetic resonance imaging
is still insufficient to map territories of individual motor units, it is possible
to demonstrate nonuniform activation between subregions or compartments of muscle.
Taken together, the attributes of the T
2 mapping technique hold great potential for demonstrating aberrant muscle activation
patterns in pathology and positive adaptation to exercise or rehabilitative intervention.
KEYWORDS
