Line scan CPMG technique for studies of exercised muscle

The proton relaxation time, T₂, of anterior tibialis muscle was studied using a line scan Carr-Purcell-Meiboom-Gill (CPMG) imaging technique both before and after exercise. Decomposition of the signal decay revealed a short and a long component with values in the 16-22 ms, and 65-95 ms range, respectively, after biexponential fitting of the decay curves. A significant decrease in the fraction of the short phase to the overall signal was observed following exercise with little variation of the component relaxation times. Conventional 2D-FT CPMG was also used to investigate the same muscle for comparison purposes. These T₂ decay curves, however, were only suitable for monoexponential modeling. Exercise induced an increase of 30% in T₂ values calculated from the ID-FT CPMG data sets. Although the mechanism behind the biexponential T₂ decay is not fully understood, the line scan CPMG technique has great potential to study muscle physiology with very high temporal resolution determined by the TR period, though volume coverage is limited to a single tissue column. The approach may provide a greater ability to study physiological mechanisms within muscle, including water compartmentation and exchange when compared to conventional 2D-FT imaging sequences