Alterations in Resting-State BOLD MRI Fractal Dimension After Swedish Massage

Blood oxygen−level dependent (BOLD) magnetic resonance signals can be used to probe regional microvascular function. The complexity of BOLD signals over time can vary because of altered blood flow or volume or through metabolic change. Because massage therapy is known to change muscle metabolism and microvasculature, this study was done to determine whether noninvasive BOLD imaging and its subsequent change in complexity can visualize the effect of Swedish massage. Resting-state BOLD magnetic resonance scans were acquired before and after Swedish massage, which included the effleurage and petrissage techniques in 6 healthy subjects. The target region was the L4 area of the erector spinae and multifidus muscles. BOLD data was acquired with an echo time of 35 ms, repetition time of 250 ms, 3 slices, and 2400 time points. Signal complexity was evaluated using fractal dimension (FD) relative dispersion (FD_RD) and power spectral (FD_PS) mapping techniques. There was a significant decrease (P < 0.01) in complexity of FD_PS from 1.16 ± 0.12 to 1.08 ± 0.09 after massage. Lower FD has been theorized to be the result of increased low-frequency fluctuations in microvasculature, perhaps due to elevated vascular pulsatility and hence greater perfusion. Thus, we believe this is the first time the effect of therapeutic massage on muscle has been imaged.