Sayumi Mihira, Presenter: Nothing to Disclose

Tosiaki Miyati PhD, Abstract Co-Author: Nothing to Disclose

Saori Watanabe, Abstract Co-Author: Nothing to Disclose

Masaki Hara MD, PhD, Abstract Co-Author: Nothing to Disclose

Yuta Shibamoto MD, PhD, Abstract Co-Author: Nothing to Disclose

Harumasa Kasai, Abstract Co-Author: Nothing to Disclose

Nobuyuki Arai MS, Abstract Co-Author: Nothing to Disclose

Makoto Kawano, Abstract Co-Author: Nothing to Disclose

To evaluate detailed information on the diffusion of human skeletal muscle, we analyzed the diffusion of lower muscles by triexponential function.

On a 1.5-T MRI, single-shot diffusion echo planar imaging was used with b values of 0 to 3000 s/mm2 (16 points), a sensitivity encoding technique, effective TE of 118 ms, TR of 3200 ms, and an imaging matrix of 96x95. We obtained the signal decay at each b value from regions of interest within the tibialis anterior (TA), the gastrocnemius lateralis (GL), the gastrocnemius medialis (GM), and the soleus muscle (SL) of healthy volunteers (n=11). After the noise correction was performed, the resulting signal attenuation curve was fitted with the following triexponential function, Sb=ftri-1stexp(-b*ADCtri-1st)+ftri-2ndexp(-b*ADCtri-2nd)+ftri-3rdexp(-b*ADCtri-3rd), where Sb was the signal intensity with each b value, ADCtri-1st , ADCtri-2nd and ADCtri-3rd were ADC of the tri-1st,tri-2nd and tri-3rd component, respectively. While ftri-1st, ftri-2nd and ftri-3rd were fraction of tri-1st，tri-2nd and tri-3rd components, respectively. We obtained the ADC and the fraction of the each component in the triexponential function, and compared with those acquired using the mono and biexponential functions. Moreover we assessed the relationship between these values and the age or the fat fraction (FF).  

There was a positive correlation between the ADC of tri-2nd component in GM and age ( R2=0.405，P<0.05). The fraction of fast muscle in the GM appeared to be relatively larger than in other muscles, and a previous study indicated that it tended to decrease with age. Tri-1st, tri-2nd, and tri-3rd component were principally involved in the perfusion, free diffusion, and restricted diffusion of the water molecules in human skeletal muscle, respectively.

Triexponential analysis makes it possible to obtain more detailed information on the diffusion of skeletal muscles.

Triexponential analysis increase the amount of muscle functional information, and might be useful for assessing muscle aging, degeneration of muscle.

Mihira, S, Miyati, T, Watanabe, S, Hara, M, Shibamoto, Y, Kasai, H, Arai, N, Kawano, M, Diffusion Analysis of Skeletal Muscle by Triexponential Function.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11014583.html