Gregory Lemberskiy BA, Presenter: Nothing to Disclose

Dmitry S. Novikov PhD, Abstract Co-Author: Nothing to Disclose

Amir Paydar MD, Abstract Co-Author: Nothing to Disclose

Thorsten Feiweier DIPLPHYS, PhD, Abstract Co-Author: Employee, Siemens AG Stockholder, Siemens AG Patent holder, Siemens AG

Leon Axel MD, PhD, Abstract Co-Author: Nothing to Disclose

Els Fieremans PhD, Abstract Co-Author: Nothing to Disclose

A random permeable barrier model (RPBM) has been suggested [Nature Physics 2011, 7:508; PNAS 2014, doi:10.1073/pnas.1316944111] to quantify cell size and membrane permeability using time-dependent diffusion MRI. We apply this framework to monitor the recovery of an atrophied calf muscle.

Calf muscles of a 30 y/o male, recovering from a posterior tibial (PT) tendon rupture on one foot, were scanned using a Trio 3T Tim system (Siemens AG, Erlangen) with a Tx/Rx CP extremity coil. The injured leg was in a non-weight bearing cast for 6 weeks, where it atrophied from inactivity, after which both calf muscles were scanned. The volunteer was then enrolled in physical therapy after his cast was removed and switched to a walking boot. Subsequent scans of the affected leg occurred after 4 and 8 weeks. Regions were manually outlined on T2-weighted anatomical images, Fig.(a, b), to study the time-dependent diffusion Fig.(c) in the Anterior Tibialis (AT), Extensor Digitorum Longus (EDL), Gastrocnemius Medialis (GM), Gastrocnemius Lateralis (GL), Peroneous Longus (PL), PT and Soleus (SOL). RPBM was used to extract fiber diameter and permeability from each region.

Fig.(d)-(j) show signs of recovery across all muscle groups with no changes in membrane permeability. After 8 weeks, fiber diameters of AT, SOL, and EDL of the injured leg surpassed those of the healthy leg by 1.5%, 19.5%, and 5.3% respectively. After 8 weeks fiber diameters of the immobilized PT and GM were still 22.8% and 24.8% smaller than those of the control leg.

Large differences in fiber diameter were observed between immobilized and control muscle regions. RPBM was sensitive to recovery processes during physical therapy. E.g., inversion and plantarflexion were avoided in the early stages of physical therapy. Congruently, our analysis shows that muscle groups associated with such movements initially showed minimal signs of recovery (PT) and continued atrophy (EDL, GM), while recovery was observed in the AT, GL and SOL early on due to walking and dorsiflexion.

Time-dependent diffusion MRI with RPBM allows for quantifying subtle changes in myofiber diameter, and enables non-invasive monitoring of the process of muscle building and healing. Such quantitative information could be utilized in the field of physical therapy and sports medicine for developing efficient casts and exercises.

Lemberskiy, G, Novikov, D, Paydar, A, Feiweier, T, Axel, L, Fieremans, E, Longitudinal Study of Myofiber Diameter Recovery after Injury Using Time-dependent Diffusion MRI.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14004048.html