Background: Changes in magnetization transfer are implicated in numerous myopathies including limb-girdle muscle dystrophy [1,2]. However, it is important to establish normal values in a healthy population, to enable its use as a biomarker of disease. In this study we assess quantitative magnetization transfer (qMT) parameters in different muscle groups to provide normative values, and establish whether there are differences between muscle groups.

6 healthy subjects participated in the study. All data was acquired using a Siemens Prisma 3T system using an 18ch receive body coil for signal acquisition. qMT sets of images were acquired from forearm, mid-thigh and calf with total acquisition as described by Sinclair et al [3] and taking 20 minutes per region.

MR Acquisition: Data acquisition consisted of a T₁ map, generated using the DESPOT1 sequence [4], a B₁map, generated using an Actual Flip angle Imaging (AFI) sequence [5] and a set of 14 qMT images with 6 offset frequencies (1kHz, 2kHz, 5kHz, 10 kHz, 50 kHz and 100kHz) acquired with MT flip angles of 350 and 500°. Imaging parameters were as follows; 128x128 matrix with FOV 180x180mm, slice thickness = 5mm, 16 slices (no gap), acceleration factor = 2. B1 maps were acquired at half in slice resolution (64x64 matrix).

Data Analysis: Data processing was performed using home-built C++ programs. ITK [6] was used for image read/write and other imaging operations support. Processing was performed as described by Sinclair et al. [3] using AGLLIB [7] non-linear least squares fitting from corrected qMT images. MITK [8] was used to draw ROI on the interested muscle groups. Seven parameters (T₁^a, f, T₂^a, T₂^b, MTR, RM₀^a, R/g) were derived from the fitted results.

Mean values of the seven parameters are tabulated against the muscle group of interest (Table 1). Correlations between different muscle groups within the same subject are also determined (Table 2), which notable correlations are observed between certain muscle groups such as the T₂^b between Tibialis-anterior and Gastrocnemius M. (corr. 0.9871), or T₁^a between Soleus and Gastrocnemius L. (corr. -0.8984).Values for qMT parameters found in this study are in agreement with those present by Sinclair et al. Correlations between individual subjects muscle groups show significant correlation for multiple parameters (e.g. Soleus and Gastrocnemius L.) indicating that variation in qMTR parameters across subjects are biological in origin and can individually provide potential biomarkers for disease. On-going subject recruitments is expected to further minimize data variance and hence improve the result.This study establishes normative values for qMT parameters in different muscle groups. In addition, correlation of parameters across muscle groups show significant correlation indicating that variation is biological in origin. This makes them potential individual biomarkers of myopathies, each susceptible to different biological mechanisms.