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The muscular dystrophy Duchenne (DMD) is a severe illness of inherited muscular dystrophies, which typically causes early death by cardiac and respiratory muscle failure in the third decade of life and for which, until recently, a curative therapy has remained undiscovered.
Due to new promising possibilities therapies the aim of the present study was to achieve an improvement of the diagnostic efficiency for warranty of optimal treatment by analyzing of static and dynamic patterns.
21 patients with DMD participated in the study, each of whom underwent the static and dynamic analysis in the time from December 2003 until November 2004.
Eight thigh-muscles or muscle groups were initially defined for the analysis on both sides. The examinations were divided into two parts:
1. Fat percentage rates were calculated with the help of static MRI-sequences and the graphic editing program Mipav in VOI-based regions of the individual thigh-muscles in T1- and T2-weighted sequences. Left and right sides and relaxation times were compared as well as a potential dependence on patient age evaluated.
2. ROI-based Enhancement curves and parameters in the individual thigh-muscles were determined with the help of the contrast agent-enhancement in the dynamic sequences, for which Dynalab provided the necessary modules.
The parameters were checked for their adequacy as diagnostic markers.
The results show high correlations between both the comparative fat rates of the thighs and the comparative relaxation times (T1/T2).
Muscle evaluation by percentage calculation of the fat rates can thus be evaluated independently from side and relaxation time.
Furthermore clear correlations between fat mass and patients’ age have been determined, which means that the fat mass can be confirmed as a useful marker of the actual situation of the illness. It manifested as progressive muscular destruction with selective protection of separate muscles, in particular the M. gracilis and the M. sartorius, followed by M. semitendinosus/M.semimembranosus.
In the results of the dynamic MRI the defined parameters PeakEnhancement, InitialPE, Integral and MITR demonstrated considerable correlation with age, exhibiting dwindling signal intensity in the older patients. This signal intensity was shown in the different muscles in different value. Again, M.gracilis and M.sartorius showed the highest signal intensities with the least signal decrease with increasing patients’ age. Therefore, these four parameters can be valued as adequate functional parameters, which have the ability to characterise the particular muscle accurately and directly within the organ and to consequently replace established clinical methods of assessment of muscular microcirculation. Due to low signal intensities and subsequent marginal differences of the individual SI-values of the individual muscles of the parameter MITR, an accurate estimation and differentiation is hindered, for which reason PeakEnhancement, InitialpE und Integral provide more precise statements than the defined parameter MITR. The parameter Integral which decreases in dystrophic muscles is of remarkable significance for the perfusion in a diagnostic capacity. With high signal intensities, this parameter can outstandingly characterize and differentiate the individual muscles.
Therefore the MRI is able to provide an exact analysis of certain muscle regions non-invasively and thus offer a more holistic image of the dimensions of the illness. Using the methods in the present study enables an accurate estimation of the severity of the illness, an opportunity to observe the progression and better plan biopsies. Finally, the methods used in the present study enable evaluations of new therapies in DMD-research, through which an improvement of diagnostic capability is made possible.
It is to be expected that these methods will be put to use in clinical daily routine.