Imaging and skeletal muscle disease.

Imaging techniques have assumed increasing importance in the diagnostic approach to patients with muscle disease. These techniques include computed tomography, ultrasound, and magnetic resonance imaging (MRI). For most disorders of muscle, ultrasound and MRI are more useful than computed tomography. Advantages of ultrasound include accessibility at the bedside and lower cost. However, MRI remains the gold standard for detecting changes in muscle tissue. In some cases, MRI examinations can take the place of muscle biopsy for diagnosis. New advances in MRI include diffusion-weighted imaging, which permits assessment of fluid motion in muscles, and blood-oxygen-level-dependent imaging to evaluate tissue oxygenation.