Objective: The purpose of our study was to evaluate (a) the characteristics of muscle strain injuries on MRI and (b) the potential of a frequency-selective fat suppression technique for diagnosing such injuries.
Materials and methods: Muscle strain injuries in seven athletes were examined by MRI. Spin echo sequences were obtained with and without fat suppression sequences. The absolute values of the contrast-to-noise (C/N) ratios for lesion versus muscle or fat were then compared for both types of images.
Results: We obtained two types of characteristic findings for muscle strain. Lesions of the fascia and adjacent muscles showed a characteristic spray-like or fan-like appearance, extending longitudinally from a shared tendon to the muscle belly in five athletes. This finding was better displayed on coronal images. In contrast, lesions inside a muscle showed a diffuse and inhomogeneous appearance in two athletes. The absolute C/N ratios for lesion versus fat and lesion versus muscle were not significantly different for images with and without fat suppression according to the sign test. However, fat-suppressed images revealed subtle abnormalities that were not seen on conventional images.
Conclusion: Magnetic resonance can provide detailed information on muscle strain injuries, especially when coronal fat-suppressed images are obtained.