Proton magnetic resonance spectroscopy and diffusion-weighted imaging in the evaluation of musculoskeletal tumors

Musculoskeletal system neoplasms must be accessed by a multidisciplinary clinical team, comprised by an orthopedic oncologist, a pathologist and a radiologist. Most of times, the central question to be answered before treatment is whether the tumor has malignant characteristics or not. After treatment, the question shifts to whether the tumor has been completely resected or destroyed and if there is tumor recidive or not. In order to answer these questions, each one of the specialists relies on appropriate methods. The radiologist begins the analysis with radiography, which provides significant contribution for the evaluation of bone tumors, but is limited in cases of soft tissue neoplasms. Computed tomography which provides better definition of bone lesions, particularly in the axial skeleton, also presents limitations in the definition of extraosseous lesions. Such limitations are being partially overcome with the utilization of multidetector equipment. However, magnetic resonance imaging (MRI) is the method that significantly improves soft tissue resolution, besides being able to provide early detection of bone lesions, in cases where a tumor replaces the bone marrow. Even with the utilization of MRI, many times one cannot assure whether a lesion is malignant or not. In some cases there is an overlap of imaging findings between malignant and benign tumors. Kransdorf et al. have presented an extensive list of differential diagnosis for soft tissue lesions, classifying them in accordance with age and site, but in general, with no pathogno-