Magnetic resonance imaging of musculoskeletal neoplasms.

MRI has been shown to be very useful in the work-up of musculoskeletal neoplasms. The lack of ionizing radiation, the superb contrast resolution, and the ability to directly scan the sagittal and coronal planes make MRI a very attractive imaging mode for treatment planning. With spin-echo MRI, maximum contrast between tumor and fatty tissues generally occurs with short TR and TE times (T1-weighted images). Likewise, maximum contrast between tumor and muscle, tendon, or ligaments occurs with long values of TR and TE (T2-weighted images). Early experience suggests that the already exceptional contrast resolution seen with MRI can be improved even more with the administration of intravenous contrast agents. Just as with CT, fatty tumors can usually be easily distinguished from other tissue types with MRI by means of their differential intensity behavior at different pulse sequences. Fluid-filled tumors, such as unicameral bone cysts or aneurysmal bone cysts may be suspected in the same manner, especially if a fluid-fluid level is seen within the lesion. Otherwise, MRI has not been useful so far in noninvasively determining the histologic type of tumors. Our experience and that of others suggests that MRI is equal or superior to CT in the work-up of musculoskeletal neoplasms. This is especially striking when it is remembered that one is comparing an immature MRI technology with a mature CT technology. Although CT presently has a central role in the staging of musculoskeletal tumors, MRI will shortly supplant it in many cases.