Bone Malignancies

Abstract

Functional imaging, in particular dynamic contrast-enhanced MRI (DCE-MRI), has a role in differentiating benign from malignant cartilaginous tumors. Chondrosarcoma grade I or atypical cartilaginous tumor enhances within 10 s. of arterial enhancement. Enchondroma enhances after 10 s. or not at all. FDG-PET has the same uptake patterns in both enchondroma and chondrosarcoma grade I. A second diagnostic application is in identifying the small interstitial space of giant cell tumor. The resulting washout can be used in detecting recurrent disease.

Functional imaging techniques are becoming more important as it is shown that morphologic criteria, basically tumor volume, are insufficient to monitor response to treatment. DCE-MRI can be used to identify residual viable tumor after chemotherapy. DCE-MRI targets parameters that define angiogenesis. Under therapy, changes in capillary permeability (time-intensity curve shape and slope) and vascular density (maximum enhancement) are often observed before changes in tumor volume.

There have been conflicting reports on the usefulness of glucose metabolism imaged by ¹⁸F-deoxyglucose positron emission tomography (¹⁸F-FDG-PET) as a parameter to assess response to chemotherapy in sarcoma. Issues such as low specificity and differences between various sarcoma types need to be addressed. However, differences in metabolic volume depicted with ¹⁸F-FDG-PET have been reported to correlate with response. This tumor component correlates with the viable tumor as defined by early enhancement on DCE-MRI and seems a promising venue of further research. PET is gaining a place in detecting recurrent disease, also at sites distant from the original tumor.