Perfusion Magnetic Resonance Imaging (MRI) is a valuable functional imaging technique employed in radiology to assess tumor vascular characteristics. By monitoring the early enhancement patterns of tumors following intravenous administration of a gadolinium contrast bolus, Perfusion MRI provides crucial insights into tumor vascularity, capillary permeability, and interstitial fluid volume. In the context of musculoskeletal radiology, this technique is increasingly utilized in specialized centers worldwide, especially for soft tissue and bone tumors. Perfusion MRI aids in various clinical scenarios, such as guiding biopsy site selection to avoid necrotic areas and differentiating between tumor recurrence and benign granulation tissue. Furthermore, it plays a significant role in lesion characterization and distinguishing between benign and malignant musculoskeletal conditions.
Perfusion MRI operates on the principle of tracking the arrival and washout of gadolinium contrast within a tumor over time. This necessitates rapid image acquisition with high temporal resolution, typically capturing images every 2 to 3 seconds, throughout the contrast agent’s transit, which spans approximately 3 to 5 minutes. Following these dynamic scans, standard static post-contrast sequences in two orthogonal planes are usually acquired to complete the MRI protocol.
Data analysis in Perfusion MRI involves specialized post-processing software. Initially, a region of interest (ROI) is meticulously drawn in an artery proximal to the tumor to establish the arterial input function. Subsequently, one or more ROIs are placed within the tumor itself and in healthy muscle tissue to serve as a reference standard. The signal intensity changes within these ROIs are then plotted against time, generating a time-intensity curve (TIC) for each region.
In the specific context of cartilage tumors, Perfusion MRI has demonstrated utility in differentiating enchondromas from chondrosarcomas. A crucial parameter in this differentiation is the time to peak enhancement, with a cutoff of 10 seconds often used to categorize enhancement as fast or slow. However, it is important to acknowledge that overlap exists in the early enhancement kinetics of chondrosarcomas and enchondromas. For instance, some enchondromas may exhibit rapid enhancement, while certain atypical cartilaginous tumors (ACTs), a low-grade form of chondrosarcoma, can show slow enhancement patterns.
In conclusion, Perfusion MRI represents a valuable tool in the radiologic differential diagnosis of chondrosarcoma, particularly when distinguishing it from enchondroma. While the technique offers quantitative measures of tumor perfusion dynamics and can aid in risk stratification, radiologists should be aware of the potential for overlap in enhancement patterns and integrate Perfusion MRI findings with other clinical and imaging modalities for a comprehensive diagnostic assessment.
