Multiparametric MRI with MR Fingerprinting and Ivim for Noninvasive Differentiation of Radiation Necrosis and Tumor Recurrence after SRS
Abstract
Purpose
Differentiating radiation necrosis from tumor recurrence after stereotactic radiosurgery (SRS) remains a major challenge in neuro-oncology, as conventional MRI often fails to reliably distinguish these tissue types. Magnetic Resonance Fingerprinting (MRF) is a novel quantitative imaging technique that simultaneously measures multiple tissue parameters, including T1 and T2 relaxation times. Intravoxel Incoherent Motion (IVIM) imaging provides quantitative assessment of tissue diffusion and microvascular perfusion. Combining these advanced MRI techniques may offer complementary biomarkers for noninvasive lesion characterization. This study investigates the potential of MRF and IVIM to distinguish radiation necrosis from tumor recurrence in post-SRS patients.
Methods
Six patients with histologically confirmed post-SRS lesions (seven necrotic regions, three recurrent tumors) underwent MRF to generate T1 and T2 maps, alongside IVIM to quantify apparent diffusion coefficient (ADC) and perfusion fraction. Quantitative lesion values were compared with normal white matter in healthy volunteers and with previously published tumor datasets. Histopathologic confirmation was obtained via surgical resection to validate imaging findings.
Results
MRF and IVIM identified distinct relaxation, diffusion, and perfusion signatures that differentiated radiation necrosis from tumor recurrence. Radiation necrosis demonstrated substantially higher T1 and T2 values and elevated ADC, reflecting tissue breakdown and increased water mobility, while perfusion fraction was markedly reduced, indicating diminished microvascularity. Recurrent tumors exhibited lower relaxation times, reduced diffusion, and higher perfusion, consistent with viable, vascularized tumor microenvironment. These differences were consistently across all lesions and were clearly distinguishable from normal white matter.
Conclusion
This study demonstrates that MRF combined with IVIM offers a noninvasive, quantitative approach for differentiating radiation necrosis from tumor recurrence after SRS. The technique provides complementary biomarkers of tissue characterization, highlighting its potential to improve post-treatment assessment and guide clinical decision-making, and potentially reducing invasive procedures. These findings underscore the innovative utility of advanced multi-parametric quantitative MRI in neuro-oncology imaging.