Advanced Magnetic Resonance Imaging Techniques for Assessing Brain Metastases Response Following Stereotactic...

Post-stereotactic radiosurgery (SRS) enlargement of brain metastases often creates diagnostic uncertainty that delays appropriate intervention. This study evaluates the combined role of delayed contrast-enhanced magnetic resonance imaging (MRI) (treatment response assessment maps, TRAM) and multiparametric MRI, including diffusion, perfusion, and spectroscopy in distinguishing tumour progression from radiation-induced changes.

A retrospective analysis was performed on 23 patients with 24 enlarging lesions following SRS. All patients underwent advanced MRI, including TRAM, dynamic susceptibility contrast perfusion (relative cerebral blood volume), and MR spectroscopy [MRS] (choline/creatine ratio). The diagnostic performance of each modality was assessed against radiological follow-up at 12 months.

Of 22 evaluable lesions, 13 were classified as radiation-related changes and 9 as true progression. TRAM alone (clearance decrease >0%) demonstrated 100% sensitivity but only 38% specificity (accuracy 63%). Perfusion imaging (relative cerebral blood volume ≥2.0) achieved 77% accuracy, while MRS (choline/creatine ≥1.8) yielded 90% accuracy with 88% sensitivity and 92% specificity. Combining TRAM and MRS further improved performance. The best diagnostic accuracy (95%) was achieved through integrated neuroradiologist interpretation of all modalities, with 100% sensitivity and 92% specificity.

Advanced MRI incorporating TRAM, diffusion, perfusion, and spectroscopy improves diagnostic accuracy in post-SRS assessment of brain metastases. This multimodal approach enhances lesion characterization and supports timely treatment decisions, including reirradiation, surgery, or surveillance.