Detection of Osseous Spinal Metastasis with T1-Weighted Dynamic Contrast-Enhanced MRI and ¹⁸F-FDG PET/CT: Assessing Agreement in Biopsy-Proved Cases

BACKGROUND AND PURPOSE: ¹⁸F-FDG PET/CT and conventional MRI are common first-line imaging modalities for assessment of osseous spinal lesions. Dynamic contrast-enhanced MR imaging (DCE-MRI) is an advanced technique that quantifies vascular perfusion parameters like vessel permeability (K_trans) and plasma volume (V_p), which are markers of viable tumor. Although DCE-MRI and ¹⁸F-FDG PET/CT are individually recognized for tumor detection, comparisons between V_p and PET-obtained maximum standardized uptake value (SUV_max) have not been performed. This study evaluates the concordance between V_p and SUV_max in detecting pathologically confirmed, nontreated osseous spinal metastases. MATERIALS AND METHODS: Nontreated osseous spinal metastases biopsy-confirmed between February 2015 and January 2022 with available DCE-MRI and ¹⁸F-FDG PET/CT scans were retrospectively analyzed. Exclusion criteria included radiation therapy near lesions and therapy between scans. Mean K_trans and V_p were obtained from DCE-MRI via the extended Tofts model and compared with PET SUV_max values. A V_p threshold of 2.10 and PET SUV_max thresholds of 2.00, 2.50, and 4.00 were used to detect metastases. Agreement was assessed via McNemar tests (α = .05). RESULTS: Eighty-five metastases across 69 patients (mean age: 64.15 [SD, 12.13] years; 35 men) were evaluated. At an SUV_max threshold of 2.00, V_p demonstrated a high agreement of 81.18% (69/85) with SUV_max in detecting biopsy-confirmed tumors. Agreement with other SUV_max thresholds was lower: 67.06% (57/85) for an SUV_max of 2.50 and 48.24% (41/85) for an SUV_max of 4.00, as expected. V_p identified the most metastases at 84, compared with 68, 56, and 40 for SUV_max thresholds of 2.00, 2.50, and 4.00, respectively (P < .001). CONCLUSIONS: V_p and SUV_max showed agreement in detecting osseous spinal metastases. However, when common thresholds for these metrics are applied, V_p exceeds SUV_max in identifying viable tumor. DCE-MRI plays a crucial role in detecting spinal metastases and, in some instances, more accurately detects biopsy-positive lesions compared with ¹⁸F-FDG PET/CT.