Quantitative ROI-analysis of native Flash-2D, Flash-3D and hepatospecific contrast-enhanced VIBE MR imaging in liver metastases in patients with neuroendocrine cancer

Objectives To investigate the rate of successful characterization of liver metastases in patients with gastroenteropancreatic neuroendocrine tumours (GEP-NETs) with increased SSR2-receptor, we evaluated different MRI-sequences in GEP-NET patients, measuring contrast ratio (CR) of liver metastases in native and contrast-enhanced MRI (CE-MRI). Findings were correlated to 68Ga-DOTATOC PET.

Methods 16 patients with GEP-NETs were examined using native MRI (1.5 Tesla; fl2D- [AT 3min, ST 6.6mm, TE 4.76, TR 168, Matrix 256/0/0/154, FOV 300*400] / fl3D-sequences [AT 1min, ST 3mm, TE 1.5, TR 3.68, Matrix 384/0/0/202, FOV 292*390]), CE-MRI (Gd-EOB-DTPA, Primovist®, VIBE-sequences [AT 13min, ST 4mm, TE 1.16, TR 3.25, Matrix 320/0/0/180, FOV 285*500]) and 68Ga-DOTATOC PET/CT (Figure 1a). ROI-analyses were performed in order to quantify CR between normal liver-tissue and GEP-NET-metastases. For subgroup analysis, lesions were divided in three categories, depending on lesion diameter: <1cm; 1-3cm; >3cm.

Results 103 liver metastases were detected in all modalities. In overall assessment, quantitative ROI-analyses presented an improved CR of 3 in CE-MRI compared to 1.8 in fl2D- and 1.8 in fl3D-sequences (p<0.001). Also after subgroup analysis, CE-MRI presented with higher CR-values compared to native fl2D- and fl3D (p < 0.001; Fig.1a-b).

Conclusions Structural imaging using native MRI with fl2D-and fl3D-sequences in combination with the molecular imaging modality 68Ga-DOTATOC PET seems to be an adequate imaging modality for the assessment of liver lesions in GEP-NET-patients. Even though CE-MRI was superior to native MRI, a signal improvement of approximately double to liver background seems to be enough to detect and quantify liver metastases in daily routine.