Diagnostic accuracy of MR imaging to identify and characterize focal liver lesions: comparison between gadolinium and superparamagnetic iron oxide contrast media

Abstract

To compare the diagnostic value of gadolinium (Gd) and ultrasmall superparamagnetic iron oxide (SPIO) contrast media for characterization of focal liver lesions (FLL), we retrospectively evaluated the results of magnetic resonance (MR) imaging in 68 patients (40 M, 28 F, age from 22 to 81 yrs) of which 36 with diagnosis of colo-rectal cancer, 26 with hepatic cirrhosis and 6 with incidental imaging detection of FLL. MR (Gyroscan Intera 1.5 T, Philips Medical Systems) study was performed using T1 and T2 fast-field-echo (FFE) and T2 turbo-spin-echo (TSE) sequences in axial and coronal views. Dynamic multi-phases gadolinium Gd-enhanced T1-FFE-Bh images were obtained in arterial, portal and equilibrium phases, followed by SPIO-enhanced T2-FFE scans. A qualitative analysis of pre- and post-contrast MR images to classify FLL as benign or malignant was performed using a 3-point scoring system: 0= benign; 1= suspicious for malignancy; 2= malignant. A total of 118 lesions were evaluated. In particular, histology (n=18), cytology (n=14) or clinical-imaging follow-up data (n=86) demonstrated 4 adenomas, 29 cysts, 3 focal steatosis, 25 hemangiomas, 1 focal vascular abnormality, 5 fibrotic lesions as well as 13 regenerative nodules, 6 dysplastic, 14 hepatocellular carcinomas (HCC), 17 metastasis and 1 cholangiocarcinoma. For MR imaging, diagnostic accuracy, sensitivity, specificity, positive (PPV) and negative (NPV) predictive values of Gd vs. SPIO images were respectively 83% vs. 92%, 79% vs. 74%, 85% vs. 99% (P=0.002), 68% vs. 96% (P=0.005) and 91% vs. 90%, respectively. The results suggest that SPIO-MR provides a diagnostic incremental value, as specificity and PPV, particularly to characterize FLL compared to Gd-MR; thus, we strongly recommend the use of SPIO when liver lesion characterization is requested and Gd images are uncertain.

Keywords: MR imaging; contrast media; focal liver lesions (FLL); gadolinium; superparamagnetic iron oxide (SPIO).

Figure 1

A small (1 cm) capillary hemangioma, proven by biopsy, was located in the segment VIII; dynamic magnetic resonance (MR) images after gadolinium (Gd) administration show focal faint enhancement by the lesion (white circle) only in the arterial phase (A) with no focal abnormality in portal (B) and equilibrium (C) phases (score =1; false positive finding); T2 weighted MR images before (D) and after (E) superparamagnetic iron oxide (SPIO) administration show homogeneous contrast distribution in the liver with diffuse hypointensity and no focal abnormalities (score =0; true negative finding).

Figure 2

A small (1 cm) dysplastic nodule, proven by biopsy, was located in the segment VIII; dynamic magnetic resonance (MR) images after gadolinium (Gd) administration show focal faint enhancement by the lesion (white circle) only in the arterial phase (A) with no focal abnormality in portal (B) and equilibrium (C) phases (score =1; false positive finding); T2 weighted MR images before (D) and after (E) superparamagnetic iron oxide (SPIO) administration show homogeneous contrast distribution in the liver with diffuse hypointensity and no focal abnormalities (score =0; true negative finding).

Figure 3

A small (5 mm) hepatocellular carcinoma, proven by biopsy, was located in the segment VI; dynamic magnetic resonance (MR) images after gadolinium (Gd) administration show no focal abnormalities in the arterial (A), portal (B) and equilibrium (C) phases (score =0; false negative finding); T2 weighted MR images before (D) and after (E) superparamagnetic iron oxide (SPIO) administration show diffuse liver hypointensity and focal faint hyperintensity (white circle) in the VI hepatic segment in the post-contrast MR image (E) (score =2; true positive finding).