Optimal pulse sequence for ferumoxides-enhanced MR imaging used in the detection of hepatocellular carcinoma: a comparative study using seven pulse sequences

Abstract

Objective: To identify the optimal pulse sequence for ferumoxides-enhanced magnetic resonance (MR) imaging in the detection of hepatocelluar carcinomas (HCCs).

Materials and methods: Sixteen patients with 25 HCCs underwent MR imaging following intravenous infusion of ferumoxides. All MR studies were performed on a 1.5-T MR system, using a phased-array coil. Ferumoxides (Feridex IV) at a dose of 15 micromol/Kg was slowly infused intravenously, and axial images of seven sequences were obtained 30 minutes after the end of infusion. The MR protocol included fast spin-echo (FSE) with two echo times (TR3333-8571/TE18 and 90-117), singleshot FSE (SSFSE) with two echo times (TRinfinity/TE39 and 98), T2*-weighted gradient- recalled acquisition in the steady state (GRASS) (TR216/TE20), T2*-weighted fast multiplanar GRASS (FMPGR) (TR130/TE8.4-9.5), and T2*-weighted fast multiplanar spoiled GRASS (FMPSPGR) (TR130/TE8.4-9.5). Contrast-to-noise ratios (CNRs) of HCCs determined during the imaging sequences formed the basis of quantitative analysis, and images were qualitatively assessed in terms of lesion conspicuity and image artifacts. The diagnostic accuracy of all sequences was assessed using receiver operating characteristic (ROC) analysis.

Results: Quantitative analysis revealed that the CNRs of T2*-weighted FMPGR and T2*-weighted FMPSPGR were significantly higher than those of the other sequences, while qualitative analysis showed that image artifacts were prominent at T2*-weighted GRASS imaging. Lesion conspicuity was statistically significantly less clear at SSFSE imaging. In term of lesion detection, T2*-weighted FMPGR, T2*- weighted FMPSPGR, and proton density FSE imaging were statistically superior to the others.

Conclusion: T2*-weighted FMPGR, T2*- weighted FMPSPGR, and proton density FSE appear to be the optimal pulse sequences for ferumoxidesenhanced MR imaging in the detection of HCCs.

Fig. 1

A 35-year-old man with a 6.0-cm hepatocellular carcinoma (HCC) in segment V. Ferumoxides-enhanced proton density fast spin-echo (FSE) (TR5000/TE18) (A), T2-weighted FSE (TR5000/TE90) (B), proton density single-shot FSE (SSFSE) (TR∞/TE39) (C), T2-weighted SSFSE (TR∞/TE98) (D), T2*-weighted gradient-recalled acquisition in the steady state (GRASS) (TR216/TE20/flip angle 60°) (E), T2*-weighted fast multiplanar GRASS (FMPGR) (TR130/TE8.4/flip angle 30°) (F), and T2*-weighted fast multiplanar spoiled GRASS (FMPSPGR) (TR130/TE8.4/flip angle 30°) (G) images show a discrete HCC with a high signal (arrows). T2*-weighted FMPGR had the highest CNR (88.0), and T2*-weighted FMPSPGR had the second highest CNR (83.0). The CNRs of proton density FSE, T2-weighted FSE, T2*-weighted GRASS, proton density SSFSE, and T2-weighted SSFSE were 72.5, 33.5, 33.0, 26.0, and 22.3, respectively.

Fig. 2

A 41-year-old woman with a 2.8-cm HCC in segment VIII. T2-weighted FSE (A), T2-weighted SSFSE (B), T2*-weighted FMPGR (C), and T2*-weighted FMPSPGR (D) images depict a high-signal HCC (arrow). The highest CNR (76.0) was seen at T2*-weighted FMPGR imaging, while lesion conspicuity was significantly lower at SSFSE than at other sequences.

Fig. 3

A 59-year-old man with an HCC (not shown). Ferumoxides-enhanced T2*-weighted GRASS (A), T2*-weighted FMPGR (B), and T2*-weighted FMPSPGR (C) images show significant pulsation artifacts due to the heart and aorta. Particularly at T2*-weighted GRASS imaging, the heartbeat artifact may interfere with depiction of the lesion in the left hepatic lobe.

Fig. 4

Graph showing composite receiver operating characteristic (ROC) curves for pooled data reviewed by three observers. Areas under ROC curves indicate the relative accuracy with which HCCs were detected at ferumoxides-enhanced MR imaging obtained during the seven sequences. T2*-weighted FMPGR, T2*-weighted FMPSPGR, and proton density FSE were statistically superior to the other sequences. According to the three readers, the mean areas under the composite ROC curves were 0.965 ± 0.015 for the T2*-weighted FMPGR sequence, 0.964 ± 0.016 for T2*-weighted FMPSPGR, and 0.958 ± 0.017 for proton density FSE, respectively.

Fig. 5

A 60-year-old man with two HCCs measuring 0.6 cm and 0.3 cm in segment VIII. Ferumoxides-enhanced proton density FSE (A), T2-weighted FSE (B), T2*-weighted FMPGR (C), and T2*-weighted FMPSPGR (D) images show two discrete, high-signal HCCs (large arrow and small arrow). Proton density SSFSE (E) and T2-weighted SSFSE (F) images do not demonstrate these small lesions.