Contrast-Enhanced Susceptibility Weighted Imaging with Ultrasmall Superparamagnetic Iron Oxide Improves the Detection of Tumour Vascularity in A HCC-LM3 Nude Mouse Model
Shuohui Yang1, Jiang Lin1, Fang Lu2, Yuanyuan Dai1, Zhihong Han3, and Caixia Fu4

1Radiology, Zhongshan Hospital, Shanghai Medical College, Fudan University, Shanghai, China, People's Republic of, 2Radiology, Shuguang Hosipital, Shanghai University of Traditional Chinese Medicine, Shanghai, China, People's Republic of, 3Pathology, Shuguang Hosipital, Shanghai University of Traditional Chinese Medicine, Shanghai, China, People's Republic of, 4Siemens Shenzhen Magnetic Resonance Ltd., Shenzhen, China, People's Republic of


Hepatocellular carcinoma (HCC) is a hyper-vascular tumor and knowledge of the intratumoral vascularity is essential. Susceptibility weighted imaging (SWI) uses magnitude and filtered-phase information to provide high sensitivity to susceptibility changes caused by hemorrhage, calcium, iron, and small veins. It has been used to visualize normal or pathologic vascular structures that are not visible on conventional MRI. Ultrasmall superparamagnetic iron oxide (USPIO) is an intravascular blood pool contrast medium. After intravenous administration, it can cause a greater effect on local magnetic field inhomogeneities and results in higher susceptibility differences between all intratumoral vessels and the tumor on SWI. This study showed that USPIO-enhanced SWI could further enhance the demonstration of tumor vascularity inside HCC when compared to unenhanced SWI in an orthotopic xenograft nude mice HCC model.


To evaluate the effectiveness of contrast-enhanced susceptibility weighted imaging with ultrasmall superparamagnetic iron oxide (USPIO-enhanced SWI) in assessment of intratumoural vascularity in hepatocellular carcinoma (HCC).


This experiment was approved by our institutional ethics and animal care committee. Orthotopic xenograft HCC-LM3 nude mice were first established and MRI was performed on a 1.5 Tesla MR scanner (MAGNETOM Aera; Siemens Healthcare, Erlangen, Germany) equipped with a 16-channel wrist surface coil one month later. Three groups of mice, ten in each, were imaged with SWI before and after intravascular bolus injection of a self-made USPIO at three different doses of 4, 8 and 12 mg Fe/kg respectively in the corresponding nude mice group 1-3. SWI scan parameters were: TR/TE, 30/20 ms; field of view, 120 mm; Flip Angle, 15°; section thickness, 0.9 mm; intersection gap, 0 mm; voxel size, 0.5 ×0.5 × 0.9 mm3; bandwidth, 150 Hz/Px; scan time, 1 min 38 s. All SWI images were evaluated in random order by two experienced radiologists with 10 and 23 years’ experience. The degree of intratumoral susceptibility signal intensity (ITSS) was scored. ITSS-to-tumor contrast-to-noise ratio (ITSST-CNR) was measured. These measurements were compared between unenhanced and USPIO-enhanced SWI at each dose and differences in the measurements among different dose groups were estimated. The tumor specimens were removed and studied pathologically with various staining methods. Correlation of ITSS scoring on SWI with tumor micro-vessel density (MVD) was analyzed.


Compared with unenhanced SWI, significantly higher scorings of ITSS were identified on USPIO-enhanced SWI at doses of 8 mg Fe/kg (Z = -2.000, P = 0.046) (Figures 1, 2) and 12 mg Fe/kg (Z = -2.333, P = 0.020). Among three different dose groups of USPIO-enhanced SWI, significant differences of ITSS scorings were found (χ2 = 8.011, P = 0.018). The Mann-Whitney U test demonstrated the difference was significant between groups with doses of 4 and 8 mg Fe/kg (Z = -2.251, P = 0.024). The significantly higher values of ITSST-CNR were found on USPIO-enhanced SWI at all doses than on unenhanced SWI (P < 0.05). There were also statistically significant differences of ITSST-CNR on enhanced SWI among three different dose groups (χ2 = 10.524, P = 0.005). Significantly higher ITSST-CNR at a dose of 8 mg Fe/kg was observed than that at 4 mg Fe/kg (Z = -3.326, P = 0.001). Kappa values for inter-observer agreement on ITSS scoring on USPIO-enhanced SWI in Group 1, 2 and 3 were 0.492, 0.825 and 0.720 (P < 0.05), while those values on unenhanced SWI were lower. High intraclass correlation coefficients between two radiologists were observed for measuring ITSST-CNR in all three dose groups on USPIO-enhanced SWI images (P < 0.001). Pathologically, large amounts of iron particles were found within tumour vessels (Figure 3). Significantly positive correlation between ITSS scoring on USPIO-enhanced SWI at a dose of 8 mg Fe/kg and histological MVD was found (Spearman’s rho, r = 0.905, P = 0.000) (Figure 4).


HCC is a solid tumor featured by abundant vascularity and aberrant microvasculature. In the development and progression of HCC, the tumor neovascularization plays a crucial role in providing the essential blood supply to the tumor [1, 2]. Prior studies have shown that unenhanced SWI could be used in liver imaging to improve the detection of siderotic nodules, hemorrhage and venous vasculatures in HCC [3, 4, 5]. USPIO is an intravascular blood pool contrast medium. After intravenous administration, it can cause a greater effect on local magnetic field inhomogeneities and results in higher susceptibility differences between all intratumoral vessels and the tumor on SWI [6, 7]. In our tumor model, by pathologically excluding the susceptibility changes caused by hemorrhage, USPIO swallowed by macrophages and iron deposition, we reached the conclusion that the retained iron particles in tumor vessels resulted in the pronounced ITSS and higher ITSST-CNR on USPIO-enhanced SWI. Based on the significantly positive correlation found between ITSS scoring and histological MVD and the highest ITSST-CNR value obtained at a dose of 8 mg Fe/kg, we could conclude that 8 mg Fe/kg might be the optimal dose for USPIO-enhanced SWI.


USPIO-enhanced SWI improves the detection of intratumoural vascularity in HCC. A dose of 8 mg Fe/kg may be optimal. USPIO-enhanced SWI may have the potential to noninvasively and quantitatively identify tumor angiogenesis in HCC and monitor its response to various treatments.


This work is supported by National Natural Science Foundation of China (Nos. 81371542, 81403204 and 81272568) and Shanghai Health Committee (No. XBR2013115).


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Intratumoural susceptibility signal intensity is scored grade 3 on the unenhanced susceptibility weighted image of a nude mouse xenograft hepatocellular carcinoma model (white arrows).

After administration of ultrasmall superparamagnetic iron oxide particles at a dose of 8 mg Fe/kg, intratumoural susceptibility signal intensity on this same slice on the susceptibility weighted image is scored by the same reviewer as grade 4 (white arrows).

Anti-CD31 immunohistochemistry with iron particles counterstaining shows large amounts of iron particles within HCC tumour vessels (black arrows) (magnification×400).

Significantly positive correlation between ITSS scoring on USPIO-enhanced SWI and MVD was found in Group 2(r = 0.905, P = 0.000), but no correlation was found in Group 1 and 3 (P > 0.05). Group 1: 4 mg Fe/kg, Group 2: 8 mg Fe/kg, Group 3: 12 mg Fe/kg.

Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)