Study of the intra-arterial distribution of Fe3O4 nanoparticles in a model of colorectal neoplasm induced in rat liver by MRI and spectrometry.

PURPOSE: To evaluate, in an experimental model, the reliability of MRI for determining whether a higher iron concentration was obtained in tumor tissue than in normal liver parenchyma after intra-arterial administration of Fe3O4 lipophilic nanoparticles. MATERIALS AND METHODS: WAG/RijCrl rats were inoculated in the left hepatic lobe with 25,000 syngeneic CC-531 colon adenocarcinoma cells, after which they were randomized into two groups: control (CG) and infused (IG). After confirming tumor induction, the IG rats received intra-arterial suspensions of Fe3O4 nanoparticles (2.6 mg) in Lipiodol® (0.15 mL). To calculate the iron concentration, [Fe], in the tumor and liver tissues of both groups of rats, measurements of signal intensity from the tumors, healthy liver tissue, and paravertebral muscles were made on a 1.5T MRI system in gradient-echo DP* and T2*-weighted sequences. In addition, samples were collected to quantify the [Fe] by inductively coupled plasma-mass spectrometry (ICP-MS), as well as for histological analysis. Statistical analysis was performed with non-parametric tests, and Bland-Altman plots were produced; P values <0.05 were considered significant. RESULTS: In the CG rats (n = 23), the mean [Fe] values estimated by MRI and ICP-MS were 13.2 µmol·g⁻¹ and 5.9 µmol·g⁻¹, respectively, in the tumors, and 19.0 µmol ·g⁻¹ and 11.7 µmol·g⁻¹, respectively, in the hepatic tissue. In the IG rats (n = 19), the values obtained by MRI and ICP-MS were 148.9 µmol·g⁻¹ and 9.4 µmol · g⁻¹, respectively, in the tumors, and 115.3 µmol·g⁻¹ and 11.6 µmol·g⁻¹, respectively, in the healthy liver tissue. The IG results revealed a clear disagreement between MRI and ICP-MS. In the comparative analysis between the groups regarding the [Fe] values obtained by ICP-MS, significant differences were found for the tumor samples (P < 0.001), but not for the hepatic tissue (P = 0.92). Under microscopy, scattered intravascular deposits of nanoparticles were observed, especially in the tumors. CONCLUSION: ICP-MS demonstrated significant uptake of exogenous iron in tumor tissue. MRI was useful for quantifying the [Fe] in the different tissues in the CG animals, but not in the IG animals. Although the irregular distribution of nanoparticles caused an important bias in the measurements obtained by MRI, the relative increase in iron content inside the tumor was suggested.

Overall breast density in MR mammography: diagnostic and therapeutic implications in breast cancer.

The objective of this study was to assess the efficacy of MR mammography (MRM) in evaluating breast cancer extent in women with fatty or dense breasts, and its contribution to the therapeutic approach. The authors reviewed 97 carcinomas detected in 93 women (both symptomatic and from screening) that were classified in two groups according to breast density pattern. Mammography, ultrasound (US), and MRM were performed to evaluate size, extension of the in situ component, presence of multifocal/multicentric disease, and contralateral involvement. Results obtained on mammography plus US were balanced against MRM, considering pathologic analysis as the gold standard. For fatty breasts (n=47), exact measurement was found on mammography plus US and on MRM alone in 70%, underestimation on mammography plus US 23.5% and on MRM 11% (P=0.005). For dense breasts (n=50), exact measurement was found on mammography plus US in 40% and on MRM alone 68%, underestimation on mammography plus US 52% and on MRM 10% (P=0.005). Overall, good correlation (R>0.71) was found between pathologic and clinical size with all imaging methods; nevertheless, when evaluating multifocal/multicentric disease, a poor correlation was observed between histologic assessment and mammography plus US (R=0.52), but it was excellent with regard to MRM (R=0.99). In fatty breasts, the combination of mammography and US allows for a precise assessment of tumoral extension. However, these results show that in dense breasts, MRM is superior to mammography plus US, suggesting that its systematic use in this group of patients is justifiable.