Monocrystalline Iron Oxide Nanoparticles: Possible Solution to the Problem of Surgically Induced Intracranial Contrast Enhancement in Intraoperative MR Imaging
Michael Knauth
,a,
Thomas Egelhofa,
Stephanie U. Rotha,
Christian R. Wirtza and
Klaus Sartora
a From the Departments of Neuroradiology (M.K., T.E., K.S.), Neuropathology (S.U.R.), and Neurosurgery (C.R.W.), University of Heidelberg Medical School, Heidelberg, Germany.
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FIG 1. Surgically induced intracranial contrast enhancement. Thirty minutes after a superficial cortical electrocoagulation has been performed, T1-weighted images (500/20/4) obtained after the IV administration of a paramagnetic contrast agent show intense enhancement at the edge of the electrocoagulation. The differentiation of this surgically induced intracranial contrast enhancement from tumor enhancement can be difficult.
A, Obtained 5 min after the IV administration of a paramagnetic contrast agent.
B, Obtained 15 min after the IV administration of a paramagnetic contrast agent.
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FIG 2. T1-weighted images and MIONs.
A, Sixteen hours after the IV administration of MIONs, T1-weighted images (500/20/4) do not show intraparenchymal hyperintensities.
B, Superficial cortical electrocoagulation was performed. Thirty minutes later, the T1-weighted images (500/20/4) do not show any intraparenchymal hyperintensities that could be confused with residual tumor. Note the hypointensity representing the electrocoagulation (arrowhead).
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FIG 3.
A, Two weeks after the stereotactic implantation of C6-glioma cells and 16 hours after the IV administration of MIONs, a preoperative T1-weighted image (500/20/4) shows the huge right-hemispheric tumor hyperintense to brain.
B, Partial resection of the tumor was performed, which is mirrored by better depiction of the third ventricle (arrowhead). There is still massive residual tumor.
Important: note the absence of interfering surgically induced changes (compare fig 1 and fig 4).
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FIG 4. In the animals in which C6-gliomas were (partially) resected, MIONs made it possible to determine the presence or absence of residual tumor, whereas the IV injection of a paramagnetic contrast agent produced confusing findings.
A, Two weeks after the stereotactic implantation of C6-glioma cells and 16 hours after the IV administration of MIONs, a preoperative T1-weighted image shows a right-hemispheric tumor hyperintense to brain.
B, Tumor was almost completely resected and postoperative MR image, obtained 30 min after the end of the operation, does not show hyperintense residual tumor. Because of brain shift, the resection cavity is almost completely filled with brain tissue. Also note the absence of surgically induced phenomena.
C, T1-weighted imaging was repeated after the IV administration of a paramagnetic contrast agent and shows intense surgically induced contrast enhancement (arrow), indistinguishable from residual enhancing tumor.
D, Histologic section shows multiple intraparenchymal bleeds due to surgery (arrowheads) but no residual tumor, except a small intraventricular tumor nodule (white arrow) that was too small for MR imaging detection.
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