Multimodal visibility (radiography, computed tomography, and magnetic resonance imaging) of microspheres for transarterial embolization tested in porcine kidneys.

OBJECTIVE: The objective of this study was to test multimodal visibility (radiography, computed tomography [CT], and magnetic resonance imaging [MRI]) of microspheres for transarterial embolization in porcine kidneys. MATERIALS AND METHODS: Currently available embolization particles (microspheres) were modified. A dense x-ray material (barium sulfate) was added to create visibility for radiography and CT. A magnetic substance (iron oxide) was additionally added to create visibility for MRI. This chemical modification was performed for particles with sizes of 100 ± 25 and 700 ± 50 µm. Three different prototypes per size class (samples A, B, and C) resulted, each with a different degree of barium sulfate but with the same degree of iron oxide. The currently available embolization particles with sizes of 100 ± 25 and 700 ± 50 µm were used as controls (sample control). Eight renal arteries of 4 pigs were embolized. Study end points were size distribution evaluated in vitro as well as qualitative and quantitative particle visibility evaluated in vivo. RESULTS: The size distribution of the particles with a size of 100 ± 25 µm was between 96 ± 11 µm for sample A and 102 ± 13 µm for the sample control without significant differences (n.s.). The size distribution of the particles with a size of 700 ± 50 µm was between 691 ± 20 µm for sample A and 716 ± 34 µm for sample C without significant differences (n.s.). For radiography, the particles with sizes of 100 ± 25 and 700 ± 50 µm for samples A, B, and C were definitely visible during the embolization. The sample control was definitely not visible. For CT and MRI (T1-weighted [T1w] and T2-weighted [T2w]), the particles with sizes of 100 ± 25 and 700 ± 50 µm for samples A, B, and C were definitely visible after the embolization. The sample control was definitely not visible. For CT, the signal-to-noise ratio for samples A, B, and C increased significantly after the embolization (eg, sample A, particles with a size of 100 ± 25 µm: 66.5% ± 23.7%, P < 0.05). The signal-to-noise ratio for the sample control did not change after the embolization (eg, sample control, particles with a size of 700 ± 25 µm: -0.2% ± 15.2%, n.s.). For MRI (T1w and T2w), the signal-to-noise ratio for samples A, B, and C decreased significantly after the embolization (eg, sample B, particles with a size of 700 ± 50 µm, T1w: -72.9% ± 6.6%; P < 0.05). The signal-to-noise ratio for the sample control did not change after the embolization (eg, sample control, particles with a size of 100 ± 25 µm, T2w: 6.2% ± 16.1%, n.s.). CONCLUSIONS: In this study, the chemical modification of the currently available microspheres for transarterial embolization resulted in a size distribution comparable with the currently available microspheres and created multimodal visibility for radiography, CT, and MRI.

Multimodal visibility of a modified polyzene-F-coated spherical embolic agent for liver embolization: feasibility study in a porcine model.

PURPOSE: To evaluate multimodal visibility of modified currently available microspheres on radiography, magnetic resonance (MR) imaging, and computed tomography (CT) in a porcine liver model. MATERIALS AND METHODS: Livers of four pigs were embolized with two sizes (100 µm ± 25 and 700 µm ± 50) of modified Embozene Microspheres embedded with different densities of barium sulfate and iodine as radiopaque materials (intensity groups A-C, with increasing intensity from A to C for 100 µm and intensities A and C for 700 µm) and iron oxide as magnetic substance for MR imaging visibility. Pigs embolized with currently available Embozene Microspheres served as control groups. Pre- and postinterventional MR imaging (T1- and T2-weighted) and CT were performed. Qualitative and quantitative (ie, determination of signal-to-noise ratio [SNR]) particle visibility was evaluated on radiography, MR imaging, and CT. RESULTS: Modified particles of both sizes were visible on radiography, MR imaging, and CT. Particles in the control group were not visible. For modified particles of both sizes, SNRs measured on MR imaging decreased significantly after embolization (eg, cluster analysis of group A, 100 µm ± 50 particles, T1-weighted, -74.6% ± 3.4; P = .03). For modified particles of both sizes, SNR measured on CT increased significantly after embolization (eg, cluster analysis of group A, 700 µm ± 25 particles, +54.3% ± 13.5; P = .03). CONCLUSIONS: Modification of currently available Embozene Microspheres was successful, with multimodal visibility on radiography, MR imaging, and CT in porcine liver. In the future, this might improve procedure accuracy and allow monitoring, control, and improvement of embolotherapy during and after the procedure.

Settlement and adhesion of algal cells to hexa(ethylene glycol)-containing self-assembled monolayers with systematically changed wetting properties.

Protein resistance of self-assembled monolayers (SAMs) of hexa(ethylene glycols) (EG(6)) has previously been shown to be dependent on the alkoxyl end-group termination of the SAM, which determines wettability [S. Herrwerth, W. Eck, S. Reinhardt, and M. Grunze, J. Am. Chem. Soc. 125, 9359 (2003)]. In the present study, the same series of hexa(ethylene glycols) was used to examine the correlation between protein resistance and the settlement and adhesion of eukaryotic algal cells, viz., zoospores of the macroalga Ulva and cells of the diatom Navicula, which adhere to the substratum through the secretion of protein-containing glues. Results showed that the initial settlement of Ulva zoospores was highest on the hydrophilic EG(6)OH but that cells were only weakly adhered. The number of Ulva zoospores and Navicula cells firmly adhered to the SAMs systematically increased with decreasing wettability, as shown for the protein fibrinogen. The data are discussed in terms of hydration forces and surface charges in the SAMs.