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

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. 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. 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.). 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.