Optiray 350

The needle insertions were performed under 3D fluoroscopy (XperGuide; Philips Healthcare, Best, the Netherlands). Whereas US is a common imaging technique used for needle guidance, 3D fluoroscopy is a more recent technique that consists of overlaying live x-ray fluoroscopy with CBCT. 2 A 3D soft tissue CBCT data set was acquired after injection of a contrast agent (Optiray 350; Covidien, Hazelwood, MI) for better visualization of the tumor and the surrounding healthy tissue. From the 3D data set, an optimal CBCT slice with the tumor clearly visible was selected to define a planned needle path. The needle planning was interactively performed by drawing a line from the center of the tumor toward the skin surface (Fig. 2). Live 3D fluoroscopy and US imaging were acquired simultaneously with DOS acquisition to assure registration of the tissue characterization with the actual location of the needle tip. A total of 9 insertions were performed in the animals. At the end of the experiment, the liver was excised for gross tissue investigation. A cut-through was performed along the needle path in the tumor to observe the tissue structure, and a tissue biopsy at the last position of the needle was obtained for histological investigation.