Respiratory-Gated MRgHIFU in Upper Abdomen Using an MR-Compatible In-Bore Digital Camera

Figure 2

MR-ARFI prepared MRgHIFU thermoablation in sheep kidney. (a) Respiratory-gated MR-ARFI was performed according to [19] and permitted accurate visualisation of the focal point located in the inferior pole of the left kidney. A coronal slice is shown. FOV is 128 mm square. The scale of ARFI through-plane tissue displacement is provided at the left side in microns. (b) The position of the interface between the kidney and signal-suppressed perirenal fat was measured over 4 minutes of respiratory-gated MR-ARFI acquisition and demonstrated a very low level of residual motion in the submillimetre range. Because the tracked interface is smooth and orientated orthogonally to the main axis of motion (S/I), the actual resolution is higher than the intrinsic voxel size (1 mm in plane). (c) and (d) Multiplanar respiratory-gated MR thermometry during 8 mm pattern HIFU volumetric ablation in sheep kidney. The white arrows indicate the incidence direction of the HIFU beam. K: kidney, L: liver, W: coupling water, M: paravertebral muscles, B: bowel, and F: perirenal fat tissue. A temperature elevation colour scale is provided. FOV is 128 mm square. (e) Zoom-in of frame (d) around the focal zone. (f) Voxelwise temporal plot of temperature elevation, shown within the focal zone and for one unheated voxel located in the opposite pole of the treated kidney. Note the excellent baseline stability.