Real-time volumetric MRI thermometry of focused ultrasound ablation in vivo: a feasibility study in pig liver and kidney

• Published in: NMR in biomedicine 2011-02, Vol.24 (2), p.145-153
• Main Authors: Quesson, Bruno, Laurent, Christophe, Maclair, Gregory, de Senneville, Baudouin Denis, Mougenot, Charles, Ries, Mario, Carteret, Thibault, Rullier, Anne, Moonen, Chrit T.W.
• Format: Article
• Language: English
• Subjects: ablation; Acoustics; Anesthesia; Animals; Bioengineering; Computer Science; Energy; Engineering Sciences; Feasibility Studies; high-intensity focused ultrasound (HIFU); High-Intensity Focused Ultrasound Ablation - methods; Kidney; Kidney - pathology; Kidney - surgery; Life Sciences; Liver; Liver - pathology; Liver - surgery; Magnetic resonance imaging; Magnetic Resonance Imaging - methods; MRI thermometry; N.M.R; Perfusion; Protons; Signal and Image processing; Skin; Sonication; Standard deviation; Sus scrofa - surgery; Temperature; Temperature effects; Thermography - methods; Time Factors; Tumors; Ultrasound
• ISSN: 0952-3480; 1099-1492; 1099-1492
• DOI: 10.1002/nbm.1563

MR thermometry offers the possibility to precisely guide high‐intensity focused ultrasound (HIFU) for the noninvasive treatment of kidney and liver tumours. The objectives of this study were to demonstrate therapy guidance by motion‐compensated, rapid and volumetric MR temperature monitoring and to evaluate the feasibility of MR‐guided HIFU ablation in these organs. Fourteen HIFU sonications were performed in the kidney and liver of five pigs under general anaesthesia using an MR‐compatible Philips HIFU platform prototype. HIFU sonication power and duration were varied. Volumetric MR thermometry was performed continuously at 1.5 T using the proton resonance frequency shift method employing a multi‐slice, single‐shot, echo‐planar imaging sequence with an update frequency of 2.5 Hz. Motion‐related suceptibility artefacts were compensated for using multi‐baseline reference images acquired prior to sonication. At the end of the experiment, the animals were sacrificed for macroscopic and microscopic examinations of the kidney, liver and skin. The standard deviation of the temperature measured prior to heating in the sonicated area was approximately 1°C in kidney and liver, and 2.5°C near the skin. The maximum temperature rise was 30°C for a sonication of 1.2 MHz in the liver over 15 s at 300 W. The thermal dose reached the lethal threshold (240CEM43) in two of six cases in the kidney and four of eight cases in the liver, but remained below this value in skin regions in the beam path. These findings were in agreement with histological analysis. Volumetric thermometry allows real‐time monitoring of the temperature at the target location in liver and kidney, as well as in surrounding tissues. Thermal ablation was more difficult to achieve in renal than in hepatic tissue even using higher acoustic energy, probably because of a more efficient heat evacuation in the kidney by perfusion. Copyright © 2010 John Wiley & Sons, Ltd. The combination of fast temperature imaging by magnetic resonance with efficient motion compensation provides precise, volumetric and quantitative monitoring of temperature evolution within the targeted organ (kidney or liver) and the surrounding tissues during high‐intensity focused ultrasound (HIFU) ablation. The temporal resolution of 400ms/volume allowed for the noninvasive measurement of the local temperature distribution, which is of particular interest for highly perfused and/or mobile organ targets, such as kidney and liver tumours.