title: In vivo characterization of tissue thermal properties of the kidney during local hyperthermia induced by MR-guided high-intensity focused ultrasound.
abstract: The purpose of this study was to evaluate quantitatively in vivo the tissue thermal properties during high-intensity focused ultrasound (HIFU) heating. For this purpose, a total of 52 localized sonications were performed in the kidneys of six pigs with HIFU monitored in real time by volumetric MR thermometry. The kidney perfusion was modified by modulation of the flow in the aorta by insertion of an inflatable angioplasty balloon. The resulting temperature data were analyzed using the bio-heat transfer model in order to validate the model under in vivo conditions and to estimate quantitatively the absorption (α), thermal diffusivity (D) and perfusion (w(b)) of renal tissue. An excellent correspondence was observed between the bio-heat transfer model and the experimental data. The absorption and thermal diffusivity were independent of the flow, with mean values (± standard deviation) of 20.7 ± 5.1 mm(3) K J(-1) and 0.23 ± 0.11 mm(2) s(-1), respectively, whereas the perfusion decreased significantly by 84% (p < 0.01) with arterial flow (mean values of w(b) of 0.06 ± 0.02 and 0.008 ± 0.007 mL(-1) mL s(-1)), as predicted by the model. The quantitative analysis of the volumetric temperature distribution during nondestructive HIFU sonication allows the determination of the thermal parameters, and may therefore improve the quality of the planning of noninvasive therapy with MR-guided HIFU.
authors.affiliation: Laboratory for Molecular and Functional Imaging, CNRS/Université Bordeaux 2, Bordeaux, France.
authors.forename: François
authors.initials: F
authors.lastname: Cornelis
authors.forename: Nicolas
authors.initials: N
authors.lastname: Grenier
authors.forename: Chrit T
authors.initials: CT
authors.lastname: Moonen
authors.forename: Bruno
authors.initials: B
authors.lastname: Quesson
mesh_terms: D000800:Angioplasty, Balloon; D000818:Animals; D006801:Humans; D006979:Hyperthermia, Induced / Q000379:methods*; D007668:Kidney / Q000000981:diagnostic imaging* / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D023421:Models, Animal; D013010:Sonication / Q000379:methods; D013552:Swine; D013696:Temperature; D014464:Ultrasonic Therapy / Q000379:methods; D014465:Ultrasonics / Q000379:methods*; D014463:Ultrasonography