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.

Simulation techniques in hyperthermia treatment planning

“…Unfortunately, these methods are cumbersome, can lead to complications, and provide information only for a small number of locations. The development of MR hybrid hyperthermia systems with thermal imaging capability has opened the door to acquisition of thermal tissue properties during heating (135) and validation of preplanned SAR (67) and temperature profiles (58). However, since only a limited number of such hybrid systems are currently available, it will take time before real-time treatment planning re-optimization based on thermal simulations has matured sufficiently to be accepted for clinical hyperthermia treatments.…”

The accuracy and precision of two non-invasive, magnetic resonance-guided focused ultrasound-based thermal diffusivity estimation methods

“…They applied their technique to several ex vivo tissues and in vivo rabbit thigh muscle, reporting precision errors of less than 10%. Subsequent studies have applied their method in ex vivo perfused porcine kidney (precision of 10% [13]), in vivo porcine kidney (precision of 40–50% [14]), and in vivo porcine thigh muscle (precision of 10% [15]). In those studies, the maximum focal temperature and noise in temperature measurements varied significantly, limiting the value of directly comparing precision values.…”

Analytical estimation of ultrasound properties, thermal diffusivity, and perfusion using magnetic resonance-guided focused ultrasound temperature data

“…In the past, applying (1) for analytical estimation of ultrasound and thermal properties has required eliminating the time integral through the assumption of instantaneous heating (Parker 1983, Cheng and Plewes 2002, Anand and Kaczkowski 2008, 2009, Dragonu et al 2009, Cornelis et al 2011, Zhang et al 2013, 2015) or simplifying the integrand for evaluation by neglecting perfusion (Cline et al 1994, Dillon et al 2012, 2013, 2014) and/or utilizing only the center-line, on-axis solution (Parker 1985, Kress and Roemer 1987, Cline et al 1994, Dillon et al 2012). To our knowledge, the full analytical solution of (1) cannot be directly evaluated.…”

“…In recent years, MRTI has been used in estimation techniques for determining a variety of ultrasound (Salomir et al 2000, Dragonu et al 2009, Dillon et al 2012, 2013, Appanaboyina et al 2013, Alon et al 2013), thermal (Cline et al 1994, Salomir et al 2000, Cheng and Plewes 2002, Huttunen et al 2006, Sumi and Yanagimura 2007, Dragonu et al 2009, Cornelis et al 2011, Zhang et al 2013, Appanaboyina et al 2013, Alon et al 2013, Dillon et al 2013, 2014, Zhang et al 2013, 2015), and perfusion properties (Cheng and Plewes 2002, Huttunen et al 2006, Dragonu et al 2009, Cornelis et al 2011, Appanaboyina et al 2013, Alon et al 2013, Dillon et al 2015). …”