New 434MHz interstitial hyperthermia system monitored by microwave radiometry: theoretical and experimental results

Abstract

A new complete microwave interstitial hyperthermia system monitored automatically by microwave radiometry and working at 434 MHz is described in this paper. This system, which includes a new radiometer with two internal temperature references, is detailed. All its characteristics for microwave heating and radiometry are presented. The new possibilities are shown through numerous experiments on acrylamide phantom and excised tissues, which have been carried out for different antennae implantation corresponding to the clinical situation. The clinic protocol, associate to the brachytherapy, imposes the use of semi-loop catheters. Coaxial antennae, inserted in these catheters, are not, therefore, positioned in a rectilinear manner but undergo a curve. So, models based on the FDTD formalism are developed to determine the theoretical power deposition. Owing to these models, the effects of this physical motive on radiation diagrams can be taken into account. The results of the power deposition are presented for two antennae. Thermal patterns can then be determined by the solution of the bioheat-transfer equation in the steady state. Also, the comparison of the results given by the new interstitial hyperthermia system with those obtained with the previous 915 MHz one shows an improvement of the thermal performances.

Conformal microwave array (CMA) applicators for hyperthermia of diffuse chest wall recurrence

“…It is well known that MW antennas can be used not only for depositing energy, but also as sensitive receivers to collect temperature-dependent blackbody radiation from nearby tissue. Microwave radiometers with multiple frequency bands to interrogate different tissue volumes at depth have demonstrated usefulness in monitoring temperature profiles of tissues up to 5 cm depth (43–47) and for control of microwave hyperthermia (48–50). Potentially simpler single band radiometers have also been proposed for balancing the power levels of multiple antenna arrays during hyperthermia treatment (30, 51, 52).…”

Characterization of a digital microwave radiometry system for noninvasive thermometry using a temperature-controlled homogeneous test load

“…Microwave radiometry is a spectral based noninvasive temperature sensing technique primarily developed for use in remote sensing applications such as geophysical explorations and radio astronomy (Kenney andMcClain 1964, Schanda 1976). Over the past three decades, it has also been explored as a complementary technique for detecting cancer (Sterzer 1987, Carr 1989, Cheever and Foster 1992, Mouty et al 1998, Bardati et al 1992, monitoring subcutaneous tissue temperature at depths, most notably inside infant brains (Maruyma et al 2000, Karanasiou et al 2005, Bardati et al 2004, Hand et al 2001, monitoring and control of interstitial microwave antenna (Camart et al 2000) and superficial microwave sources (Ohba et al 1995, Stauffer et al 1999, Jacobsen et al 2000 during hyperthermia treatments. Like infrared thermography, microwave radiometry relies on black body radiation emitted by lossy objects in the electromagnetic spectrum with the advantage that the penetration depth could be extended to several centimeters by sampling different regions in the microwave frequency spectrum.…”

Can we settle with single-band radiometric temperature monitoring during hyperthermia treatment of chestwall recurrence of breast cancer using a dual-mode transceiving applicator?

“…For a single antenna system, these sparse data sets can nevertheless produce useful depth-temperature information. Combined with a priori information on antenna radiation patterns and tissue dielectric and thermal properties, viable estimates of average temperature in selected tissue volumes can be obtained (Bardati et al 1991, Camart et al 2000, Jacobsen and Stauffer 2003. However, for a full scan of multiple frequencies in a multiple antenna system, the temperature scanning time increases rapidly and can lead to unacceptable cooling during the radiometric listening period while microwave heating power is switched off.…”