Measurements of effective thermal conductivity during hyperthermia: a comparison of experimental and clinical results.

Temperature and effective thermal conductivity (including the convective effects due to tissue blood flow) profiles have been mapped both within a perfused phantom model containing a differentially perfused pseudo-tumour and in patients undergoing microwave (915 MHz) hyperthermia. These measurements demonstrate the influence of differential thermal characteristics of tumour vs. normal tissue on the temperature distributions obtained during hyperthermia. Effective thermal conductivity was measured using a self-heated thermistor probe, and temperature profiles were measured by means of conventional thermocouples and fibre-optic temperature probes. Measurements of effective thermal conductivity obtained in patients prior to microwave hyperthermia, and temperature profiles obtained once steady-state treatment conditions had been attained, show a strong relation between the effective thermal conductivity profile and the ability to obtain therapeutic temperatures without excessive heating of intervening tissues. These observations were confirmed in phantom experiments, demonstrating that this perfused phantom is a more realistic physical model than the conventional unperfused gels usually employed as physical models for hyperthermia experiments. These results demonstrate that tissue thermal clearance is an important determinant of treatment temperature fields, independent of and in addition to the SAR distribution of the particular applicator. Effective thermal conductivity measurements of the different tissues constituting the volume to be heated could be an important index in the planning and optimization of treatment strategies.

[Dermo-hypodermic lymphoid pseudotumors with follicular hyperplasia. Apropos of a case]. / Pseudo-tumeurs lymphoïdes dermohypodermiques avec hyperplasie folliculaire. A propos d'une observation.

We report the case of a female patient with ubiquitously distributed cutaneous and subcutaneous nodules measuring 2 to 6 cm along their long axis. These nodules first developed at the age of 63 years and subsequently appeared in crops separated by spontaneous remissions. Studies of removed nodules demonstrated diffuse lymphoid follicular hyperplasia suggesting a tumor and raising difficult nosologic problems, especially regarding relationships with the extranodal multicentric Castleman syndrome. In march 1987, biopsy of a large scapular nodule spreading into the striated muscle suggested possible transformation into a low grade malignant lymphoma of the lymphoplasmocytoid type.

A new method for thermal dosimetry in microwave hyperthermia using microwave radiometry for temperature control.

Microwave radiometry has been used during the last few years in some clinical centres (Lille, Freiburg, Strasbourg, Brussels) for the non-invasive control of temperature during microwave hyperthermia. The principal objective of this paper is to present an atraumatic thermal dosimetry system based on numerical simulations of hyperthermia and radiometric temperature measurements for TEM propagation. To gauge the feasibility and performance of the method, a one-dimensional model in a homogeneous medium is considered, neglecting the curvature of the tissue layer. The good correlation between the theoretical and experimental values obtained allowed the likely thermal profile on the probe axis to be computed using the dielectric and thermal properties of the medium and measurement of the radiometric and cutaneous temperatures.

Microwave hyperthermia controlled by microwave radiometry: technical aspects and first clinical results.

Microwave systems combining microwave heating generators (434, 915 or 2450 MHz) with microwave radiometers (1-2 GHz or 2-4 GHz) have been used for two years in hyperthermia therapy. Technical aspects (generator, radiometer, applicator), experiments and first clinical results are detailed.