Perfusion and thermal field during hyperthermia. Experimental measurements and modelling in recurrent breast cancer

Abstract

Recurrences of malignant tumours in the chest wall are proposed as a valuable model of tissue mainly perfused by small size vessels (the so-called 'phase III' vessels). Invasive thermal measurements have been performed on two patients affected by cutaneous metastasis of malignant tumours during hyperthermic sessions. Thermal probes were inserted into catheters implanted into the tissue at different depths. In one of the catheters a probe connected with laser-Doppler equipment was inserted to assess blood perfusion in the tumour periphery. The perfusion was monitored throughout the sessions, and a noticeable temporal variability was observed. The effect of the perfusion on the thermal map in the tissue was evaluated locally and the 'effective conductivity' of the perfused tissue was estimated by means of the numerical integration of the 'bio-heat' equation. The tumour temperature, at the site where the perfusion probe is located, can be predicted by the numerical model provided two free parameters, alpha and beta, are evaluated with a fitting procedure. Alpha is related to the effective conductivity and beta to the SAR term of the bio-heat equation. The model aimed at estimating the 'effective conductivity' K(eff) of the perfused tissue, and average values of K(eff) of 0.27 +/- 0.03 W m(-1) degrees C(-1) in Patient 1 and of 0.665 +/- 0.005 W m(-1) degrees C(-1) in Patient 2 were obtained throughout the treatment. However, when the average temperature in a larger tumour volume is to be predicted but only a single, 'local' measurement of the perfusion is available and is assumed to be representative for the whole region, the model results are far less satisfactory. This is probably due to the fact that changes of blood perfusion throughout hyperthermic sessions occur to different extents within the tumour volume, and the differences in perfusion cannot be ignored. The above result suggests that, in addition to the 'temperature map', also a 'perfusion map' within the heated volume should be monitored routinely throughout hyperthermic sessions.

Review of Temperature Dependence of Thermal Properties, Dielectric Properties, and Perfusion of Biological Tissues at Hyperthermic and Ablation Temperatures

“…While small animal studies suggest tumors to be highly sensitive to hyperthermia with reduction in blood flow or vascular shutdown commencing at 42–43 °C, there is evidence that tumors in large animals, and more importantly human tumors are considerably less sensitive (105–111). Vujaskovic et al .…”

“…It is evident that the choice of modeling the temperature dependence of the electrical as well as thermal and perfusion properties have significant effects on the electrical field and temperature distribution in computer models, respectively (17, 18, 30, 64, 123). Thus, accurate models require the consideration of temperature-dependent properties, and among tissue properties in many cases perfusion and its temperature dependence is often dominating and of primary importance (30, 79, 111, 124). …”

Cancer laser therapy using gold nanoparticles

“…The dynamic alterations in perfusion caused by heating are investigated and discussed. 74 Different laser applicators are described, along with a new laser probe for transluminal application, making selective coagulation possible.…”

Magnetic Nanoparticles in Cancer Diagnosis and Hyperthermic Treatment

“…More "exotic" therapies, such as the gamma-knife, can be used to treat inoperable tumors such as those in the brain where surgical intervention would risk damage to primary functional centers. Hyperthermia as primary therapy (directly killing cancer cells) requires heating the entire tumor by at least 10 • C. Ideally, rapid energy deposition increasing the temperature by 25 • C will minimize damage to nearby healthy tissue by limiting thermal diffusion and dissipation [57] while completely necroting tumor tissue. Perfusion in tissue has been found to increase thermal diffusion rates from ∼20% to a factor of 2 near major vasculature [58].…”