Determination and validation of the actual 3D temperature distribution during interstitial hyperthermia of prostate carcinoma

Abstract

To determine the thermal dose of a hyperthermia treatment, knowledge of the three-dimensional (3D) temperature distribution is mandatory. The aim of this paper is to validate an interstitial hyperthermia treatment planning system with which the full 3D temperature distribution can be obtained in individual patients. Within a phase I study, 12 patients with prostate cancer were treated with interstitial hyperthermia using our multi electrode current source interstitial hyperthermia treatment (MECS IHT) system. The temperature distribution was measured from within the heating devices and by additional thermometry. The perfusion level was estimated and the heating implant reconstructed. The steady-state temperature distribution was calculated using our interstitial hyperthermia treatment planning system. The simulated temperature distribution was validated by individually comparing the measured and simulated thermo-sensors, both for the thermometry integrated with the heating applicators and the additional thermometry. The entire procedure was also performed on a no-flow agar-agar phantom. It was shown that the calculated temperature distribution of an individual patient during MECS interstitial hyperthermia is very heterogeneous. The validation indicates that the calculated temperature elevations match the measurements within approximately 1 degrees C. Possible improvements are more precise reconstruction, incorporation of discrete vasculature and using a temperature-dependent, heterogeneous perfusion distribution. Further technical improvements of the MECS-IHT system may also result in better temperature calculations.

Local hyperthermia combined with radiotherapy and-/or chemotherapy: Recent advances and promises for the future

“…An alternative method to obtain tissue-specific properties is by iterative parameter reconstruction based on matching temperature simulations with measurements [109]. The potential of this approach was recently evaluated using invasive measurements to reconstruct the patient and temperature dependent-tissue properties [110].…”

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“…Subject-specific, absolute RF heating can be determined in a cadaver or a live human by solving equation (10) first and later equation (12). Solution to equation (10) gives the baseline temperature distribution.…”

“…Solution to equation (10) gives the baseline temperature distribution. Solution to equation (12) gives the RF-induced temperature changes over the baseline temperatures. Spatially unique correlations between the whole head/body average SAR and RF heating can be developed using direct fluoroptic temperature measurements to estimate RF heating in humans.…”

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