New experimental model for single liver lobe hyperthermia in small animals using non-directional microwaves.

Ionuț Tudorancea,Vlad Porumb,Radu Iliescu,Alexandru Trandabăţ,Decebal Neaga,Bogdan Tamba,Gabriel M Dimofte,Alfred S Lewin

doi:10.1371/journal.pone.0184810

Abstract

PurposeOur aim was to develop a new experimental model for in vivo hyperthermia using non-directional microwaves, applicable to small experimental animals. We present an affordable approach for targeted microwave heat delivery to an isolated liver lobe in rat, which allows rapid, precise and stable tissue temperature control.Materials and methodsA new experimental model is proposed. We used a commercial available magnetron generating 2450 MHz, with 4.4V and 14A in the filament and 4500V anodic voltage. Modifications were required in order to adjust tissue heating such as to prevent overheating and to allow for fine adjustments according to real-time target temperature. The heating is controlled using a virtual instrument application implemented in LabView® and responds to 0.1° C variations in the target. Ten healthy adult male Wistar rats, weighing 250–270 g were used in this study. The middle liver lobe was the target for controlled heating, while the rest of the living animal was protected.ResultsIn vivo microwave delivery using our experimental setting is safe for the animals. Target tissue temperature rises from 30°C to 40°C with 3.375°C / second (R2 = 0.9551), while the increment is lower it the next two intervals (40–42°C and 42–44°C) with 0.291°C/ s (R2 = 0.9337) and 0.136°C/ s (R2 = 0.7894) respectively, when testing in sequences. After reaching the desired temperature, controlled microwave delivery insures a very stable temperature during the experiments.ConclusionsWe have developed an inexpensive and easy to manufacture system for targeted hyperthermia using non-directional microwave radiation. This system allows for fine and stable temperature adjustments within the target tissue and is ideal for experimental models testing below or above threshold hyperthermia

Highlights

Numerous experiments have been undertaken using heat in cancer therapies, with a wide range of delivery methods, generating a local, regional or whole-body hyperthermia [1,2,3,4,5,6,7,8,9,10]
In vivo microwave delivery using our experimental setting is safe for the animals
Target tissue temperature rises from 30 ̊C to 40 ̊C with 3.375 ̊C / second (R2 = 0.9551), while the increment is lower it the two intervals (40–42 ̊C and 42–44 ̊C) with 0.291 ̊C/ s (R2 = 0.9337) and 0.136 ̊C/ s (R2 = 0.7894) respectively, when testing in sequences

Summary

Introduction

Numerous experiments have been undertaken using heat in cancer therapies, with a wide range of delivery methods, generating a local, regional or whole-body hyperthermia [1,2,3,4,5,6,7,8,9,10]. Heat induced alterations in target tissue depend on the temperature achieved and the duration of the exposure. The failure of the early approaches using direct heat-induced cell killing has prompted interest in the biological effects of mild hyperthermia (39–42 ̊C), especially in conjunction with other cancer therapies. Mild hyperthermia improves tumor oxygenation, inhibits damage repair while potentially improving nanotechnology-based targeted delivery [26]

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