Low-cost, small animal thermal ablation system

 The goal of this project was to develop a cheap, simple and robust ablation system for creating small thermal lesions in animals. As soon as biological tissues are exposed to temperatures > 40 degree Celsius for several minutes (~>30) tissue necrosis occurs and introduces cell death. This technique is used in cancer therapy to kill cells and to destroy tumors. 

Schematic of small animal ablation example in a mouse brain to study brain cancer treatments.

The understanding of ablation techniques and the development of heating algorithms/strategies rely on animal research studies. To provide a low cost system for ablation studies in small animals (mice,rats) I developed a simple system including a graphic user interface.

Schematic connection sketch for the micro-controller and electronic board.

The system uses an Arduino-Uno Micro-Controller (MC) board and an ordinary, resistive thermistor. The graphic user interface (GUI) communicates with the MC about 4 times per second. In a first request voltage is read from the thermistor to determine the actual temperature. Then in a second step the GUI/program calculates the necessary voltage to reach the required set-temperature (defined by user) and  sends the info to the MC. On the MC the voltage reaching the thermistor will be set accordingly. An integrated PI (proportional/integral) controller regulates the voltage to keep the temperature at the thermistor constant.

Graphic user interface for the Thermistor control

Total costs of the utilities < $50 (Micro controller board $25, Thermistor $8, Wires, etc $17)

Links:
Thermistor:
http://www.mouser.com/ProductDetail/Honeywell/112-102EAJ-B01/?qs=F1jq4PciTHu%252b30xNPtI64w%3D%3D&gclid=CJzDjPjl1bkCFdSd4Aod5VYA8A

Radiofrequency tumor ablation with COMSOL (tutorial)

Radiofrequency ablation modeled with COMSOL

Tissue ablation is the destruction of diseased (pathologic) tissue with the aim to cure a disease. One way to achieve this is via thermal methods (i.e. thermal ablation), by either heating or cooling to temperatures lethal to cells (typically below -40 °C (-40 °F), or above 50 °C (122 °F)). A number of different physical principles can be employed for heating and cooling tissue, such as radiofrequency (RF) electric current, microwaves, laser, ultrasound, and cryogenic cooling. In our lab we perform research on ablation using heating by RF currents, or cryogenic freezing.

In this tutorial I am using COMSOL to simulate radiofrequency tumor ablation for 15 minutes. Following will be covered in the tutorial:

• Radiofrequency heating via single cool-tip electrode
• Automatic Voltage PI-control for constant heating temperature in tissue
• Arrhenius tissue damage model
• Bioheat equation / perfusion decrease due to tissue damage

Download the tutorial (pdf): https://dl.dropboxusercontent.com/u/41416749/COMSOL/COMSOL%20RFA%20%2B%20ARRH%20-%20Tutorial.pdf