Microwave based cancer treatment for deep-seated tumors
Cancer is a leading cause of death in the western countries, preceded only by cardiovascular diseases. An improved treatment of cancer would lead to an improved life expectancy of the population. Recent decades of clinical research has shown that addition of hyperthermia to radiation or to chemotherapy improves cure rates of locally advanced tumors.
Despite the technological advantages that have been made in selectively increasing the temperature of tumor tissue, there are still considerable limitations on the ability to deliver prescribed thermal dose. In particular, the clinically achievable temperatures are 40-41C instead of goal temperature of 43C. Our approach to resolve this problem is to develop an applicator that is capable of modifying the focus size depending of the tumor position and volume. Adaptation of a heating pattern is firstly planned by using of novel focusing technique based on time reversal and later realized by specifically developed antenna applicator. Our approach has potential to overcome limitations of present techniques and create new standarts of hyperthermia treatment, which makes the treatment more accessible to patients.
Hyperthermia is type of cancer treatment, in which tumor is exposed to elevated temperature of 40 - 44°C for a sufficiently long period of time (typically an one hour). The aim of the treatment is to achieve cell death or render the cells more sensitive to ionizing radiation or chemotherapy, without any additional long term side effect. The cytotoxic effect of hyperthermia increases significantly with higher therapeutic temperatures. Electromagnetics heating is, due to its versatility, the most developed as well as most clinically used technique. The major challenge with this technique is, due to the large wavelengths and high absorption rates in tissues, the limited focusing of energy to small, deep seated tumors. The widely used technique to treat tumors in the depth of the body is based on driven constructive wave interference from antenna array placed around a patient. Our approach to resolve the challenge of an adequate heating of those tumors is to develop an applicator that is capable of modifying the focus size depending of the tumor position and volume. The ambition of this project is to employ a large number of independent antennas, placed in multiple rings around the patient, which allows us to work with high frequencies and, consequently, to shrink the foci spot in the target area. Using low frequencies, on the other hand, is advantagenous for heating of large or deeper seated tumors.
We have developed a novel focusing technique for treatment planning based on time reversal. The advantage of using this method comes from the fact that it can be easily used for treatment planning with both sinusoidal and UWB pulse regimes. Moreover, the speed of the method is independent on the number of antennas, which makes the whole approach attractive for clinical use. In order to validate the feasibility of the proposed approach, we have developed a laboratory prototype consisting of an antenna applicator and a wide band multi-channel system to steer it. The achieved experimental results have shown a great promise and encourages a development of a clinical prototype of the TR-hyperthermia system. In present stage, the clinical system for treatment tumors of head and neck (H&N) is under development. Due to the dismal prognosis of patients with advanced carcinomas in H&N accompanied by side effects of current methods, there is considerable clinical need for such a system. The current emphasis is on the development of UWB antenna applicator which provides safe and comfortable treatment.
The performance of the clinical system will be firstly examined on anthropomorphic phantoms. After successful evaluation, the system will be available for Phase I. Patient Study av Sahlgrenska University Hospital. Although the current development is concentrated on a H&N region, the methods and approaches are viable for other tumor sites. The final system will consists of several exchangeable applicators specifically designed for tumor treatment of specific part of the body.
MedTech West partner
Dr. Hana Dobšíček Trefná, Department of Signal Processing and Biomedical Engineering, S2, Chalmers University of Technology
Technical research partner
Prof. Mikael Persson, Department of Signal Processing and Biomedical Engineering, S2, Chalmers University of Technology.
Dr. Andreas Fhager, Department of Signal Processing and Biomedical Engineering, S2, Chalmers University of Technology.
Dr. Johanna Gellermann, MD Berlin
Jonas Gårding, Elekta AB
Ola Svarm, Elekta AB
For more information on this project, contact Henrik Mindedal at firstname.lastname@example.org
Dobsicek Trefna, Hana; Togni, P.; Shiee, Reza; Vrba, J.; Persson, Mikael: Design of a wideband multi-channel system for time reversal hyperthermia. International Journal of Hyperthermia, 28 (2) pp. 175-183. http://dx.doi.org/10.3109/02656736.2011.641655
Dobsicek Trefna, Hana; Vrba, J.; Persson, Mikael: Evaluation of a patch antenna applicator for time reversal hyperthemia. International Journal of Hyperthermia, 26 (2) pp. 185-197. http://dx.doi.org/10.3109/02656730903436434
Dobsicek Trefna, Hana; Vrba, Jan; Persson, Mikael: Time-reversal focusing in microwave hyperthermia for deep-seated tumors. Physics in Medicine and Biology, 55 (8) pp. 2167-2185. http://dx.doi.org/10.1088/0031-9155/55/8/004