The Head and Neck challenge
There are two closely related objectives of this project; the technical development and the clinical application. The main aim of the clinical part is to establish hyperthermia treatment in Gothenburg. The objective of the technical part is to develop a new applicator for treatment of Head and Neck (H&N) tumors. The methods and approaches are however viable for other tumor sites.
There is a clinical need for system enabling treatments of deep-seated tumors in H&N region. Tumors in the head and neck region are often discovered late because of the accompanying behavior of the typical patients (smoking and over-consumption of alcohol).
Locally advanced tumors are often inoperable and will be treated by a high dose radio-chemotherapy. This is especially true for big size tumors, which show a high amount of necrotic parts or parts, which are not adequately perfused and lead to unpleasant outcomes or recurrences after radio-chemotherapy. In these patients, the addition of hyperthermia can significantly improve the treatment outcome. Heating of the head and neck is however challenging, since it contains complicated structures with areas requiring heat protection.
The Children Brain Tumor challenge
Information to follow.
The Chalmers approach; Microwave hyperthermia for deep-seated tumors
The main challenge of current hyperthermia treatment is to adequately heat whole volumes of deep-seated tumors without overheating surrounding healthy tissues. The clinically achievable temperatures are 40-41°C compared to the goal temperature of 43°C. To resolve this problem, the Chalmers research group has developed an applicator capable of modifying the focus size according to the tumor position and volume.
The motivation for the foci-spot size adjustments lies in restraining hot spots near the tumor, which are difficult to suppress and limits reaching of higher tumor temperatures. Adaptation of heating pattern can be realized by varying the operating frequency of the antennas and potentially by using UWB pulse sequences instead of pure harmonic signals used in the present heating equipment.
The ambition of this project is to employ a large number of independent antennas, placed in multiple rings around the patient, which allows working with high frequencies and consequently shrinking the foci spot in the target area. Using low frequencies, on the other hand, is advantageous for heating of large or deep-seated tumors.
A new generation of hyperthermia systems should therefore provide the possibility of a wide range of frequency variations. Moreover, combined design of traditional single frequency system with a UWB pulse regime has a potential to further improve the energy distribution in the treated area and thus open up new possibilities in DHT treatment.
Computations using Time Reversal (TR)
Chalmers researchers have developed a novel focusing technique for treatment planning based on time reversal (TR). The main idea of the time reversal method is that an event can be reversed in time and played back. The experiments typically consist of two steps. First, a wave field is generated and measured at different fixed positions as a function of time and stored. Next, the measurements at each position are reversed in time, which results in the time reversed signals.
In the second step, the measurement positions are used as sources where the time reversed signals are applied simultaneously. The resulting waves propagate back through the medium and interfere constructively at the position of the original source.
Time Reversal in action
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, Chalmers has 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 great promise and encourage the development of a clinical prototype of the TR hyperthermia system.