IIT Madras redesigns a microwave hyperthermia applicator to hold steady heat through an hour-long cancer session

Heating a tumour by a few degrees can make radiotherapy and chemotherapy work better. Keeping that heat steady for a full treatment session has long been harder than it sounds. Engineers at IIT Madras say they have fixed one of the main reasons it goes wrong, with a redesigned microwave applicator that maintained stable coupling through a 60-minute laboratory test window. These were tissue-phantom experiments, not patient treatments.

The work, reported in late October 2026 by Research Matters, a Gubbi Labs science-news outlet and by Electronics For You, comes from a group with a long record in hyperthermia devices.

What hyperthermia does

Clinical hyperthermia raises tumour tissue to roughly 40–44 °C. At these temperatures, cancer cells become more sensitive to radiation and to some drugs, partly because heat interferes with the way they repair DNA damage and partly because it changes blood flow in the tumour. It is used alongside standard treatment, not instead of it, for cancers such as breast, cervical, head-and-neck and some sarcomas.

For tumours near the surface, a common approach is an external microwave applicator: an antenna placed against the skin that sends electromagnetic energy into the tissue. Between the antenna and the skin sits a water bolus, a bag of circulating deionised water that couples the energy into the body and keeps the skin cool enough to avoid burns.

The problem: drift

The bolus causes a problem of its own. As a session goes on, heat from the antenna and the tissue warms the water. Water's electrical properties change noticeably with temperature, so a warming bolus gradually detunes the antenna. Engineers call this impedance detuning. When it happens, more of the microwave energy is reflected back towards the generator, less reaches the tumour, and the dose the clinician planned drifts during treatment.

According to the reports, the IIT Madras team decided not to treat the antenna, the water and the tissue as separate design problems. They used a multiphysics framework that models electromagnetics, heat transfer and fluid flow together, then redesigned the applicator's internal structure to match.

The redesign and the results

The new applicator works at 434 MHz, a frequency used for superficial hyperthermia, and adds small cooling fins with a carefully controlled flow of coolant through the bolus. The aim is to keep the water temperature, and therefore the antenna's tuning, almost constant.

The reported figures:

• Temperature variation inside the water bolus fell from 5.13 °C to 0.38 °C, below the roughly 1 °C level the researchers treat as the stability threshold.
• The report describes power coupling above 96% across 60 minutes in the experimental setup.
• It heated tissue to a depth of about 31 mm, with more than 75% of the energy deposited in tissue.

The tests were carried out on flat, synthetic tissue phantoms, materials that mimic the electrical and thermal properties of human tissue, not on patients. The reports do not mention clinical trials or regulatory approval, and the full peer-reviewed paper was not available for independent review at the time of writing.

Why it matters for India

Hyperthermia systems are expensive and mostly imported, so few Indian cancer centres offer the treatment, even though India carries a heavy burden of breast, cervical and head-and-neck cancers, which are the cancers where superficial and endocavitary hyperthermia are most used. A stable, locally designed applicator is one building block for cheaper systems that regional hospitals could use. Reliable dosing also matters for regulators and clinicians: a treatment is hard to standardise if the heat a patient receives changes over the course of a session.

The next steps are the usual ones for a medical device: tests on curved, more realistic phantoms and tissue models, integration with temperature monitoring, and eventually clinical evaluation.

Sources

• https://researchmatters.in/news/a-new-microwave-device-from-iit-madras-overcomes-long-standing-thermal-cancer-therapy-hurdle
• https://www.electronicsforu.com/news/the-antenna-designed-to-beat-heating-drift-in-cancer-therapy
• http://tech-talk.iitm.ac.in/heat-that-tumour/
• https://www.indiascienceandtechnology.gov.in/research/endocavitary-microwave-applicator-integrated-hyperthermia-and-radiotherapy-treatment-locally
• https://www.iitm.ac.in/happenings/press-releases-and-coverages/iit-madras-researchers-develop-ultrasound-based-temperature