A therapy demonstrated in mice, called minimally invasive image-guided ablation or MINIMA, consists of a ferromagnetic thermoseed navigated to a tumor, using magnetic propulsion gradients generated by an MRI scanner, before being remotely heated to kill nearby cancer cells. Researchers say the findings establish proof-of-concept for precise, effective treatment of hard-to-reach glioblastoma, along with other cancers, such as prostate, that could benefit from less invasive therapies.

“MINIMA is a new MRI-guided therapy that has the potential to avoid traditional side effects by precisely treating the tumor without harming healthy tissues,” said Professor Mark Lythgoe with the University College London Centre for Advanced Biomedical Imaging. “Because the heating seed is magnetic, the magnetic fields in the MRI scanner can be used to remotely steer the seed through tissue to the tumor. Once at the tumor, the seed can then be heated, destroying the cancer cells, while causing limited damage to surrounding healthy tissues.”

The UCL team demonstrated three key components of MINIMA to a high level of accuracy – precise seed imaging, navigation through brain tissue using a tailored MRI system (tracked to within 0.3 mm accuracy), and eradicating the tumor by heating it in a mouse model.

Ferromagnetic thermoseeds are spherical in shape, 2 mm in size, and made of a metal alloy. They are implanted superficially into tissue before being navigated to the cancer.

UCL Centre for Advanced Biomedical Imaging’s Rebecca Baker said: “Using an MRI scanner to deliver a therapy in this way allows the therapeutic seed and the tumor to be imaged throughout the procedure, ensuring the treatment is delivered with precision and without having to perform open surgery. This could be beneficial to patients by reducing recovery times and minimizing the chance of side effects.”

MRI scanners are readily available in hospitals around the world and are pivotal in the diagnosis of diseases such as cancer. The work at UCL shows that MINIMA has the potential to elevate an MRI scanner from a diagnostic device to a therapeutic platform.

Lythgoe added: “We are now able to image and navigate a thermoseed in real-time through the brain using an MRI scanner. As MRI is already used to detect the boundaries of cancers, the seed can be moved precisely to ensure it does not stray into surrounding healthy tissue. As the seed is guided through the tissue, it can be heated to destroy the cancer. This combines therapy and diagnosis into a single device, creating a completely new class of imaging therapy.”