Novel ultrasound technique shows promise for detecting residual brain tumor tissue during surgery

Surgeons removing a brain tumor face an old problem: they cannot always tell where the cancer ends and healthy tissue begins. A new ultrasound technique called shear wave elastography may change that. In a study published in Frontiers in Oncology, researchers found that this type of scan detected leftover tumor tissue with 94 percent sensitivity—nearly three times better than a surgeon's eye alone, which caught only 36 percent of residual cancer.

The study involved 26 patients at four London hospitals: The Institute of Cancer Research, the National Hospital for Neurology and Neurosurgery, The Royal London Hospital, and University Hospital Southampton. During surgery, researchers performed shear wave scans and standard 2D ultrasounds before, during, and after tumor removal. They also asked surgeons to identify suspicious tissue before showing them the scan results. All three approaches were then compared against post-operative MRI scans, the current gold standard.

Shear wave elastography works by measuring how stiff tissue is. The technique sends vibrations through brain tissue and detects how fast they travel—stiffer tissue transmits the waves more quickly. Brain tumors tend to be stiffer than normal brain tissue, so the scan creates a map of suspicious stiff areas that surgeons can then examine and remove. The advantage is speed and cost. MRI scans, while more accurate, are expensive, rarely available in operating rooms, and would add nearly two hours to surgery time. Shear wave scans can be performed in real time during the operation itself.

The findings came with a caveat. While shear wave scans excelled at detecting tumor tissue that was actually there, they also produced more false alarms than surgeons did. The scans had 77 percent specificity—meaning they sometimes flagged normal tissue as suspicious—compared with 100 percent specificity for surgeon judgment. Standard ultrasound fell between the two at 63 percent specificity. For this reason, researchers believe the technique works best not as a replacement for surgical expertise but as a supplement to it, giving surgeons additional confidence that they have removed all removable cancer.

The stakes are clear. Patient outcomes from brain tumor surgery improve significantly when surgeons remove as much tumor as possible. Incomplete removal increases the risk that cancer will return. Dagmar Krafft, a 54-year-old patient who was not part of the study, experienced this firsthand. She was diagnosed with brain cancer in 2013 after suffering a seizure during an orchestral rehearsal where she played violin. Radiotherapy shrank the tumor, and she entered surveillance. Six years later, in 2019, a routine scan revealed the cancer had relapsed. She underwent surgery to remove as much tumor as possible and now receives regular monitoring. When asked about the new scanning technique, she called it fantastic, saying any technology that helps surgeons do their jobs more safely is encouraging.

Professor Jeffrey Bamber, the study's leader at The Institute of Cancer Research, emphasized the practical value. Shear wave scanning can quickly and affordably map the stiffness of brain and tumor tissue during surgery, he said, allowing surgeons to locate and remove tissue they might otherwise miss. Professor Kevin Harrington, head of the Division of Radiotherapy and Imaging at the same institution, noted that the scan provides real-time guidance as surgeons decide which tissue to remove, with potential to improve outcomes while minimizing damage to healthy brain.

Mr Neil Dorward, a consultant neurosurgeon at the National Hospital for Neurology and Neurosurgery and co-researcher on the study, called the technique a practical means of detecting removable tumor that may not be visible to the operating surgeon. The surgeon must still use experience to decide whether to remove flagged areas, he said, but the technique has potential to substantially improve surgical outcomes.

The research was funded by the Royal Free Charity and the Engineering and Physical Sciences Research Council, part of UKRI. While the findings are promising, researchers emphasize that larger clinical trials are needed before the technique can be recommended as standard practice. The study is the first to demonstrate shear wave elastography's potential as a neurosurgical tool to confirm during surgery that tumor removal is complete.