Handheld Infrared Imaging Device Supports Tumor Margin Assessment During Surgery

Frozen-section pathology takes time and can miss residual disease, potentially leading to repeat surgery and delayed therapy. These limitations highlight the need for rapid, label-free chemical analysis at the point of care. To support this assessment, researchers have developed a handheld mid-infrared imaging spectrometer that generates high-resolution chemical maps of tissue during surgery.

Developed at the University of Houston, the photothermal mid-infrared spectroscopic imaging (MIRSI) device integrates a laboratory instrument into a portable handheld probe linked by fiber to a compact base unit. The platform generates label-free chemical images without stains or dyes by mapping the molecular composition of tissue. The device is detailed in a study published in Optica on September 17, 2026.

The system delivers visible and mid-infrared light through optical fibers to a handheld probe. Instead of traditional lenses, mirrors allow the two beams to travel along the same optical path, while a dichroic component combines them and a parabolic mirror focuses them onto the sample. The instrument then detects small heat-induced changes caused by mid-infrared absorption, with raster scanning used to build detailed chemical maps.

The prototype was validated against a state-of-the-art benchtop MIRSI system using human cervical and ovarian cancer tissues, human bone marrow biopsy tissue, and mouse kidney tissue. The team also measured polymers with distinct signatures to confirm chemical specificity. Spectra from biological tissue matched reference Fourier-transform infrared measurements with a cosine similarity of 0.935, and chemical images correlated with benchtop results at r = 0.90.

The handheld system resolved features as small as 2 micrometers, surpassing the spatial resolution achievable with direct infrared detection. In side-by-side testing, its image quality and chemical detail were comparable to those of the benchtop platform. The current prototype provides spectral coverage from 1150 to 1400 cm−1.

The researchers next plan to broaden the system’s spectral coverage to capture more complete molecular signatures and increase imaging speed for practical freehand use. Before clinical deployment, further studies will be needed to evaluate repeatability, safety, and diagnostic performance under real-world conditions. 

Beyond intraoperative margin assessment and clinical diagnosis, potential applications include polymer manufacturing, pharmaceutical quality control, and forensic analysis where chemical composition must be measured outside specialized laboratories.

“Ultimately, this technology could make it possible to assess tissue during cancer surgery. After removing a suspected tumor, a surgeon could scan the freshly excised tissue to help determine whether it is malignant or whether cancer cells remain at the surgical margin. This complementary information would be available while the patient is still in the operating room instead of having to wait for results from laboratory testing,” said Rohith Reddy, research team leader at the University of Houston.

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