UCL uses short-wave IR imaging to identify tumors

22 Mar 2023

Platform combining NIR and SWIR could be used for fluorescence-guided neuroblastoma surgery.

Differentiating between tumors and healthy tissue is a key part of cancer surgery, and optical imaging techniques are set to play a significant role in the determination.

Several approaches make use of more than one wavelength of illumination, to maximize the imaging data returned to clinicians and exploit the different spectral and fluorescence responses demonstrated by different tissues and cell structures.

These have included the use of hyperspectral cameras, as in the platform designed by the HELICoiD project to image human brain cancers; and the WUSTL dual-wavelength near-IR (NIR) technique capitalizing on the wavelength-dependent attenuation of light in tissue to determine fluorophore depth.

A project at University College London has now demonstrated a multispectral NIR and shortwave IR (SWIR) fluorescence imaging device, said by the researchers to be the first of its kind. The device, initially intended for the treatment of neuroblastoma tumors in children, was described in Cancer Research.

"Fluorescence-guided surgery uses near-infrared dyes emitting from 700 to 950 nanometers, where tissue shows diminished autofluorescence compared to visible light wavelengths, enabling higher target-to-background ratios," commented the team in its paper. "However, there is growing interest in the window of 1000 to 1350 nanometers, the short-wave infrared region, where autofluorescence, absorption and scattering are further reduced."

The project noted that at present there is a lack of clinically approved SWIR fluorophore dyes, but the decreased cost of InGaAs sensors used in the imaging of these wavelengths has stimulated development of devices capable of measuring SWIR fluorescence, leading to a corresponding wish to investigate the technology for clinical use.

Ever-increasing need for novel technologies

UCL synthesized a suitable SWIR dye for its study by conjugating two NIR dyes, including one known to be also active in the SWIR range, to a dinutuximab-beta protein. A bespoke imaging platform was designed in which tissue was illuminated by light at a set of wavelengths between 785 and 1350 nanometers, creating both NIR and SWIR fluorescence, with the latter being collected by a cryogenically cooled InGaAs camera.

Tests on tissue phantoms indicated that the NIR/SWIR platform achieved a minimum detection volume of 0.9 mm³ and depth penetration up to 3 millimeters. A pilot study to assess the tumor uptake of the marker in mice then confirmed that SWIR fluorescence imaging enabled higher tumor-to-background signal ratio and superior depth penetration compared with in vivo NIR imaging alone, according to the project.

The next steps will see UCL and Great Ormond Street Hospital working to fast-track the technology into the operating theater within the next 12 months, to benefit children with neuroblastoma tumors.

"Paediatric surgical oncology faces an ever-increasing need for novel technologies and devices that can help visualize tumours intraoperatively," commented Laura Privitera, lead author of the study. "Fluorescence-guided surgery is a game-changing innovation that will help surgeons to obtain safer and more complete resection. I look forward to seeing this technology translated into the clinical environment."