A new imaging method, which was developed by the teams of Professors Jinyang Liang and Fiorenzo Vetrone at the Institut national de la recherche scientifique (INRS), can measure the temperature in 2D without contact and in next to no time. The results of their research were published in the journal Nature Communications. This precise, real-time temperature detection could one day improve photothermal therapy and help with the early detection of skin cancer.
This technology, known as Single-Shot Photoluminescence Lifetime Imaging Thermometry (SPLIT), is based on the luminescence of nanoparticles doped with rare earth ions. “They are considered nano thermometers because their luminous properties change with the temperature of the environment. They are also biocompatible, ”says Professor Vetrone, a pioneer in this field.
Instead of time-consuming imaging of the luminescence point by point, SPLIT uses a new type of ultra-high-speed camera to track how quickly the luminescence of these nanoparticles decays in each point in space. “Our camera differs from a conventional one, in which every click produces an image: our camera captures all images of a dynamic event in one snapshot. Then we reconstruct them one by one, ”says Xianglei Liu, a PhD student at INRS and the lead author of this article.
The temperature can then be detected by checking how quickly the emitted light is blocked out. Since it is in real time, SPLIT can track the phenomenon as it happens. For the first time, it enables luminescence thermometry based on the lifetime of the nanoparticle with a moving sample. “Compared to existing thermometric techniques, SPLIT is faster and has a higher resolution. This enables more accurate temperature sensing with an advanced and economical solution, ”adds Professor Liang, an expert in ultrafast imaging.
Health applications
Professors Liang and Vetrone believe that the SPLIT technology could improve the ability to detect and treat skin cancer, among other things. At present, the ability to detect melanomas, and in particular micromelanomas, is still limited. Existing diagnostic approaches are limited by their invasiveness, resolution, and accuracy, resulting in a multitude of unnecessary biopsies.
With optical thermometry, cancer cells could be detected, the faster metabolism of which leads to a higher temperature than that of normal tissue and makes them more visible with SPLIT.
To detect melanoma, clinics can use a thermal imaging camera, but the resolution is low. “SPLIT marks an important step in technical development. With a high resolution, the technology could be used to precisely localize the cancer mole, ”says Professor Liang.
In addition to detection, this technology could also be used to monitor the dose of light during certain types of treatment. For example, photothermal therapy attacks cancer cells using the heat generated by exposure to near-infrared light. “We want to eradicate the cancer, but not the surrounding tissue. If the temperature is too high, treatment could be reduced or interrupted for a while. If it’s too low, we can turn up the light to get the right dose, ”says Vetron.
In 2020, the Canadian Cancer Society estimated that 8,000 Canadians alone were diagnosed with this form of cancer.
Source:
National Institute for Scientific Research – INRS
Journal reference:
Liu, X. et al. (2021) Fast, wide-field upconversion luminescence lifetime thermometry, made possible by compressed, single-shot, ultra-high-speed imaging. Nature communication. doi.org/10.1038/s41467-021-26701-1.
