What is it about?

Near-infrared spectroscopy (NIRS) uses the difference in absorption coefficients of oxygenated hemoglobin (HbO) and deoxygenated hemoglobin (HbR) near 805 nm to estimate hemoglobin concentration levels and monitor the hemodynamic responses of biological tissues. When matter is irradiated by microwaves, it generates ultrasonic signals, a process known as the thermoacoustic effect. Microwave thermoacoustic tomography (TAT) is an imaging technique based on the thermoacoustic effect. When sensors placed outside the tissue receive this signal, the system reconstructs images of the distribution of chromophores within the tissue. To overcome drawbacks of the two imaging techniques, this paper builds a dual-modality system by combining a NIRS system and a TAT system to image biological tissues. Results show that this dual-modality system could measure oxygen metabolism and simultaneously provide anatomical structure changes of biological tissues. This dual-modality imaging system can take advantages of two imaging techniques, compensating for the limitations of each.

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Why is it important?

NIRS technology enables non-invasive monitoring of biological tissue functional activities, albeit with lower spatial resolution; TAT technology possesses higher spatial resolution but relies on a single contrast source. NIRS-TAT dual-modality imaging allows simultaneous acquisition of functional response images and anatomical structural change images when biological tissues undergo functional activities. Analyzing and processing the reconstructed images from both modalities can, on one hand, assist in enhancing the spatial resolution of functional near-infrared imaging of biological tissues and endow it with depth resolution capabilities; on the other hand, it enables TAT to perform functional imaging. Results of dual-modality imaging can be cross-validated and mutually complementary.


This dual-modality imaging technique achieves a synergistic combination of the strengths of both modalities. Feasibility of this method was validated through forearm occlusion experiments in humans, yielding imaging results that are mutually correlated and cross-validated. This approach enhances the imaging capability of tissue functional near-infrared light to the resolution level of TAT, providing a reference basis for similar studies. We also found that although the hemoglobin concentration varied consistently with many other published papers, the TAT signal intensity of veins showed an opposite variation tendency in the venous occlusion stage compared with other existing work. A detailed explanation is given to account for the discrepancy, thus, providing another possibility for the forearm experiments using TAT.

Li Su
University of Electronic Science and Technology of China

Read the Original

This page is a summary of: Developing a near-infrared spectroscopy and microwave-induced thermoacoustic tomography-based dual-modality imaging system, Review of Scientific Instruments, December 2021, American Institute of Physics,
DOI: 10.1063/5.0067878.
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