Diffuse optical imaging
Diffuse optical imaging (DOI) is a method of imaging using near-infrared spectroscopy (NIRS) or fluorescence-based methods. When used to create 3D volumetric models of the imaged material DOI is referred to as diffuse optical tomography, whereas 2D imaging methods are classified as diffuse optical imaging. The technique has many applications to neuroscience, sports medicine, wound monitoring, and cancer detection. Typically DOI techniques monitor changes in concentrations of oxygenated and deoxygenated hemoglobin and may additionally measure redox states of cytochromes. The technique may also be referred to as diffuse optical tomography (DOT), near infrared optical tomography (NIROT) or fluorescence diffuse optical tomography (FDOT), depending on the usage. In neuroscience, functional measurements made using NIR wavelengths, DOI techniques may classify as functional near infrared spectroscopy fNIRS.
Diffuse optical imaging (DOI) is a method of imaging using near-infrared spectroscopy (NIRS)[1] or fluorescence-based methods.[2] When used to create 3D volumetric models of the imaged material DOI is referred to as diffuse optical tomography, whereas 2D imaging methods are classified as diffuse optical imaging.
The technique has many applications to neuroscience, sports medicine, wound monitoring, and cancer detection. Typically DOI techniques monitor changes in concentrations of oxygenated and deoxygenated hemoglobin and may additionally measure redox states of cytochromes. The technique may also be referred to as diffuse optical tomography (DOT),[3] near infrared optical tomography (NIROT) or fluorescence diffuse optical tomography (FDOT), depending on the usage.
In neuroscience, functional measurements made using NIR wavelengths, DOI techniques may classify as functional near infrared spectroscopy fNIRS.
Physical mechanism
[edit]Biological tissues can be considered strongly diffusive media, since during light propagation the scattering phenomenon is dominant over absorption in the so-called "therapeutic window" spectral range. Photon migration in diffusive media is described by the heuristic model of the diffusion equation, which offers analytical solutions for some specific geometries. Starting from the measured absorption and scattering coefficients, it is possible to derive the concentrations of tissues' main chromophores.[4]
Diffuse optical imaging can be implemented in time domain, frequency domain or continuous wave, in reflectance or transmittance configuration.
Limitations and Advances in Diffuse Optical Tomography
[edit]Although diffuse optical tomography (DOT) enables greater imaging depth—on the order of several centimeters—compared to other optical imaging techniques, it suffers from key limitations, including relatively low spatial resolution and slow image acquisition and reconstruction times[5][6][7]
To overcome these limitations, a number of improvements have been proposed across the imaging pipeline. These include advances in acquisition strategies,[5] signal processing techniques,[6] and reconstruction algorithms.[7]
Confocal Time-of-Flight Diffuse Optical Tomography
[edit]Conventional DOT suffers from image degradation due to the highly scattering nature of biological tissues, which leads to poor contrast and depth localization. Confocal Time-of-Flight Diffuse Optical Tomography (TOF-DOT) addresses this by using time-gated detection to selectively collect early-arriving photons that have taken more direct paths through tissue. This reduces the influence of multiply scattered photons and improves the signal-to-noise ratio.[6]
The TOF-DOT method thereby enhances image resolution and contrast, offering improved clarity in reconstructed images. Both simulations and experimental studies on tissue phantoms have demonstrated superior imaging performance compared to traditional DOT methods. However, this technique has yet to be validated in vivo.[6]
See also
[edit]- Optical tomography
- Computed tomography laser mammography
- Diffuse optical mammography
- Diffusive optical imaging in neuroscience
- Near-infrared window in biological tissue
- Radiative transfer equation and diffusion theory for photon transport in biological tissue
- Time-domain diffuse optics
References
[edit]- ^ Durduran, T; et al. (2010). "Diffuse optics for tissue monitoring and tomography". Rep. Prog. Phys. 73 (7) 076701. Bibcode:2010RPPh...73g6701D. doi:10.1088/0034-4885/73/7/076701. PMC 4482362. PMID 26120204.
- ^ "Harvard.edu Diffuse Optical Imaging". Archived from the original on June 16, 2012. Retrieved August 20, 2012.
- ^ Jiang, Huabei (2018-09-03). Diffuse Optical Tomography. CRC Press. doi:10.1201/b10482. ISBN 978-1-315-21748-2. S2CID 118019227.
- ^ Martelli, Fabrizio; Del Bianco, Samuele; Ismaelli, Andrea; Zaccanti, Giovanni (2009). Light Propagation through Biological Tissue and Other Diffusive Media: Theory, Solutions, and Software. doi:10.1117/3.824746. ISBN 978-0-8194-8183-2.
- ^ a b Jiang, Jingjing; Ackermann, Meret; Russomanno, Emanuele; Di Costanzo Mata, Aldo; Charbon, Edoardo; Wolf, Martin; Kalyanov, Alexander (2022). "Resolution and penetration depth of reflection-mode time-domain near infrared optical tomography using a ToF SPAD camera". Biomedical Optics Express. 13 (12): 6711–6723. doi:10.1364/BOE.470985. PMC 9774846. PMID 36589570.
- ^ a b c d Zhao, Yifan; Raghuram, Aditya; Kim, Hye Jin; Hielscher, Andreas H.; Robinson, Joshua T.; Veeraraghavan, Ashok (2021). "High Resolution, Deep Imaging Using Confocal Time-of-Flight Diffuse Optical Tomography". IEEE Transactions on Pattern Analysis and Machine Intelligence. 43 (7): 2206–2219. arXiv:2101.11680. doi:10.1109/TPAMI.2021.3075366. PMID 33891548.
- ^ a b Hielscher, Andreas H.; Bluestone, Ayana Y.; Abdoulaev, G. S.; Klose, Alexander D.; Lasker, Jeffrey; Stewart, Mark; Netz, Uwe; Beuthan, Juergen (2002). "Near-Infrared Diffuse Optical Tomography". Disease Markers. 18 (5–6): 313–337. doi:10.1155/2002/164252. PMC 3851113. PMID 14646043.