and NIR-II can be used in intraoperative real-time imaging in high-resolution
PET/NIR-II imaging and will likely bring high impact to the patient imaging and
image-guided therapy. It would be important to test the advantages of PET/NIR-II
dual-modal probes in clinic. PAI has the both excellent advantages of optical and
ultrasonic imaging due to the high spatial resolution and low scattering of
acoustics. It provides a novel way to link different imaging systems at deeper
penetration depth. It is expected that PAI/NIR-II dual-modal imaging will make
rapid progress, because many dyes can serve as reporters for both PAI and optical
imaging. By now, NIR-II-based three-modal imaging systems (e.g., NIR-II/MRI/
PET or NIR-II/PET/PAI) are still unknown on how to design, but such multimodal imaging systems hold great promise for acquiring complementary information. For example, with an NIR-II/MRI/PET trimodal imaging system, the
high sensitivity and unlimited penetration depth of PET could be used for wholebody screening and then reduce the volume of tissue that needs to be scanned.
MRI involves no radiation, and high-resolution images could be obtained. NIR-II
imaging would provide real-time imaging and molecular and functional information on diseases. It is noted that the integration of several imaging modalities into
one system is a great challenge due to the different hardware and the imaging
mechanisms.
4. NIR-II-based guide therapy: Compared with the visible imaging, one of the most
advantages of NIR-II imaging is that the photon scattering and autofluorescence
background are very low. So, in my opinion, intraoperative NIR-II image-guided
surgery will be the most likely to be the clinical application. In addition, it will be
helpful to integrate other clinic imaging modalities, such as PET or MRI, which
will obtain more information beyond the single NIR-II imaging.
5. 3D NIR-II imaging: Because of the relative deeper NIR-II penetration depth, the
NIR-II photons may significantly achieve 3D volumetric tissue imaging. For
example, the current brain neurology is mainly relying on optical microscopy
and electron microscopy (EM) of thin tissue slices, which brings in additional
difficulties and extra heavy work in the 3D reconstruction. Combined with tissueclearing techniques, NIR-II fluorescence imaging may potentially afford volumetric brain imaging to achieve close-to-EM resolution on the whole organ or
even whole body in deep volumetric scanning depth without tissue slicing.
6. NIR-II imaging system: The ability to maximize the full benefits of any NIR-II
imaging is highly reliant on the thorough understanding of the requirements of
each imaging system and the physical characteristics of the complementary
fluorophores probes. The NIR-II imaging system can be described as acquisition
of NIR-II emission signals from fluorophores probes using an image capturing
system. Besides selecting suitable filters based on the fluorophores’ optical
characteristics (excitation/emission wavelengths and brightness), the hardware
platforms (scan rate, lenses, collimators, working distance, exposure duration),
and software algorithms for signal processing and image acquisition are designed
to reduce undesired thermal noise often associated with NIR-II imaging and to
enhance the signal-to-noise ratio. It would therefore be critical to adopt a
systems–level approach to plan research efforts where the requirements of the
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S. He and Z. Cheng
PET/NIR-II imaging and will likely bring high impact to the patient imaging and
image-guided therapy. It would be important to test the advantages of PET/NIR-II
dual-modal probes in clinic. PAI has the both excellent advantages of optical and
ultrasonic imaging due to the high spatial resolution and low scattering of
acoustics. It provides a novel way to link different imaging systems at deeper
penetration depth. It is expected that PAI/NIR-II dual-modal imaging will make
rapid progress, because many dyes can serve as reporters for both PAI and optical
imaging. By now, NIR-II-based three-modal imaging systems (e.g., NIR-II/MRI/
PET or NIR-II/PET/PAI) are still unknown on how to design, but such multimodal imaging systems hold great promise for acquiring complementary information. For example, with an NIR-II/MRI/PET trimodal imaging system, the
high sensitivity and unlimited penetration depth of PET could be used for wholebody screening and then reduce the volume of tissue that needs to be scanned.
MRI involves no radiation, and high-resolution images could be obtained. NIR-II
imaging would provide real-time imaging and molecular and functional information on diseases. It is noted that the integration of several imaging modalities into
one system is a great challenge due to the different hardware and the imaging
mechanisms.
4. NIR-II-based guide therapy: Compared with the visible imaging, one of the most
advantages of NIR-II imaging is that the photon scattering and autofluorescence
background are very low. So, in my opinion, intraoperative NIR-II image-guided
surgery will be the most likely to be the clinical application. In addition, it will be
helpful to integrate other clinic imaging modalities, such as PET or MRI, which
will obtain more information beyond the single NIR-II imaging.
5. 3D NIR-II imaging: Because of the relative deeper NIR-II penetration depth, the
NIR-II photons may significantly achieve 3D volumetric tissue imaging. For
example, the current brain neurology is mainly relying on optical microscopy
and electron microscopy (EM) of thin tissue slices, which brings in additional
difficulties and extra heavy work in the 3D reconstruction. Combined with tissueclearing techniques, NIR-II fluorescence imaging may potentially afford volumetric brain imaging to achieve close-to-EM resolution on the whole organ or
even whole body in deep volumetric scanning depth without tissue slicing.
6. NIR-II imaging system: The ability to maximize the full benefits of any NIR-II
imaging is highly reliant on the thorough understanding of the requirements of
each imaging system and the physical characteristics of the complementary
fluorophores probes. The NIR-II imaging system can be described as acquisition
of NIR-II emission signals from fluorophores probes using an image capturing
system. Besides selecting suitable filters based on the fluorophores’ optical
characteristics (excitation/emission wavelengths and brightness), the hardware
platforms (scan rate, lenses, collimators, working distance, exposure duration),
and software algorithms for signal processing and image acquisition are designed
to reduce undesired thermal noise often associated with NIR-II imaging and to
enhance the signal-to-noise ratio. It would therefore be critical to adopt a
systems–level approach to plan research efforts where the requirements of the
116
S. He and Z. Cheng