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Gold Nanomaterials at Work in Biomedicine *
Published in Valerio Voliani, Nanomaterials and Neoplasms, 2021
Xuan Yang, Miaoxin Yang, Pang Bo, Madeline Vara, Younan Xia
Photoacoustic imaging shares the advantages of both optical and ultrasonic modalities, and has emerged as a versatile imaging modality for various kinds of biomedical applications [528–531]. Ultrasonic imaging typically suffers from poor resolution, due to the relatively low intensity of an ultrasound source compared to that of a laser. With the use of a highly focused laser as the excitation source, the resolution can become compatible with an optical system. The scattering effect of ultrasound is 2–3 orders of magnitude weaker than that of light, so ultrasound can offer a higher resolution in deep tissue imaging than optical modalities [528]. The acoustic signals can then be directly collected and converted into an image as in photoacoustic microscopy (PAM) or reconstructed with an inverse algorithm as in photoacoustic tomography (PAT). The imaging depth can be pushed up to tens of millimeters, with a spatial resolution ranging from submicrometer to millimeter [528–531]. With these benefits, PA imaging is a promising technique that can bridge the resolution and penetration gaps between optical imaging and conventional radiological medical imaging.
Photoacoustic Neuroimaging
Published in Yu Chen, Babak Kateb, Neurophotonics and Brain Mapping, 2017
Lihong V. Wang, Jun Xia, Junjie Yao
For photoacoustic microscopy (PAM) (Yao and Wang 2013), which uses a focused single-element ultrasonic transducer to raster scan the tissue, the distribution of initial pressure can be approximated by simply back projecting the temporal signal along the acoustic axis. For photoacoustic computed tomography (PACT) (Xu and Wang 2006), whose receiving elements are unfocused and thus have a large acceptance angle, the initial pressure can be reconstructed only by merging data from all transducer elements.
Chemical and Molecular Imaging of Deep Tissue through Photoacoustic Detection of Chemical Bond Vibrations
Published in Lingyan Shi, Robert R. Alfano, Deep Imaging in Tissue and Biomedical Materials, 2017
According to its specific application areas, PAI is typically operated at three different modes to realize 3D imaging of a tissue as depicted in Fig. 14.4. The first and most straightforward one is based on focused photons or phonons, and raster scanning of the optical beam or tissue as shown in Fig. 14.4a. This modality is known as photoacoustic microscopy (PAM). In PAM, focused ultrasound transducer can largely enhance the collecting efficiency of photoacoustic signal with an improved spatial resolution less than 100 μm. A tightly focused optical beam can further push the lateral resolution to the optical resolution regime, which is also known as optical-resolution PAM, with the sacrifice of penetration depth less than 1 mm. By assuming the sound velocity in tissue to be ∼1.54 mm/μs, the time-of-flight ultrasound signal is converted into depth information in tissue. The 3D image is then resolved by combining the time-of-flight depth signal with the raster scanning information.
Recent advances in imaging technologies for assessment of retinal diseases
Published in Expert Review of Medical Devices, 2020
Taha Soomro, Neil Shah, Magdalena Niestrata-Ortiz, Timothy Yap, Eduardo M. Normando, M. Francesca Cordeiro
Ophthalmology as a medical field has advanced at great speed, with new imaging techniques improving our understanding and management of ocular pathology. This has occurred hand in hand with new therapeutics available in the form anti-vascular endothelial growth factor agents, as well as novel gene therapies being developed alongside stem cell therapies for treatment of degenerative or hereditary retinal pathologies [2]. In terms of horizon scanning, in the future we will have more accurate, multimodal imaging with better resolution of ocular structures. Quantitative, non-invasive, serial microvascular analysis, oxygenation measurement and review of real-time cellular changes in patients with retinal pathologies, will be possible using the combination of technologies such as OCT angiography, photoacoustic microscopy, and novel molecular imaging. Better surgical outcomes through using intraoperative OCT will be available. Using artificial intelligence, telemedicine, and providing wider access to personalized smart device-based imaging systems, will allow patients to get faster and more personalized care.