[ { "id": "authors:3jnmv-04h77", "collection": "authors", "collection_id": "3jnmv-04h77", "cite_using_url": "https://authors.library.caltech.edu/records/3jnmv-04h77", "type": "article", "title": "Microwave Ablation Monitoring Using Thermoacoustic and Ultrasound Tomography", "author": [ { "family_name": "Garrett", "given_name": "David C.", "orcid": "0000-0002-9747-8494", "clpid": "Garrett-David-C" }, { "family_name": "Aborahama", "given_name": "Yousuf", "orcid": "0000-0002-9527-8923", "clpid": "Aborahama-Yousuf" }, { "family_name": "Xu", "given_name": "Jinhua", "clpid": "Xu-Jinhua" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "Microwave ablation is an established minimally invasive technique that induces thermal necrosis in centimeter-scale tumors in organs such as the liver and kidney. However, the efficacy of clinical protocols is challenged by patient-specific and tissue-specific variations that may require personalized parameters to achieve optimal therapeutic outcomes. To address these limitations, we introduce an imaging technique employing modulated microwave signals that maintain peak and average powers comparable to those of existing clinical systems (\u223c100\u2013200\u00a0W). This modulation introduces time-varying tissue heating, generating detectable thermoacoustic signals that are used to reconstruct images proportional to the spatial heat deposition. When combined with thermal models of the tissue, we estimate the spatial temperature profile and ablation status over time. We validate this approach in ex vivo bovine liver compared against ultrasound tomography and tissue dissection. This approach may enable closed-loop monitoring and adaptive control of ablation procedures to optimize lesion coverage while sparing surrounding healthy tissue.", "doi": "10.1109/jmw.2025.3612329", "pmcid": "PMC13132507", "issn": "2692-8388", "publisher": "IEEE", "publication": "IEEE Journal of Microwaves", "publication_date": "2026-03", "series_number": "2", "volume": "6", "issue": "2", "pages": "531 - 539" }, { "id": "authors:b5xwh-vt765", "collection": "authors", "collection_id": "b5xwh-vt765", "cite_using_url": "https://authors.library.caltech.edu/records/b5xwh-vt765", "type": "article", "title": "Transcranial photoacoustic tomography de-aberrated using boundary elements", "author": [ { "family_name": "Sastry", "given_name": "Karteekeya", "orcid": "0000-0001-7659-4878", "clpid": "Sastry-Karteekeya" }, { "family_name": "Aborahama", "given_name": "Yousuf", "orcid": "0000-0002-9527-8923", "clpid": "Aborahama-Yousuf" }, { "family_name": "Luo", "given_name": "Yilin", "orcid": "0000-0002-4611-3049", "clpid": "Luo-Yilin" }, { "family_name": "Zhang", "given_name": "Yang", "orcid": "0000-0002-4533-4325", "clpid": "Zhang-Yang" }, { "family_name": "Cui", "given_name": "Manxiu", "orcid": "0000-0003-0788-9511", "clpid": "Cui-Manxiu" }, { "family_name": "Cao", "given_name": "Rui", "orcid": "0000-0003-4444-7528", "clpid": "Cao-Rui" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "Photoacoustic tomography holds tremendous potential for neuroimaging due to its functional magnetic resonance imaging (fMRI)-like functional contrast and greater specificity, richer contrast, portability, open platform, faster imaging, magnet-free and quieter operation, and lower cost. However, accounting for the skull-induced acoustic distortion remains a long-standing challenge due to the problem size. This is aggravated in functional imaging, where high accuracy is needed to detect minuscule functional changes. Here, we develop an acoustic solver based on the boundary-element method (BEM) to model the skull and de-aberrate the images. BEM uses boundary meshes and compression for superior computational efficiency compared to volumetric discretization-based methods. We demonstrate BEM's higher accuracy and favorable scalability relative to the widely used pseudo-spectral time-domain method (PSTD). In imaging through an ex-vivo adult human skull, BEM outperforms PSTD in several metrics. Our work establishes BEM as a valuable and naturally suited technique in photoacoustic tomography and lays the foundation for BEM-based de-aberration methods.", "doi": "10.1109/tmi.2025.3526000", "issn": "0278-0062", "publisher": "IEEE", "publication": "IEEE Transactions on Medical Imaging", "publication_date": "2025-01-06", "pages": "1-1" }, { "id": "authors:wmj0j-gqz79", "collection": "authors", "collection_id": "wmj0j-gqz79", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160708-083655411", "type": "article", "title": "Effects of Photoacoustic Imaging and Photothermal Ablation Therapy Mediated by Targeted Hollow Gold Nanospheres in an Orthotopic Mouse Xenograft Model of Glioma", "author": [ { "family_name": "Lu", "given_name": "Wei", "clpid": "Lu-Wei" }, { "family_name": "Melancon", "given_name": "Marites P.", "clpid": "Melancon-M-P" }, { "family_name": "Xiong", "given_name": "Chiyi", "clpid": "Xiong-Chiyi" }, { "family_name": "Huang", "given_name": "Qian", "clpid": "Huang-Qian" }, { "family_name": "Elliott", "given_name": "Andrew", "clpid": "Elliott-A" }, { "family_name": "Song", "given_name": "Shaoli", "clpid": "Song-Shaoli" }, { "family_name": "Zhang", "given_name": "Rui", "clpid": "Zhang-Rui" }, { "family_name": "Flores", "given_name": "Leo G., II", "clpid": "Flores-L-G-II" }, { "family_name": "Gelovani", "given_name": "Juri G.", "clpid": "Gelovani-J-G" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Stafford", "given_name": "R. Jason", "clpid": "Stafford-R-J" }, { "family_name": "Li", "given_name": "Chun", "clpid": "Li-Chun" } ], "abstract": "Advancements in nanotechnology have made it possible to create multifunctional nanostructures that can be used simultaneously to image and treat cancers. For example, hollow gold nanospheres (HAuNS) have been shown to generate intense photoacoustic signals and induce efficient photothermal ablation (PTA) therapy. In this study, we used photoacoustic tomography, a hybrid imaging modality, to assess the intravenous delivery of HAuNS targeted to integrins that are overexpressed in both glioma and angiogenic blood vessels in a mouse model of glioma. Mice were then treated with near-infrared laser, which elevated tumor temperature by 20.7\u00b0C. We found that PTA treatment significantly prolonged the survival of tumor-bearing mice. Taken together, these results show the feasibility of using a single nanostructure for image-guided local tumor PTA therapy with photoacoustic molecular imaging.", "doi": "10.1158/0008-5472.CAN-10-4557", "pmcid": "PMC3185126", "issn": "0008-5472", "publisher": "American Association for Cancer Research", "publication": "Cancer Research", "publication_date": "2011-10-01", "series_number": "19", "volume": "71", "issue": "19", "pages": "6116-6121" }, { "id": "authors:tgsyr-1st63", "collection": "authors", "collection_id": "tgsyr-1st63", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160706-132545201", "type": "article", "title": "Photoacoustic imaging of living mouse brain vasculature using hollow gold nanospheres", "author": [ { "family_name": "Lu", "given_name": "Wei", "clpid": "Lu-Wei" }, { "family_name": "Huang", "given_name": "Qian", "clpid": "Huang-Qian" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wen", "given_name": "Xiaoxia", "clpid": "Wen-Xiaoxia" }, { "family_name": "Zhou", "given_name": "Min", "clpid": "Zhou-Min" }, { "family_name": "Guzatov", "given_name": "Dmitry", "clpid": "Guzatov-D" }, { "family_name": "Brecht", "given_name": "Peter", "clpid": "Brecht-P" }, { "family_name": "Su", "given_name": "Richard", "clpid": "Su-Richard" }, { "family_name": "Oraevsky", "given_name": "Alexander", "orcid": "0000-0002-9212-6211", "clpid": "Oraevsky-A-A" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" }, { "family_name": "Li", "given_name": "Chun", "clpid": "Li-Chun" } ], "abstract": "Photoacoustic tomography (PAT) also referred to as optoacoustic tomography (OAT) is a hybrid imaging modality that employs nonionizing optical radiation and ultrasonic detection. Here, we describe the application of a new class of optical contrast agents based on mesoscopic hollow gold nanospheres (HAuNS) to PAT. HAuNS are \u223c40 nm in diameter with a hollow interior and consist of a thin gold wall. They display strong resonance absorption tuned to the near-infrared (NIR) range, with an absorption peak at 800 nm, whose photoacoustic efficiency is significantly greater than that of blood. Following surface conjugation with thiolated poly(ethylene glycol), the pegylated HAuNS (PEG-HAuNS) had distribution and elimination half-lives of 1.38 \u00b1 0.38 and 71.82 \u00b1 30.46 h, respectively. Compared with PAT images based on the intrinsic optical contrast in nude mice, the PAT images acquired within 2 h after intravenous administration of PEG-HAuNS showed the brain vasculature with greater clarity and detail. The image depicted brain blood vessels as small as \u223c100 \u03bcm in diameter using PEG-HAuNS as contrast agents. Preliminary results showed no acute toxicity to the liver, spleen, or kidneys in mice following a single imaging dose of PEG-HAuNS. Our results indicate that PEG-HAuNS are promising contrast agents for PAT, with high spatial resolution and enhanced sensitivity.", "doi": "10.1016/j.biomaterials.2009.12.007", "pmcid": "PMC2813997", "issn": "0142-9612", "publisher": "Elsevier", "publication": "Biomaterials", "publication_date": "2010-03", "series_number": "9", "volume": "31", "issue": "9", "pages": "2617-2626" }, { "id": "authors:azkvj-87b32", "collection": "authors", "collection_id": "azkvj-87b32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160908-103450834", "type": "article", "title": "Photoacoustic microscopy with 2-\u03bcm transverse resolution", "author": [ { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Maslov", "given_name": "Konstantin", "orcid": "0000-0003-3408-8840", "clpid": "Maslov-K-I" }, { "family_name": "Li", "given_name": "Li", "clpid": "Li-Li" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "We present a new-generation optical-resolution confocal photoacoustic microscope, consisting of a 0.25\u2013numerical aperture optical microscope objective and a 75-MHz center-frequency spherically focused ultrasonic transducer. Experiments verified that this microscope has a transverse resolution of 2\u03bcm, which is the highest to our knowledge among all photoacoustic imaging systems. In situ imaging of mouse ears shows the feasibility of resolving individual red blood cells in microvessels using the current system.", "doi": "10.1117/1.3339912", "pmcid": "PMC2857454", "issn": "1083-3668", "publisher": "Society of Photo-Optical Instrumentation Engineers", "publication": "Journal of Biomedical Optics", "publication_date": "2010-02", "series_number": "2", "volume": "15", "issue": "2", "pages": "Art. No. 021302" }, { "id": "authors:k2fr8-89q37", "collection": "authors", "collection_id": "k2fr8-89q37", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160921-154206358", "type": "article", "title": "Three-dimensional combined photoacoustic and optical coherence microscopy for in vivo microcirculation studies", "author": [ { "family_name": "Li", "given_name": "Li", "clpid": "Li-Li" }, { "family_name": "Maslov", "given_name": "Konstantin", "orcid": "0000-0003-3408-8840", "clpid": "Maslov-K-I" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "Photoacoustic microscopy is predominantly sensitive to optical absorption, while optical coherence tomography relies on optical backscattering. Integrating their complementary contrasts can provide comprehensive information about biological tissue. We have developed a dual-modality microscope that combines the two for studying microcirculation. Three-dimensional imaging of microvasculature and its local environment has been demonstrated at micrometer-order resolution using endogenous contrast in vivo.", "doi": "10.1364/OE.17.016450", "pmcid": "PMC2855548", "issn": "1094-4087", "publisher": "Optical Society of America", "publication": "Optics Express", "publication_date": "2009-09-14", "series_number": "19", "volume": "17", "issue": "19", "pages": "16450-16455" }, { "id": "authors:492ak-pr731", "collection": "authors", "collection_id": "492ak-pr731", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160921-152451146", "type": "article", "title": "Tangential resolution improvement in thermoacoustic and photoacoustic tomography using a negative acoustic lens", "author": [ { "family_name": "Pramanik", "given_name": "Manojit", "clpid": "Pramanik-M" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "We developed a novel concept of using a negative acoustic lens to increase the acceptance angle of an unfocused large-area ultrasonic transducer (detector), leading to more than twofold improvement of the tangential resolution in both thermoacoustic and photoacoustic tomography. In both thermoacoustic and photoacoustic tomography, for a given transducer bandwidth, the aperture size of the detector affects the tangential resolution greatly when the object of interest is near the detector surface. We were able to overcome such tangential resolution deterioration by attaching an acoustic concave lens, made of acrylic in front of the flat detector surface. We then quantified the tangential resolution improvement using phantom images. We also showed that the use of the negative lens preserves the shape of an object after the image is reconstructed.", "doi": "10.1117/1.3103778", "pmcid": "PMC2858381", "issn": "1083-3668", "publisher": "Society of Photo-Optical Instrumentation Engineers", "publication": "Journal of Biomedical Optics", "publication_date": "2009-03", "series_number": "2", "volume": "14", "issue": "2", "pages": "Art. No. 024028" }, { "id": "authors:8rwne-5ae18", "collection": "authors", "collection_id": "8rwne-5ae18", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160921-155919948", "type": "article", "title": "Adaptive and Robust Methods of Reconstruction (ARMOR) for Thermoacoustic Tomography", "author": [ { "family_name": "Xie", "given_name": "Yao", "clpid": "Xie-Yao" }, { "family_name": "Guo", "given_name": "Bin", "clpid": "Guo-Bin" }, { "family_name": "Liu", "given_name": "Jian", "orcid": "0000-0001-8552-1400", "clpid": "Liu-Jian" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "In this paper, we present new adaptive and robust methods of reconstruction (ARMOR) for thermoacoustic tomography (TAT), and study their performances for breast cancer detection. TAT is an emerging medical imaging technique that combines the merits of high contrast due to electromagnetic or laser stimulation and high resolution offered by thermal acoustic imaging. The current image reconstruction methods used for TAT, such as the delay-and-sum (DAS) approach, are data-independent and suffer from low-resolution, high sidelobe levels, and poor interference rejection capabilities. The data-adaptive ARMOR can have much better resolution and much better interference rejection capabilities than their data-independent counterparts. By allowing certain uncertainties, ARMOR can be used to mitigate the amplitude and phase distortion problems encountered in TAT. The excellent performance of ARMOR is demonstrated using both simulated and experimentally measured data.", "doi": "10.1109/TBME.2008.919112", "issn": "0018-9294", "publisher": "IEEE", "publication": "IEEE Transactions on Biomedical Engineering", "publication_date": "2008-12", "series_number": "12", "volume": "55", "issue": "12", "pages": "2741-2752" }, { "id": "authors:pskxb-yy786", "collection": "authors", "collection_id": "pskxb-yy786", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160923-155924471", "type": "article", "title": "Negative lens concept for photoacoustic tomography", "author": [ { "family_name": "Li", "given_name": "Changhui", "clpid": "Li-Changhui" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "Although a small point ultrasound transducer has a wide acceptance angle, its small active area leads to a high thermal-noise-induced electric voltage in the transducer, thus the sensitivity is low. By contrast, a finite-size flat transducer has high sensitivity, but the acceptance angle is small, which limits its application in reconstruction-based photoacoustic tomography (PAT). Here, we propose a negative lens concept to increase the acceptance angle of a flat transducer without losing sensitivity. Phantom experiments demonstrate that use of this concept greatly increases the detection region for PAT with high sensitivity.", "doi": "10.1103/PhysRevE.78.021901", "pmcid": "PMC2602847", "issn": "1539-3755", "publisher": "American Physical Society", "publication": "Physical Review E", "publication_date": "2008-08", "series_number": "2", "volume": "78", "issue": "2", "pages": "Art. No. 021901" }, { "id": "authors:9817s-tvc07", "collection": "authors", "collection_id": "9817s-tvc07", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160922-135211398", "type": "article", "title": "Design and evaluation of a novel breast cancer detection system combining both thermoacoustic (TA) and photoacoustic (PA) tomography", "author": [ { "family_name": "Pramanik", "given_name": "Manojit", "clpid": "Pramanik-M" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Li", "given_name": "Changhui", "clpid": "Li-Changhui" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "We have developed a novel scanner for breast cancer detection, integrating both thermoacoustic and photoacoustic techniques to achieve dual contrast(microwave and light absorption) imaging. This scanner is nonionizing, low cost, and can potentially provide high-resolution, dual modality three-dimensional images of the breast. The scanner uses front instead of side breast compression and dry instead of gel ultrasonic coupling. Here we present the design of the breast scanner along with initial tissue phantom study results as a precursor to an actual patient study.", "doi": "10.1118/1.2911157", "pmcid": "PMC2673632", "issn": "0094-2405", "publisher": "American Association of Physicists in Medicine", "publication": "Medical Physics", "publication_date": "2008-06", "series_number": "6", "volume": "35", "issue": "6", "pages": "2218-2223" }, { "id": "authors:958p6-rnk26", "collection": "authors", "collection_id": "958p6-rnk26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160927-140749582", "type": "article", "title": "Simultaneous Molecular and Hypoxia Imaging of Brain Tumors In Vivo Using Spectroscopic Photoacoustic Tomography", "author": [ { "family_name": "Li", "given_name": "Meng-Lin", "clpid": "Li-Meng-Lin" }, { "family_name": "Oh", "given_name": "Jung-Taek", "clpid": "Oh-Jung-Taek" }, { "family_name": "Xie", "given_name": "Xueyi", "clpid": "Xie-Xueyi" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wang", "given_name": "Wei", "orcid": "0000-0002-5257-7675", "clpid": "Wang-Wei" }, { "family_name": "Li", "given_name": "Chun", "clpid": "Li-Chun" }, { "family_name": "Lungu", "given_name": "Gina", "clpid": "Lungu-Gina" }, { "family_name": "Stoica", "given_name": "George", "orcid": "0000-0001-8071-4828", "clpid": "Stoica-G" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "Noninvasive molecular and functional imaging in vivo is promising for detecting and monitoring various physiological conditions in animals and ultimately humans. To this end, we present a novel noninvasive technology, spectroscopic photoacoustic tomography (SPAT), which offers both strong optical absorption contrast and high ultrasonic spatial resolution. Optical contrast allows spectroscopic separation of signal contributions from multiple optical absorbers (e.g., oxyhemoglobin, deoxyhemoglobin, and a molecular contrast agent), thus enabling simultaneous molecular and functional imaging. SPAT successfully imaged with high resolution the distribution of a molecular contrast agent targeting integrin overexpressed in human U87 glioblastomas in nude mouse brains. Simultaneously, SPAT also imaged the hemoglobin oxygen saturation and the total hemoglobin concentration of the vasculature, which revealed hypoxia in tumor neovasculature. Therefore, SPAT can potentially lead to better understanding of the interrelationships between hemodynamics and specific biomarkers associated with tumor progression.", "doi": "10.1109/JPROC.2007.913515", "issn": "0018-9219", "publisher": "IEEE", "publication": "Proceedings of the IEEE", "publication_date": "2008-03", "series_number": "3", "volume": "96", "issue": "3", "pages": "481-489" }, { "id": "authors:wkvq0-xt231", "collection": "authors", "collection_id": "wkvq0-xt231", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160923-134112679", "type": "article", "title": "Image distortion in thermoacoustic tomography caused by microwave diffraction", "author": [ { "family_name": "Li", "given_name": "Changhui", "clpid": "Li-Changhui" }, { "family_name": "Pramanik", "given_name": "Manojit", "clpid": "Pramanik-M" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "We report an intrinsic image distortion in microwave-induced thermoacoustic tomography. The distortion, due to microwave diffraction in the object to be imaged, leads to nonuniform excitation of acoustic pressure during microwave illumination. Both numerical simulations and phantom experiments demonstrate this phenomenon. A method of partial correction is also provided.", "doi": "10.1103/PhysRevE.77.031923", "issn": "1539-3755", "publisher": "American Physical Society", "publication": "Physical Review E", "publication_date": "2008-03", "series_number": "3", "volume": "77", "issue": "3", "pages": "Art. No. 031923" }, { "id": "authors:467j6-30h14", "collection": "authors", "collection_id": "467j6-30h14", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161118-103745094", "type": "article", "title": "Noninvasive imaging of hemoglobin concentration and oxygenation in the rat brain using high-resolution photoacoustic tomography", "author": [ { "family_name": "Wang", "given_name": "Xueding", "clpid": "Wang-Xueding" }, { "family_name": "Xie", "given_name": "Xueyi", "clpid": "Xie-Xueyi" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" }, { "family_name": "Stoica", "given_name": "George", "orcid": "0000-0001-8071-4828", "clpid": "Stoica-G" } ], "abstract": "Simultaneous transcranial imaging of two functional parameters, the total concentration of hemoglobin and the hemoglobin oxygen saturation, in the rat brain in vivo is realized noninvasively using laser-based photoacoustic tomography (PAT). As in optical diffusion spectroscopy, PAT can assess the optical absorption of endogenous chromophores, e.g., oxygenated and deoxygenated hemoglobins, at multiple optical wavelengths. However, PAT can provide high spatial resolution because its resolution is diffraction-limited by photoacoustic signals rather than by optical diffusion. Laser pulses at two wavelengths are used sequentially to acquire photoacoustic images of the vasculature in the cerebral cortex of a rat brain through the intact skin and skull. The distributions of blood volume and blood oxygenation in the cerebral cortical venous vessels, altered by systemic physiological modulations including hyperoxia, normoxia, and hypoxia, are visualized successfully with satisfactory spatial resolution. This technique, with its prominent sensitivity to endogenous contrast, can potentially contribute to the understanding of the interrelationship between neural, hemodynamic, and metabolic activities in the brain.", "doi": "10.1117/1.2192804", "issn": "1083-3668", "publisher": "Society of Photo-Optical Instrumentation Engineers", "publication": "Journal of Biomedical Optics", "publication_date": "2006-03", "series_number": "2", "volume": "11", "issue": "2", "pages": "Art. No. 024015" }, { "id": "authors:kbhnr-9pc57", "collection": "authors", "collection_id": "kbhnr-9pc57", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160711-133809050", "type": "article", "title": "Thermoacoustic and Photoacoustic Tomography of Thick Biological Tissues toward Breast Imaging", "author": [ { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Fornage", "given_name": "Bruno D.", "clpid": "Fornage-B-D" }, { "family_name": "Jin", "given_name": "Xing", "clpid": "Jin-Xing" }, { "family_name": "Xu", "given_name": "Minghua", "clpid": "Xu-Minghua" }, { "family_name": "Hunt", "given_name": "Kelly K.", "clpid": "Hunt-K-K" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "Microwave-based thermoacoustic tomography (TAT) and laser-based photoacoustic tomography (PAT) in a circular scanning configuration were both developed to image deeply seated lesions and objects in biological tissues. Because malignant breast tissue absorbs microwaves more strongly than benign breast tissue, cancers were imaged with good spatial resolution and contrast by TAT in human breast mastectomy specimens. Based on the intrinsic optical contrast between blood and chicken breast muscle, an embedded blood object that was 5 cm deep in the tissue was also detected using PAT at a wavelength of 1064 nm.", "doi": "10.1177/153303460500400509", "issn": "1533-0346", "publisher": "SAGE Publications", "publication": "Technology in Cancer Research and Treatment", "publication_date": "2005-10", "series_number": "5", "volume": "4", "issue": "5", "pages": "559-565" }, { "id": "authors:m289g-zzb69", "collection": "authors", "collection_id": "m289g-zzb69", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161118-125233243", "type": "article", "title": "Deeply penetrating photoacoustic tomography in biological tissues enhanced with an optical contrast agent", "author": [ { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "Photoacoustic tomography (PAT) in a circular scanning configuration was developed to image deeply embedded optical heterogeneity in biological tissues. While the optical penetration was maximized with near-infrared laser pulses of 800-nm wavelength, the optical contrast was enhanced by Indocyanine Green (ICG) dye whose absorption peak matched the laser wavelength. This optimized PAT was able to image objects embedded at depths of as much as 5.2 cm, 6.2 times the 1/e optical penetration depth, in chicken breast muscle at a resolution of <780 \u00b5m and a sensitivity of <7 pmol of ICG in blood. The resolution was found to deteriorate slowly with increasing imaging depth. The effects of detection bandwidth on the quality of images acquired simultaneously by four different ultrasonic transducers are described.", "doi": "10.1364/OL.30.000507", "issn": "0146-9592", "publisher": "Optical Society of America", "publication": "Optics Letters", "publication_date": "2005-03-01", "series_number": "5", "volume": "30", "issue": "5", "pages": "507-509" }, { "id": "authors:f3841-y2m64", "collection": "authors", "collection_id": "f3841-y2m64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161118-132318724", "type": "article", "title": "Imaging of tumor angiogenesis in rat brains in vivo by photoacoustic tomography", "author": [ { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wang", "given_name": "Xueding", "clpid": "Wang-Xueding" }, { "family_name": "Xie", "given_name": "Xueyi", "clpid": "Xie-Xueyi" }, { "family_name": "Stoica", "given_name": "George", "orcid": "0000-0001-8071-4828", "clpid": "Stoica-G" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "Green laser pulses at a wavelength of 532 nm from a Q-switched Nd:YAG laser were employed as irradiation sources for photoacoustic tomography (PAT). The vascular structure of the brain was imaged clearly, with optimal contrast, because blood has strong absorption near this wavelength. The photoacoustic images of rat brain tumors in this study clearly reveal the angiogenesis that is associated with tumors. Brain tumors can be identified based on the distorted vascular architecture of brain tumorigenesis and related vascular changes, such as hemorrhage. This research demonstrates that PAT can potentially provide a powerful tool for small-animal biological research.", "doi": "10.1364/AO.44.000770", "issn": "0003-6935", "publisher": "Optical Society of America", "publication": "Applied Optics", "publication_date": "2005-02-10", "series_number": "5", "volume": "44", "issue": "5", "pages": "770-775" }, { "id": "authors:b5vmm-92v87", "collection": "authors", "collection_id": "b5vmm-92v87", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161118-130710638", "type": "article", "title": "Half-time image reconstruction in thermoacoustic tomography", "author": [ { "family_name": "Anastasio", "given_name": "Mark A.", "orcid": "0000-0002-3192-4172", "clpid": "Anastasio-M-A" }, { "family_name": "Zhang", "given_name": "Jin", "clpid": "Zhang-Jin" }, { "family_name": "Pan", "given_name": "Xiaochuan", "clpid": "Pan-Xiaochuan" }, { "family_name": "Zou", "given_name": "Yu", "clpid": "Zou-Yu" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "Thermoacoustic tomography (TAT) is an emerging imaging technique with great potential for a wide range of biomedical imaging applications. We propose and investigate reconstruction approaches for TAT that are based on the half-time reflectivity tomography paradigm. We reveal that half-time reconstruction approaches permit for the explicit control of statistically complementary information that can result in the optimal reduction of image variances. We also show that half-time reconstruction approaches can mitigate image artifacts due to heterogeneous acoustic properties of an object. Reconstructed images and numerical results produced from simulated and experimental TAT measurement data are employed to demonstrate these effects.", "doi": "10.1109/TMI.2004.839682", "issn": "0278-0062", "publisher": "IEEE", "publication": "IEEE Transactions on Medical Imaging", "publication_date": "2005-02", "series_number": "2", "volume": "24", "issue": "2", "pages": "199-210" }, { "id": "authors:edpsk-dhy33", "collection": "authors", "collection_id": "edpsk-dhy33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161207-155728543", "type": "article", "title": "Photoacoustic Tomography of a Nanoshell Contrast Agent in the in Vivo Rat Brain", "author": [ { "family_name": "Wang", "given_name": "Yiwen", "clpid": "Wang-Yiwen" }, { "family_name": "Xie", "given_name": "Xueyi", "clpid": "Xie-Xueyi" }, { "family_name": "Wang", "given_name": "Xueding", "clpid": "Wang-Xueding" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Gill", "given_name": "Kelly L.", "clpid": "Gill-Sharp-K-L" }, { "family_name": "O'Neal", "given_name": "D. Patrick", "clpid": "O'Neal-D-P" }, { "family_name": "Stoica", "given_name": "George", "orcid": "0000-0001-8071-4828", "clpid": "Stoica-G" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "This study demonstrates the feasibility of using nanoshells in vivo as a new contrast-enhancing agent for photoacoustic tomography. Deep penetrating near-infrared light was employed to image the in vivo distribution of poly(ethylene glycol)-coated nanoshells circulating in the vasculature of a rat brain. The images, captured after three sequential administrations of nanoshells, present a gradual enhancement of the optical absorption in the brain vessels by up to 63%. Subsequent clearance of the nanoshells from the blood was imaged for \u223c6 h after the administrations.", "doi": "10.1021/nl049126a", "issn": "1530-6984", "publisher": "American Chemical Society", "publication": "Nano Letters", "publication_date": "2004-09", "series_number": "9", "volume": "4", "issue": "9", "pages": "1689-1692" }, { "id": "authors:a1r6z-83746", "collection": "authors", "collection_id": "a1r6z-83746", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161207-145717339", "type": "article", "title": "Multiple-bandwidth photoacoustic tomography", "author": [ { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wang", "given_name": "Xueding", "clpid": "Wang-Xueding" }, { "family_name": "Stoica", "given_name": "George", "orcid": "0000-0001-8071-4828", "clpid": "Stoica-G" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "Photoacoustic tomography, also referred to as optoacoustic tomography, employs short laser pulses to generate ultrasonic waves in biological tissues. The reconstructed images can be characterized by the convolution of the structure of samples, the laser pulse and the impulse response of the ultrasonic transducer used for detection. Although the laser-induced ultrasonic waves cover a wide spectral range, a single transducer can receive only part of the spectrum because of its limited bandwidth. To systematically analyse this problem, we constructed a photoacoustic tomographic system that uses multiple ultrasonic transducers simultaneously, each at a different central frequency. The photoacoustic images associated with the different transducers were compared and analysed. The system was tested by imaging both mouse brains and phantom samples. The vascular vessels in the brain were revealed by all of the transducers, but the image resolutions differed. The higher frequency detectors provided better image resolution while the lower frequency detectors delineated the major structural traits with a higher signal\u2013noise ratio.", "doi": "10.1088/0031-9155/49/7/018", "issn": "0031-9155", "publisher": "IOP", "publication": "Physics in Medicine and Biology", "publication_date": "2004-04-07", "series_number": "7", "volume": "49", "issue": "7", "pages": "1329-1338" }, { "id": "authors:4fzft-hpd10", "collection": "authors", "collection_id": "4fzft-hpd10", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161207-150017901", "type": "article", "title": "Noninvasive photoacoustic angiography of animal brains in vivo with near-infrared light and an optical contrast agent", "author": [ { "family_name": "Wang", "given_name": "Xueding", "clpid": "Wang-Xueding" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wegiel", "given_name": "Malgorzata A.", "clpid": "Wegiel-M-A" }, { "family_name": "Bornhop", "given_name": "Darryl J.", "clpid": "Bornhop-D-J" }, { "family_name": "Stoica", "given_name": "George", "orcid": "0000-0001-8071-4828", "clpid": "Stoica-G" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "Optical contrast agents have been widely applied to enhance the sensitivity and specificity of optical imaging with near-infrared (NIR) light. However, because of the overwhelming scattering of light in biological tissues, the spatial resolution of traditional optical imaging degrades drastically as the imaging depth increases. Here, for the first time to our knowledge, we present noninvasive photoacoustic angiography of animal brains in vivo with NIR light and an optical contrast agent. When indocyanine green polyethylene glycol, a novel absorption dye with prolonged clearance, is injected into the circulatory system of a rat, it obviously enhances the absorption contrast between the blood vessels and the background tissues. Because NIR light can penetrate deep into the brain tissues through the skin and skull, we are able to successfully reconstruct the vascular distribution in the rat brain from the photoacoustic signals. On the basis of differential optical absorption with and without contrast enhancement, a photoacoustic angiograph of a rat brain is acquired that matches the anatomical photograph well and exhibits high spatial resolution and a much-reduced background. This new technology demonstrates the potential for dynamic and molecular biomedical imaging.", "doi": "10.1364/OL.29.000730", "issn": "0146-9592", "publisher": "Optical Society of America", "publication": "Optics Letters", "publication_date": "2004-04-01", "series_number": "7", "volume": "29", "issue": "7", "pages": "730-732" }, { "id": "authors:5nea1-rj480", "collection": "authors", "collection_id": "5nea1-rj480", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170131-110249709", "type": "article", "title": "Three-dimensional laser-induced photoacoustic tomography of mouse brain with the skin and skull intact", "author": [ { "family_name": "Wang", "given_name": "Xueding", "clpid": "Wang-Xueding" }, { "family_name": "Pang", "given_name": "Yongjiang", "clpid": "Pang-Yongjiang" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Stoica", "given_name": "George", "orcid": "0000-0001-8071-4828", "clpid": "Stoica-G" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "Three-dimensional laser-induced photoacoustic tomography, also referred to as optoacoustic tomography, is developed to image animal brain structures noninvasively with the skin and skull intact. This imaging modality combines the advantages of optical contrast and ultrasonic resolution. The distribution of optical absorption in a mouse brain is imaged successfully. The intrinsic optical contrast reveals not only blood vessels but also other detailed brain structures, such as the cerebellum, hippocampus, and ventriculi lateralis. The spatial resolution is primarily diffraction limited by the received photoacoustic waves. Imaged structures of the brain at different depths match the corresponding histological pictures well.", "doi": "10.1364/OL.28.001739", "issn": "0146-9592", "publisher": "Optical Society of America", "publication": "Optics Letters", "publication_date": "2003-10-01", "series_number": "19", "volume": "28", "issue": "19", "pages": "1739-1741" }, { "id": "authors:yycdx-xhh28", "collection": "authors", "collection_id": "yycdx-xhh28", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170201-084721718", "type": "article", "title": "Transmission- and side-detection configurations in ultrasound-modulated optical tomography of thick biological tissues", "author": [ { "family_name": "Li", "given_name": "Jun", "clpid": "Li-Jun" }, { "family_name": "Sakad\u017ei\u0107", "given_name": "Sava", "clpid": "Sakad\u017ei\u0107-S" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "Ultrasound-modulated optical tomography of thick biological tissues was studied based on speckle-contrast detection. Speckle decorrelation was investigated with biological tissue samples of various thicknesses. Images of optically absorbing objects buried in biological tissue samples with thicknesses up to 50 mm were obtained in a transmission-detection configuration. The image contrast was more than 30%, and the spatial resolution was approximately 2 mm. In addition, a side-detection scheme along with two specific configurations were examined, and the advantages were demonstrated. Experimental results implied feasibility of applying the ultrasound-modulation technique to characterize optical properties in inhomogeneous biological tissues.", "doi": "10.1364/AO.42.004088", "issn": "0003-6935", "publisher": "Optical Society of America", "publication": "Applied Optics", "publication_date": "2003-07-01", "series_number": "19", "volume": "42", "issue": "19", "pages": "4088-4094" }, { "id": "authors:ykahz-66n91", "collection": "authors", "collection_id": "ykahz-66n91", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160608-160149843", "type": "article", "title": "Noninvasive laser-induced photoacoustic tomography for structural and functional in vivo imaging of the brain", "author": [ { "family_name": "Wang", "given_name": "Xueding", "clpid": "Wang-Xueding" }, { "family_name": "Pang", "given_name": "Yongjiang", "clpid": "Pang-Yongjiang" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Xie", "given_name": "Xueyi", "clpid": "Xie-Xueyi" }, { "family_name": "Stoica", "given_name": "George", "orcid": "0000-0001-8071-4828", "clpid": "Stoica-G" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "Imaging techniques based on optical contrast analysis can be used to visualize dynamic and functional properties of the nervous system via optical signals resulting from changes in blood volume, oxygen consumption and cellular swelling associated with brain physiology and pathology. Here we report in vivo noninvasive transdermal and transcranial imaging of the structure and function of rat brains by means of laser-induced photoacoustic tomography (PAT). The advantage of PAT over pure optical imaging is that it retains intrinsic optical contrast characteristics while taking advantage of the diffraction-limited high spatial resolution of ultrasound. We accurately mapped rat brain structures, with and without lesions, and functional cerebral hemodynamic changes in cortical blood vessels around the whisker-barrel cortex in response to whisker stimulation. We also imaged hyperoxia- and hypoxia-induced cerebral hemodynamic changes. This neuroimaging modality holds promise for applications in neurophysiology, neuropathology and neurotherapy.", "doi": "10.1038/nbt839", "issn": "1087-0156", "publisher": "Nature Publishing Group", "publication": "Nature Biotechnology", "publication_date": "2003-07", "series_number": "7", "volume": "21", "issue": "7", "pages": "803-806" }, { "id": "authors:t683v-65653", "collection": "authors", "collection_id": "t683v-65653", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170203-092623874", "type": "article", "title": "Ultrasound-modulated optical tomography of biological tissue by use of contrast of laser speckles", "author": [ { "family_name": "Li", "given_name": "Jun", "clpid": "Li-Jun" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "Ultrasound-modulated optical tomography based on the measurement of laser-speckle contrast was investigated. An ultrasonic beam was focused into a biological-tissue sample to modulate the laser light passing through the ultrasonic column inside the tissue. The contrast of the speckle pattern formed by the transmitted light was found to depend on the ultrasonic modulation and could be used for imaging. Variation in the speckle contrast reflected optical inhomogeneity in the tissue. With this technique, two-dimensional images of biological-tissue samples of as much as 25 mm thick were successfully obtained with a low-power laser. The technique was experimentally compared with speckle-contrast-based, purely optical imaging and with parallel-detection imaging techniques, and the advantages over each were demonstrated.", "doi": "10.1364/AO.41.006030", "issn": "0003-6935", "publisher": "Optical Society of America", "publication": "Applied Optics", "publication_date": "2002-10-01", "series_number": "28", "volume": "41", "issue": "28", "pages": "6030-6035" }, { "id": "authors:25xe5-vjx74", "collection": "authors", "collection_id": "25xe5-vjx74", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170203-125952256", "type": "article", "title": "Microwave-induced thermoacoustic tomography: Reconstruction by synthetic aperture", "author": [ { "family_name": "Feng", "given_name": "Dazi", "clpid": "Feng-Dazi" }, { "family_name": "Xu", "given_name": "Yuan", "orcid": "0000-0001-9326-2197", "clpid": "Xu-Yuan" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "We have applied the synthetic-aperture method to linear-scanning microwave-induced thermoacoustic tomography in biological tissues. A nonfocused ultrasonic transducer was used to receive thermoacoustic signals, to which the delay-and-sum algorithm was applied for image reconstruction. We greatly improved the lateral resolution of images and acquired a clear view of the circular boundaries of buried cylindrical objects, which could not be obtained in conventional linear-scanning microwave-induced thermoacoustic tomography based on focused transducers. Two microwave sources, which had frequencies of 9 and 3 GHz, respectively, were used in the experiments for comparison. The 3 GHz system had a much larger imaging depth but a lower signal\u2013noise ratio than the 9 GHz system in near-surface imaging.", "doi": "10.1118/1.1418015", "issn": "0094-2405", "publisher": "American Association of Physicists in Medicine", "publication": "Medical Physics", "publication_date": "2001-12", "series_number": "12", "volume": "28", "issue": "12", "pages": "2427-2431" }, { "id": "authors:yje3r-wez91", "collection": "authors", "collection_id": "yje3r-wez91", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170203-111054770", "type": "article", "title": "Microwave-induced thermoacoustic tomography using multi-sector scanning", "author": [ { "family_name": "Xu", "given_name": "Minghua", "clpid": "Xu-Minghua" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "A study of microwave-induced thermoacoustic tomography of inhomogeneous tissues using multi-sector scanning is presented. A short-pulsed microwave beam is used to irradiate the tissue samples. The microwave absorption excites time-resolved acoustic waves by thermoelastic expansion. The amplitudes of the acoustic waves are strongly related to locally absorbed microwave-energy density. The acoustic waves may propagate in all spatial directions. A focused ultrasonic transducer is employed to acquire temporal acoustic signals from multiple directions. Each detected signal is converted into a one-dimensional (1D) image along the acoustic axis of the transducer. The cross-sectional images of the tissue samples are calculated by combining all of the 1D images acquired in the same planes.", "doi": "10.1118/1.1395037", "issn": "0094-2405", "publisher": "American Association of Physicists in Medicine", "publication": "Medical Physics", "publication_date": "2001-09", "series_number": "9", "volume": "28", "issue": "9", "pages": "1958-1963" }, { "id": "authors:scg7s-q0627", "collection": "authors", "collection_id": "scg7s-q0627", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170203-135907488", "type": "article", "title": "Scanning microwave-induced thermoacoustic tomography: Signal, resolution, and contrast", "author": [ { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "Scanning thermoacoustic tomography was explored in the microwave region of the electromagnetic spectrum. Short microwave pulses were used to induce acoustic waves by thermoelastic expansion in biological tissues. Cross sections of tissue samples were imaged by a linear scan of the samples while a focused ultrasonic transducer detected the time-resolved thermoacoustic signals. Based on the microwave-absorption properties of normal and cancerous breast tissues, the piezoelectric signals in response to the thermoacoustic contrast were investigated over a wide range of electromagnetic frequencies and depths of tumor locations. The axial resolution is related to the temporal profile of the microwave pulses and to the impulse response of the ultrasonic transducer. The lateral resolution is related to the numerical aperture of the ultrasonic transducer as well as to the frequency spectra of the piezoelectric signals in the time window corresponding to the axial resolution. Gain compensation, counteracting the microwave attenuation, was applied to enhance the image contrast.", "doi": "10.1118/1.1333409", "issn": "0094-2405", "publisher": "American Association of Physicists in Medicine", "publication": "Medical Physics", "publication_date": "2001-01", "series_number": "1", "volume": "28", "issue": "1", "pages": "4-10" }, { "id": "authors:2c31g-q6g49", "collection": "authors", "collection_id": "2c31g-q6g49", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170203-152231282", "type": "article", "title": "Scanning thermoacoustic tomography in biological tissue", "author": [ { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" }, { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" } ], "abstract": "Microwave-induced thermoacoustic tomography was explored to image biological tissue. Short microwave pulses irradiated tissue to generate acoustic waves by thermoelastic expansion. The microwave-induced thermoacoustic waves were detected with a focused ultrasonic transducer. Each time-domain signal from the ultrasonic transducer represented a one-dimensional image along the acoustic axis of the ultrasonic transducer similar to an ultrasonic A-scan. Scanning the system perpendicularly to the acoustic axis of the ultrasonic transducer would generate multi-dimensional images. Two-dimensional tomographic images of biological tissue were obtained with 3-GHz microwaves. The axial and lateral resolutions were characterized. The time-domain piezo-electric signal from the ultrasonic transducer in response to the thermoacoustic signal was simulated theoretically, and the theoretical result agreed with the experimental result very well.", "doi": "10.1118/1.598984", "issn": "0094-2405", "publisher": "American Association of Physicists in Medicine", "publication": "Medical Physics", "publication_date": "2000-05", "series_number": "5", "volume": "27", "issue": "5", "pages": "1195-1202" }, { "id": "authors:d32dt-94k95", "collection": "authors", "collection_id": "d32dt-94k95", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170308-133716543", "type": "article", "title": "Microwave-induced acoustic imaging of biological tissues", "author": [ { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" }, { "family_name": "Zhao", "given_name": "Xuemei", "clpid": "Zhao-Xuemei" }, { "family_name": "Sun", "given_name": "Haitao", "clpid": "Sun-Haitao" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" } ], "abstract": "We present tomographic imaging of biological tissues by use of microwave-induced acoustic signal. It was demonstrated that the acoustic signal was proportional to the intensity of the incident microwave and was related to the absorption property of microwave in the medium. Pulsed microwave radiation was used to illuminate the samples. Absorbed microwave energy caused thermoelastic expansion that radiated acoustic waves. A focused ultrasonic transducer detected the time-resolved acoustic signals. Each acoustic signal was converted into a one-dimensional image. A linear scanning of the ultrasonic transducer yielded multiple one-dimensional images, which formed a two-dimensional image. The imaging contrast is based on the difference in the dielectric constants among biological tissues. Because of the large contrast in microwave absorption among different tissue types, microwave-induced acoustic tomography could potentially provide a new modality for detecting early-stage cancers.", "doi": "10.1063/1.1149986", "issn": "0034-6748", "publisher": "American Institute of Physics", "publication": "Review of Scientific Instruments", "publication_date": "1999-09", "series_number": "9", "volume": "70", "issue": "9", "pages": "3744-3748" }, { "id": "authors:fpbb7-j5406", "collection": "authors", "collection_id": "fpbb7-j5406", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170309-090305443", "type": "article", "title": "Frequency-swept ultrasound-modulated optical tomography of scattering media", "author": [ { "family_name": "Wang", "given_name": "Lihong V.", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong-V" }, { "family_name": "Ku", "given_name": "Geng", "clpid": "Ku-Geng" } ], "abstract": "A novel frequency-swept ultrasound-modulated optical tomography technique was developed to image scattering media. A frequency-swept ultrasonic wave was used to modulate the laser light passing through a scattering medium. The modulated light was received by an optical detector and was heterodyned with a reference frequency sweep. The heterodyned signal was recorded in the time domain and was then analyzed in the frequency domain to yield a one-dimensional image along the ultrasonic axis. Multiple one-dimensional images obtained at various positions perpendicular to the ultrasonic axis were combined to yield a two-dimensional tomographic image of the medium.", "doi": "10.1364/OL.23.000975", "issn": "0146-9592", "publisher": "Optical Society of America", "publication": "Optics Letters", "publication_date": "1998-06-15", "series_number": "12", "volume": "23", "issue": "12", "pages": "975-977" } ]