The authors would like to acknowledge the engineering team at SonoVol Inc. for their technical support. This work was partially sponsored by the American Heart Association Collaborative Sciences Award (18CSA34080277), to J. Yao and W. Yang; The United States National Institutes of Health (NIH) grants R21EB027981, R21 EB027304, RF1 NS115581 (BRAIN Initiative), R01 NS111039, R01 EB028143; The United States National Science Foundation (NSF) CAREER award 2144788; the Chan Zuckerberg Initiative Grant (2020-226178), to J. Yao; and NIH grants R21NS127163 and R01NS099590 to W. Yang.

All animal procedures were approved by the Duke University Medical Center Animal Care and Use Committee and were conducted in accordance with the United States Public Health Service&#39;s Policy on Humane Care and Use of Laboratory Animals. Male and female C57BL/6J mice (see Table of Materials) were used for these studies. A minimum of three animals were imaged per stroke model group. See Figure 2 for the workflow followed in this protocol.
<p class="jove_content biglege...

Non-Invasive Integrated PAUSAT Whole-Brain Imaging of Ischemic Stroke

<ol>
	<li>Durukan, A., Tatlisumak, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acute+ischemic+stroke:+overview+of+major+experimental+rodent+models,+pathophysiology,+and+therapy+of+focal+cerebral+ischemia.">Acute ischemic stroke: overview of major experimental rodent models, pathophysiology, and therapy of focal cerebral ischemia.</a> Pharmacology Biochemistry and Behavior. 87 (1), 179-197 (2007).</li><li>Vander Worp, H. B., van Gijn, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+Practice.+Acute+ischemic+stroke.">Clinical Practice. Acute ischemic stroke.</a> The New England Journal of Medicine. 357 (6), 572-579 (2007).</li><li>Tannenbaum, J., Bennett, B. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Russell+and+Burch's+3Rs+then+and+now:+the+need+for+clarity+in+definition+and+purpose.">Russell and Burch's 3Rs then and now: the need for clarity in definition and purpose.</a> Journal of the American Association for Laboratory Animal Science. 54 (2), 120-132 (2015).</li><li>Hochrainer, K., Yang, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stroke+proteomics:+from+discovery+to+diagnostic+and+therapeutic+applications.">Stroke proteomics: from discovery to diagnostic and therapeutic applications.</a> Circulation Research. 130 (8), 1145-1166 (2022).</li><li>Wang, L. V., Yao, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+practical+guide+to+photoacoustic+tomography+in+the+life+sciences.">A practical guide to photoacoustic tomography in the life sciences.</a> Nature Methods. 13 (8), 627-638 (2016).</li><li>Aldrich, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Basic+physics+of+ultrasound+imaging.">Basic physics of ultrasound imaging.</a> Critical Care Medicine. 35 (5), S131-S137 (2007).</li><li>Jacques, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+properties+of+biological+tissues:+a+review.">Optical properties of biological tissues: a review.</a> Physics in Medicine and Biology. 58 (11), R37-R61 (2013).</li><li>Li, M., Tang, Y., Yao, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photoacoustic+tomography+of+blood+oxygenation:+a+mini+review.">Photoacoustic tomography of blood oxygenation: a mini review.</a> Photoacoustics. 10, 65-73 (2018).</li><li>Menozzi, L., Yang, W., Feng, W., Yao, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sound+out+the+impaired+perfusion:+Photoacoustic+imaging+in+preclinical+ischemic+stroke.">Sound out the impaired perfusion: Photoacoustic imaging in preclinical ischemic stroke.</a> Frontiers in Neuroscience. 16, 1055552 (2022).</li><li>Gessner, R. C., Frederick, C. B., Foster, F. S., Dayton, P. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acoustic+angiography:+a+new+imaging+modality+for+assessing+microvasculature+architecture.">Acoustic angiography: a new imaging modality for assessing microvasculature architecture.</a> International Journal of Biomedical Imaging. 2013, 936593 (2013).</li><li>Dayton, P. A., Rychak, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+ultrasound+imaging+using+microbubble+contrast+agents.">Molecular ultrasound imaging using microbubble contrast agents.</a> Frontiers in Bioscience. 12, 5124-5142 (2007).</li><li>Isayama, K., Pitts, L. H., Nishimura, M. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+2,+3,+5-triphenyitetrazolium+chloride+staining+to+delineate+rat+brain+infarcts.">Evaluation of 2, 3, 5-triphenyitetrazolium chloride staining to delineate rat brain infarcts.</a> Stroke. 22 (11), 1394-1398 (1991).</li><li>Ruan, J., Yao, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Behavioral+tests+in+rodent+models+of+stroke.">Behavioral tests in rodent models of stroke.</a> Brain Hemorrhages. 1 (4), 171-184 (2020).</li><li>Parthasarathy, A. B., Kazmi, S. M. S., Dunn, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+imaging+of+ischemic+stroke+through+thinned+skull+in+mice+with+Multi+Exposure+Speckle+Imaging.">Quantitative imaging of ischemic stroke through thinned skull in mice with Multi Exposure Speckle Imaging.</a> Biomedical Optics Express. 1 (1), 246-259 (2010).</li><li>Hingot, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Early+ultrafast+ultrasound+imaging+of+cerebral+perfusion+correlates+with+ischemic+stroke+outcomes+and+responses+to+treatment+in+mice.">Early ultrafast ultrasound imaging of cerebral perfusion correlates with ischemic stroke outcomes and responses to treatment in mice.</a> Theranostics. 10 (17), 7480-7491 (2020).</li><li>Menozzi, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+non-invasive+brain+imaging+of+ischemic+stroke+by+integrated+photoacoustic,+ultrasound+and+angiographic+tomography+(PAUSAT).">Three-dimensional non-invasive brain imaging of ischemic stroke by integrated photoacoustic, ultrasound and angiographic tomography (PAUSAT).</a> Photoacoustics. 29, 100444 (2022).</li><li>Llovera, G., Roth, S., Plesnila, N., Veltkamp, R., Liesz, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modeling+stroke+in+mice:+permanent+coagulation+of+the+distal+middle+cerebral+artery.">Modeling stroke in mice: permanent coagulation of the distal middle cerebral artery.</a> Journal of Visualized Experiments. (89), e51729 (2014).</li><li>Trotman-Lucas, M., Kelly, M. E., Janus, J., Fern, R., Gibson, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+alternative+surgical+approach+reduces+variability+following+filament+induction+of+experimental+stroke+in+mice.">An alternative surgical approach reduces variability following filament induction of experimental stroke in mice.</a> Disease Models &amp; Mechanisms. 10 (7), 931-938 (2017).</li><li>Labat-Gest, V., Tomasi, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photothrombotic+ischemia:+a+minimally+invasive+and+reproducible+photochemical+cortical+lesion+model+for+mouse+stroke+studies.">Photothrombotic ischemia: a minimally invasive and reproducible photochemical cortical lesion model for mouse stroke studies.</a> Journal of Visualized Experiments. (76), e50370 (2013).</li><li>Matsumoto, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualising+peripheral+arterioles+and+venules+through+high-resolution+and+large-area+photoacoustic+imaging.">Visualising peripheral arterioles and venules through high-resolution and large-area photoacoustic imaging.</a> Scientific Reports. 8 (1), 14930 (2018).</li><li>Xu, Y., Wang, L. V., Ambartsoumian, G., Kuchment, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reconstructions+in+limited-view+thermoacoustic+tomography.">Reconstructions in limited-view thermoacoustic tomography.</a> Medical Physics. 31 (4), 724-733 (2004).</li><li>Yal Tang, ., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-fidelity+deep+functional+photoacoustic+tomography+enhanced+by+virtual+point+sources.">High-fidelity deep functional photoacoustic tomography enhanced by virtual point sources.</a> Photoacoustics. 29, 100450 (2023).</li><li>Zheng, W., Huang, C., Zhang, H., Xia, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Slit-based+photoacoustic+tomography+with+co-planar+light+illumination+and+acoustic+detection+for+high-resolution+vascular+imaging+in+human+using+a+linear+transducer+array.">Slit-based photoacoustic tomography with co-planar light illumination and acoustic detection for high-resolution vascular imaging in human using a linear transducer array.</a> Biomedical Engineering Letters. 12 (2), 125-133 (2022).</li><li>Wang, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Slit-enabled+linear-array+photoacoustic+tomography+with+near+isotropic+spatial+resolution+in+three+dimensions.">Slit-enabled linear-array photoacoustic tomography with near isotropic spatial resolution in three dimensions.</a> Optics Letters. 41 (1), 127-130 (2016).</li><li>Vu, T., Li, M., Humayun, H., Zhou, Y., Yao, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+generative+adversarial+network+for+artifact+removal+in+photoacoustic+computed+tomography+with+a+linear-array+transducer.">A generative adversarial network for artifact removal in photoacoustic computed tomography with a linear-array transducer.</a> Experimental Biology and Medicine. 245 (7), 597-605 (2020).</li><li>Zhang, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deep-E:+A+fully-dense+neural+network+for+improving+the+elevation+resolution+in+linear-array-based+photoacoustic+tomography.">Deep-E: A fully-dense neural network for improving the elevation resolution in linear-array-based photoacoustic tomography.</a> IEEE Transactions on Medical Imaging. 41 (5), 1279-1288 (2022).</li><li>Hauptmann, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Model-based+learning+for+accelerated,+limited-view+3-D+photoacoustic+tomography.">Model-based learning for accelerated, limited-view 3-D photoacoustic tomography.</a> IEEE Transactions on Medical Imaging. 37 (6), 1382-1393 (2018).</li><li>Li, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+deep-tissue+functional+and+molecular+imaging+by+integrated+photoacoustic,+ultrasound,+and+angiographic+tomography+(PAUSAT).">Three-dimensional deep-tissue functional and molecular imaging by integrated photoacoustic, ultrasound, and angiographic tomography (PAUSAT).</a> IEEE Transactions on Medical Imaging. 41 (10), 2704-2714 (2022).</li></ol>

There are a few vital aspects of this method that, if done incorrectly, can lead to significantly decreased image quality and quantitative analysis. The most commonly occurring result of user-error in PAUSAT images is either a lack of signal or very low signal strength, both of which can occur for a variety of reasons. One such reason is a problem with the acoustic coupling. Large air bubbles in the water surrounding the mouse&#39;s head during imaging can often block the ultrasound from travelling to or from the transdu...

Blood transports oxygen (via the hemoglobin protein) and other important nutrients to tissues in our bodies. When the flow of blood through tissues is interrupted (ischemia), severe damage to the tissues can occur, the most immediate effects of which are due to a lack of oxygen (hypoxia). Ischemic stroke is the result of interrupted blood flow to a certain region of the brain. The brain damage resulting from an ischemic stroke can occur within minutes of a vessel blockage, and can often have debilitating and lasting effects1,2. A highly valuable strategy to evaluate the physiopathology after ischemic stroke and identify and test new treatments is the use of small-animal models in the lab. Treatments discovered in the lab aim to be translated to clinical use and improve patients&#39; lives. However, the use of animals in biomedical research needs to be carefully evaluated according to Russell and Burch&#8217;s 3Rs principles: replacement, reduction, and refinement3. The objective of the reduction component is to reduce the number of animals without compromising data collection. With this in mind, being able to longitudinally evaluate the lesion evolution via noninvasive imaging allows a great advantage in reducing the number of animals required, as well as maximizing the information obtained from each animal4.
Photoacoustic tomography (PAT) is a hybrid imaging modality that combines optical absorption contrast with ultrasound imaging spatial resolution5. The imaging mechanism of PAT is as follows. An excitation laser pulse is illuminated on the target being imaged. Assuming the target absorbs light at the wavelength of the excitation laser, it will increase in temperature. This quick increase in temperature results in a thermoelastic expansion of the target. The expansion causes an ultrasound wave to propagate out from the target. By detecting the ultrasound wave at many positions, the time required for the wave to propagate from the target to the detectors can be used to create an image through a reconstruction algorithm. The ability of PAT to detect optical absorption in deep tissue regions differentiates PAT from ultrasound imaging, which detects boundaries of differing acoustic impedances of tissues5. In the visible and near-infrared spectra, the primary highly absorbing biomolecules that are abundant in organisms are hemoglobin, lipids, melanin, and water7. Of particular interest in the study of stroke is hemoglobin. Since oxyhemoglobin and deoxyhemoglobin have different optical absorption spectra, PAT can be used with multiple excitation laser wavelengths to determine the relative concentration of the two states of the protein. This allows the oxygen saturation of hemoglobin (sO2), or blood oxygenation, to be quantified in and outside of the infarct region8,9. This is an important measure in ischemic stroke, as it can indicate the level of oxygen in the damaged brain tissue following ischemia.
Acoustic angiography (AA) is a contrast-enhanced ultrasound imaging method that is particularly useful for imaging the morphology of vasculature in vivo10. The method relies on the use of a dual-element wobbler transducer (a low frequency element and a high frequency element) in conjunction with microbubbles injected into the circulatory system of the imaging subject. The low-frequency element of the transducer is used for transmitting at the resonant frequency of the microbubbles (e.g., 2 MHz), while the high-frequency element is used to receive the super harmonic signals of the microbubbles (e.g., 26&#160;MHz). When excited at a resonant frequency, the microbubbles have a strong nonlinear response, resulting in the production of super harmonic signals that surrounding body tissues do not produce11. By receiving with a high-frequency element, this ensures that only the microbubble signals are detected. Since the microbubbles are confined to the blood vessels, the result is an angiographic image of blood vessel morphology. AA is a powerful method for imaging ischemic stroke, as the microbubbles that flow through the circulatory system are not be able to flow through blocked vessels. This allows AA to detect regions of the brain that are not perfused due to ischemic stroke, which indicates the infarct region.
Preclinical ischemic stroke research generally relies on the use of histology and behavioral testing to assess the location and severity of the stroke. Triphenyltetrazolium chloride (TTC) staining is a common histological analysis used to determine the stroke infarct volume. However, it can only be used at an endpoint, since it requires the animal to be euthanized12. Behavioral tests can be used to determine motor function impairment at multiple time points, but they cannot provide quantitative anatomical or physiological values13. Biomedical imaging provides a more quantitative approach to studying the effects of ischemic stroke noninvasively and longitudinally9,14,15. However, existing imaging technologies (such as small-animal magnetic resonance imaging [MRI]) can come at a high cost, be unable to provide concurrent structural and functional information, or have limited penetration depth (as most optical imaging techniques).
Here, we combine photoacoustic, ultrasound, and angiographic tomography (PAUSAT; see system diagram in Figure 1), which allows for complementary structural and functional information of blood perfusion and oxygenation following ischemic stroke16. These are two important aspects in assessing the severity of injury and monitoring the recovery or response to treatments. Using these integrated imaging methods can increase the amount of information obtained by each animal, reducing the number of animals required and providing more information in the study of potential treatments for ischemic stroke.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/65319/65319fig01.jpg" /> 
Figure 1: PAUSAT diagram. (A) Complete schematic of the PAUSAT system, including the laser and OPO used for PAT. (B) Inside view of the PAUSAT system, including two ultrasound transducers. The dual-element wobbler transducer is used for both B-mode ultrasound and AA, and the linear-array transducer is used for PAT. Both transducers are mounted on the same 2D motorized stage, allowing for scanning to generate volumetric data. This figure has been modified from16. <a href="https://www.jove.com/files/ftp_upload/65319/65319fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>20 GA catheter</td>
			<td>BD Insyte Autoguard Winged</td>
			<td>381534</td>
			<td>For mouse intubation</td>
		</tr>
		<tr>
			<td>2,3,5-Triphenyltetrazolium chloride</td>
			<td>Sigma</td>
			<td>T8877</td>
			<td>Necessary for TTC-staining brain for validation</td>
		</tr>
		<tr>
			<td>532nm Laser</td>
			<td>Quantel</td>
			<td>Q-smart 850</td>
			<td>Laser used to pump the OPO for PAT</td>
		</tr>
		<tr>
			<td>Automatic Ventilator Rovent Jr.</td>
			<td>Kent Scientific</td>
			<td>RV-JR</td>
			<td>To keep mice under anesthesia during surgical procedure</td>
		</tr>
		<tr>
			<td>Black braided silk 4-0 USP</td>
			<td>Surgical Specialties</td>
			<td>SP116</td>
			<td>Used for sutures on the neck for pMCAO surgery</td>
		</tr>
		<tr>
			<td>Bupivacaine</td>
			<td>Hospira</td>
			<td>0409-1159-18</td>
			<td>Used prior to closing wounds during surgical procedure</td>
		</tr>
		<tr>
			<td>C57BL/6 Mice</td>
			<td>Jackson Lab</td>
			<td>#000664</td>
			<td>Mice used for studying ischemic stroke (2-6 month old male/female)</td>
		</tr>
		<tr>
			<td>Clear suture</td>
			<td>Ethicon</td>
			<td>8606</td>
			<td>Used for closing wound (PT stroke and pMCAO). A clear suture won&#39;t interfere with PAT</td>
		</tr>
		<tr>
			<td>Cold Light LED</td>
			<td>Schott</td>
			<td>KL 1600</td>
			<td>Needed to create PT stroke</td>
		</tr>
		<tr>
			<td>Disposable Razor Blade</td>
			<td>Accutec Blades</td>
			<td>74-0002</td>
			<td>For sectioning mouse brain</td>
		</tr>
		<tr>
			<td>Electric drill</td>
			<td>JSDA</td>
			<td>JD-700</td>
			<td>Used to expose MCA during pMCAO procedure</td>
		</tr>
		<tr>
			<td>Electrocauterization tool</td>
			<td>Wet-Field</td>
			<td>Wet-Field Bipolar-RG</td>
			<td>Stops blood flow after drilling during pMCAO procedure</td>
		</tr>
		<tr>
			<td>Hair removal gel</td>
			<td>Veet</td>
			<td>8282651</td>
			<td>Used to remove hair from mouse prior to imaging</td>
		</tr>
		<tr>
			<td>High Temperature Cautery Loop Tip</td>
			<td>BOVIE Medical Corporation</td>
			<td>REF AA03</td>
			<td>Used to avoid bleeding when separating the temporal muscle from the skull</td>
		</tr>
		<tr>
			<td>IR Detector Card</td>
			<td>Thorlabs</td>
			<td>VRC5</td>
			<td>Used to ensure light path is aligned</td>
		</tr>
		<tr>
			<td>Laser Power Meter</td>
			<td>Ophir</td>
			<td>StarBright, P/N 7Z01580</td>
			<td>Can be used to calibrate the laser energy prior to imaging</td>
		</tr>
		<tr>
			<td>Laser Speckle Imaging System</td>
			<td>RWD Life Science Co.</td>
			<td>RFLSI-III</td>
			<td>Can be used to validate stroke surgery success</td>
		</tr>
		<tr>
			<td>Lubricant Eye Ointment</td>
			<td>Soothe</td>
			<td>AB31336</td>
			<td>Can be used to avoid drying of the eyes</td>
		</tr>
		<tr>
			<td>Manually adjustable stage</td>
			<td>Thorlabs</td>
			<td>L490</td>
			<td>Used with custom ramp for multiple focal depth AA imaging</td>
		</tr>
		<tr>
			<td>Modified Vega Imaging System</td>
			<td>Perkin Elmer</td>
			<td>LLA00061</td>
			<td>System containing both B-mode/AA and PAT transducers</td>
		</tr>
		<tr>
			<td>Optical Parametric Oscillator</td>
			<td>Quantel</td>
			<td>versaScan-L532</td>
			<td>Allows for tuning of excitation wavelength in a large range</td>
		</tr>
		<tr>
			<td>Programmable Ultrasound System</td>
			<td>Verasonics</td>
			<td>Vantage 256</td>
			<td>Used for PAT part of system</td>
		</tr>
		<tr>
			<td>Rose Bengal</td>
			<td>Sigma</td>
			<td>330000</td>
			<td>Necessary to induce PT stroke</td>
		</tr>
		<tr>
			<td>Suture</td>
			<td>LOOK</td>
			<td>SP116</td>
			<td>Used for permanent ligation of CCA</td>
		</tr>
		<tr>
			<td>Temperature Contoller</td>
			<td>Physitemp</td>
			<td>TCAT-2</td>
			<td>Used to maintain stable body temperature of mice during procedures</td>
		</tr>
		<tr>
			<td>VesselVue Microbubbles</td>
			<td>Perkin Elmer</td>
			<td>P-4007001</td>
			<td>Used for acoustic angiography (2.43 &#215; 10^9 microbubbles/mL)</td>
		</tr>
	</tbody>
</table>

integrated photoacoustic, ultrasound, and angiographic tomography (pausat) for noninvasive whole-brain imaging of ischemic stroke

Presented here is an experimental ischemic stroke study using our newly developed noninvasive imaging system that integrates three acoustic-based imaging technologies: photoacoustic, ultrasound, and angiographic tomography (PAUSAT). Combining these three modalities helps acquire multi-spectral photoacoustic tomography (PAT) of the brain blood oxygenation, high-frequency ultrasound imaging of the brain tissue, and acoustic angiography of the cerebral blood perfusion. The multi-modal imaging platform allows the study of cerebral perfusion and oxygenation changes in the whole mouse brain after stroke. Two commonly used ischemic stroke models were evaluated: the permanent middle cerebral artery occlusion (pMCAO) model and the photothrombotic (PT) model. PAUSAT was used to image the same mouse brains before and after a stroke and quantitatively analyze both stroke models. This imaging system was able to clearly show the brain vascular changes after ischemic stroke, including significantly reduced blood perfusion and oxygenation in the stroke infarct region (ipsilateral) compared to the uninjured tissue (contralateral). The results were confirmed by both laser speckle contrast imaging and triphenyltetrazolium chloride (TTC) staining. Furthermore, stroke infarct volume in both stroke models was measured and validated by TTC staining as the ground truth. Through this study, we have demonstrated that PAUSAT can be a powerful tool in noninvasive and longitudinal preclinical studies of ischemic stroke.

Author Spotlight: Integrated Photoacoustic, Ultrasound, and Angiographic Tomography (PAUSAT) for NonInvasive Whole-Brain Imaging of Ischemic Stroke  

Integrated Photoacoustic, Ultrasound, and Angiographic Tomography (PAUSAT) for NonInvasive Whole-Brain Imaging of Ischemic Stroke

There are a few experimental challenges. For example, the presence of hair in the scalp can cause artifact in the acquired images. The age of the animal also plays a key role since the thickness of the skull is currently a limitation for the detection of deeper signals.Many purely optical imaging techniques require an invasive procedure and can only image about one millimeter deep. With PAUSAT, we combine the advantages of both ultrasound and optical imaging. We can get both structural and functional information surrounding ischemic stroke in a completely safe and non-invasive way.Being able to evaluate the evolution of an injury with or without treatment from the same animal at different time points allows us to collect very valuable information. And also to reduce the number of animals required for different studies. We are constantly working on ways to improve the imaging speed, depth, resolution and contrast for both photoacoustic and ultrasound imaging.With better imaging systems, we can answer more fundamental biological questions and evaluate new experimental treatments.

Imaging of blood vessel morphology in the brain 
AA generates blood vessel morphology images by exciting microbubbles in the circulatory system at their resonant frequency and receiving the super harmonic response of the microbubbles. By using the customized ramp (Figure 2C) attached to a manually adjustable stage, we can image the mouse brain with AA mode at two different focal depths. When deeper regions are targeted, more superficial regions (such as the cerebral cor...

Watch this Scientific Journal Video about Integrated Photoacoustic, Ultrasound, and Angiographic Tomography PAUSAT for NonInvasive Whole-Brain Imaging of Ischemic Stroke at JoVE.com

This work demonstrates the use of a multimodal ultrasound-based imaging platform for noninvasive imaging of ischemic stroke. This system allows for the quantification of blood oxygenation through photoacoustic imaging and impaired perfusion in the brain through acoustic angiography.

Presented here is an experimental ischemic stroke study using our newly developed noninvasive imaging system that integrates three acoustic-based imaging ...

integrated-photoacoustic-ultrasound-angiographic-tomography-pausat

Research

JoVE Journal

Neuroscience

948 ビュー.  Duke University. いくつかの実験的な課題があります。例えば、頭皮に毛が存在すると、取得した画像にアーチファクトが生じる可能性があります。頭蓋骨の厚さは現在、より深い信号の検出の制限であるため、動物の年齢も重要な役割を果たします。多くの純粋な光学イメージング技術は侵襲的な手順を必要とし、約1ミリメートルの深さしかイメージングできません。PAUSATでは、...

ビデオ: 著者スポットライト:虚血性脳卒中の非侵襲的全脳イメージングのための統合光音響、超音波、血管造影断層撮影法(PAUSAT)  

This work demonstrates the use of a multimodal ultrasound-based imaging platform for noninvasive imaging of ischemic stroke. This system allows for the quantification of blood oxygenation through photoacoustic imaging and impaired perfusion in the brain through acoustic...

integrated photoacoustic ophthalmoscopy and spectral-domain optical coherence tomography

Integrated Photoacoustic Ophthalmoscopy and Spectral-domain Optical Coherence Tomography

Photoacoustic ophthalmology (PAOM), an optical-absorption-based imaging modality, provides the complementary evaluation of the retina to the currently available ophthalmic imaging technologies. We report the using of PAOM integrated with spectral-domain optical coherence tomography (SD-OCT) for simultaneous multimodal retinal imaging in...

non-invasive parenchymal, vascular and metabolic high-frequency ultrasound and photoacoustic rat deep brain imaging

Non-invasive Parenchymal, Vascular and Metabolic High-frequency Ultrasound and Photoacoustic Rat Deep Brain Imaging

The present work describes a new protocol to perform non-invasive high-frequency ultrasound and photoacoustic based imaging on rat brain, to efficiently visualize deep subcortical regions and their vascular patterns by directing signals on skull foramina naturally present on animal...

a high-performance compact photoacoustic tomography system for in vivo small-animal brain imaging

A High-performance Compact Photoacoustic Tomography System for In Vivo Small-animal Brain Imaging

A compact pulsed-laser diode-based photoacoustic tomography (PLD-PAT) system for high-speed in vivo brain imaging in small animals is...

A High-performance Compact Photoacoustic Tomography System for In Vivo Small-animal Brain Imaging

a coregistered ultrasound and photoacoustic imaging protocol for the transvaginal imaging of ovarian lesions

A Coregistered Ultrasound and Photoacoustic Imaging Protocol for the Transvaginal Imaging of Ovarian Lesions

We report a coregistered ultrasound and photoacoustic imaging protocol for the transvaginal imaging of ovarian/adnexal lesions. The protocol may be valuable to other translational photoacoustic imaging studies, especially those using commercial ultrasound arrays for the detection of photoacoustic signals and standard delay-and-sum beamforming algorithms for imaging.

optimized management of endovascular treatment for acute ischemic stroke

Optimized Management of Endovascular Treatment for Acute Ischemic Stroke

The outcome of patients with acute ischemic stroke depends on swift restoration of cerebral blood flow. This protocol aims at optimizing the management of such patients by minimizing peri-procedural timings and rendering the time from hospital admission to reperfusion as short as...

novel photoacoustic microscopy and optical coherence tomography dual-modality chorioretinal imaging in living rabbit eyes

Novel Photoacoustic Microscopy and Optical Coherence Tomography Dual-modality Chorioretinal Imaging in Living Rabbit Eyes

This manuscript describes the novel setup and operating procedure of a photoacoustic microscopy and optical coherence tomography dual-modality system for noninvasive, label-free chorioretinal imaging of larger animals, such as...

induction of acute ischemic stroke in mice using the distal middle artery occlusion technique

Author Spotlight: Establishing a Reliable Distal MCA Occlusion Model in Mice for Stroke Research

Here, we present a protocol to establish a distal middle cerebral artery occlusion (dMCAO) model through transcranial electrocoagulation in C57BL/6J mice and evaluate the subsequent neurological behavior and histopathological...

Occlusion of Distal Middle Artery to Develop an Ischemic Stroke Mouse Model

https://cloudfront.jove.com/CDNSource/teasers/66134_b.jpg

a rat model of middle cerebral artery occlusion/reperfusion without damaging the anatomical structure of cerebral vessels

Author Spotlight: Development of a Rat Model for Ischemic Stroke with Preserved Cerebral Vascular Integrity Using Microsurgical Techniques

The current protocol describes a rat model of middle cerebral artery occlusion/reperfusion that preserves the anatomical structure of cerebral vessels without causing...

Middle Cerebral Artery Occlusion in Rats with Preserved Vascular Anatomy

https://cloudfront.jove.com/CDNSource/teasers/66635_b.jpg

whole-brain 3d activation and functional connectivity mapping in mice using transcranial functional ultrasound imaging

Whole-Brain 3D Activation and Functional Connectivity Mapping in Mice using Transcranial Functional Ultrasound Imaging

This protocol describes the quantification of volumetric cerebral hemodynamic variations in the mouse brain using functional ultrasound (fUS). Procedures for 3D functional activation map following sensory stimulation as well as resting-state functional connectivity are provided as illustrative examples, in anesthetized and awake...

transient middle cerebral artery occlusion model of stroke

Author Spotlight: Assessing Ischemic Stroke Damage Through Middle Cerebral Artery Occlusion Model 

This protocol describes the model of transient focal cerebral ischemia in mice through intraluminal occlusion of the middle cerebral artery. Additionally, examples of outcome assessment are shown using magnetic resonance imaging and behavioral...

A Model of Transient Cerebral Ischemia by Occlusion of Middle Cerebral Artery

https://cloudfront.jove.com/CDNSource/teasers/65857_b.jpg

pet imaging of neuroinflammation using [11c]dpa-713 in a mouse model of ischemic stroke

PET Imaging of Neuroinflammation Using [11C]DPA-713 in a Mouse Model of Ischemic Stroke

Positron Emission Tomography (PET) imaging of translocator protein 18 kDa (TSPO) provides a non-invasive means to visualize the dynamic role of neuroinflammation in the development and progression of brain diseases. This protocol describes TSPO-PET and ex vivo autoradiography to detect neuroinflammation in a mouse model of ischemic...

PET Imaging of Neuroinflammation Using [11C]DPA-713 in a Mouse Model of Ischemic Stroke

osmotic drug delivery to ischemic hindlimbs and perfusion of vasculature with microfil for micro-computed tomography imaging

Osmotic Drug Delivery to Ischemic Hindlimbs and Perfusion of Vasculature with Microfil for Micro-Computed Tomography Imaging

We show here the in vivo insertion of an osmotic pump for constant local drug delivery and the creation of hindlimb ischemia in a mouse model. Moreover, the hindlimb vasculature is perfused with Microfil, a silicone radiopaque agent, to prepare for micro-computed tomography (micro-CT)...

an in vivo assessment of blood-brain barrier disruption in a rat model of ischemic stroke

An In Vivo Assessment of Blood-Brain Barrier Disruption in a Rat Model of Ischemic Stroke

The overall goal of this procedure is to provide a highly reproducible technique for in vivo assessment of the blood-brain barrier disruption in rat models of ischemic...

An In Vivo Assessment of Blood-Brain Barrier Disruption in a Rat Model of Ischemic Stroke

serial two-photon tomography of the whole marmoset brain for neuroanatomical analyses

Author Spotlight: Mapping Primate Brain Connectivity 

Serial two-photon tomography (STPT) imaging is a technique to image a mass of tissue in its three-dimensional shape by combining two-photon imaging with automatic stage control and microtome slicing. Here we describe a protocol for implementing it for marmoset brains to better understand their structural features.

Volumetric Imaging and Axonal Projection Mapping in the Marmoset Brain

https://cloudfront.jove.com/CDNSource/teasers/67694_b.jpg

Serial Two-Photon Tomography of the Whole Marmoset Brain for Neuroanatomical Analyses

pulsed laser diode-based desktop photoacoustic tomography for monitoring wash-in and wash-out of dye in rat cortical vasculature

Pulsed Laser Diode-Based Desktop Photoacoustic Tomography for Monitoring Wash-In and Wash-Out of Dye in Rat Cortical Vasculature

A compact pulsed laser diode-based desktop photoacoustic tomography (PLD-PAT) system is demonstrated for high-speed dynamic in vivo imaging of small animal cortical...

pipeline for planning and execution of transcranial ultrasound neuromodulation experiments in humans

Author Spotlight: Advancing Human Brain Modulation &amp;#8211; Optimized Protocols for Transcranial Ultrasound Stimulation Experiments

Transcranial ultrasound stimulation (TUS) is an emerging non-invasive neuromodulation technique that requires careful planning of acoustic and thermal simulations. The methodology describes an image processing and ultrasound simulation pipeline for efficient, user-friendly, streamlined planning for human TUS...

High-Precision TUS: Planning and Execution with Acoustic and Thermal Simulations

https://cloudfront.jove.com/CDNSource/teasers/66972_b.jpg

whole animal imaging of drosophila melanogaster using microcomputed tomography

Whole Animal Imaging of Drosophila melanogaster using Microcomputed Tomography

A protocol is presented that allows for the visualization of intact Drosophila melanogaster at any stage of development using microcomputed...

Whole Animal Imaging of Drosophila melanogaster using Microcomputed Tomography

Murine PAUSAT Imaging

To set up the imaging system, start by leaving the 532 nanometer laser on for 15 minutes to warm up. Next, place a customized ramp attached to a manually adjustable stage next to the imaging membrane. Attach a mouse tooth holder with a connected breathing tube to the ramp, and secure a heating pad on the ramp surface.Once the laser has warmed up, place a near IR detector card in front of the fiber bundle input and check the laser alignment by ensuring that the laser light enters the bundle. Begin animal preparation by trimming the hair of the anesthetized mouse's head with an electric shaver from near the eyes to behind the ears. Apply a hair removal cream to the top of the head.After leaving it on for five minutes, wipe the cream off with a wet cotton swab. Repeat the application until the skin of the head is fully depilated. Just before transferring the animal to the system's platform, use a 27 gauge needle to retro-orbitally inject 100 microliters of microbubbles at stock concentration.Now, put one drop of the eye protection lotion on the eyes. Begin PAUSAT imaging by filling the imaging window with distilled water on the surface for acoustic coupling. Next, secure the mouse's head in the tooth holder and ensure proper anesthesia and air flow.Using a heating lamp and a rectal probe connected to a temperature controller, keep the animal's body temperature at 37 degrees Celsius. Open the imaging application and navigate to the B mode ultrasound. Use the live ultrasound window to adjust the mouse's head to the desired position manually and the stage height accordingly.Adjust the value of the ultrasound transmission frequency in B mode to 16 megahertz. Then, input the save directory information in the imaging application. Next, select the desired region of the brain scan by using the floating box.Press the acquire static button and check the scan results once the image acquisition is completed to ensure the desired region imaging. To perform acoustic angiography imaging, return to Image Acquisition, then change the mode to Acoustic Angiography. Next, input the desired scan protocol parameters, setting the frame spacing at 0.2 millimeters and 10 frames per position.Check scan results under image analysis to ensure image quality. To image with photoacoustic tomography, open the optical parametric oscillator, or OPO application, and set it to 756 nanometers. Then, manually translate the linear array transducer to the previously determined coordinates to automatically co-register the wobbler volumes and the linear array volumes.Open the laser application and turn on the 532 nanometer laser. Set the scanning parameters as 0.4 millimeters step size, 20 millimeters scan length, and 10 frames averaged per position. Now, open the ultrasound data acquisition system MATLAB program, and press the run button.Next, press start in the scanning application. Once the scan is complete, open the MATLAB saving program. Change the save name to the desired file name and press Run.Then change the OPO wavelength to 798 nanometers and repeat scanning. Acoustic angiographic, or AA imaging, showed that in the uninjured brain, both hemispheres present a similar distribution of blood vessels. Similar results are observed in the photoacoustic images at two different wavelengths.Notable signal reduction in the right lateral cortex was observed in the AA images of electrocauterized mice. The same region also showed reduced tissue oxygenation suggesting ischemia. PAUSAT imaging can identify stroke areas based on the photo thrombotic stroke model by identifying upper cortex region with reduced blood flow supply and decreased oxygen saturation.Mouse age can affect imaging since the skull becomes thicker and results in different acoustic impedance resulting in decreased imaging depth for older mice.