This work was supported by the National Institutes of Health (R01-EB014496). The authors would like to thank Iason Apostolakis for his contribution to the experiments.

This protocol was approved by the Institutional Animal Care and Use Committee of Columbia University. All the data acquisition and processing were performed using the Matlab environment.
1. Experimental Set-up
<ol>
	<li>Degas an ex vivo canine liver sample during 90 min. Put the liver sample in a tank filled with degassed Phosphate Buffered Solution (Figure 1). Fix the liver sample on an acoustic absorber with needles at the extremities of the liver.</li>
	<li>Insert a 64-element, 0.32 mm pitch, 2.5 MHz center frequency phased array (imaging) through a circular hole located in the center of a 93-element hemispherical array HIFU transducer (therapeutic) at 4.5 MHz center frequency, 70 mm focal depth and 1.7 mm x 0.4 mm focal size11. Align both transducers co-axially and fix the imaging transducer into the therapeutic transducer with adjustment screws.
	<ol>
		<li>Cover the HIFU transducer with a volume-controlled polyurethane membrane filled with flowing degassed water to cool it down. Mount the transducer assembly on a computer-controlled 3-D positioner.</li>
	</ol>
	</li>
	<li>Connect the HIFU transducer to a function generator sending a 25 Hz amplitude modulated sine waveform with 500 mV maximum amplitude. Connect the imaging transducer to a fully programmable ultrasound system using the software Matlab. 
	Note: A software associated with the ultrasound system and using the Matlab environment has to be installed on the computer connected to the system. A 50 dB RF amplifier and a matching network should be placed between the HIFU transducer and the function generator to respectively amplify the power and match the impedance.</li>
	<li>Create a polar grid, using Matlab, starting 50 mm from the surface of the array and 40 mm deep in the radial direction with a spatial step of 9.625 &#181;m and of 90&#176; in the azimuthal direction with 128 lines and which origin is the focus of the diverging wave. Define the source of the diverging wave 10.24 mm (half the size of the aperture) behind the surface of the array and centered in the lateral direction.
	<ol>
		<li>Create a Cartesian grid, using Matlab, starting 50 mm from the surface of the array and 40 mm deep in the axial direction with a spatial step of 9.625 &#181;m and 20 mm wide in the lateral direction with 64 lines for the plane wave. Define the source of the plane wave on the surface of the array. For each grid, compute the time from the source to each point of the grid and back to each element of the array.</li>
	</ol>
	</li>
	<li>Enter &#8220;ReconMat_DW&#8221; for diverging wave imaging or &#8220;ReconMat_PW&#8221; for plane wave imaging in the Matlab command window and press &#8220;Enter&#8221; to create a reconstruction matrix associated with a standard delay-and-sum algorithm for each grid. Apply the delay-and-sum algorithm to each vector of the standard basis and retrieve the non-zeros elements of the resulting matrix11. Allocate the non-zero elements obtained from the resulting matrix to the sparse matrix at the corresponding location. Save the reconstruction matrix on the computer hard drive. 
	Note: The diverging and the plane wave methods use two distinct reconstruction matrices.
	<ol>
		<li>Cast the reconstruction matrix to a GPU matrix. Enter &#8220;SetUpP4_2Flash_4B_streaming_DW&#8221; for diverging wave imaging or &#8220;SetUpP4_2Flash_4B_streaming_PW&#8221; for plane wave imaging in the Matlab command window and press &#8220;Enter&#8221; to create a setup file for the ultrasound channel data acquisition using the script associated with the phased array and provided by the manufacturer of the ultrasound system. Name the setup file &#8220;P4-2Flash_DivergingWave.mat&#8221; for diverging wave imaging and &#8220;P4-2Flash_PlaneWave.mat&#8221; for plane wave imaging. 
		&#160;Note: A commercial software package has to be installed on the computer to cast the reconstruction sparse matrix to a GPU matrix.</li>
	</ol>
	</li>
	<li>Synchronize the ultrasound system with the function generator using an external trigger so that high frame rate ultrasound data acquisition of the liver starts at the same time as HIFU.</li>
	<li>Open Matlab. Run the setup script &#8220;SetUpP4_2Flash_4B.m&#8221; provided by the ultrasound system manufacturer to use B-mode imaging. Name the created setup file: &#8220;P4-2Flash_4B_Bmode.mat&#8221;. Use the &#8220;VSX&#8221; command and when &#8220;Name of .mat file to process:&#8221; is prompted, enter the name of the setup file &#8220;P4-2Flash_4B_Bmode.mat&#8221;. Move both transducers and use the B-mode display that appeared on the computer screen to position them in the targeted region of the liver to ablate. Target a region approximately 1 cm under the surface of the liver to avoid high ultrasound attenuation due to absorption. Save a conventional B-mode image of the liver on the computer. 
	Note: Here we performed HIFU ablations at 11 different locations in two liver specimens by moving the transducers with the 3-D positioner for each ablation.</li>
</ol>
2. Ultrasound Data Acquisition
<ol>
	<li>Open Matlab. Use the &#8220;VSX&#8221; command and when &#8220;Name of .mat file to process:&#8221; is prompted, enter the name of the setup file &#8220;P4-2Flash_DivergingWave.mat&#8221; for diverging wave imaging or &#8220;P4-2Flash_PlaneWave.mat&#8221; for plane wave imaging. Start the HIFU and apply it during 2min to the targeted region.</li>
	<li>Acquire the RF channel data at 1,000 frames per second during 2 min using diverging waves. Alternatively, acquire the RF channel data at 1,000 frames per second during 2 min using plane waves.</li>
	<li>Transfer the data to a host computer every 200 frames via a PCI express cable. Alternatively, for real-time streaming, acquire the RF channel data at 167 frames per second during 2 min using plane waves and transfer the data to a host computer every 2 frames. 
	Note: The imaging methods with set of 200 frames provides high temporal resolution within each set but create gaps between each set and is appropriate for off-line processing. The imaging method at 167 fps has a lower temporal resolution but does not create any gaps across the entire ablation time and is appropriate for real-time streaming.</li>
	<li>Cast the RF channel data matrix to a single precision GPU matrix with Matlab. Multiply the RF channel data matrix by the reconstruction matrix to obtain the reconstructed RF data11.</li>
</ol>
3. Displacement Imaging
<ol>
	<li>Create a 6th order Butterworth low pass filter at 4 MHz cutoff frequency using the DSP System Toolbox of Matlab. Apply this low pass filter to the reconstructed RF data to filter out the 4.5 MHz HIFU component.</li>
	<li>Estimate the axial displacement between consecutive frames using 1-D normalized cross-correlation with a 3.1mm-window length and 90% overlap.</li>
	<li>Create a 6th order Butterworth low pass filter at 100 Hz cutoff frequency using the DSP System Toolbox of Matlab. Apply this low pass filter to the temporal displacement data using Matlab to retrieve the 50 Hz-oscillatory frequency component.</li>
	<li>Define a region of interest (ROI) as the focal region at -6 dB (1.7 x 0.4 mm in water) and located 70 mm away from the transducer surface. Extract the displacement data in this ROI. Estimate the displacement signal-to-noise ratio (SNRd) at the focal region after 2 min of ablation as the ratio between the mean displacement and the standard deviation of the displacement in the ROI.</li>
	<li>Extract the 50 Hz temporal displacement signal at the focus from the displacement matrix data. Convert the temporal displacement signal at the focus into audible sound using Matlab.</li>
</ol>

<ol>
	<li>Al-Bataineh, O., Jenne, J., Huber, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+and+future+applications+of+high+intensity+focused+ultrasound+in+cancer.">Clinical and future applications of high intensity focused ultrasound in cancer.</a> Cancer Treat Rev. 38, 346-353 (2012).</li><li>Dewhirst, M. W., Viglianti, B. L., Lora-Michiels, M., Hanson, M., Hoopes, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Basic+principles+of+thermal+dosimetry+and+thermal+thresholds+for+tissue+damage+from+hyperthermia.">Basic principles of thermal dosimetry and thermal thresholds for tissue damage from hyperthermia.</a> Int J Hyperthermia. 19, 267-294 (2003).</li><li>Napoli, 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=MR-guided+high-intensity+focused+ultrasound:+current+status+of+an+emerging+technology.">MR-guided high-intensity focused ultrasound: current status of an emerging technology.</a> Cardiovasc Intervent Radiol. 36, 1190-1203 (2013).</li><li>Gudur, M. S., Kumon, R. E., Zhou, Y., Deng, C. 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R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Combined+ultrasonic+thermal+ablation+with+interleaved+ARFI+image+monitoring+using+a+single+diagnostic+curvilinear+array:+a+feasibility+study.">Combined ultrasonic thermal ablation with interleaved ARFI image monitoring using a single diagnostic curvilinear array: a feasibility study.</a> Ultrason Imaging. 33, 217-232 (2011).</li><li>Athanasiou, 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=Breast+lesions:+quantitative+elastography+with+supersonic+shear+imaging--preliminary+results.,+Radiology.">Breast lesions: quantitative elastography with supersonic shear imaging--preliminary results., Radiology.</a> 256, 297-303 (2010).</li><li>Maleke, C., Konofagou, E. 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The authors declare that they have no competing financial interests.

Real-time monitoring of HIFU lesions is important to ensure proper and efficient lesion delivery. As the lesion forms, the tissue stiffens and its motion amplitude under excitation decreases. Applying HIFU in a region of the tissue results in an acoustic radiation force that induces tissue displacement. The relative change in displacement is a surrogate of relative change in tissue stiffness. This technique offers the advantage of monitoring HIFU lesion without stopping the treatment in contrast to other ultrasound based...

High Intensity Focused Ultrasound (HIFU) is a technique that generates temperature elevation at the focal region and can be used to ablate cancerous tissue 1. Temperature elevation at the focus causes thermal lesions in the tissue 2. In order to avoid overtreating a region and to reduce treatment duration, it is imperative to reliably monitor the ablation. Magnetic resonance-guided focused ultrasound (MRgFUS) is the main technique used in clinic to guide and monitor HIFU treatment 3. MRI provides high spatial resolution images of the treated region with tissue displacement or thermal dose but has a frame rate of 0.1-1 Hz and is costly. Several ultrasound-based techniques such as B-mode imaging 4, passive acoustic mapping 5, shear wave imaging 6 and acoustic radiation force impulse 7 have been developed to guide and monitor thermal ablation. However, B-mode imaging and passive acoustic mapping do not provide imaging of mechanical properties of the ablated region which is useful to the operator to improve lesion delivery. 
Shear wave imaging and acoustic radiation force impulse can both characterize the elasticity of the tissue by measuring acoustic radiation force-induced displacements 7,8. However, in both methods, the HIFU treatment is typically interrupted to monitor the ablation. Our group has developed a technique called Harmonic Motion Imaging for Focus Ultrasound (HMIFU) which can monitor the HIFU treatment with ultrasound without stopping the ablation9,10. Briefly, a HIFU transducer sends an amplitude-modulated wave to the region to ablate while simultaneously generating an oscillatory motion in the focal region. A co-axially aligned ultrasound transducer is used to image this oscillation. The magnitude of the induced motion is related to the stiffness of the tissue.
To ensure proper lesion delivery, the temporal resolution of real-time monitoring is of key interest in ablation guidance. Recently, our group has shown real-time streaming of displacement at a frame rate up to 15 Hz, imaged with diverging waves in a narrow field of view and using a fast image reconstruction method 11. Several beamforming techniques can be used to image the displacements. A large field of view can be obtained with diverging wave imaging by changing the delay profile but the axial direction is not aligned with the HIFU beam on the lateral regions and the wave is attenuated due to geometric spreading in the lateral direction, which can affect the quality of the displacement estimation. In contrast, the lateral field of view for plane wave is upper bounded by the active aperture but the axial direction is aligned with the HIFU beam at the focus and there is no geometric spreading in the lateral direction. Depending on the type of application, one or the other imaging method can be selected. The objectives of this protocol are to show how plane wave imaging can provide real-time streaming of displacements images using HMIFU during ablation and to compare the quality of the motion estimation between diverging and plane wave imaging.

<table border="0" cellpadding="0" cellspacing="0">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr>
			<td>P4-2 Phased array</td>
			<td>ATL</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>H-178 HIFU transducer</td>
			<td>Sonic Concepts</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>3-D positioner</td>
			<td>Velmex Inc.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>AT33522A function generator</td>
			<td>Agilent Technologies</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>V-1 ultrasound system</td>
			<td>Verasonics</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>3100L RF amplifier</td>
			<td>ENI</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Matching network</td>
			<td>Sonic Concepts</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Degasing system</td>
			<td>Sonic Concepts</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Programming software</td>
			<td>Matlab</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Jacket software package</td>
			<td>Accelereyes</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

real-time monitoring of high intensity focused ultrasound (hifu) ablation of in vitro canine livers using harmonic motion imaging for focused ultrasound (hmifu)

Harmonic Motion Imaging for Focused Ultrasound (HMIFU) is a technique that can perform and monitor high-intensity focused ultrasound (HIFU) ablation. An oscillatory motion is generated at the focus of a 93-element and 4.5 MHz center frequency HIFU transducer by applying a 25 Hz amplitude-modulated signal using a function generator. A 64-element and 2.5 MHz imaging transducer with 68kPa peak pressure is confocally placed at the center of the HIFU transducer to acquire the radio-frequency (RF) channel data. In this protocol, real-time monitoring of thermal ablation using HIFU with an acoustic power of 7 W on canine livers in vitro is described. HIFU treatment is applied on the tissue during 2 min and the ablated region is imaged in real-time using diverging or plane wave imaging up to 1,000 frames/second. The matrix of RF channel data is multiplied by a sparse matrix for image reconstruction. The reconstructed field of view is of 90&#176; for diverging wave and 20 mm for plane wave imaging and the data are sampled at 80 MHz. The reconstruction is performed on a Graphical Processing Unit (GPU) in order to image in real-time at a 4.5 display frame rate. 1-D normalized cross-correlation of the reconstructed RF data is used to estimate axial displacements in the focal region. The magnitude of the peak-to-peak displacement at the focal depth decreases during the thermal ablation which denotes stiffening of the tissue due to the formation of a lesion. The displacement signal-to-noise ratio (SNRd) at the focal area for plane wave was 1.4 times higher than for diverging wave showing that plane wave imaging appears to produce better displacement maps quality for HMIFU than diverging wave imaging.

Real-time streaming of HMI displacement during HIFU ablation can be obtained using diverging and plane wave imaging. Figure 2 is a video screen capture showing real-time display of acoustic radiation force induced displacement using plane wave imaging in in vitro canine livers during HIFU ablation. The displacements are streamed in real-time on the computer screen at a display frame rate of 4.5 Hz. Positive displacements are shown in red and negative displacements in blue. Lesions were successfu...

Watch this Scientific Journal Video about Real-time Monitoring of High Intensity Focused Ultrasound HIFU Ablation of In Vitro Canine Livers Using Harmonic Motion Imaging for Focused Ultrasound HMIFU a

Real-time Monitoring of High Intensity Focused Ultrasound HIFU Ablation of In Vitro Canine Livers Using Harmonic Motion Imaging for Focused Ultrasound HMIFU

This article describes real-time monitoring of HIFU ablation in canine liver with high frame rate ultrasound imaging using diverging and plane wave imaging. Harmonic Motion Imaging for Focused Ultrasound is used to image the decrease of acoustic radiation force induced displacement in the ablated region.

Real-time Monitoring of High Intensity Focused Ultrasound (HIFU) Ablation of In Vitro Canine Livers Using Harmonic Motion Imaging for Focused Ultrasound (HMIFU)

Harmonic Motion Imaging for Focused Ultrasound (HMIFU) is a technique that can perform and monitor high-intensity focused ultrasound (HIFU) ablation. An ...

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Research

JoVE Journal

Bioengineering

9.9K Görüntüleme.  Columbia University. This article describes real-time monitoring of HIFU ablation in canine liver with high frame rate ultrasound imaging using diverging and plane wave imaging. Harmonic Motion Imaging for Focused Ultrasound is used to image the decrease of acoustic radiation force induced displacement in the ablated region.

Video: Real-time Monitoring of High Intensity Focused Ultrasound HIFU Ablation of In Vitro Canine Livers Using Harmonic Motion Imaging for Focused Ultrasound HMIFU

Contrast Ultrasound Targeted Treatment of Gliomas in Mice via Drug-Bearing Nanoparticle Delivery and Microvascular Ablation

We are developing minimally-invasive contrast agent microbubble based therapeutic approaches in which the permeabilization and/or ablation of the microvasculature are controlled by varying ultrasound pulsing parameters.  Specifically, we are testing whether such approaches may be used to treat malignant brain tumors through drug delivery and microvascular ablation.  Preliminary studies have been performed to determine whether targeted drug-bearing nanoparticle delivery can be facilitated by the ultrasound mediated destruction of "composite" delivery agents comprised of 100nm poly(lactide-co-glycolide) (PLAGA) nanoparticles that are adhered to albumin shelled microbubbles. We denote these agents as microbubble-nanoparticle composite agents (MNCAs). When targeted to subcutaneous C6 gliomas with ultrasound, we observed an immediate 4.6-fold increase in nanoparticle delivery in MNCA treated tumors over tumors treated with microbubbles co-administered with nanoparticles and a 8.5 fold increase over non-treated tumors. Furthermore, in many cancer applications, we believe it may be desirable to perform targeted drug delivery in conjunction with ablation of the tumor microcirculation, which will lead to tumor hypoxia and apoptosis. To this end, we have tested the efficacy of non-theramal cavitation-induced microvascular ablation, showing that this approach elicits tumor perfusion reduction, apoptosis, significant growth inhibition, and necrosis. Taken together, these results indicate that our ultrasound-targeted approach has the potential to increase therapeutic efficiency by creating tumor necrosis through microvascular ablation and/or simultaneously enhancing the drug payload in gliomas.

Insonation of microbubbles is a promising strategy for tumor ablation at reduced time-averaged acoustic powers, as well as for the targeted delivery of therapeutics. The purpose of the present study is to develop low duty cycle ultrasound pulsing strategies and nanocarriers to maximize non-thermal microvascular ablation and payload delivery to subcutaneous C6 gliomas.

We are developing minimally-invasive contrast agent microbubble based therapeutic approaches in which the permeabilization and/or ablation of the ...

Decellularization and Recellularization of Whole Livers

The liver is a complex organ which requires constant perfusion for delivery of nutrients and oxygen and removal of waste in order to survive1. Efforts to recreate or mimic the liver microstructure with grounds up approach using tissue engineering and microfabrication techniques have not been successful so far due to this design challenge. In addition, synthetic biomaterials used to create scaffolds for liver tissue engineering applications have been limited in inducing tissue regeneration and repair in large part due to the lack of specific cell binding motifs that would induce the proper cell functions2. Decellularized native tissues such blood vessels3and skin4on the other hand have found many applications in tissue engineering, and have provided a practical solution to some of the challenges. The advantage of decellularized native matrix is that it retains, to an extent, the original composition, and the microstructure, hence enhancing cell attachment and reorganization5.
In this work we describe the methods to perform perfusion-decellularization of the liver, such that an intact liver bioscaffold that retains the structure of major blood vessels is obtained. Further, we describe methods to recellularize these bioscaffolds with adult primary hepatocytes, creating a liver graft that is functional in vitro, and has the vessel access necessary for transplantation in vivo.

Perfusion decellularization is a novel technique to produce whole liver scaffolds that retains the organ's extracellular matrix composition and microarchitecture. Herein, the method of preparing whole organ scaffolds using perfusion decellularization and subsequent repopulation with hepatocytes is described. Functional and transplantable liver grafts can be generated using this technique.

The liver is a complex organ which requires constant perfusion for delivery of nutrients and oxygen and removal of waste in order to survive1. Efforts to ...

Induction of Adhesion-dependent Signals Using Low-intensity Ultrasound

In multicellular organisms, cell behavior is dictated by interactions with the extracellular matrix. Consequences of matrix-engagement range from regulation of cell migration and proliferation, to secretion and even differentiation. The signals underlying each of these complex processes arise from the molecular interactions of extracellular matrix receptors on the surface of the cell. Integrins are the prototypic receptors and provide a mechanical link between extracellular matrix and the cytoskeleton, as well as initiating some of the adhesion-dependent signaling cascades. However, it is becoming increasingly apparent that additional transmembrane receptors function alongside the integrins to regulate both the integrin itself and signals downstream. The most elegant of these examples is the transmembrane proteoglycan, syndecan-4, which cooperates with &alpha;5&beta;1-integrin during adhesion to fibronectin. In vivo models demonstrate the importance of syndecan-4 signaling, as syndecan-4-knockout mice exhibit healing retardation due to inefficient fibroblast migration1,2. In wild-type animals, migration of fibroblasts toward a wound is triggered by the appearance of fibronectin that leaks from damaged capillaries and is deposited by macrophages in injured tissue. Therefore there is great interest in discovering strategies that enhance fibronectin-dependent signaling and could accelerate repair processes.
The integrin-mediated and syndecan-4-mediated components of fibronectin-dependent signaling can be separated by stimulating cells with recombinant fibronectin fragments. Although integrin engagement is essential for cell adhesion, certain fibronectin-dependent signals are regulated by syndecan-4. Syndecan-4 activates the Rac1 protrusive signal3, causes integrin redistribution1, triggers recruitment of cytoskeletal molecules, such as vinculin, to focal adhesions4, and thereby induces directional migration3. We have looked for alternative strategies for activating such signals and found that low-intensity pulsed ultrasound (LIPUS) can mimic the effects of syndecan-4 engagement5. In this protocol we describe the method by which 30 mW/cm2, 1.5 MHz ultrasound, pulsed at 1 kHz (Fig. 1) can be applied to fibroblasts in culture (Fig. 2) to induce Rac1 activation and focal adhesion formation. Ultrasound stimulation is applied for a maximum of 20 minutes, as this combination of parameters has been found to be most efficacious for acceleration of clinical fracture repair6. The method uses recombinant fibronectin fragments to engage &alpha;5&beta;1-integrin, without engagement of syndecan-4, and requires inhibition of protein synthesis by cycloheximide to block deposition of additional matrix by the fibroblasts., The positive effect of ultrasound on repair mechanisms is well documented7,8, and by understanding the molecular effect of ultrasound in culture we should be able to refine the therapeutic technique to improve clinical outcomes.

This protocol describes the stimulation of cultured fibroblasts with low-intensity pulsed ultrasound, which drives focal adhesion formation and Rac1 activation by mimicking engagement of the transmembrane matrix receptor, syndecan-4. This approach allows investigation of a successful clinical technique at the cellular level, thereby providing opportunities for refinement of the therapy.

In multicellular organisms, cell behavior is dictated by interactions with the extracellular matrix. Consequences of matrix-engagement range from ...

Wideband Optical Detector of Ultrasound for Medical Imaging Applications

Optical sensors of ultrasound are a promising alternative to piezoelectric techniques, as has been recently demonstrated in the field of optoacoustic imaging. In medical applications, one of the major limitations of optical sensing technology is its susceptibility to environmental conditions, e.g. changes in pressure and temperature, which may saturate the detection. Additionally, the clinical environment often imposes stringent limits on the size and robustness of the sensor. In this work, the combination of pulse interferometry and fiber-based optical sensing is demonstrated for ultrasound detection. Pulse interferometry enables robust performance of the readout system in the presence of rapid variations in the environmental conditions, whereas the use of all-fiber technology leads to a mechanically flexible sensing element compatible with highly demanding medical applications such as intravascular imaging. In order to achieve a short sensor length, a pi-phase-shifted fiber Bragg grating is used, which acts as a resonator trapping light over an effective length of 350 &#181;m. To enable high bandwidth, the sensor is used for sideway detection of ultrasound, which is highly beneficial in circumferential imaging geometries such as intravascular imaging. An optoacoustic imaging setup is used to determine the response of the sensor for acoustic point sources at different positions.

Optical detection of ultrasound is impractical in many imaging scenarios because it often requires stable environmental conditions. We demonstrate an optical technique for ultrasound sensing in volatile environments with miniaturization and sensitivity levels appropriate for optoacoustic imaging in restrictive scenarios, e.g. intravascular applications.

Optical sensors of ultrasound are a promising alternative to piezoelectric techniques, as has been recently demonstrated in the field of optoacoustic ...

Universal Hand-held Three-dimensional Optoacoustic Imaging Probe for Deep Tissue Human Angiography and Functional Preclinical Studies in Real Time

The exclusive combination of high optical contrast and excellent spatial resolution makes optoacoustics (photoacoustics) ideal for simultaneously attaining anatomical, functional and molecular contrast in deep optically opaque tissues. While enormous potential has been recently demonstrated in the application of optoacoustics for small animal research, vast efforts have also been undertaken in translating this imaging technology into clinical practice. We present here a newly developed optoacoustic tomography approach capable of delivering high resolution and spectrally enriched volumetric images of tissue morphology and function in real time. A detailed description of the experimental protocol for operating with the imaging system in both hand-held and stationary modes is provided and showcased for different potential scenarios involving functional and molecular studies in murine models and humans. The possibility for real time visualization in three dimensions along with the versatile handheld design of the imaging probe make the newly developed approach unique among the pantheon of imaging modalities used in today&#8217;s preclinical research and clinical practice.

We provide herein a detailed description of the experimental protocol for imaging with a newly developed hand-held optoacoustic (photoacoustic) system for three-dimensional functional and molecular imaging in real time. The demonstrated powerful performance and versatility may define new application areas of the optoacoustic technology in preclinical research and clinical practice.

The exclusive combination of high optical contrast and excellent spatial resolution makes optoacoustics (photoacoustics) ideal for simultaneously ...

Eye Irritation Test (EIT) for Hazard Identification of Eye Irritating Chemicals using Reconstructed Human Cornea-like Epithelial (RhCE) Tissue Model

To comply with the Seventh Amendment to the EU Cosmetics Directive and EU REACH legislation, validated non-animal alternative methods for reliable and accurate assessment of ocular toxicity in man are needed. To address this need, we have developed an eye irritation test (EIT) which utilizes a three dimensional reconstructed human cornea-like epithelial (RhCE) tissue model that is based on normal human cells. The EIT is able to separate ocular&#160;irritants and corrosives (GHS Categories 1 and 2 combined) and those that do not require labeling (GHS No Category). The test utilizes two separate protocols, one designed for liquid chemicals and a second, similar protocol for solid test articles. The EIT prediction model uses a single exposure period (30 min for liquids, 6 hr for solids) and a single tissue viability cut-off (60.0% as determined by the MTT assay). Based on the results for 83 chemicals (44 liquids and 39 solids) EIT achieved 95.5/68.2/ and 81.8% sensitivity/specificity and accuracy (SS&#38;A) for liquids, 100.0/68.4/ and 84.6% SS&#38;A for solids, and 97.6/68.3/ and 83.1% for overall SS&#38;A. The EIT will contribute significantly to classifying the ocular irritation potential of a wide range of liquid and solid chemicals without the use of animals to meet regulatory testing requirements. The EpiOcular EIT method was implemented in 2015 into the OECD Test Guidelines as TG 492.

Eye Irritation Test EIT for Hazard Identification of Eye Irritating Chemicals using Reconstructed Human Cornea-like Epithelial RhCE Tissue Model

We have developed an eye irritation test which utilizes a three dimensional reconstructed human cornea-like epithelial (RhCE) tissue model. The test is able to discriminate between ocular irritant and corrosive materials (GHS Categories 1 and 2 combined) and those that do not require labeling (GHS No Category).

To comply with the Seventh Amendment to the EU Cosmetics Directive and EU REACH legislation, validated non-animal alternative methods for reliable and ...

Real Time Monitoring of Intracellular Bile Acid Dynamics Using a Genetically Encoded FRET-based Bile Acid Sensor

F&#246;rster Resonance Energy Transfer (FRET) has become a powerful tool for monitoring protein folding, interaction and localization in single cells. Biosensors relying on the principle of FRET have enabled real-time visualization of subcellular signaling events in live cells with high temporal and spatial resolution. Here, we describe the application of a genetically encoded Bile Acid Sensor (BAS) that consists of two fluorophores fused to the farnesoid X receptor ligand binding domain (FXR-LBD), thereby forming a bile acid sensor that can be activated by a large number of bile acids species and other (synthetic) FXR ligands. This sensor can be targeted to different cellular compartments including the nucleus (NucleoBAS) and cytosol (CytoBAS) to measure bile acid concentrations locally. It allows rapid and simple quantitation of cellular bile acid influx, efflux and subcellular distribution of endogenous bile acids without the need for labeling with fluorescent tags or radionuclei. Furthermore, the BAS FRET sensors can be useful for monitoring FXR ligand binding. Finally, we show that this FRET biosensor can be combined with imaging of other spectrally distinct fluorophores. This allows for combined analysis of intracellular bile acid dynamics and i) localization and/or abundance of proteins of interest, or ii) intracellular signaling in a single cell.

We provide a detailed protocol to study bile acid dynamics in living cells using a genetically encoded BAS FRET sensor. This Bile Acid Sensor represents a unique tool to study (regulation of) bile acid transport and FXR activation in a wide range of cell types.

F&#246;rster Resonance Energy Transfer (FRET) has become a powerful tool for monitoring protein folding, interaction and localization in single cells. ...

Proper Positioning and Restraint of a Rat Hind Limb for Focused High Resolution Imaging of Bone Micro-architecture Using In Vivo Micro-computed Tomography

The use of in vivo micro-computed tomography (&#181;CT) is a powerful tool which involves the non-destructive imaging of internal structures at high resolutions in live animal models. This allows for repeated imaging of the same rodent over time. This feature not only reduces the total number of rodents required in an experimental design and thereby reduces the inter-subject variation that can arise, but also allows researchers to assess longitudinal or life-long responses to an intervention. To acquire high quality images that can be processed and analyzed to more accurately quantify outcomes of bone micro-architecture, users of in vivo &#181;CT scanners must properly anesthetize the rat, and position and restrain the hind limb. To do this, it is imperative that the rat be anesthetized to a level of complete relaxation, and that pedal reflexes are lost. These guidelines may be modified for each individual rat, as the rate of isoflurane metabolism can vary depending on strain and body size. Proper technique for in vivo &#181;CT image acquisition enables accurate and consistent measurement of bone micro-architecture within and across studies.

Proper Positioning and Restraint of a Rat Hind Limb for Focused High Resolution Imaging of Bone Micro-architecture Using In Vivo Micro-computed Tomography

This paper instructs users of in vivo micro-computed tomography (&#181;CT) scanners how to anesthetize, correctly position and restrain the hind limb of a rat for minimal movement during high-resolution imaging of the tibia. The result is high quality images that can be processed to accurately quantify bone micro-architecture.

The use of in vivo micro-computed tomography (&#181;CT) is a powerful tool which involves the non-destructive imaging of internal structures at high ...

Focused Ion Beam Lithography to Etch Nano-architectures into Microelectrodes

With advances in electronics and fabrication technology, intracortical microelectrodes have undergone substantial improvements enabling the production of sophisticated microelectrodes with greater resolution and expanded capabilities. The progress in fabrication technology has supported the development of biomimetic electrodes, which aim to seamlessly integrate into the brain parenchyma, reduce the neuroinflammatory response observed after electrode insertion and improve the quality and longevity of electrophysiological recordings. Here we describe a protocol to employ a biomimetic approach recently classified as nano-architecture. The use of focused ion beam lithography (FIB) was utilized in this protocol to etch specific nano-architecture features into the surface of non-functional and functional single shank intracortical microelectrodes. Etching nano-architectures into the electrode surface indicated possible improvements of biocompatibility and functionality of the implanted device. One of the benefits of using FIB is the ability to etch on manufactured devices, as opposed to during the fabrication of the device, facilitating boundless possibilities to modify numerous medical devices post-manufacturing. The protocol presented herein can be optimized for various material types, nano-architecture features, and types of devices. Augmenting the surface of implanted medical devices can improve the device performance and integration into the tissue.

We have shown that the etching of nano-architecture into intracortical microelectrode devices may reduce the inflammatory response and has the potential to improve electrophysiological recordings. The methods described herein outline an approach to etch nano-architectures into the surface of non-functional and functional single shank silicon intracortical microelectrodes.

With advances in electronics and fabrication technology, intracortical microelectrodes have undergone substantial improvements enabling the production of ...

Functional Transcranial Doppler Ultrasound for Monitoring Cerebral Blood Flow

Functional transcranial Doppler ultrasound (fTCD) is the use of transcranial Doppler ultrasound (TCD) to study neural activation occurring during stimuli such as physical movement, activation of tactile sensors in the skin, and viewing images. Neural activation is inferred from an increase in the cerebral blood flow velocity (CBFV) supplying the region of the brain involved in processing sensory input. For example, viewing bright light causes increased neural activity in the occipital lobe of the cerebral cortex, leading to increased blood flow in the posterior cerebral artery, which supplies the occipital lobe. In fTCD, changes in CBFV are used to estimate changes in cerebral blood flow (CBF).
With its high temporal resolution measurement of blood flow velocities in the major cerebral arteries, fTCD complements other established functional imaging techniques. The goal of this Methods paper is to give step-by-step instructions for using fTCD to perform a functional imaging experiment. First, the basic steps for identifying the middle cerebral artery (MCA) and optimizing the signal will be described. Next, placement of a fixation device for holding the TCD probe in place during the experiment will be described. Finally, the breath-holding experiment, which is a specific example of a functional imaging experiment using fTCD, will be demonstrated.

Functional transcranial Doppler ultrasound complements other functional imaging modalities, with its high temporal resolution measurement of stimulus-induced changes in cerebral blood flow within the basal cerebral arteries. This Methods paper gives step-by-step instructions for using functional transcranial Doppler ultrasound to perform a functional imaging experiment.&#160;

Functional transcranial Doppler ultrasound (fTCD) is the use of transcranial Doppler ultrasound (TCD) to study neural activation occurring during stimuli ...