This work is supported in part by the U.S. Army Medical Research Material Command under W81XWH-08-1-0503, and W81XWH-12-1-0066, by AHA grants no 0655441U and 15SDG25740015 as well as by NIH R21 HL081892, R21 HL130899, R21 HL089175, RC1 DK087365, R01 DK098526, R01 DK118964, R01 CA140338, R01 CA234428, by Lantheus Medical Imaging and by GE Healthcare, Oslo, Norway.

The institutional review boards of both Thomas Jefferson University and the Hospital of the University of Pennsylvania approved this protocol. The protocol is compliant with the Health Insurance Portability and Accountability Act. The United States Food and Drug Administration (FDA) issued an Investigational New Drug approval (IND # 124,465 to F. Forsberg) for this protocol. GE Healthcare (Oslo, Norway) provided the UCA used in this research (Sonazoid; Table 1). Sonazoid is not approved by the FDA for any clinical applications in the United Sates, which is why an IND was necessary. Other UCAs with FDA approval1 can be used off-label at the discretion of the treating physician if deemed potentially clinically useful.
NOTE: The full protocol and statistical analysis plan are available at https:// clinicaltrials.gov/ct2/show/NCT02489045. Trial registration number: NCT # 02489045.
1. Subject preparation
<ol>
	<li>Review the subject&#8217;s known drug allergies or intolerances in particular any known allergy to the UCA being used.</li>
	<li>Exclude subjects with unstable cardiopulmonary conditions or who are generally medically unstable.</li>
	<li>Put the subject on a stretcher in the supine position.</li>
	<li>Place an 18 - 22 gauge cannula in a vein in the subject&#8217;s right or left arm for the UCA infusion.</li>
	<li>Make sure emergency services (e.g., a crash cart) will be available within the hospital in case of any acute adverse reactions. 
	NOTE: UCAs are very safe with serious anaphylactoid-type reactions reported at a rate of less than 0.01%.20</li>
</ol>
2. UCA preparation (Specific to Sonazoid)
<ol>
	<li>Prepare three (3) vials with 48 &#181;L of microbubbles (6 mL)&#160;for each subject by resuspending according to the manufacturer&#8217;s instructions. The UCA is supplied as a dry powder within 10 mL sealed vials. The headspace of the vials contains perfluorobutane.
	<ol>
		<li>Perforate the stopper of the UCA vial with a chemospike.</li>
		<li>Remove the protective cap from the syringe port of the chemospike and add 2 mL of sterile water.</li>
		<li>With the syringe remaining attached to the chemospike, immediately shake the product for 1 minute to ensure a homogeneous product.</li>
		<li>Withdraw the product into the syringe and re-inject the product back into the vial again. This is to avoid dilution of the product due to the dead-space volume in the chemospike.</li>
		<li>Remove the syringe from the syringe port and reattach the protective cap. The concentration of the reconstituted UCA is 8 &#181;L microbubbles/mL.</li>
		<li>Repeat the reconstitution procedure for the other 2 vials.</li>
	</ol>
	</li>
	<li>Use saline (0.9% NaCl solution) to fill up the connecting tubes before being connected to a 3-way stopcock. The stopcock will then be connected to the extension tubing leading to the cannula.</li>
	<li>Draw all three (3) vials of suspended UCA into a 10 mL syringe, and place it in a syringe pump at the same level or below the patient, and connect directly to the stopcock.</li>
	<li>After the initial ultrasound imaging and after the stopcock has been opened, infuse the NaCl solution at a rate of 120 mL/hour, and co-infuse Sonazoid at a rate of 0.024 &#181;L per kg body weight per minute (suspension infusion rate of 0.18 mL/kg/hour). 
	NOTE: This infusion rate was selected based on our group&#8217;s previous experiences with Sonazoid infusion in portal hypertension subjects undergoing SHAPE13,14,21. The exact resuspension procedure and infusion method will vary depending on the UCA used.</li>
</ol>
3. Initial ultrasound imaging
<ol>
	<li>Power up an ultrasound scanner (e.g., Logiq E10, version R2) and select the C1-6-D curvilinear probe.</li>
	<li>Select an abdominal preset on the ultrasound scanner and use a curvi-linear array (typically with a 1-6 or 2-8 MHz bandwidth) to acquire grayscale images of both the portal and a hepatic vein in the same imaging plane and at similar depths (Figure 1). This is generally best achieved via a subcostal approach.</li>
	<li>Optimize the images based on Good Clinical Practice and take care to select the hepatic vein region away from the inferior vena cava to avoid the influence of retrograde flow.</li>
</ol>
4. SHI and SHAPE imaging
<ol>
	<li>Activate the SHI contrast imaging mode in dual display mode (i.e., running real-time B-mode and SHI simultaneously) using the Subharmonic Contrast touch panel button and activate Contrast mode. Then select SUBH-AM on the rotary control.
	<ol>
		<li>Perform SHI at a transmit frequency of 2.5 MHz and obtain the received signals at 1.25 MHz.</li>
		<li>Use pulse-shaping to maximize the generation of subharmonic microbubble signals, such as a Gaussian windowed binomial filtered square wave with Sonazoid,21 but this is scanner and UCA dependent.17 
		NOTE: The choice of imaging frequency and pulse shape may not be available to end-users.</li>
	</ol>
	</li>
	<li>Confirm the patency of the portal and the hepatic vein as well as the presence of microbubbles, which can take up to 1-2 minutes from the start of the infusion.</li>
	<li>Activate the SHAPE automated optimization code to optimize SHAPE by compensating for varying depth and attenuation.22,23&#160;Select TIC Analysis on the touch panel followed by F6 and then the k button.</li>
	<li>The SHAPE optimization algorithm will acquire subharmonic data for every acoustic output level. Once data acquisition is complete, position an ROI on the portal vein in the contrast sample window (top left on the TIC Analysis screen).
	<ol>
		<li>Plot the average subharmonic data within the ROI as a function of acoustic output and fit a logistic curve to the data. Select the inflection point of this curve (or rather the peak in the derivative curve shown underneath) as the optimized power, as this has been shown to be the point of greatest SHAPE sensitivity.22,23&#160;One such set of curves is shown in Figure 2.</li>
	</ol>
	</li>
	<li>Adjust the acoustic output power to the value identified in step 4.4.1, which will ensure the maximum change in subharmonic amplitudes a function of ambient pressure (i.e., maximizing the sensitivity of SHAPE).</li>
	<li>Acquire subharmonic data from the microbubbles (i.e., SHAPE) in 5-15 s segments during the infusion of the UCA suspension (Figure 3).</li>
</ol>
5. SHAPE data processing
<ol>
	<li>Once the optimized SHI cine-loop has been acquired (step 5.6) select &#8220;TIC Analysis&#8221; on the touch panel.
	<ol>
		<li>Make sure &#8220;Motion Tracking&#8221; is activated on the touch panel, which adjusts the ROI position for each frame to compensate for any breathing or other motion.</li>
		<li>Make sure dB is selected as the unit for the Y-axis on the traces in the analysis window.</li>
	</ol>
	</li>
	<li>In the contrast sample window (top left on the screen) select identical ROIs (elliptical regions are default) within the hepatic and portal veins. In the analysis window (to the right) the subharmonic signal (in dB) within each vessel is averaged over all the frames in a 0.5 MHz bandwidth around 1.25 MHz.</li>
	<li>Calculate the final SHAPE gradient (in dB) as the difference in the mean subharmonic signal between the hepatic and the portal vein ROIs. Based on current studies, the optimal operating point for identifying CSPH is -0.11 dB and the linear regression equation is HVPG = 0.81 x SHAPE + 9.43.14 It is important to note that this cutoff and equation are both scanner and UCA dependent.</li>
</ol>

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L. <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:+imaging+with+contrast-enhanced+subharmonic+US+-+initial+experience.">Breast lesions: imaging with contrast-enhanced subharmonic US - initial experience.</a> Radiology. 244 (3), 718-726 (2007).</li><li>Sridharan, 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=Characterizing+breast+lesions+using+quantitative+parametric+3D+subharmonic+imaging:+a+multi-center+study.">Characterizing breast lesions using quantitative parametric 3D subharmonic imaging: a multi-center study.</a> Academic Radiology. 27 (8), 1065-1074 (2020).</li><li>Forsberg, F., 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=Subharmonic+and+endoscopic+contrast+imaging+of+pancreatic+masses:+a+pilot+study.">Subharmonic and endoscopic contrast imaging of pancreatic masses: a pilot study.</a> Journal of Ultrasound in Medicine. 37 (1), 123-129 (2018).</li><li>Delaney, L. J., 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=Characterization+of+adnexal+masses+using+contrast-enhanced+subharmonic+imaging:+a+pilot+study.">Characterization of adnexal masses using contrast-enhanced subharmonic imaging: a pilot study.</a> Journal of Ultrasound in Medicine. 39 (5), 977-985 (2020).</li><li>Eisenbrey, J. R., 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=Contrast-enhanced+subharmonic+and+harmonic+ultrasound+of+renal+masses+undergoing+percutaneous+cryoablation.">Contrast-enhanced subharmonic and harmonic ultrasound of renal masses undergoing percutaneous cryoablation.</a> Academic Radiology. 22 (7), 820-826 (2015).</li><li>Gupta, I., 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=Transrectal+subharmonic+ultrasound+imaging+for+prostate+cancer+detection.">Transrectal subharmonic ultrasound imaging for prostate cancer detection.</a> Urology. 138 (4), 106-112 (2020).</li><li>Shi, W. T., Forsberg, F., Raichlen, J. S., Needleman, L., Goldberg, B. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pressure+dependence+of+subharmonic+signals+from+contrast+microbubbles.">Pressure dependence of subharmonic signals from contrast microbubbles.</a> Ultrasound in Medicine and Biology. 25 (2), 275-283 (1999).</li><li>Halldorsdottir, V. G., 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=Subharmonic+contrast+microbubble+signals+for+noninvasive+pressure+estimation+under+static+and+dynamic+flow+conditions.">Subharmonic contrast microbubble signals for noninvasive pressure estimation under static and dynamic flow conditions.</a> Ultrasonic Imaging. 33 (3), 153-164 (2011).</li><li>Nio, A. Q. X., 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=Optimal+control+of+SonoVue+microbubbles+to+estimate+hydrostatic+pressure.">Optimal control of SonoVue microbubbles to estimate hydrostatic pressure.</a> IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. 67 (3), 557-567 (2020).</li><li>Eisenbrey, J. R., 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=Chronic+liver+disease:+noninvasive+subharmonic+aided+pressure+estimation+of+hepatic+venous+pressure+gradient.">Chronic liver disease: noninvasive subharmonic aided pressure estimation of hepatic venous pressure gradient.</a> Radiology. 268 (2), 581-588 (2013).</li><li>Gupta, I., 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=Diagnosing+portal+hypertension+with+noninvasive+subharmonic+pressure+estimates+from+an+ultrasound+contrast+agent.">Diagnosing portal hypertension with noninvasive subharmonic pressure estimates from an ultrasound contrast agent.</a> Radiology. , (2020).</li><li>Nam, K., 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=Monitoring+neoadjuvant+chemotherapy+for+breast+cancer+by+using+three-dimensional+subharmonic+aided+pressure+estimation+and+imaging+with+US+contrast+agents:+preliminary+experience.">Monitoring neoadjuvant chemotherapy for breast cancer by using three-dimensional subharmonic aided pressure estimation and imaging with US contrast agents: preliminary experience.</a> Radiology. 285 (1), 53-62 (2017).</li><li>Dave, J. K., 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=Non-invasive+intra-cardiac+pressure+measurements+using+subharmonic-aided+pressure+estimation:+proof+of+concept+in+humans.">Non-invasive intra-cardiac pressure measurements using subharmonic-aided pressure estimation: proof of concept in humans.</a> Ultrasound in Medicine and Biology. 43 (11), 2718-2724 (2017).</li><li>Esposito, C., Dickie, K., Forsberg, F., Dave, J. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Developing+an+interface+and+investigating+optimal+parameters+for+real-time+intra-cardiac+subharmonic+aided+pressure+estimation.">Developing an interface and investigating optimal parameters for real-time intra-cardiac subharmonic aided pressure estimation.</a> IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. , (2020).</li><li>Bosch, J., Groszmann, R. J., Shah, V. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evolution+in+the+understanding+of+the+pathophysiological+basis+of+portal+hypertension:+How+changes+in+paradigm+are+leading+to+successful+new+treatments.">Evolution in the understanding of the pathophysiological basis of portal hypertension: How changes in paradigm are leading to successful new treatments.</a> Journal of Hepatology. 62, 121-130 (2015).</li><li>Procopet, B., Berzigotti, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diagnosis+of+cirrhosis+and+portal+hypertension:+imaging,+non-invasive+markers+of+fibrosis+and+liver+biopsy.">Diagnosis of cirrhosis and portal hypertension: imaging, non-invasive markers of fibrosis and liver biopsy.</a> Gastroenterology Report. 5 (2), 79-89 (2017).</li><li>Dietrich, C. F., 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=Guidelines+and+good+clinical+practice+recommendations+for+contrast-enhanced+ultrasound+(CEUS)+in+the+liver-update+2020+WFUMB+in+cooperation+with+EFSUMB,+AFSUMB,+AIUM,+and+FLAUS.">Guidelines and good clinical practice recommendations for contrast-enhanced ultrasound (CEUS) in the liver-update 2020 WFUMB in cooperation with EFSUMB, AFSUMB, AIUM, and FLAUS.</a> Ultrasound in Medicine and Biology. , (2020).</li><li>Gupta, I., 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=Effect+of+pulse+shaping+on+subharmonic+aided+pressure+estimation+in+vitro+and+in+vivo.">Effect of pulse shaping on subharmonic aided pressure estimation in vitro and in vivo.</a> Journal of Ultrasound in Medicine. 36 (1), 3-11 (2017).</li><li>Dave, J. K., 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=On+the+implementation+of+an+automated+acoustic+output+optimization+algorithm+for+subharmonic+aided+pressure+estimation.">On the implementation of an automated acoustic output optimization algorithm for subharmonic aided pressure estimation.</a> Ultrasonics. 53 (4), 880-888 (2013).</li><li>Gupta, I., Eisenbrey, J. R., Machado, P., Stanczak, M., Wallace, K., Forsberg, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+factors+impacting+subharmonic-+aided+pressure+estimation+(SHAPE).">On factors impacting subharmonic- aided pressure estimation (SHAPE).</a> Ultrasonic Imaging. 41 (1), 35-48 (2019).</li><li>Eisenbrey, J. R., Daecher, A., Kramer, M. R., Forsberg, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+needle+and+catheter+size+on+commercially+available+ultrasound+contrast+agents.">Effects of needle and catheter size on commercially available ultrasound contrast agents.</a> Journal of Ultrasound in Medicine. 34 (11), 1961-1968 (2015).</li></ol>

Drs. Forsberg, Gupta, Wallace and Eisenbrey have a patent pending on the SHAPE technology. Dr. Wallace is an employee of GE.

Noninvasive, accurate measurement of pressures within the human body has long been an important but elusive clinical goal. The protocol for SHAPE measurements presented here achieves this goal. The most critical component of the SHAPE procedure is the optimization algorithm, since subharmonic data not acquired at the optimal acoustic power output will correlate poorly with hydrostatic pressures.17,22,23&#160;The initial version ...

A number of different ultrasound contrast agents (UCAs) are approved for clinical use in cardiology (in particular left ventricular opacification) and radiology (in particular adult and pediatric liver lesion characterization) across the world.1&#160;The sensitivity and specificity of ultrasound imaging can be improved by intravenous (IV) injection of gas-filled microbubbles (diameter &#60; 10 &#956;m) encapsulated by a lipid or protein shell as UCAs that traverse the entire vasculature and enhance signals by up to 30 dB.1&#160;These UCAs not only enhance the backscattered ultrasound signals, but at sufficient acoustic pressures (&#62; 200 kPa) they also act as nonlinear oscillators. Hence, significant energy components will be produced in the received echoes ranging from subharmonic and harmonic to ultraharmonic frequencies.1,2&#160;These nonlinear signal components can be extracted from tissue and linear bubble echoes (e.g., using pulse inversion) and used to create contrast-specific imaging modalities such as subharmonic imaging (SHI), which receives at half the transmit frequency (i.e., at f0/2).3&#160;Our group has demonstrated in human clinical trials that SHI can detect the blood flow in neovessels and arterioles associated with a variety of&#160;tumors and tissues.4,5,6,7,8,9
We have advocated the use of UCAs not as vascular tracers, but as sensors for noninvasive pressure estimation in the circulatory system by monitoring subharmonic contrast bubble amplitude variations.10&#160;This innovative technique, called subharmonic-aided pressure estimation (SHAPE), relies on the inverse linear correlation between the amplitude of the subharmonic signals and hydrostatic pressure (up to 186 mmHg) measured for most commercial UCAs in vitro (r2 &#62; 0.90) as summarized in Table 1.10,11&#160;However, it should be noted that not all UCAs exhibit this behavior. Most notably, it has been shown that subharmonic signals from the UCA SonoVue (known as Lumason in the USA) initially rise with hydrostatic pressure increases, followed by a plateau and a decreasing phase.12&#160;Nonetheless, SHAPE offers the possibility of allowing pressure gradients in the heart and throughout the cardiovascular system as well as interstitial fluid pressure in tumors to be obtained noninvasively.13,14,15,16,17&#160;Recently, we implemented a real-time version of the SHAPE algorithm on a commercial ultrasound scanner and provided proof-of-concept that SHAPE can provide in vivo pressure estimates with errors of less than 3 mmHg in the left and right ventricles of patients.16,17
The most experience with SHAPE to date has been for&#160;diagnosing portal hypertension with more than 220 subjects enrolled &#160;and initial findings confirmed in a multi-center trial.13,14&#160;Portal hypertension is defined as an increase in the pressure gradient between the portal vein and hepatic veins or the inferior vena cava exceeding 5 mmHg, while clinically significant portal hypertension (CSPH) requires a gradient or its equivalent, a hepatic venous pressure gradient (HVPG) &#8805; 10 mmHg.18&#160;CSPH is associated with an increased risk of gastroesophageal varices, ascites, hepatic decompensation, post-operative decompensation, and hepatocellular carcinoma.18,19&#160;Patients who develop ascites have a 50% three-year mortality and those who develop spontaneous infection of the ascites fluid carry a 70% one-year mortality. Patients with cirrhosis have a 5-10% yearly incidence of gastroesophageal variceal formation, and a 4-15% yearly incidence of bleeding; each bleeding episode carries up to a 20% risk of death.18,19
This manuscript describes how to conduct a SHAPE study using commercially available equipment and UCAs with an emphasis on identifying portal hypertension in the liver of patients. The critical calibration procedure required to achieve the highest sensitivity to estimating pressure changes is explained in detail.

<table><tbody><tr><td>2 mL syringe</td><td>Becton Dickinson</td><td>309637</td><td>Used for reconstituting Sonazoid</td></tr><tr><td>10 mL saline-filled syringe</td><td>Becton Dickinson</td><td>306545</td><td>Used for flushing line to verify IV access</td></tr><tr><td>500 mL saline bag</td><td>Baxter Healthcare Corp</td><td>2131323</td><td>Used for co-infusion with Sonazoid</td></tr><tr><td>C1-6-D curvi-linear proble</td><td>GE Healthcare</td><td>H40472LT</td><td>Used for liver imaging</td></tr><tr><td>Chemoprotect Spike</td><td>Codan USA</td><td>C355</td><td>Chemospike used for reconstituting Sonazoid</td></tr><tr><td>Discofix C Blue</td><td>B. Braun Medical Inc</td><td>16494C</td><td>3-way stopcock</td></tr><tr><td>Intrafix Safeset 180 cm</td><td>B. Braun Medical Inc</td><td>4063000</td><td>Infusion tubing</td></tr><tr><td>Logiq E10 ultrasound scanner</td><td>GE Healthcare</td><td>H4928US</td><td>Used for conventional ultrasound imaging as well as for SHI and SHAPE</td></tr><tr><td>Luer lock 10 mL syringe</td><td>Becton Dickinson</td><td>300912</td><td>For infusion of Sonazoid</td></tr><tr><td>Medfusion 3500 syringe pump</td><td>Smiths Medical</td><td>3500-500</td><td>Used for infusing Sonazoid at 0.18 mL/kg/hour</td></tr><tr><td>Perfusor-leitung tubing 150 mm</td><td>B. Braun Medical Inc</td><td>8722960</td><td>Extension line enabling syringe connection to patient&#039;s IV access</td></tr><tr><td>SHI/SHAPE software</td><td>GE Healthcare</td><td>H4920CI</td><td>Contrast-specific imaging software</td></tr><tr><td>Sigma Spectrum infusion system</td><td>Baxter Healthcare Corp</td><td>35700BAX</td><td>Pump used for co-infusing saline at 120 mL/hour</td></tr><tr><td>Sonazoid</td><td>GE Healthcare</td><td></td><td>Gas-filled microbubble based ultrasound contrast agent</td></tr><tr><td>sterile water, 2 mL</td><td>B. Braun Medical Inc</td><td></td><td>Used for reconstituting Sonazoid</td></tr><tr><td>ultrasound gel</td><td>Cardinal Health</td><td>USG-250BT</td><td>Used for contact between probe and patient</td></tr><tr><td>Venflon IV cannula 22GA</td><td>Becton Dickinson</td><td>393202</td><td>Cannula needle for obtaining IV access</td></tr></tbody></table>

contrast-enhanced subharmonic aided pressure estimation (shape) using ultrasound imaging with a focus on identifying portal hypertension

Noninvasive, accurate measurement of pressures within the human body has long been an important but elusive clinical goal. Contrast agents for ultrasound imaging are gas-filled, encapsulated microbubbles (diameter &#60; 10 &#956;m) that traverse the entire vasculature and enhance signals by up to 30 dB. These microbubbles also produce nonlinear oscillations at frequencies ranging from the subharmonic (half of the transmit frequency) to higher harmonics. The subharmonic amplitude has an inverse linear relationship with the ambient hydrostatic pressure. Here an ultrasound system capable of performing real-time, subharmonic aided pressure estimation (SHAPE) is presented. During ultrasound contrast agent infusion, an algorithm for optimizing acoustic outputs is activated. Following this calibration, subharmonic microbubble signals (i.e., SHAPE) have the highest sensitivity to pressure changes and can be used to noninvasively quantify pressure. The utility of the SHAPE procedure for identifying portal hypertension in the liver is the emphasis here, but the technique has applicability across many clinical scenarios.

As with all ultrasound imaging examinations, the first consideration for liver SHAPE is to obtain the best possible baseline grayscale images of the target region and to ensure (using Doppler imaging) that there are no intrahepatic portal venous shunts or other vascular abnormalities present. In the case of liver imaging for diagnosing portal hypertension the key is to visualize both the portal vein and a hepatic vein at the same depth to minimize the impact of attenuation (Figure 1).
<p...

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Contrast-Enhanced Subharmonic Aided Pressure Estimation SHAPE Using Ultrasound Imaging with a Focus on Identifying Portal Hypertension

A protocol for noninvasively estimating ambient pressures utilizing subharmonic ultrasound imaging of infused contrast microbubbles (following appropriate calibration) is described with examples from human patients with chronic liver disease.

Contrast-Enhanced Subharmonic Aided Pressure Estimation (SHAPE) Using Ultrasound Imaging with a Focus on Identifying Portal Hypertension

Noninvasive, accurate measurement of pressures within the human body has long been an important but elusive clinical goal. Contrast agents for ultrasound ...

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2.3K Views.  Thomas Jefferson University. Een protocol voor het niet-invasief schatten van omgevingsdrukken met behulp van subharmonische echografie van geïnfundeerde contrastmicrobubbels (na de juiste kalibratie) wordt beschreven met voorbeelden van menselijke patiënten met chronische leverziekte.

Video: Contrast-Enhanced Subharmonic Aided Pressure Estimation SHAPE Using Ultrasound Imaging with a Focus on Identifying Portal Hypertension

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 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.

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

Invasive Hemodynamic Characterization of the Portal-hypertensive Syndrome in Cirrhotic Rats

This is a detailed protocol describing invasive hemodynamic measurements in cirrhotic rats for the characterization of portal hypertensive syndrome. Portal hypertension (PHT) due to cirrhosis is responsible for the most severe complications in patients with liver disease. The full picture of the portal hypertensive syndrome is characterized by increased portal pressure (PP) due to the increased intrahepatic vascular resistance (IHVR), hyperdynamic circulation, and increased splanchnic blood flow. Progressive splanchnic arterial vasodilation and increased cardiac output with elevated heart rate (HR) but low arterial pressure characterizes the portal hypertensive syndrome.
Novel therapies are currently being developed that aim to decrease PP by either targeting IHVR or increased splanchnic blood flow &#8212; but side effects on systemic hemodynamics may occur. Thus, a detailed characterization of portal venous, splanchnic, and systemic hemodynamic parameters, including measurement of PP, portal venous blood flow (PVBF), mesenteric arterial blood flow, mean arterial pressure (MAP), and HR is needed for preclinical evaluation of the efficacy of novel treatments for PHT. Our video article provides the reader with a structured protocol for performing invasive hemodynamic measurements in cirrhotic rats. In particular, we describe the catheterization of the femoral artery and the portal vein via an ileocolic vein and the measurement of portal venous and splanchnic blood flow via perivascular Doppler-ultrasound flow probes. Representative results of different rat models of PHT are shown.

Here we describe a detailed protocol for invasive measurements of hemodynamic parameters including portal pressure, splanchnic blood flow, and systemic hemodynamics in order to characterize the portal hypertensive syndrome in rats.

This is a detailed protocol describing invasive hemodynamic measurements in cirrhotic rats for the characterization of portal hypertensive syndrome. ...

Medicine

Measurement of the Hepatic Venous Pressure Gradient and Transjugular Liver Biopsy

Here we provide a detailed protocol describing the clinical procedure of hepatic venous pressure gradient (HVPG) measurement in patients with advanced chronic liver disease followed by an instruction for transjugular biopsy. Under local anesthesia and ultrasound guidance, a catheter introducer sheath is placed in the right internal jugular vein. Using&#160;fluoroscopic guidance, a balloon catheter is advanced into the inferior vena cava (IVC) and inserted into a large hepatic vein. Correct and sufficient wedge position of the catheter is ensured by injecting contrast media while the balloon is blocking the outflow of the cannulated hepatic vein. After calibrating the external pressure transducer, continuous pressure recordings are obtained with triplicate recordings of the wedged hepatic venous pressure (WHVP) and free hepatic venous pressure (FHVP). The difference between FHVP and WHVP is referred to as HVPG, with values &#8805;10 mm Hg indicating clinically significant portal hypertension (CSPH). Before removing the catheter, pressure readings obtained in the IVC at the same level, as well as the right atrial pressure are recorded.
Finally, a transjugular liver biopsy can be obtained via the same vascular route. Different systems are available; however, core biopsy needles are preferred over aspiration needles, especially for cirrhotic livers. Again, under fluoroscopic guidance a biopsy needle introducer sheath is advanced into an hepatic vein. Next, the transjugular biopsy needle is gently advanced through the introducer sheath: (i) in case of aspiration biopsy, the needle is advanced into the liver parenchyma under aspiration and then removed quickly, or (ii) in case of a core biopsy, the cutting-mechanism is triggered inside the parenchyma. Several separate passages can be safely performed to obtain sufficient liver specimens via transjugular biopsy. In experienced hands, the combination of these procedures takes about 30-45 min.

Here, we present a protocol for measurement of hepatic venous pressure gradient (HVPG),the gold standard to diagnose clinically significant portal hypertension. Moreover, we describe how to perform a transjugular liver biopsy within the same session.

Here we provide a detailed protocol describing the clinical procedure of hepatic venous pressure gradient (HVPG) measurement in patients with advanced ...

Point-of-Care Ultrasound: A Review of Ultrasound Parameters for Predicting Difficult Airways

Airway management remains a crucial part of perioperative care. The conventional approach to assessing potentially difficult airways emphasizes the LEMON method, which looks for and evaluates the Mallampati classification, signs of obstruction, and neck mobility. Clinical findings help predict a higher likelihood of difficult tracheal intubation, but no clinical result reliably excludes difficult intubation. Ultrasound as an adjunct to clinical examination can provide the clinician with a dynamic anatomical airway assessment, which is impossible with clinical examination alone. In the hands of anesthesiologists, ultrasound is becoming more popular in the perioperative period. This method is particularly applicable for identifying proper endotracheal tube positioning in specific patient populations, such as those who are morbidly obese and patients with head and neck cancer or trauma. The focus is on identifying the normal anatomy, correctly positioning the endotracheal tube, and refining the parameters that predict difficult intubation. Several ultrasound measurements are clinical indicators of difficult direct laryngoscopy in the literature. A meta-analysis revealed that the distance from the skin to the epiglottis (DSE) is most associated with a difficult laryngoscopy. An ultrasound of the airway could be applied in routine practice as an adjunct to the clinical examination. A full stomach, rapid sequence intubation, gross visual anatomical abnormalities, and restricted neck flexibility prevent using ultrasound to assess the airway. The airway evaluation is performed with a linear array transducer of 12-4 MHz, with the patient in the supine position, with no pillow, and with the head and neck in a neutral position. The central axis of the neck is where the ultrasound parameters are measured. These image acquisitions guide the standard ultrasound examination of the airway.

A point-of-care ultrasound (POCUS) is a simple, non-invasive, and portable tool that enables dynamic airway assessment. Several studies have attempted to determine the role of ultrasound parameters as an adjunct to clinical examination in predicting difficult laryngoscopies.

Airway management remains a crucial part of perioperative care. The conventional approach to assessing potentially difficult airways emphasizes the LEMON ...

Imaging the Abdominal Aorta with Point-of-Care Ultrasound

An Approach to Point-Of-Care Ultrasound Evaluation of the Abdominal Aorta

Disorders of the abdominal aorta, including aneurysms and dissection, have potentially high rates of morbidity and mortality. While computed tomography (CT) is the current gold standard to image the abdominal aorta, the process of obtaining a CT may be time-consuming, requires the use of intravenous contrast dye, and involves exposure to ionizing radiation. Point-of-care Ultrasound (POCUS) can be performed at the bedside and has excellent sensitivity and specificity for the diagnosis of abdominal aortic aneurysm and excellent specificity for the diagnosis of abdominal aortic dissection. Additionally, POCUS is non-invasive, cost-effective, lacks ionizing radiation, requires no intravenous contrast dye, and can be performed without taking the patient from a critical care area. Screening for abdominal aortic aneurysm (AAA) can be done in primary care settings as well. 
This article will review the approach to POCUS of the abdominal aorta to evaluate such critical pathology. In this paper, we will review the sonographic anatomy of the abdominal aorta as well as the choice of the ultrasound probe, description of POCUS image acquisition, and some pearls and pitfalls of using POCUS to aid in the diagnosis of potentially life-threatening abdominal aortic pathology.

Author Spotlight: Using Point-of-Care Ultrasound for Comprehensive Evaluation of the Abdominal Aorta

This protocol reviews the steps to image the abdominal aorta with point-of-care ultrasound. We discuss image acquisition, troubleshooting imaging pitfalls and artifacts, and the recognition of life-threatening abdominal aortic pathology.

Disorders of the abdominal aorta, including aneurysms and dissection, have potentially high rates of morbidity and mortality. While computed tomography ...

Gastric Ultrasound Technique for Mitigating Peri-Procedural Aspiration Risk

Gastric Point of Care Ultrasound in Adults: Image Acquisition and Interpretation

Over the past two decades, diagnostic point-of-care ultrasound (POCUS) has emerged as a rapid and non-invasive bedside tool for addressing clinical inquiries related to gastric content. One emerging concern pertains to patients about to undergo sedation and/or endotracheal intubation: the elevated risk of aspiration from the patient&#39;s stomach contents. Aspiration of gastric contents into the lungs poses a serious and potentially life-threatening complication. This occurs more frequently when the stomach is considered &#34;full&#34; and can be affected by the techniques employed for airway management, making it potentially preventable. To mitigate the risk of peri-procedural aspiration, two distinct medical specialties (anesthesiology and critical care medicine) have independently developed techniques to utilize ultrasonography for identifying patients requiring &#34;full stomach&#34; precautions. Due to these separate specialties, the work of each group remains relatively unfamiliar outside its respective field. This article presents descriptions of both techniques for gastric ultrasound. Furthermore, it explains how these approaches can complement each other when one of them falls short. Regarding image acquisition, the article covers the following topics: indications and contraindications, selection of the appropriate probe, patient positioning, and troubleshooting. The article also delves into image interpretation, complete with example images. Additionally, it demonstrates how one of the two techniques can be employed to estimate gastric fluid volume. Lastly, the article briefly discusses medical decision-making based on the findings of this examination.

Author Spotlight: Point-of-Care Ultrasound for Gastric Content Assessment and Risk Stratification in Perioperative Care 

This protocol introduces two methods for image acquisition in gastric ultrasonography. Additionally, tips are provided for interpreting this information to assist in medical decision-making.

Over the past two decades, diagnostic point-of-care ultrasound (POCUS) has emerged as a rapid and non-invasive bedside tool for addressing clinical ...

Diaphragmatic Ultrasound in Adults: Image Acquisition and Interpretation

Diaphragm dysfunction is a widely recognized concern across numerous medical specialties and clinical settings. Timely and accurate assessment of the diaphragm is vital not only in critically ill patients, where it has a role in weaning from mechanical ventilation&#160;and respiratory outcomes, but also in the perioperative arena as a diagnostic tool to detect phrenic nerve function. Diaphragmatic assessment has traditionally utilized fluoroscopy and nerve studies that are time-consuming, costly, and non-portable. Point-of-care ultrasound (POCUS) overcomes these barriers and can be used as a tool for non-invasive screening of diaphragm function. However, POCUS for diaphragmatic dysfunction currently suffers from several issues such as a lack of consensus guidelines, a multiplicity of protocols, and poor interoperator reliability among existing protocols, most notably with the assessment of dome of diaphragm excursion and diaphragmatic thickening. To address these issues, this manuscript reviews the available literature on diaphragmatic POCUS and identifies an image acquisition technique that is both simple to perform and has high interoperator reliability. This technique first describes a qualitative evaluation of diaphragm excursion, followed by a quantitative assessment of the excursion of the zone of apposition. The technique is described stepwise along with all the following: patient positioning, transducer selection, probe placement, image optimization, and interpretation.

Point-of-care ultrasound (POCUS) is an essential technique for screening for diaphragmatic dysfunction due to its portability, non-invasiveness, and real-time imaging capabilities. Although current diaphragmatic POCUS protocols exist, they suffer from poor interoperator reliability and lack consensus guidelines. Here we describe a technique that is reproducible and simple to perform.

Diaphragm dysfunction is a widely recognized concern across numerous medical specialties and clinical settings. Timely and accurate assessment of the ...

Application of Laparoscopic Ultrasonography in Primary Choledochal Suture during Combined Two-lens Surgery

Gallstones combined with common bile duct stones are a common clinical disease. The minimally invasive treatments include laparoscopic cholecystectomy + laparoscopic common bile duct exploration (LC+LCBDE) and endoscopic retrograde cholangiopancreatography + laparoscopic cholecystectomy (ERCP+LC). LCBDE can resolve two issues in a single procedure, whereas ERCP+LC requires a two-step approach. As more studies have shown, common bile duct exploration with stone extraction followed by primary closure may lead to faster recovery and improved quality of life for patients.
Anatomical variations in bile ducts and vessels are well-known to be common. Laparoscopic ultrasound (LUS) is instrumental in clarifying the hepatic portal area's anatomical structures, determining biliary duct orientation, identifying spatial relationships between biliary ducts, hepatic arteries, and portal veins, and minimizing the risk of biliary injury.
The procedure is illustrated here through a detailed case description. After administering general anesthesia, a laparoscopic approach was routinely established to inspect the abdominal cavity and assess lesions. Laparoscopic ultrasound was employed to evaluate the gallbladder triangle within the hepatic portal region, including the anatomy of bile ducts and vessels. The gallbladder triangle was dissected, followed by a 5-0 needle incision of the bile duct wall. Choledochoscopy was performed for stone extraction, with confirmation of normal duodenal papillary function. Continuous suturing of the bile duct wall was achieved using 5-0 polydioxanone monofilament suture material. Concurrently, laparoscopic ultrasound verified complete stone clearance and assessed suture integrity.

Here, we develop and present a T-tube and intrabiliary stent-free technique utilizing dual-lens visualization (via laparoscope and choledochoscope) combined with laparoscopic ultrasonography (LUS) to perform primary choledochal suture.

Gallstones combined with common bile duct stones are a common clinical disease. The minimally invasive treatments include laparoscopic cholecystectomy + ...

Echocardiographic Assessment Using Subxiphoid-Only Examination for Hypotensive Patients

Point-of-care ultrasound, or POCUS, has gathered significant interest as a tool to augment clinical decision-making in the care of acutely ill patients. Patients with hemodynamic instability, in particular, require immediate intervention and are at high risk for further cardiovascular and/or respiratory decompensation. POCUS examination of these patients, therefore, requires a protocol that is sufficient to answer clinicians' questions while still retaining adequate brevity to be feasible in a short period of time at the bedside. Here, we demonstrate a protocol for obtaining such information by the Echocardiographic Assessment using Subxiphoid-Only - Mean Arterial Pressure, or EASy MAP exam, a focused ultrasonographic assessment of the cardiovascular and respiratory systems. The cardiovascular portion of the examination utilizes the subcostal window to obtain views of the heart and inferior vena cava (IVC); this is then supplemented by anterior upper lung and posterolateral diaphragmatic pleural views for the respiratory portion. All six views (cardiac, IVC, left and right anterior upper lung, and left and right posterolateral pleural) are obtained using a low-frequency phased array transducer. We discuss some of the common pitfalls encountered in obtaining these images and the basics of interpreting the most common findings; also described is a 12-point scale for rating the quality of the images obtained from the cardiac view and a small number of supplementary views that may be considered when clinically relevant.

The protocol here provides a rapid, phenotype-based approach for focused ultrasound evaluation of the hypotensive patient, using subcostal images of the inferior vena cava and heart, with additional views of the upper lungs and pleural spaces.

Point-of-care ultrasound, or POCUS, has gathered significant interest as a tool to augment clinical decision-making in the care of acutely ill patients. ...

Using Point of Care Ultrasound to Augment Acquisition of Physical Exam Skills: Organs

Source: Joseph H. Donroe, Rachel Liu; Yale School of Medicine, USA
Point of care ultrasound (POCUS) is used by clinicians for diagnosis, ongoing monitoring, and/or procedural guidance at the time of patient care. Many medical schools are now teaching POCUS as a part of their basic clinical skills training, in addition to history, physical exams, and clinical reasoning. Besides being an independent skill, POCUS is also an incredibly useful tool for augmenting the teaching and learning of the physical exam.
Learning the physical exam involves combining the knowledge of anatomy and physiology with the technical skills of performing maneuvers. This can be especially difficult when learning the physical exam on a healthy subject, where certain exam findings can be difficult to appreciate by palpation or percussion. Ultrasound is an imaging modality that can highlight anatomy and physiology in real-time and, when performed in conjunction with the physical exam, can lead to the improved acquisition of exam skills.
Examination of the cardiovascular system, lungs, abdomen, and thyroid can be a challenging skill for trainees to acquire, but an ultrasound can help to simplify the learning. With ultrasound, we can visualize the closing of heart valves and the timing of systole and diastole, thus adding visual clues to auscultation. Palpation of certain body parts, such as the popliteal and abdominal aorta, thyroid, liver edge, gall bladder, and spleen, are commonly met with uncertainty by learners. These body parts are easily visible using ultrasound, allowing learners to confirm hand placement and verify findings. Measurements of diaphragmatic excursion and liver span by percussion can also be confirmed under ultrasound, thus providing a standard for improving percussion technique. Finally, visualization of the internal jugular vein using ultrasound can improve inspection for jugular venous distension.
Studies have demonstrated that ultrasound training improves elements of the cardiac, pulmonary, abdominal, musculoskeletal, and vascular exams. Additionally, integrating ultrasound teaching with other clinical skills results in high student satisfaction and improved confidence in performing the physical exam. In this video, we will demonstrate how to use POCUS to facilitate learning the examination of the thyroid, lung, heart, liver, and spleen in a healthy subject.

Contrast-Enhanced Subharmonic Aided Pressure Estimation (SHAPE) Using Ultrasound Imaging with a Focus on Identifying Portal Hypertension

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