Contrast-enhanced subharmonic aided pressure estimation for assessment of intracranial pressure in vivo.

BACKGROUND: Intracranial pressure (ICP) monitoring in children currently requires invasive techniques. Subharmonic aided pressure estimation (SHAPE) uses contrast-enhanced ultrasound (CEUS) to measure intravascular and interstitial pressure, but utility in ICP measurements has yet to be explored. OBJECTIVE: The objective of this study was to investigate SHAPE as a novel tool for noninvasive ICP measurements in fetal lambs. MATERIALS AND METHODS: Eighteen fetal lambs at 107-139 days gestational age (term = 145 days) underwent subdural ICP catheter placement. The brain was imaged in the coronal plane in CEUS mode optimized for SHAPE, while infusing an US contrast agent into the fetal circulation. After SHAPE calibration, saline was infused via the subdural catheter to increase ICP. Five-second SHAPE cine clips were obtained at various ICPs. Subharmonic intensity values of the whole brain and thalami were correlated with ICP values using mixed effects linear regression analyses and the strength of the relationship was evaluated by Spearman's rank-order correlation. RESULTS: Forty-nine experiments produced 723 datapoints, including SHAPE intensity values and mean ICP measurements. There was a statistically significant inverse relationship between SHAPE intensity values and ICP measurements in the whole brain and thalami (median rho value - 0.58 and - 0.56, respectively). CONCLUSION: SHAPE intensity values of the brain demonstrate an inverse and statistically significant correlation with in vivo ICP measurements in an animal model.

3D Harmonic and Subharmonic Imaging for Characterizing Breast Lesions: A Multi-Center Clinical Trial.

OBJECTIVE: Breast cancer is the most frequent type of cancer among women. This multi-center study assessed the ability of 3D contrast-enhanced ultrasound to characterize suspicious breast lesions using clinical assessments and quantitative parameters. METHODS: Women with suspicious breast lesions scheduled for biopsy were enrolled in this prospective, study. Following 2D grayscale ultrasound and power Doppler imaging (PDI), a contrast agent (Definity; Lantheus) was administrated. Contrast-enhanced 3D harmonic imaging (HI; transmitting/receiving at 5.0/10.0 MHz), as well as 3D subharmonic imaging (SHI; transmitting/receiving at 5.8/2.9 MHz), were performed using a modified Logiq 9 scanner (GE Healthcare). Five radiologists independently scored the imaging modes (including standard-of-care imaging) using a 7-point BIRADS scale as well as lesion vascularity and diagnostic confidence. Parametric volumes were constructed from time-intensity curves for vascular heterogeneity, perfusion, and area under the curve. Diagnostic accuracy was determined relative to pathology using receiver operating characteristic (ROC) and reverse, step-wise logistical regression analyses. The κ-statistic was calculated for inter-reader agreement. RESULTS: Data were successfully acquired in 219 cases and biopsies indicated 164 (75%) benign and 55 (25%) malignant lesions. SHI depicted more anastomoses and vascularity than HI (P < .021), but there were no differences by pathology (P > .27). Ultrasound achieved accuracies of 82 to 85%, which was significantly better than standard-of-care imaging (72%; P < .03). SHI increased diagnostic confidence by 3 to 6% (P < .05), but inter-reader agreements were medium to low (κ < 0.52). The best regression model achieved 97% accuracy by combining clinical reads and parametric SHI. CONCLUSIONS: Combining quantitative 3D SHI parameters and clinical assessments improves the characterization of suspicious breast lesions.

Ultrasound Pressure Estimation for Diagnosing Portal Hypertension in Patients Undergoing Dialysis for Chronic Kidney Disease.

OBJECTIVES: Hepatic venous pressure gradient (HVPG) is considered the standard in quantifying portal hypertension, but can be unreliable in dialysis patients. A noninvasive ultrasound technique, subharmonic-aided pressure estimation (SHAPE), may be a valuable surrogate of these pressure estimates. This study compared SHAPE and HVPG with pathology findings for fibrosis in dialysis patients. METHODS: This was a subgroup study from an IRB-approved trial that included 20 patients on dialysis undergoing SHAPE examinations of portal and hepatic veins using a modified Logiq 9 scanner (GE, Waukesha, WI), during infusion of Sonazoid (GE Healthcare, Oslo, Norway). SHAPE was compared to HVPG and pathology findings using the Ludwig-Batts scoring system for fibrosis. Logistic regression, ROC analysis, and t-tests were used to compare HVPG and SHAPE with pathological findings of fibrosis. RESULTS: Of 20 cases, 5 had HVPG values corresponding to subclinical and clinical portal hypertension (≥6 and ≥10 mmHg, respectively) while 15 had normal HVPG values (≤5 mmHg). SHAPE and HVPG correlated moderately (r = 0.45; P = .047). SHAPE showed a trend toward correlating with fibrosis (r = 0.42; P = .068), while HVPG did not (r = 0.18; P = .45). SHAPE could differentiate between mild (stage 0-1) and moderate to severe (stage 2-4) fibrosis (-10.4 ± 4.9 dB versus -5.4 ± 3.2 dB; P = .035), HVPG could not (3.0 ± 0.6 mmHg versus 4.8 ± 0.7 mmHg; P = .30). ROC curves showed a diagnostic accuracy for SHAPE of 80%, while HVPG reached 76%. CONCLUSION: Liver fibrosis staging in dialysis patients evaluated for portal hypertension appears to be more accurately predicted by SHAPE than by HVPG; albeit in a small sample size.

Diagnosing Portal Hypertension with Noninvasive Subharmonic Pressure Estimates from a US Contrast Agent.

Background The current standard for assessing the severity of portal hypertension is the invasive acquisition of hepatic venous pressure gradient (HVPG). A noninvasive US-based technique called subharmonic-aided pressure estimation (SHAPE) could reduce risk and enable routine acquisition of these pressure estimates. Purpose To compare quantitative SHAPE to HVPG measurements to diagnose portal hypertension in participants undergoing a transjugular liver biopsy. Materials and Methods This was a prospective cross-sectional trial conducted at two hospitals between April 2015 and March 2019 (ClinicalTrials.gov identifier, NCT02489045). This trial enrolled participants who were scheduled for transjugular liver biopsy. After standard-of-care transjugular liver biopsy and HVPG pressure measurements, participants received an infusion of a US contrast agent and saline. During infusion, SHAPE data were collected from a portal vein and a hepatic vein, and the difference was compared with HVPG measurements. Correlations between data sets were determined by using the Pearson correlation coefficient, and statistical significance between groups was determined by using the Student t test. Receiver operating characteristic analysis was performed to determine the sensitivity and specificity of SHAPE. Results A total of 125 participants (mean age ± standard deviation, 59 years ± 12; 80 men) with complete data were included. Participants at increased risk for variceal hemorrhage (HVPG ≥12 mm Hg) had a higher mean SHAPE gradient compared with participants with lower HVPGs (0.79 dB ± 2.53 vs -4.95 dB ± 3.44; P < .001), which is equivalent to a sensitivity of 90% (13 of 14; 95% CI: 88, 94) and a specificity of 80% (79 of 99; 95% CI: 76, 84). The SHAPE gradient between the portal and hepatic veins was in good overall agreement with the HVPG measurements (r = 0.68). Conclusion Subharmonic-aided pressure estimation is an accurate noninvasive technique for detecting clinically significant portal hypertension. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Kiessling in this issue.

Hepatic Vein Contrast-Enhanced Ultrasound Subharmonic Imaging Signal as a Screening Test for Portal Hypertension.

BACKGROUND: Portal hypertension is the underlying cause of most complications associated with cirrhosis, with the hepatic venous pressure gradient (HVPG) used for diagnosis and disease progression. Subharmonic imaging (SHI) is a contrast-specific imaging technique receiving at half the transmit frequency resulting in better tissue suppression. AIMS: To determine whether the presence of optimized SHI signals inside the hepatic vein can be used as a screening test for portal hypertension. METHODS: This prospective trial had 131 patients undergoing SHI examination of portal and hepatic veins using a modified Logiq 9 scanner (GE, Waukesha, WI). Images acquired after infusion of the ultrasound contrast agent Sonazoid (GE Healthcare, Oslo, Norway) were assessed for the presence of optimized SHI signals in the hepatic vein and compared to the HVPG values obtained as standard of care. RESULTS: Of 131 cases, 64 had increased HVPG values corresponding to subclinical (n = 31) and clinical (n = 33) portal hypertension (> 5 and > 10 mmHg, respectively), and 67 had normal HVPG values (< 5 mmHg). Two readers performed independent, binary qualitative assessments of the acquired digital clips. Reader one (experienced radiologist) achieved for the subclinical subgroup sensitivity of 98%, specificity of 88%, and ROC area of 0.93 and for the clinical subgroup sensitivity of 100% and specificity of 61%, with an ROC area of 0.74. Reader two (less experienced radiologist) achieved for the subclinical subgroup sensitivity of 77%, specificity of 76%, and ROC area of 0.76 and for the clinical subgroup sensitivity of 88% and specificity of 63%, with an ROC area of 0.70. Readers agreement was of 83% with kappa value of 0.66. CONCLUSION: The presence of optimized SHI signals inside the hepatic vein can be a qualitative screening test for portal hypertension, which could reduce the need for invasive diagnostic procedures.

Characterization of Adnexal Masses Using Contrast-Enhanced Subharmonic Imaging: A Pilot Study.

OBJECTIVES: This pilot study evaluated whether contrast-enhanced subharmonic imaging (SHI) could be used to characterize adnexal masses before surgical intervention. METHODS: Ten women (with 12 lesions) scheduled for surgery of an ovarian mass underwent an SHI examination of their adnexal region using a modified LOGIQ E9 scanner (GE Healthcare, Waukesha, WI) with an endocavitary transducer, in which digital clips were acquired by pulse destruction-replenishment SHI across the lesions. Time-intensity curves were created offline to quantitatively evaluate SHI parameters (fractional tumor perfusion, peak contrast intensity, time to peak contrast enhancement, and area under the time-intensity curve), which were compared to pathologic characterizations of the lesions. RESULTS: Of the 12 masses, 8 were benign, and 4 were malignant. A qualitative analysis of the SHI images by an experienced radiologist resulted in diagnostic accuracy of 70%, compared to 56% without contrast, whereas an inexperienced radiologist improved from 50% to 58% accuracy, demonstrating the benefit of SHI. A quantitative analysis of SHI parameters produced diagnostic accuracy as high as 81%. Peak contrast intensity was significantly greater in malignant than benign masses (mean ± SD, 0.109 ± 0.088 versus 0.046 ± 0.030 arbitrary units; P = .046). Malignant masses also showed significantly greater perfusion than benign masses (24.79% ± 25.34% versus 7.62% ± 6.50%; P = .045). When the radiologist reads were combined with the most predictive quantitative SHI parameter (percent perfusion), diagnostic accuracy improved to 84% for the experienced radiologist and 96% for the novice radiologist. CONCLUSIONS: Results indicate that SHI for presurgical characterization of adnexal masses may improve the determination of malignancy and diagnostic accuracy, albeit based on a small sample size.

On Factors Affecting Subharmonic-aided Pressure Estimation (SHAPE).

Subharmonic-aided pressure estimation (SHAPE) estimates hydrostatic pressure using the inverse relationship with subharmonic amplitude variations of ultrasound contrast agents (UCAs). We studied the impact of varying incident acoustic outputs (IAO), UCA concentration, and hematocrit on SHAPE. A Logiq 9 scanner with a 4C curvilinear probe (GE, Milwaukee, Wisconsin) was used with Sonazoid (GE Healthcare, Oslo, Norway) transmitting at 2.5 MHz and receiving at 1.25 MHz. An improved IAO selection algorithm provided improved correlations ( r from -0.85 to -0.95 vs. -0.39 to -0.98). There was no significant change in SHAPE gradient as the pressure increased from 10 to 40 mmHg and hematocrit concentration was tripled from 1.8 to 4.5 mL/L (Δ0.00-0.01 dB, p = 0.18), and as UCA concentration was increased from 0.2 to 1.2 mL/L (Δ0.02-0.05 dB, p = 0.75). The results for the correlation between the SHAPE gradient and hematocrit values for patients ( N = 100) in an ongoing clinical trial were also calculated showing a poor correlation value of 0.14. Overall, the SHAPE gradient is independent of hematocrit and UCA concentration. An improved algorithm for IAO selection will make SHAPE more accurate.

Eye Gaze Patterns Associated with Aggressive Tendencies in Adolescence.

Social information processing theory hypothesizes that aggressive children pay more attention to cues of hostility and threat in others' behavior, consequently leading to over-interpretation of others' behavior as hostile. While there is abundant evidence of aggressive children demonstrating hostile attribution biases, less well documented is whether such biases stem from over-attendance and hypersensitivity to hostile cues in social situations. Over-attendance to hostile cues would be typified by deviations at any stage of the multi-stage process of social information processing models. While deviations at later stages in social information processing models are associated with aggressive behavior in children, the initial step of encoding has historically been difficult to empirically measure, being a low level automatic process unsuitable for self-report. We employed eye-tracking methodologies to better understand the visual encoding of such social information. Eye movements of ten 13-18 year-old children referred from clinical and non-clinical populations were recorded in real time while the children viewed scenarios varying between hostile, non-hostile and ambiguous social provocation. In addition, the children completed a brief measure of risk of aggression. Aggressive children did attend more to the social scenarios with hostile cues, in particular attending longest to those hostile scenarios where the actor in the scenario had a congruent emotional response. These findings corroborate social information processing theory and the traditional bottom-up processing hypotheses that aggressive behavior relates to increased attention to hostile cues.

Effect of Pulse Shaping on Subharmonic Aided Pressure Estimation In Vitro and In Vivo.

OBJECTIVES: Subharmonic imaging (SHI) is a technique that uses the nonlinear oscillations of microbubbles when exposed to ultrasound at high pressures transmitting at the fundamental frequency ie, fo and receiving at half the transmit frequency (ie, fo /2). Subharmonic aided pressure estimation (SHAPE) is based on the inverse relationship between the subharmonic amplitude of the microbubbles and the ambient pressure change. METHODS: Eight waveforms with different envelopes were optimized with respect to acoustic power at which the SHAPE study is most sensitive. The study was run with four input transmit cycles, first in vitro and then in vivo in three canines to select the waveform that achieved the best sensitivity for detecting changes in portal pressures using SHAPE. A Logiq 9 scanner with a 4C curvi-linear array was used to acquire 2.5 MHz radio-frequency data. Scanning was performed in dual imaging mode with B-mode imaging at 4 MHz and a SHI contrast mode transmitting at 2.5 MHz and receiving at 1.25 MHz. Sonazoid, which is a lipid stabilized gas filled bubble of perfluorobutane, was used as the contrast agent in this study. RESULTS: A linear decrease in subharmonic amplitude with increased pressure was observed for all waveforms (r from -0.77 to -0.93; P < .001) in vitro. There was a significantly higher correlation of the SHAPE gradient with changing pressures for the broadband pulses as compared to the narrowband pulses in both in vitro and in vivo results. The highest correlation was achieved with a Gaussian windowed binomial filtered square wave with an r-value of -0.95. One of the three canines was eliminated for technical reasons, while the other two produced very similar results to those obtained in vitro (r from -0.72 to -0.98; P <.01). The most consistent in vivo results were achieved with the Gaussian windowed binomial filtered square wave (r = -0.95 and -0.96). CONCLUSIONS: Using this waveform is an improvement to the existing SHAPE technique (where a square wave was used) and should make SHAPE more sensitive for noninvasively determining portal hypertension.

Investigation Into the Subharmonic Response of Three Contrast Agents in Static and Dynamic Flow Environments Using a Commercially Available Diagnostic Ultrasound Scanner.

OBJECTIVE: The objective of this study was to investigate the subharmonic response of Lumason (also known as SonoVue; Bracco, Milan, Italy) to static and dynamic ambient pressures, with a direct comparison to Sonazoid (GE HealthCare, Oslo, Norway) and Definity (Lantheus Medical Imaging, MA, USA). The subharmonic responses of contrast agents can be exploited to perform subharmonic-aided pressure estimation. METHODS: The subharmonic response of each ultrasound contrast agent was evaluated in both a static and dynamic tank using a commercially available Logiq E10 clinical ultrasound scanner (GE HealthCare) equipped with subharmonic imaging (SHI) and an acoustic power-optimization algorithm. A C1-6 curvilinear array that transmits at 2.5 MHz and receives at 1.25 MHz in SHI mode was used to acquire the subharmonic signals. Data was transferred offline into MATLAB (MathWorks) to perform linear regression analysis and statistical testing for significance of the slopes (i.e., agent sensitivity). RESULTS: Sonazoid and Definity showed an inverse linear dependency between subharmonic signal and hydrostatic pressure at all pressure ranges (static and dynamic) tested, with maximum sensitivity under 50 mmHg in the static tank (-0.190 and -0.194 dB/mmHg for Sonazoid and Definity, respectively). Lumason exhibited a tri-phasic subharmonic behavior, beginning with a linear trend from 0 to 90 mmHg (sensitivity = 0.069 dB/mmHg), followed by a plateau from 100 to 130 mmHg, and an inverse linear trend from 140 to 200 mmHg (sensitivity = -0.137 dB/mmHg). CONCLUSION: The subharmonic response of Lumason is tri-phasic and differs from Sonazoid and Definity. Further investigation is needed to solidify understanding of the subharmonic behavior of Lumason to identify its usefulness for subharmonic-aided pressure estimation.

Classification of Metastatic Lymph Nodes In Vivo Using Quantitative Ultrasound at Clinical Frequencies.

Quantitative ultrasound (QUS) methods characterizing the backscattered echo signal have been of use in assessing tissue microstructure. High-frequency (30 MHz) QUS methods have been successful in detecting metastases in surgically excised lymph nodes (LNs), but limited evidence exists regarding the efficacy of QUS for evaluating LNs in vivo at clinical frequencies (2-10 MHz). In this study, a clinical scanner and 10-MHz linear probe were used to collect radiofrequency (RF) echo data of LNs in vivo from 19 cancer patients. QUS methods were applied to estimate parameters derived from the backscatter coefficient (BSC) and statistics of the envelope-detected RF signal. QUS parameters were used to train classifiers based on linear discriminant analysis (LDA) and support vector machines (SVMs). Two BSC-based parameters, scatterer diameter and acoustic concentration, were the most effective for accurately detecting metastatic LNs, with both LDA and SVMs achieving areas under the receiver operating characteristic (AUROC) curve ≥0.94. A strategy of classifying LNs based on the echo frame with the highest cancer probability improved performance to 88% specificity at 100% sensitivity (AUROC = 0.99). These results provide encouraging evidence that QUS applied at clinical frequencies may be effective at accurately identifying metastatic LNs in vivo, helping in diagnosis while reducing unnecessary biopsies and surgical treatments.

Focused ultrasound neuromodulation of the spleen activates an anti-inflammatory response in humans.

Focused ultrasound stimulation (FUS) activates mechanosensitive ion channels and is emerging as a method of noninvasive neuromodulation. In preclinical studies, FUS of the spleen (sFUS) activates an anti-inflammatory neural pathway which suppresses acute and chronic inflammation. However, the relevance of sFUS for regulating inflammatory responses in humans is unknown. Here, we used a modified diagnostic ultrasound imaging system to target the spleen of healthy human subjects with 3 min of continuously swept or stationary focused pulsed ultrasound, delivered at three different energy levels within allowable safety exposure limits. Potential anti-inflammatory effects of sFUS were assessed by measuring sFUS-elicited changes in endotoxin-induced tumor necrosis factor (TNF) production in whole blood samples from insonified subjects. We found that stimulation with either continuously swept or focused pulsed ultrasound has an anti-inflammatory effect: sFUS lowers TNF production for >2 h, with TNF returning to baseline by 24 h following sFUS. This response is independent of anatomical target (i.e., spleen hilum or parenchyma) or ultrasound energy level. No clinical, biochemical, or hematological parameters are adversely impacted. This is the first demonstration that sFUS suppresses the normal inflammatory response in humans, with potential implications for noninvasive bioelectronic therapy of inflammatory disorders.

Automatic Hemorrhage Detection From Color Doppler Ultrasound Using a Generative Adversarial Network (GAN)-Based Anomaly Detection Method.

Hemorrhage control has been identified as a priority focus area both for civilian and military populations in the United States because exsanguination is the most common cause of preventable death in hemorrhagic injury. Non-compressible torso hemorrhage (NCTH) has high mortality rate and there are currently no broadly available therapies for NCTH outside of a surgical room environment. Novel therapies, which include High Intensity Focused Ultrasound (HIFU) have emerged as promising methods for hemorrhage control as they can non-invasively cauterize bleeding tissue deep within the body without injuring uninvolved regions. A major challenge in the application of HIFU with color Doppler US guidance is the interpretation and optimization of the blood flow images in real-time to identify the hemorrhagic focus. Today, this task requires an expert sonographer, limiting the utility of this therapy in non-clinical environments. In this work, we investigated the feasibility of an automated hemorrhage detection method using a Generative Adversarial Network (GAN) for anomaly detection that learns a manifold of normal blood flow variability and subsequently identifies anomalous flow patterns that fall outside the learned manifold. As an initial feasibility study, we collected ultrasound color Doppler images of femoral arteries in an animal model of vascular injury (N = 11 pigs). Velocity information of the blood flow were extracted from the color Doppler images that were used for training and testing the anomaly detection network. Normotensive images from 8 pigs were used for training, and testing was performed on normotensive, immediately after injury, 10 minutes post-injury and 30 minutes post-injury images from 3 other pigs. The residual images or the reconstructed error maps show promise in detecting hemorrhages with an AUC of 0.90, 0.87, 0.62 immediately, 10 minutes post-injury and 30 minutes post-injury respectively with an overall AUC of 0.83.

Stimulation of the hepatoportal nerve plexus with focused ultrasound restores glucose homoeostasis in diabetic mice, rats and swine.

Peripheral neurons that sense glucose relay signals of glucose availability to integrative clusters of neurons in the brain. However, the roles of such signalling pathways in the maintenance of glucose homoeostasis and their contribution to disease are unknown. Here we show that the selective activation of the nerve plexus of the hepatic portal system via peripheral focused ultrasound stimulation (pFUS) improves glucose homoeostasis in mice and rats with insulin-resistant diabetes and in swine subject to hyperinsulinemic-euglycaemic clamps. pFUS modulated the activity of sensory projections to the hypothalamus, altered the concentrations of metabolism-regulating neurotransmitters, and enhanced glucose tolerance and utilization in the three species, whereas physical transection or chemical blocking of the liver-brain nerve pathway abolished the effect of pFUS on glucose tolerance. Longitudinal multi-omic profiling of metabolic tissues from the treated animals confirmed pFUS-induced modifications of key metabolic functions in liver, pancreas, muscle, adipose, kidney and intestinal tissues. Non-invasive ultrasound activation of afferent autonomic nerves may represent a non-pharmacologic therapy for the restoration of glucose homoeostasis in type-2 diabetes and other metabolic diseases.

Improved signal processing to detect cancer by ultrasonic molecular imaging of targeted nanoparticles.

In several investigations of molecular imaging of angiogenic neovasculature using a targeted contrast agent, Renyi entropy [I(f)(r)] and a limiting form of Renyi entropy (I(f,∞)) exhibited significantly more sensitivity to subtle changes in scattering architecture than energy-based methods. Many of these studies required the fitting of a cubic spline to backscattered waveforms prior to calculation of entropy [either I(f)(r) or I(f,∞)]. In this study, it is shown that the robustness of I(f,∞) may be improved by using a smoothing spline. Results are presented showing the impact of different smoothing parameters. In addition, if smoothing is preceded by low-pass filtering of the waveforms, further improvements may be obtained.

Intraoperative Monitoring of Spinal Cord Perfusion using Ultrasound in an Ovine Model.

Ultrasound imaging can be used to visualize the spinal cord and assess localized cord perfusion. We present in vivo data in an ovine model undergoing spinal cord stimulation and propose development of transcutaneous US imaging as a potential non-invasive imaging modality in spinal cord injury.Clinical Relevance- Ultrasound imaging can be used to aid in prognosis and diagnosis by providing qualitative and quantitative characterization of the spinal cord. This modality can be developed as a low cost, portable, and non-invasive imaging technique in spinal injury patients.

A Preliminary Study of Quantitative Ultrasound for Cancer-Risk Assessment of Thyroid Nodules.

Background: Gray-scale, B-mode ultrasound (US) imaging is part of the standard clinical procedure for evaluating thyroid nodules (TNs). It is limited by its instrument- and operator-dependence and inter-observer variability. In addition, the accepted high-risk B-mode US TN features are more specific for detecting classic papillary thyroid cancer rather than the follicular variant of papillary thyroid cancer or follicular thyroid cancer. Quantitative ultrasound (QUS) is a technique that can non-invasively assess properties of tissue microarchitecture by exploiting information contained in raw ultrasonic radiofrequency (RF) echo signals that is discarded in conventional B-mode imaging. QUS provides quantitative parameter-value estimates that are a function of the properties of US scatterers and microarchitecture of the tissue. The purpose of this preliminary study was to assess the performance of QUS parameters in evaluating benign and malignant thyroid nodules. Methods: Patients from the Thyroid Health Center at the Boston Medical Center were recruited to participate. B-mode and RF data were acquired and analyzed in 225 TNs (24 malignant and 201 benign) from 208 patients. These data were acquired either before (167 nodules) or after (58 nodules) subjects underwent fine-needle biopsy (FNB). The performance of a combination of QUS parameters (CQP) was assessed and compared with the performance of B-mode risk-stratification systems. Results: CQP produced an ROC AUC value of 0.857 ± 0.033 compared to a value of 0.887 ± 0.033 (p=0.327) for the American College of Radiology Thyroid Imaging, Reporting and Data System (ACR TI-RADS) and 0.880 ± 0.041 (p=0.367) for the American Thyroid Association (ATA) risk-stratification system. Furthermore, using a CQP threshold of 0.263 would further reduce the number of unnecessary FNBs in 44% of TNs without missing any malignant TNs. When CQP used in combination with ACR TI-RADS, a potential additional reduction of 49 to 66% in unnecessary FNBs was demonstrated. Conclusion: This preliminary study suggests that QUS may provide a method to classify TNs when used by itself or when combined with a conventional gray-scale US risk-stratification system and can potentially reduce the need to biopsy TNs.

A Noninvasive Ultrasound Based Technique to Identify Treatment Responders in Patients with Portal Hypertension.

RATIONALE AND OBJECTIVE: Subharmonic aided pressure estimation (SHAPE) is based on the inverse relationship between the subharmonic amplitude of ultrasound contrast microbubbles and ambient pressure. The aim of this study was to verify if SHAPE can accurately monitor disease progression in patients identified with portal hypertension. MATERIALS & METHODS: A modified Logiq 9 scanner with a 4C curvi-linear probe (GE, Waukesha, WI) was used to acquire SHAPE data (transmitting and receiving at 2.5 and 1.25 MHz, respectively) using Sonazoid (GE Healthcare, Oslo, Norway; FDA IND 124,465). Twenty-one (median age 59 years; 12 Males) of the 178 patients enrolled in this institutional review board approved study (14F.113) were identified as having clinically significant portal hypertension based on their hepatic venous pressure gradient results ≥ 10 mmHg. Repeat SHAPE examinations were done every 6.2 months. Liver function tests and clinical indicators were used to establish treatment response. RESULTS: Of the 21 portal hypertensive subjects, 11 had successful follow up scans with an average follow up time of 6.2 months. There was a significantly larger SHAPE signal reduction in the group who were classified as treatment responders (n = 10; -4.01±3.61 dB) compared to the single nonresponder (2.33 dB; p < 0.001). Results for responders matched the corresponding clinical outcomes of improved model for end stage liver disease (MELD) scores, improvement in underlying cause of portal hypertension, improved liver function tests and reduced ascites. CONCLUSION: SHAPE can potentially monitor disease progression in portal hypertensive patients and hence, may help clinicians in patient management. A larger study would further validate this claim.

Selecting the optimal parameters for sonoporation of pancreatic cancer in a pre-clinical model.

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers in the modern world, in part due to poor delivery of chemotherapeutics. Sonoporation can be used to enhance the efficacy of standard of care therapies for PDAC. Using xenograft models of PDAC we investigate sonoporation using four ifferent ultrasound contrast agents (UCAs) and two ultrasound regimens to identify the ideal parameters to increase therapeutic efficacy. MIA-PaCa2 xenografts in over 175 immunodeficient mice were treated with gemcitabine and paclitaxel and subjected to low or high power ultrasound (60 and 200 mW/cm2 respectively) in conjunction with one of four different UCAs. The UCAs investigated were Definity®, SonoVue®, Optison™ or Sonazoid™. Tumor volumes, vascularity, hemoglobin, and oxygenation were measured and compared to controls. High power treatment in conjunction with Sonazoid sonoporation led to significantly smaller tumors when started early (tumors ~50mm3; p = .0105), while no UCAs significantly increased efficacy in the low power cohort. This trend was also found in larger tumors (~250mm3) where all four UCA agents significantly increased therapeutic efficacy in the high power group (p < .01), while only Definity and SonoVue increased efficacy in the low power cohort (p < .03). Overall, the higher power ultrasound treatment modality was more consistently effective at decreasing tumor volume and increasing vascularity characteristics. In conclusion, Sonazoid was the most consistently effective UCA at decreasing tumor volume and increasing vascularity. Thus, we are pursuing a larger phase II clinical trial to validate the increased efficacy of sonoporation in conjunction with chemotherapy in PDAC patients.

Fluidic measurement of electric field sensitivity of Ti-GaAs Schottky junction gated field effect biosensors.

We report the electric field and pH sensitivity of fluid gated metal-semiconductor hybrid (MSH) Schottky structures consisting of a Titanium layer on n-type GaAs. Compared to standard field-effect sensors, the MSH Schottky structures are 21 times more sensitive to electric field of -46.6 V/cm and show about six times larger resistance change as pH of the solution is decreased from 8.17 to 5.54. The potential change at the fluidic gate and passivation layer interface by bias voltages and pH are mirrored by the metal shunt, resulting in larger depletion widths under the Schottky junction and resistance change as compared to sensors with no Schottky junction. 2D numerical simulation results are in good agreement with the measured data and suggest thinner mesa with lower doping density can further increase device sensitivity.