In vivo human mitral valves (MV) were imaged using real-time 3D transesophageal echocardiography (rt-3DTEE), and volumetric images of the MV at mid-systole were analyzed by user-initialized segmentation and 3D deformable modeling with continuous medial representation, a compact representation of shape. The resulting MV models were loaded with physiologic pressures using finite element analysis (FEA). We present the regional leaflet stress distributions predicted in normal and diseased (regurgitant) MVs. Rt-3DTEE, semi-automated leaflet segmentation, 3D deformable modeling, and FEA modeling of the in vivo human MV is tenable and useful for evaluation of MV pathology.

The goal of this murine investigation was to evaluate the effect of an antivascular ultrasound treatment on the growth of an implanted melanoma and the consequent survival rate. Following the intravenous injection of 0.2 mL ultrasound contrast agent (Definity), therapy (n = 15) was performed on 1 mL tumors for 3 minutes with low intensity, continuous ultrasound (3 MHz; 2.4 ± 0.1 W.cm−2 [ISATA]); control mice (n = 17) received a sham treatment. Mice were euthanized once the tumor had reached 3 mL and survival percentage versus time curves were plotted. The median survival time (time for tumor to reach 3 mL) for the treated group was 23 days and for the control group was 18 days; the difference was statistically significant (P ≤ 0.0001). Antivascular ultrasound therapy reduced the growth rate of an implanted melanoma and increased survival time. The ultrasound therapy provides a further example of tumor vascular disruption and its future clinical potential should be investigated.

This study was aimed at determining if physiotherapy ultrasound (US) affected the fragile and leaky angiogenic blood vessels in a tumor. In 22 C3HV/HeN mice, a subcutaneous melanoma (K173522) was insonated (1, 2 or 3 min) with continuous 1-MHz low-intensity (spatial-average temporal-average = 2.28 W cm−2), physiotherapy US. Contrast-enhanced (0.1 mL Optison®) power Doppler US observations were made and histogram analyses of the images were performed. Before insonation, all but 7% of the tumor was perfused. The avascular area in tumors receiving 3-min treatment increased to 82% (p < 0.001). A linear regression analysis showed that each min of insonation led to a 25% reduction in tumor vascularity; the antivascular activity persisted for 24 h. Histology demonstrated disruption of vascular walls and tumor cell death in areas of vascular congestion and thrombosis. Physiotherapy US particularly targeted the vascular structures, and the effects on tumor cells appeared to be secondary to the resultant ischemia.

Background:

The measurement of carotid intima-medial thickness is a well validated measure of cardiovascular risk. Although atherosclerosis occurs in the intima, this arterial layer is not measured alone due to limitation in ultrasound resolution with standard frequency probes.

Methods:

We evaluated the feasibility of using a 55-MHz ultrasound system with high resolution to measure intima thickness in several vascular territories compared to a “standard” frequency probe.

Results:

The intima and medial thickness was measured in the brachial, radial and tibial arteries in 10 healthy subjects and 5 subjects with peripheral arterial disease. The high frequency ultrasound probe showed superior resolution compared to the standard frequency probe allowing for measurement of intima separately from media.

Conclusions:

The intima can be measured independently of media with a high degree of reproducibility using a high frequency probe. This technology may allow for early detection of cardiovascular risk and extend knowledge about the physiological changes in the early atherosclerotic development.

Rationale and Objectives

To assess the delta (Δ) projection image processing technique for visualizing tumor microvessels and for quantifying the area of tissue perfused by them on contrast-enhanced ultrasound images.

Materials and Methods

The Δ-projection algorithm was implemented to quantify perfusion by tracking the running maximum of the difference (Δ) between the contrast-enhanced ultrasound image sequence and a baseline image. Twenty-five mice with subcutaneous K1735 melanomas were imaged first with contrast-enhanced grayscale and then with contrast-enhanced power Doppler (minexCPD) ultrasound. Δ-projection images were reconstructed from the grayscale images, then used to evaluate the evolution of tumor vascularity during the course of contrast enhancement. The extent of vascularity (ratio of the perfused area to the tumor area) for each tumor was determined quantitatively from Δ-projection images and compared with the extent of vascularity determined from contrast-enhanced power Doppler images. Δ-projection and minexCPD measurements were compared using linear regression analysis.

Results

Δ-projection was successfully performed in all 25 cases. The technique allowed dynamic visualization of individual blood vessels as they filled in real-time. Individual tumor blood vessels were distinctly visible during early image enhancement. Later, as an increasing number of blood vessels were filled with the contrast agent, clusters of vessels appeared as regions of perfusion, and identification of individual vessels became difficult. Comparisons were made between the perfused area of tumors in Δ-projections and in minexCPD images. The Δ-projection perfusion measurements correlated linearly with minexCPD.

Conclusion

Δ-projection visualized tumor vessels and enabled quantitative assessment of the tumor area perfused by the contrast agent.

Four very low birth weight, very premature infants were monitored during a 12° postural elevation using diffuse correlation spectroscopy (DCS) to measure microvascular cerebral blood flow (CBF) and transcranial Doppler ultrasound (TCD) to measure macrovascular blood flow velocity in the middle cerebral artery. DCS data correlated significantly with peak systolic, end diastolic, and mean velocities measured by TCD (pA =0.036, 0.036, 0.047). Moreover, population averaged TCD and DCS data yielded no significant hemodynamic response to this postural change (p>0.05). We thus demonstrate feasibility of DCS in this population, we show correlation between absolute measures of blood flow from DCS and blood flow velocity from TCD, and we do not detect significant changes in CBF associated with a small postural change (12°) in these patients.

This study investigated whether a microbubble-containing ultrasound contrast agent had a role in the antivascular action of physiotherapy ultrasound on tumor neovasculature. Ultrasound images (B-mode and contrast-enhanced power Doppler [0.02mL Definity]) were made of 22 murine melanomas (K173522). The tumor was insonated (ISATA = 1.7 W cm−2, 1 MHz, continuous output) for 3 min and the power Doppler observations of the pre- and post-insonation tumor vascularities were analyzed. Significant reductions (p = 0.005 for analyses of color weighted fractional area) in vascularity occurred when a contrast-enhanced power Doppler study occurred prior to insonation. Vascularity was unchanged in tumors without a pre-therapy Doppler study. Histological studies revealed tissue structural changes that correlated with the ultrasound findings. The underlying etiology of the interaction between the physiotherapy ultrasound beam, the microbubble-containing contrast agent and the tumor neovasculature is unknown. It was concluded that contrast agents play an important role in the antivascular effects induced by physiotherapy ultrasound.

Background

Epidermal growth factor receptor (EGFR) inhibitors have shown only modest clinical activity when used as single agents to treat cancers. They decrease tumor cell expression of hypoxia-inducible factor 1-α (HIF-1α) and vascular endothelial growth factor (VEGF). Hypothesizing that this might normalize tumor vasculature, we examined the effects of the EGFR inhibitor erlotinib on tumor vascular function, tumor microenvironment (TME) and chemotherapy and radiotherapy sensitivity.

Methodology/Principal Findings

Erlotinib treatment of human tumor cells in vitro and mice bearing xenografts in vivo led to decreased HIF-1α and VEGF expression. Treatment altered xenograft vessel morphology assessed by confocal microscopy (following tomato lectin injection) and decreased vessel permeability (measured by Evan's blue extravasation), suggesting vascular normalization. Erlotinib increased tumor blood flow measured by Power Doppler ultrasound and decreased hypoxia measured by EF5 immunohistochemistry and tumor O2 saturation measured by optical spectroscopy. Predicting that these changes would improve drug delivery and increase response to chemotherapy and radiation, we performed tumor regrowth studies in nude mice with xenografts treated with erlotinib and either radiotherapy or the chemotherapeutic agent cisplatin. Erlotinib therapy followed by cisplatin led to synergistic inhibition of tumor growth compared with either treatment by itself (p<0.001). Treatment with erlotinib before cisplatin led to greater tumor growth inhibition than did treatment with cisplatin before erlotinib (p = 0.006). Erlotinib followed by radiation inhibited tumor regrowth to a greater degree than did radiation alone, although the interaction between erlotinib and radiation was not synergistic.

Conclusions/Significance

EGFR inhibitors have shown clinical benefit when used in combination with conventional cytotoxic therapy. Our studies show that targeting tumor cells with EGFR inhibitors may modulate the TME via vascular normalization to increase response to chemotherapy and radiotherapy. These studies suggest ways to assess the response of tumors to EGFR inhibition using non-invasive imaging of the TME.