Ultrasound in medicine & biology
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Ultrasound Med Biol · Jan 2014
Comparative StudyNew quantification methods for carotid intra-plaque neovascularization using contrast-enhanced ultrasound.
As carotid intra-plaque neovascularization (IPN) is linked to progressive atherosclerotic disease and plaque vulnerability, its accurate quantification might allow early detection of plaque vulnerability. We therefore developed several new quantitative methods for analyzing IPN perfusion and structure. From our analyses, we derived six quantitative parameters-IPN surface area (IPNSA), IPN surface ratio (IPNSR), plaque mean intensity, plaque-to-lumen enhancement ratio, mean plaque contrast percentage and number of micro-vessels (MVN)-and compared these with visual grading of IPN by two independent physicians. ⋯ IPNSA (correlation r = 0.719), IPNSR (r = 0.538) and MVN (r = 0.484) were found to be significantly correlated with visual scoring (p < 0.01). IPNSA was the best match to visual scoring. These results indicate that IPNSA, IPNSR and MVN may have the potential to replace qualitative visual scoring and to measure the degree of carotid IPN.
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Ultrasound Med Biol · Jan 2014
Microbubble type and distribution dependence of focused ultrasound-induced blood-brain barrier opening.
Focused ultrasound, in the presence of microbubbles, has been used non-invasively to induce reversible blood-brain barrier (BBB) opening in both rodents and non-human primates. This study was aimed at identifying the dependence of BBB opening properties on polydisperse microbubble (all clinically approved microbubbles are polydisperse) type and distribution by using a clinically approved ultrasound contrast agent (Definity microbubbles) and in-house prepared polydisperse (IHP) microbubbles in mice. A total of 18 C57 BL/6 mice (n = 3) were used in this study, and each mouse was injected with either Definity or IHP microbubbles via the tail vein. ⋯ Permeability of the treated region and volume of BBB opening did not significantly differ between the two types of microbubbles (p > 0.05) at peak rarefractional acoustic pressures of 0.45 and 0.6 MPa, whereas IHP microbubbles had significantly higher permeability and opening volume (p < 0.05) at the relatively lower pressure of 0.3 MPa. The results from this study indicate that microbubble type and distribution could have significant effects on focused ultrasound-induced BBB opening at lower pressures, but less important effects at higher pressures, possibly because of the stable cavitation that governs the former. This difference may have become less significant at higher pressures, where inertial cavitation typically occurs.
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Ultrasound Med Biol · Jan 2014
Development of oil-in-gelatin phantoms for viscoelasticity measurement in ultrasound shear wave elastography.
Because tissues consist of solid and fluid materials, their mechanical properties should be characterized in terms of both elasticity and viscosity. Although the elastic properties of tissue-mimicking phantoms have been extensively studied and well characterized in commercially available phantoms, their viscous properties have not been fully investigated. In this article, a set of 14 tissue-mimicking phantoms with different concentrations of gelatin and castor oil were fabricated and characterized in terms of acoustic and viscoelastic properties. ⋯ The results also confirm that increasing the gelatin concentration increases shear modulus. For phantoms containing 3%, 4%, 5%, 6% and 7% gelatin, the measured shear moduli are 2.01 ± 0.26, 3.10 ± 0.34, 4.18 ± 0.84, 8.05 ± 1.00 and 10.24 ± 1.80 kPa at 0% oil and 1.10 ± 0.22, 1.97 ± 0.20, 3.13 ± 0.63, 4.60 ± 0.60 and 8.43 ± 1.39 kPa at 20% oil, respectively. The phantom recipe developed in this study can be used in validating ultrasound shear wave elastography techniques for soft tissues.