| 1. |
- Cinthio, Magnus, et al.
(författare)
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New non-invasive method for intima-media thickness and intima-media compression measurements
- 2005
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Ingår i: Proceedings - IEEE Ultrasonics Symposium. - 1051-0117. - 0780393821 ; 1, s. 389-392
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Konferensbidrag (refereegranskat)abstract
- Intim a-media thickness (IMT) is considered as a valuable marker of early atherosclerosis. We suggest a new algorithm for simultaneous measurements of absolute diameter at diastole, distension (diameter change), IMT at diastole and the intima-media compression (IMC) with a new fast, robust, high-resolution, and automatic algorithm utilizing the ultrasonic gray-scale information. The new algorithm is evaluated in a limited in vivo study on the common carotid artery of 5 healthy volunteers. The standard deviation within an investigation was (8 ± 4 μm; range 4-14 μm) during IMC measurements, (8 ± 5 μm; range 4-16 μm) during the measurements of the IMT at diastole, (30 ±36 μm; range 6-92 μm) during the distension measurements and (48 ±49 μm; range 15-134 μm) during the measurements of the lumen diameter at diastole. The evaluation shows that the algorithm is fast and that the reproducibility and resolution are more than sufficient for in vivo studies. © 2005 IEEE.
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| 2. |
- Jansson, Tomas, et al.
(författare)
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Ultrasound Doppler for improved diagnosis of disease in the paranasal sinuses
- 2005
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Ingår i: Proceedings - IEEE Ultrasonics Symposium. - 1051-0117. - 0780393821 ; 2, s. 839-841
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Konferensbidrag (refereegranskat)abstract
- We propose a method to improve the diagnosis of infection in the paranasal sinuses, distinguishing between mucous and serous cases. The method utilizes a previously published method whereby the viscosity in a sealed container may be measured using an ultrasound Doppler method. As ultrasound propagates in a liquid medium, due to attenuation, the resulting pressure gradient will cause the liquid to move in the propagation direction - the wellknown effect of acoustic streaming. The streaming velocity will, for a given acoustic output, be proportional to the viscosity of the fluid. In this study, we verify that acoustic streaming can be induced in an anthropomorphic sinus phantom cast from a human cranium. The sinus phantom was made from agar with added graphite providing sound attenuation prior to the sinus cavity corresponding to an in vivo situation. A number of water-glycerol solutions with scattering particles, were prepared to mimic a clinically interesting range of viscosities (7-47 mPas). Using a 4.2 MHz continuous wave Doppler probe, clearly detectable mean Doppler shifts in the range of 6.5 to 20 Hz were recorded A linear relationship was found between the Doppler shifts and 1/viscosity (R2=0.94, corrected for the square-law dependence of sound speed variation due to varying glycerol concentration).
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| 3. |
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| 4. |
- Martinsson, Jesper, et al.
(författare)
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Parametric modeling of wave propagation in gas mixtures : a system identification approach
- 2005
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Ingår i: 2005 IEEE Ultrasonics Symposium. - Piscataway, NJ : IEEE Communications Society. - 0780393821 ; , s. 2288-2292
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Konferensbidrag (refereegranskat)abstract
- In ultrasonic pulse-echo systems, the observable properties are restricted to frequency dependent attenuation and phase velocity, which in turn are related to the material properties of the investigated media. In this paper we present a parametric model of the bulk modulus, composed of the basic physical building blocks of absorption (relaxation blocks). The parametric model is capable of handling the combined effect of the absorption mechanisms present in a gas or gas mixture and captures the experimental variation in the observation. The performance of the parametric model is demonstrated with pulse-echo experiments in oxygen, ethane and mixtures of the two. Compared to standard Fourier analysis techniques, the parametric model gives higher accuracy when estimating attenuation and phase velocity, and physical parameters such as relaxation strengths and relaxation frequencies can be extracted from it.
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| 5. |
- Niemi, Jan, et al.
(författare)
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Ultrasonic measurements and modelling of attenuation and phase velocity in pulp suspensions
- 2005
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Ingår i: 2005 IEEE Ultrasonics Symposium. - Piscataway, NJ : IEEE Communications Society. - 0780393821 ; , s. 775-779
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Konferensbidrag (refereegranskat)abstract
- In the manufacturing process of paper the mass fraction and material properties of the fibres in the pulp suspension are important for the quality of the finished product. This study presents two different methods of pulp characterisation. The first is based on phase velocity, which we use to investigate the composition of the pulp. Here a method is presented where the optimal number of circular shifts within the sampling window of the signal is determined which gives, in a weakly dispersive medium, a continuous phase spectrum and minimizes the likelihood of discontinuities within the bandwidth. Hence, the ambiguity in phase unwrapping is avoided. The results from phase velocity measurements show that the phase velocity weakly increases with increasing amount of fines in the suspension. The dispersion is caused by the fibres and it correlates with fibre mass fraction. The second method is based on attenuation and is used to characterise the wood fibres. The results of the attenuation experiments show that it is possible to inversely calculate wood fibre properties by fitting the model to the experimental data, if the fibre diameter distribution is known. However, the accuracy of these calculation is difficult to determined and more work in this area is required.
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