| 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. |
- Cinthio, Magnus, et al.
(författare)
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Minute roughness measurement using phase tracking for arterial wall diagnosis non-invasively in vivo
- 2007
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Ingår i: Ultrasonics Symposium, 2007. IEEE, vols 1-6. - 1051-0117. ; , s. 997-1000
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Konferensbidrag (refereegranskat)abstract
- Early diagnosis of atherosclerosis is essential as many of the risk factors are life-style dependent. We suggest a new method to measure minute roughness of the size of micrometers of the arterial wall. The method was evaluated using three silicone phantoms sized 13 fun, 23 itm and 33 pm, respectively. The mean of the measured heights of the phantoms were 8.1 mu m (SD 0.0), 23.3 mu m (SD 0.2) and 29.6 mu m (SD 0.1) in the forward direction, and 7.7 mu m (SI) 0.0), 21.9 mu m (SI) 0.2) and 27.3 mu m (SI) 3.6) In the backward direction, respectively. The phantom study shows very promising result and encourages to further evaluation and in vivo Investigations.
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| 4. |
- Cinthio, Magnus, et al.
(författare)
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Non-invasive measurements of longitudinal strain of the arterial wall
- 2007
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Ingår i: Ultrasonics Symposium, 2007. IEEE, vols 1-6. - 1051-0117. - 9781424413843 ; , s. 570-572
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Konferensbidrag (refereegranskat)abstract
- We have recently shown that there is a previous unknown longitudinal movement present in the arterial wall. The aim is now to investigate whether the longitudinal movement is associated with longitudinal strain of the arterial wall. The objective of this paper was to describe a new non-invasive ultrasonic technique that measures the longitudinal strain of arteries in human in-vivo. Results indicate that a longitudinal strain is present in the common carotid artery.
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| 5. |
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| 6. |
- 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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| 7. |
- Mogensen, Hannes, et al.
(författare)
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Non-Invasive Ultrasonic Measurement of the Relative Volume Change of the Arterial Wall - First in vivo trial
- 2008
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Ingår i: 2008 IEEE Ultrasonics symposium, vols 1-4 and appendix. - 1051-0117. ; , s. 856-858
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Konferensbidrag (refereegranskat)abstract
- The objective of this study was to show a method that combine non-invasive measurements of the relative diameter change, the radial and the longitudinal strain of the intima-media complex of arterial walls, respectively, to obtain total change in arterial wall volume for a segment of the common carotid artery. The method was evaluated in a limited trial in vivo, comprising five normotensive subjects. Compared to the volume at end-diastole, the average maximum increase in arterial wall volume during each cardiac cycle was 3.2 % (SD 1.8). The aver-age maximum decrease of the arterial wall volume was -5.7 % (SD 3.5). This provides a new way of examining and quantifying the elastic properties of arterial walls.
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| 8. |
- 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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| 9. |
- Persson, Magnus, et al.
(författare)
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Non-invasive measurement of arterial longitudinal movement
- 2002
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Ingår i: Proceedings of the IEEE Ultrasonics Symposium. - 1051-0117. ; 2, s. 1783-1786
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Konferensbidrag (refereegranskat)abstract
- In arterial vessel wall characterisation the longitudinal movements of vessels have gained little or no attention. It has been presumed that the arterial vessels move very little in the longitudinal direction. With modern high resolution ultrasound it can, however, be seen that arterial vessels move not only in the circumferential, but also in longitudinal direction. This paper describes a non-invasive, ultrasound based method which estimates the longitudinal and the circumferential movement, respectively. The method is demonstrated in a limited in vivo study of the common carotid artery. Results show that, apart from the well known circumferential movement, there is a distinct longitudinal movement.
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| 10. |
- Prager, Jens, et al.
(författare)
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Flaw detection using a selective Lamb mode excitation with phased array transducers
- 2010
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Ingår i: Proceedings of 2010 IEEE International Ultrasonics Symposium (IUS), October 11-14, 2010, San Diego. - 1051-0117. - 9781457703829 ; , s. 1156-1159
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Konferensbidrag (refereegranskat)abstract
- Lamb waves travel in plates and hollow cylinders over large distances and propagate with multiple mode shapes. Therefore the waves can be used for integrity tests of large scale structures. Each propagating wave mode has a unique dispersive character and a frequency dependent vibration pattern. Therefore, by interacting with flaws each mode is assumed to generate an individual reflection pattern depending on the flaw type, flaw orientation and size. To extract this information a frequency as well as wave number dependent mode excitation is required ensuring a single mode excitation. The challenge, however, is to control the selective mode excitation electronically to allow a sequence of consecutive tests with different wave modes to collect the data. A method is proposed using phased array wedge transducers with fluid coupling for normal force excitation of Lamb wave modes. The excitation principle is investigated analytically on plates by modelling the wave generation in the wedge and the coupling between wedge and structure. The analytical results of the excitation principle are validated by corresponding experiments where the field patterns on the wedge surface and on the plate were scanned using a laser vibrometer. The directivity of the radiated field is investigated together with the direction dependent analysis of the mode content.
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