| 1. |
- Bjarnegård, Niclas, et al.
(författare)
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Age affects proximal brachial artery stiffness : differential behaviour within the length of the brachial artery?
- 2003
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Ingår i: Ultrasound in Medicine and Biology. - 0301-5629. ; 29:8, s. 1115-1121
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Tidskriftsartikel (refereegranskat)abstract
- With increasing age, the diameter of central elastic arteries increases, whereas their distensibility decreases. The purpose of this study was to investigate the mechanical properties of the proximal brachial artery in relation to age and gender. Distensibility coefficient (DC), stiffness and compliance coefficient (CC) were calculated in 136 healthy males and females (range 9-82 y) using echo-tracking sonography. CC decreased with age in both genders, but CC was higher in males. Stiffness increased and DC decreased with age in an exponential manner, without any differences between genders. In conclusion, as in central elastic arteries, the distensibility of the proximal brachial artery decreases with age, in contrast to earlier reports on the muscular distal brachial artery. This may imply that the transition between elastic and muscular artery behavior is within the length of the brachial artery. In future studies using the brachial artery, the examination site needs to be defined.
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| 2. |
- Edler, I, et al.
(författare)
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The history of echocardiography
- 2004
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Ingår i: Ultrasound in Medicine and Biology. - 0301-5629. ; 30:12, s. 1565-1644
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Forskningsöversikt (refereegranskat)abstract
- Following a brief review of the development of medical ultrasonics from the mid-1930s to the mid-1950s, the collaboration between Edler and Hertz that began in Lund in 1953 is described. Using an industrial ultrasonic flaw detector, they obtained time-varying echoes transcutaneously from within the heart. The first clinical applications of M-mode echocardiography were concerned with the assessment of the mitral valve from the shapes of the corresponding waveforms. Subsequently, the various M-mode recordings were related to their anatomical origins. The method then became established as a diagnostic tool and was taken up by investigators outside Lund, initially in China, Germany, Japan and the USA and, subsequently, world-wide. The diffusion of echocardiography into clinical practice depended on the timely commercial availability of suitable equipment. The discovery of contrast echocardiography in the late 1960s further validated the technique and extended the range of applications. Two-dimensional echocardiography was first demonstrated in the late 1950s, with real-time mechanical systems and, in the early 1960s, with intracardiac probes. Transesophageal echocardiography followed, in the late 1960s. Stop-action two-dimensional echocardiography enjoyed a brief vogue in the early 1970s. It was, however, the demonstration by Bom in Rotterdam of real-time two-dimensional echocardiography using a linear transducer array that revolutionized and popularized the subject. Then, the phased array sector scanner, which had been demonstrated in the late 1960s by Somer in Utrecht, was applied to cardiac studies from the mid-1970s onwards. Satomura had demonstrated the use of the ultrasonic Doppler effect to detect tissue motion in Osaka in the mid-1950s and the technique was soon afterwards applied in the heart, often in combination with M-mode recording. The development of the pulsed Doppler method in the late 1960s opened up new opportunities for clinical innovation. The review ends with a mention of color Doppler echocardiography. (E-mail: kjell.lindstrom@elmat.Ith.se) (C) 2004 World Federation for Ultrasound in Medicine Biology.
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| 3. |
- Eriksson, A, et al.
(författare)
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Arterial pulse wave velocity with tissue doppler imaging
- 2002
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Ingår i: Ultrasound in Medicine and Biology. - 0301-5629. ; 28:5, s. 571-580
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a new noninvasive ultrasonic method for estimating pulse wave velocity (PWV), an important physical parameter for characterizing the elastic properties of the arterial walls. The method utilizes a relatively new color Doppler modality for measuring tissue motion (tissue Doppler imaging or TDI). In contrast to previously proposed methods, the TDI modality offers multiple recording sites along the artery that improve the PWV estimation considerably. The new PWV estimation method was evaluated through an in vitro setup consisting of an elastic vessel supplied with a pulsatile pump. The study concentrated on the effect of different system parameters controlling resolution, sensitivity and the amount of acquired data. It was shown that the system parameters have a significant effect on the PWV variance, whereas the PWV mean remains unchanged. It was also established that high temporal resolution is the most vital parameter for minimizing PWV variance. Finally, the new PWV estimation method was applied to a limited set of human carotid artery data sets, with good results. (E-mail:magnus.persson@elmat.lth.se)
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| 4. |
- Gardiner, H, et al.
(författare)
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Volume blood flow estimation in the normal and growth-restricted fetus
- 2002
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Ingår i: Ultrasound in Medicine and Biology. - 0301-5629. ; 28:9, s. 1107-1113
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Tidskriftsartikel (refereegranskat)abstract
- The objective was to compare volume blood flow (VBF) in the descending aorta (DAo) of gestational age and weight-matched growth restricted (GR) and normal (N) fetuses. A longitudinal study of 20 N was compared with 11 GR in two analyses matched for weight and gestation. DAo dimensions and flow velocity were measured simultaneously using a new technique combining an ultrasonic phase-locked echo-tracking system synchronized with a pulsed Doppler velocimeter. Cardiac output was estimated using standard echocardiographic views. DAo and semilunar valve diameters increased linearly in N and indexed cardiac output was similar in N and GR, although GR showed reduced DAo relative pulse amplitude, mean flow velocity and VBF. This synchronized technique permits calculation of VBF in human fetuses. Growth restriction is associated with reduced aortic wall pulsations and lower mean blood flow velocities and VBF in DAo secondary to increased placental impedance. (C) 2002 World Federation for Ultrasound in Medicine Biology.
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| 5. |
- Gudmundsson, Saemundur, et al.
(författare)
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Factors affecting color Doppler energy ultrasound recordings in an in-vitro model
- 1998
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Ingår i: Ultrasound in Medicine and Biology. - 0301-5629. ; 24:6, s. 899-902
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Tidskriftsartikel (refereegranskat)abstract
- Compared to conventional color Doppler ultrasound imaging, the new color Doppler modality "color Doppler energy" (CDE) has improved the possibility of visualizing blood vessels having low blood-flow velocities, but appears to be influenced by the settings of the ultrasound instrument and motion artefacts. The aim of this methodological study was to evaluate the effects of the different factors on the CDE signal. The CDE mode of a commercially available ultrasound system (Acuson 128 XP) was tested in an in vitro study. The effect of depth, angle of insonation, flow velocity, instrument power output, gain and other instrument settings were evaluated. The CDE signals obtained were stored on videotape and subsequently subjected to off-line computer analysis. The CDE signal intensity was found to be influenced mainly by fluid flow velocity, but was also affected by depth and instrument settings. Gain and power had, however, limited influence in this setting. Thus, the intensity of the CDE signal is influenced by several factors. Our results emphasize the need for optimum fixed preinstalled instrument settings when attempting to quantify organ perfusion by use of this new technique.
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| 6. |
- Hansen, F, et al.
(författare)
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Diameter and compliance in the human common carotid artery--variations with age and sex
- 1995
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Ingår i: Ultrasound in Medicine and Biology. - : Elsevier BV. - 0301-5629. ; 21:1, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- In this study, age and sex differences in diameter and compliance of the common carotid artery (CCA) were evaluated in 119 healthy subjects with a phase-locked echo-tracking system. The diameter and pulsatile diameter changes were measured, and pressure strain elastic modulus (Ep) and stiffness (beta) were calculated and used as the inverse estimate of compliance. The carotid diameter increased more rapidly in males and was larger than in females from 25 years of age. The relative diameter change was equal in both sexes, and decreased from 12% to 14% in younger subjects to approximately 5% in elderly subjects. Compliance decreased almost linearly and in parallel in males and females up to 45 years of age. Between 45 and 60 years the decrease was more marked in females than in males, whereas it was by far more marked in males between 60 and 70 years of age.
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| 7. |
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| 8. |
- Jansson, Tomas, et al.
(författare)
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Movement artefact suppression in blood perfusion measurements using a multifrequency technique
- 2002
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Ingår i: Ultrasound in Medicine and Biology. - 0301-5629. ; 28:1, s. 69-79
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Tidskriftsartikel (refereegranskat)abstract
- The standard way of suppressing movement artefacts in Doppler measurements is by means of a high-pass filter. This is because artefacts usually are of high amplitude, but have low frequencies. The immediate drawback is, then, that low-velocity blood flow is also filtered out. In this paper, a method to reduce movement artefacts in blood perfusion measurements is proposed, using simultaneous transmission and reception of multiple frequencies in a continuous-wave Doppler system. It is shown that Doppler signals originating from blood may be considered uncorrelated for a large enough frequency separation between channels, and tissue movements are more correlated. By subtracting perfusion estimates obtained by time-domain processing, correlated signals can be suppressed. The subtraction algorithm is shown to produce a linear perfusion estimate, but with twice the standard deviation compared to an estimate obtained by simply averaging channels. Movement artefacts in both in vitro and in vivo models are shown to be reduced by the algorithm. Imbalance between channels does, however, cause the artefacts to be only partly reduced. The problem can be alleviated by filtering the signals prior to subtraction, but this results in a nonlinear estimate, especially for large time constants in the filter. Some amount of filtering can still be desirable to suppress partly correlated artefacts, even if identical time-domain processing units are implemented, as could be done digitally. (E-mail: tomas.jansson@elmat.lth.se)
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| 9. |
- Jansson, Tomas, et al.
(författare)
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Ultrasound Doppler Vector Tomography - Measurements of Directional Blood Flow
- 1997
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Ingår i: Ultrasound in Medicine and Biology. - 0301-5629. ; 23:1, s. 47-57
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Tidskriftsartikel (refereegranskat)abstract
- An experimental system has been developed to verify the possibility of detecting flow activity using a technique called ultrasound Doppler vector tomography. A tomography algorithm is used to reconstruct blood flow vector fields using data from computer-controlled ultrasound continuous-wave Doppler scanning equipment. The result is a picture in which the brightness variations represent the reconstructed values of the curl of the velocity field (del x v). Continuous ultrasound is transmitted into a region with flow activity and the Doppler-shifted signals are received. To obtain measurement data suited for fan beam tomography, the scanning is performed in a plane from points encircling the region. Reconstructions have been achieved using measurement data from two different flow phantoms. A comparison between the experimental results and simulations shows good conformity. Copyright (C) 1997 World Federation for Ultrasound in Medicine & Biology.
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| 10. |
- Länne, T, et al.
(författare)
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Noninvasive measurement of diameter changes in the distal abdominal aorta in man
- 1992
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Ingår i: Ultrasound in Medicine and Biology. - 0301-5629. ; 18:5, s. 451-457
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Tidskriftsartikel (refereegranskat)abstract
- An ultrasound phase-locked, echo-tracking system was used to determine the dynamic properties of the distal abdominal aorta in 10 Caucasian male subjects (mean age, 25 years). Recordings were made at rest and during the blood pressure increase resulting from isometric exercise. The pressure diameter curve was nonlinear with an inflection at about 90-110 mmHg. Above this pressure range, the vessel was stiffer (less compliant), but the pressure diameter relationship was roughly linear above as well as below the inflection. Individual pressure diameter curves showed hysteresis, i.e., the aorta had a smaller diameter during expansion than during retraction at corresponding pressures. The pressure strain elastic modulus (Ep) and stiffness (beta) were at rest [Mean Arterial Pressure (MAP), 81 mmHg] 0.70 10(5) N/m2 and 6.0, respectively. During isometric exercise (MAP, 122 mmHg), Ep increased significantly by 91% and stiffness (beta) nonsignificantly by 27%. The variability of the compliance determinations was 5% when the ultrasonic system was combined with intra-arterial blood pressure measurements and less than 7% when combined with auscultatory blood pressure measurements. It is concluded that the phase-locked, echo-tracking system fulfills clinical requirements for routine measurements of vascular compliance.
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