Transcutaneous Interruption of Ultrasound Contrast Agents for Blood Flow Evaluation

Fowlkes, J. Brian; Sirkin, David W.; Ivey, J. A.; Gardner, Edward A.; Rhee, Richard T.; Rubin, Jonathan M.; Carson, Paul L.

doi:10.1097/00004424-199812000-00008

Cited by 8 publications

(2 citation statements)

References 18 publications

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“…One method, called contrast interruption, is currently under development in our laboratory [46]. This method could potentially be used to identify the supply vessels for a tumor, arterio-venous malformation, or other target.…”

Section: Discussionmentioning

confidence: 99%

In vivo droplet vaporization for occlusion therapy and phase aberration correction

Kripfgans

Fowlkes

Woydt

et al. 2002

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

129

131

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The objective was to determine whether a transpulmonary droplet emulsion (90%, <6 m diameter) could be used to form large gas bubbles (>30 m) temporarily in vivo. Such bubbles could occlude a targeted capillary bed when used in a large number density. Alternatively, for a very sparse population of droplets, the resulting gas bubbles could serve as point beacons for phase aberration corrections in ultrasonic imaging. Gas bubbles can be made in vivo by acoustic droplet vaporization (ADV) of injected, superheated, dodecafluoropentane droplets. Droplets vaporize in an acoustic field whose peak rarefactional pressure exceeds a well-defined threshold [1], [2]. In this new work, it has been found that intraarterial and intravenous injections can be used to introduce the emulsion into the blood stream for subsequent ADV (Band M-mode on a clinical scanner) in situ.Intravenous administration results in a lower gas bubble yield, possibly because of filtering in the lung, dilution in the blood volume, or other circulatory effects. Results show that for occlusion purposes, a reduction in regional blood flow of 34% can be achieved. Individual point beacons with a +24 dB backscatter amplitude relative to white matter were created by intravenous injection and ADV.

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Section: Discussionmentioning

confidence: 99%

In vivo droplet vaporization for occlusion therapy and phase aberration correction

Kripfgans

Fowlkes

Woydt

et al. 2002

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

129

131

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“…Equally, continuous infusions of contrast agent can be modified to produce positive or negative boluses by selective destruction of the contrast agent; hence, it is possible to get mean transit time estimates without making assumptions about the shape of the bolus [19].…”

Section: New Imaging Techniquesmentioning

confidence: 99%

Flow quantification

Rubin

1999

Eur Radiol

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IntroductionFlow measurements have been possible in ultrasound ever since the advent of Doppler; however, the measurements have been problematic and error prone. This has lead to compromises in the flow measurements that have generally been performed. These compromises have included flow velocity measurements, which are a direct outgrowth of Doppler, rather than true volume flow, and semi-quantitative parameters such as resistive indices (RIs) and pulsatility indices (PIs). Flow velocities have direct value in that conservation of volume flow due to autoregulating areas produces increases in local flow velocities at areas of stenosis. Such changes have proven very useful for the diagnosis. Also because of the Bernoulli equation, peak flow velocities can be used to estimate pressure drops in the correct circumstances such at the aortic and pulmonary valves. Although attractive because they are simple to perform, RIs and PIs have very frequently provided less than totally useful information. This may be because these measurements are only empirical, and really do not measure what they are claim to, i. e. vascular resistance. Ultimately, one would like to measure flow directly, and recent developments have moved closer to this goal. Measuring flow volumeThe first volume flow estimates were made with Doppler. The ubiquitous Doppler equation is:where Df is the Doppler shifted frequency, v is the velocity of the blood flow, c is the speed of sound, f o is the carrier frequency of the Doppler and Q is the Doppler angle. Solving for velocity and opening the range gate to include the entire width of a blood vessel, one can estimate the mean velocity through the range gate. By assuming the vessel is circular in cross section, one can estimate the radius of the blood vessel, calculate the cross-sectional area of the vessel, and by multiplying flow determine the mean velocity through the cross section by the area of the cross section. Although true in theory, these estimates lead to many problems in practice. Firstly, the cross section is almost never circular making the area estimate imprecise, and secondly, the velocity profile is hardly ever cylindrically symmetric, making the velocity sampling assumptions wrong. The usual machine-programmed volume estimating routines assume a circular cross section. Even if this assumption is correct, the effect of the error multiplies with small radii. The fractional error is DA/A = 2Dr/r, where A is area and r is radius. Thus, for example, if a vessel has a radius of 5 mm and the error in measuring the radius is 1 mm, then the fractional error will be 40 %. Such problems alone have discouraged use of this method. An additional problem is estimating the Doppler angle, yet, certain angle-independent flow techniques can theoretically decrease this problem. However, major issues still remain. A novel solution to this problem had been proposed some years ago by Hottinger and Meindl [1]. They proposed using two different beam profiles to solve the geometry problem. They used a beam with larg...

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Ultrasound Contrast Agents: Development of the Field and Current Status

Klibanov

2002

Topics in Current Chemistry

111

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Transcutaneous Interruption of Ultrasound Contrast Agents for Blood Flow Evaluation

Abstract: Acoustic fields applied transcutaneously interrupted flow of contrast agents to form temporally short negative boluses.

Cited by 8 publications

References 18 publications

In vivo droplet vaporization for occlusion therapy and phase aberration correction

In vivo droplet vaporization for occlusion therapy and phase aberration correction

Flow quantification

Ultrasound Contrast Agents: Development of the Field and Current Status

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