Subharmonic Imaging with Microbubble Contrast Agents: Initial Results

Shi, William T.; Forsberg, Flemming; Hall, Anne L.; Chiao, Richard Y.; Liu, Ji‐Bin; Miller, S.; Thomenius, Kai E.; Wheatley, Margaret A.; Goldberg, Barry B.

doi:10.1177/016173469902100201

Cited by 152 publications

(113 citation statements)

References 33 publications

Supporting

Mentioning

107

Contrasting

Order By: Relevance

“…On the other hand, encapsulated bubbles showed better correlation between the sub-harmonic amplitude changes and the ambient pressure, than the main harmonic amplitude. The sub-harmonic threshold for encapsulated microbubbles is lower by~30% than for nonencapsulated microbubbles (consistent with experimental results [6]). Also, the increase of the ambient pressure produces a decrease of about 40% of the sub-harmonic threshold.…”

Section: ) Simulation Resultssupporting

confidence: 88%

Study of pressure dependence of signals from ultrasound contrast agents

Adam

Burla

2001 Conference Proceedings of the 23rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society

View full text Add to dashboard Cite

-Noninvasive pressure estimation within the heart cavities or coronary arteries is essential for providing information on blood perfusion and viability of the organ. Some ultrasound contrast agents (UCA) are particularly well suited for pressure measurements because pressure changes affect the reflectivity of the microbubbles after their injection. In-vitro experiments were conducted with UCA (Optison) using 2.0 MHz ultrasound pulses. Preliminary results indicate that, over the pressure range of 0-210 mmHg, the rate (slope) of decline as a function of time, of the amplitudes of the first and second harmonics and that of the sub-harmonic, may be a suitable parameter for estimation of the hydrostatic pressure changes. The difference between the amplitude of the first harmonic and that of the sub-harmonic stays almost constant throughout specific time window, thus demonstrating a good and stable correlation with the hydrostatic pressure.Keywords -Noninvasive, Hydrostatic pressure, Ultrasound, Contrast agent I. INTRODUCTIONThe problem of noninvasive pressure estimation using ultrasound contrast agents (UCA) is studied here. The blood pressure measurement in heart cavities, in internal organs or in the peripheral vascular system is very important because these are the locations where the pressure needs to be known. It also allows calculation of the flow through valves, stenosed arteries, etc., and it provides essential information about the blood perfusion of the given organ. Currently such pressure measurements are invasive. The possibility of exploiting particular properties of UCA as a tool for noninvasive pressure estimation seems to be promising [1], [2]. Current investigations in this field use the assumption that changes of the ambient pressure alter significantly the bubble dimensions; consequently their resonant frequency is changed, resulting in changes in the characteristics of backscattered signal. Using harmonic and sub-harmonic frequencies instead of resonant original frequency, allows to exclude artifacts from the surrounding media and to improve signal-to-noise ratio [3].The current paper conducts comparative analysis of the pressure sensitivity of some UCA, using computer simulation. It also evaluates the parameter best correlated to the ambient pressure, using both computer simulation and 'in-vitro' experiments. The particular problem discussed here is how to avoid the UCA backscatter time dependence, so that hydrostatic pressure can be estimated. II. METHODSThe aim of the current work was to assess the sensitivity of different UCA to ambient pressure changes and determine the particular properties that may make the UCA perform as 'pressure sensors'. 1) Simulation studies4 kinds of UCA micro-bubbles (air, Albunex, octafluoropropane, Optison) were compared for their pressure sensitivity, by studying the following features: frequency shift, first harmonic amplitude, second harmonic amplitude, the sub-harmonic amplitude and its threshold, "sub-harmonic to the first harmonic" and "sub-harmonic ...

show abstract

Section: ) Simulation Resultssupporting

confidence: 88%

Study of pressure dependence of signals from ultrasound contrast agents

Adam

Burla

2001 Conference Proceedings of the 23rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society

View full text Add to dashboard Cite

show abstract

“…The strongest subharmonic response was achieved when the agent was excited at twice its resonant frequency 45 ; therefore, the attenuation peak at 10 MHz was consistent with the observed subharmonic generation efficiency at 20 MHz. The sharp drop in attenuation beyond 10 MHz indicates that the size distribution of the agent was not optimum for subharmonic imaging at higher transmit frequencies (30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40), but increasing the relative number of smaller microbubbles in the agent by filtration may enhance subharmonic emission at higher frequencies. 10,31,45 V.B.…”

mentioning

confidence: 99%

Improving the sensitivity of high‐frequency subharmonic imaging with coded excitation: A feasibility study

Shekhar

Doyley

2012

Medical Physics

View full text Add to dashboard Cite

Purpose: Subharmonic intravascular ultrasound imaging (S-IVUS) could visualize the adventitial vasa vasorum, but the high pressure threshold required to incite subharmonic behavior in an ultrasound contrast agent will compromise sensitivity-a trait that has hampered the clinical use of S-IVUS. The purpose of this study was to assess the feasibility of using coded-chirp excitations to improve the sensitivity and axial resolution of S-IVUS. Methods: The subharmonic response of Targestar-p TM , a commercial microbubble ultrasound contrast agent (UCA), to coded-chirp (5%-20% fractional bandwidth) pulses and narrowband sine-burst (4% fractional bandwidth) pulses was assessed, first using computer simulations and then experimentally. Rectangular windowed excitation pulses with pulse durations ranging from 0.25 to 3 ls were used in all studies. All experimental studies were performed with a pair of transducers (20 MHz/10 MHz), both with diameter of 6.35 mm and focal length of 50 mm. The size distribution of the UCA was measured with a Casy TM Cell counter. Results: The simulation predicted a pressure threshold that was an order of magnitude higher than that determined experimentally. However, all other predictions were consistent with the experimental observations. It was predicted that: (1) exciting the agent with chirps would produce stronger subharmonic response relative to those produced by sine-bursts; (2) increasing the fractional bandwidth of coded-chirp excitation would increase the sensitivity of subharmonic imaging; and (3) coded-chirp would increase axial resolution. The experimental results revealed that subharmonic-to-fundamental ratios obtained with chirps were 5.7 dB higher than those produced with sine-bursts of similar duration. The axial resolution achieved with 20% fractional bandwidth chirps was approximately twice that achieved with 4% fractional bandwidth sine-bursts. Conclusions: The coded-chirp method is a suitable excitation strategy for subharmonic IVUS imaging. At the 20 MHz transmission frequency and 20% fractional bandwidth, coded-chirp excitation appears to represent the ideal tradeoff between subharmonic strength and axial resolution.

show abstract

“…The frequency of insonation was 4.4 MHz, as the resonance frequency of Optison is around 2 MHz and this is the frequency range used in the ultrasound scanner employed for our preliminary SHI work [9][10]. This is in keeping with the concept of minimum threshold for subharmonic generation when the insonation frequency is twice the resonance frequency.…”

Section: Methodsmentioning

confidence: 92%

Estimation of Tumor Angiogenesis With Constrast Enhanced Subharmonic Ultrasound Imaging

Forsberg¹

2003

View full text Add to dashboard Cite

Subharmonic Imaging with Microbubble Contrast Agents: Initial Results

Cited by 152 publications

References 33 publications

Study of pressure dependence of signals from ultrasound contrast agents

Study of pressure dependence of signals from ultrasound contrast agents

Improving the sensitivity of high‐frequency subharmonic imaging with coded excitation: A feasibility study

Estimation of Tumor Angiogenesis With Constrast Enhanced Subharmonic Ultrasound Imaging

Contact Info

Product

Resources

About