Ultrasonic Attenuation Estimation in Small Plaque Samples Using a Power Difference Method

Shi, Hu; Tu, Haifeng; Dempsey, Robert J.; Varghese, Tomy

doi:10.1177/016173460702900102

Cited by 7 publications

(12 citation statements)

References 39 publications

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“…We have previously reported on a reference phantom based power difference method to calculate attenuation in small tissue samples ex-vivo [26]. We will utilize this method to compute the attenuation coefficient and to estimate the attenuation compensated equivalent scatterer size parameter [25] from the ultrasound RF data recorded.…”

Section: Methodsmentioning

confidence: 99%

“…We average 25 independent STFT realizations to obtain the expected value or power spectrum for the reference phantom. Finally the power difference approach is utilized to calculate the attenuation coefficient of plaque in-vivo [26]. The power difference method requires the computation of the normalized power spectrum (normalized using the reference phantom data collected at the same depth) both above and below the region of interest (ROI), namely plaque in the in-vivo scans along with regions at similar depths in a reference phantom.…”

Section: Methodsmentioning

confidence: 99%

“…The other advantage of using a reference phantom is that we can average data from multiple scan planes to obtain smooth reference power spectra, thus reducing the estimation error. This concept was presented in detail in [26]. In addition, note that since the in-vivo plaque structure is more complicated than the ex-vivo situation (which only contain the excised plaque), and the uniform reference phantom may not completely compensate for all system parameters.…”

Section: Methodsmentioning

confidence: 99%

“…In addition, note that since the in-vivo plaque structure is more complicated than the ex-vivo situation (which only contain the excised plaque), and the uniform reference phantom may not completely compensate for all system parameters. For the power difference method RF data was selected in regions with no plaque for the upper ROI and below the plaque for the second ROI [26]. After the attenuation coefficient was calculated, Faran’s scattering theory for glass beads similar to that described for the ex-vivo situation was used to estimate an equivalent scatterer size parameter.…”

Section: Methodsmentioning

confidence: 99%

“…In addition, many of the previous carotid plaque studies were ex-vivo studies [21–25]. Ultrasonic attenuation [21, 26], IBC [21–24, 27], and other scattering parameters such as the slope, midband fit (MBF) and the zero frequency intercept of power spectra of the RF echo signals [24, 28] have all been utilized for UTC based analysis of carotid plaque tissue.…”

Section: Introductionmentioning

confidence: 99%

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In vivo attenuation and equivalent scatterer size parameters for atherosclerotic carotid plaque: Preliminary results

et al. 2009

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We have previously reported on the equivalent scatterer size, attenuation coefficient, and axial strain properties of atherosclerotic plaque ex-vivo. Since plaque structure and composition may be damaged during a carotid endarterectomy procedure, characterization of in-vivo properties of atherosclerotic plaque is essential. The relatively shallow depth of the carotid artery and plaque enables non-invasive evaluation of carotid plaque utilizing high frequency linear array transducers. We investigate the ability of the attenuation coefficient and equivalent scatterer size parameters to differentiate between calcified, and lipidic plaque tissue. Softer plaques especially lipid rich and those with a thin fibrous cap are more prone to rupture and can be classified as unstable or vulnerable plaque. Preliminary results were obtained from 10 human patients whose carotid artery was scanned in-vivo to evaluate atherosclerotic plaque prior to a carotid endarterectomy procedure. Our results indicate that the equivalent scatterer size obtained using Faran's scattering theory for calcified regions are in the 120~180 µm range while softer regions have larger equivalent scatterer size distribution in the 280~470 µm range. The attenuation coefficient for calcified regions as expected is significantly higher than that for softer regions. In the frequency bandwidth ranging from 2.5~7.5 MHz, the attenuation coefficient for calcified regions lies between 1.4~2.5 dB/cm/MHz, while that for softer regions lies between 0.3~1.3 dB/cm/MHz.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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In vivo attenuation and equivalent scatterer size parameters for atherosclerotic carotid plaque: Preliminary results

et al. 2009

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The relationship between carotid artery plaque stability and white matter ischemic injury

Berman

Wang

Mitchell

et al. 2015

NeuroImage: Clinical

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Higher local carotid artery strain has previously been shown to be a characteristic of unstable carotid plaques. These plaques may be characterized by microvascular changes that predispose to intraplaque hemorrhage, increasing the likelihood of embolization. Little is known however, about how these strain indices correspond with imaging markers of brain health and metrics of brain structure. White matter hyperintensities (WMHs), which are bright regions seen on T2-weighted brain MRI imaging, are postulated to result from cumulative ischemic vascular injury. Consequently, we hypothesized that plaques that are more prone to microvascular changes and embolization, represented by higher strain indices on ultrasound, would be associated with an increased amount of WMH lesion volume. This relationship would suggest not only emboli as a cause for the brain degenerative changes, but more importantly, a common microvascular etiology for large and small vessel contributions to this process. Subjects scheduled to undergo a carotid endarterectomy were recruited from a neurosurgery clinic. Prior to surgery, participating subjects underwent both ultrasound strain imaging and brain MRI scans as part of a larger clinical study on vascular health and cognition. A linear regression found that maximum absolute strain and peak to peak strain in the surgical side carotid artery were predictive of WMH burden. Furthermore, the occurrence of microembolic signals monitored using transcranial Doppler (TCD) ultrasound examinations also correlated with increasing lesion burden. It is becoming increasingly recognized that cognitive decline is often multifactorial in nature. One contributing extra-brain factor may be changes in the microvasculature that produce unstable carotid artery plaques. In this study, we have shown that higher strain indices in carotid artery plaques are significantly associated with an increased WMH burden, a marker of vascular mediated brain damage.

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Relationship Between Ultrasonic Attenuation, Size and Axial Strain Parameters for Ex Vivo Atherosclerotic Carotid Plaque

Shi

Varghese

Dempsey

et al. 2008

Ultrasound in Medicine & Biology

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Many ultrasonic parameters, primarily related to attenuation and scatterer size, have been used to characterize the composition of atherosclerotic plaque tissue. In this study, we combine elastographic (axial strain ratio) and ultrasonic tissue characterization parameters, namely the attenuation coefficient and a scattering parameter associated with an "equivalent" scatterer size to delineate between fibrous, calcified, and lipidic plaque tissue. We present results obtained from 44 ex vivo atherosclerotic plaque specimens obtained after carotid endarterectomy on human patients. Our results in the frequency range 2.5 - 7.5 MHz indicate that softer plaques (with higher values of the strain ratio) are usually associated with larger equivalent scatterer size estimates (200 - 500 microm) and lower values of the attenuation coefficient slope (<1 dB/cm/MHz). On the other hand, stiffer plaques (with lower strain ratio values) are associated with smaller equivalent scatterer size estimates (100 - 200 microm) and higher values of the attenuation coefficient slope (1 - 3 dB/cm/MHz). These results indicate that ultrasonic tissue characterization and strain parameters have the potential to differentiate between different plaque types. These parameters can be estimated from radio-frequency data acquired under in vivo conditions and may help the clinician decide on appropriate interventional techniques.

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Ultrasonic Attenuation Estimation in Small Plaque Samples Using a Power Difference Method

Cited by 7 publications

References 39 publications

In vivo attenuation and equivalent scatterer size parameters for atherosclerotic carotid plaque: Preliminary results

In vivo attenuation and equivalent scatterer size parameters for atherosclerotic carotid plaque: Preliminary results

The relationship between carotid artery plaque stability and white matter ischemic injury

Relationship Between Ultrasonic Attenuation, Size and Axial Strain Parameters for Ex Vivo Atherosclerotic Carotid Plaque

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