In vivo carotid strain imaging using principal strains in longitudinal view.

Carotid plaque rupture can result in stroke or transient ischemic attack that can be devastating for patients. Ultrasound strain imaging provides a noninvasive method to identify unstable plaque likely to rupture. Axial, lateral and shear strains in carotid plaque have been shown to be linked to carotid plaque instability. Recently, there has been interest in using principal strains, which do not depend on angle of insonification of the carotid artery for quantifying instability in plaque along the longitudinal view. In this work relationships between angle dependent axial, lateral and shear strain along with axis independent principal strains are compared. Three strain indices were defined, 1) Average Mean Strain (AMS), 2) Maximum Mean Strain (MMS) and 3) Mean Standard Deviation (MSD) to identify relationships between these five strain image types in a group of 76 in vivo patients. The maximum principal strain demonstrated the highest strain values when compared to axial strain for all patients with a linear regression slope of 1.6 and a y intercept of 2.4 percent strain for AMS. The maximum shear strain when compared to shear strain had a slope of 1.15 and a y intercept of 0.21 percent for AMS. Next, the effect of insonification angle, which is the angle subtended by the artery at the location of plaque was studied. Patients were divided into three sub groups, i.e. less than 5 degrees (n = 31), between 5 and 10 degrees (n = 24) and above 10 degrees (n = 21). The angle of insonification did not make a significant difference between the three angle groups when comparing the relationship between the angle dependent and independent strain values.

A Cross-Sectional Investigation of Cognition and Ultrasound-Based Vascular Strain Indices.

OBJECTIVE: We examine the relationship between variability in the plaque strain distribution estimated using ultrasound with multiple cognitive domains including executive, language, visuospatial reasoning, and memory function. METHOD: Asymptomatic (n = 42) and symptomatic (n = 34) patients with significant (>60%) carotid artery stenosis were studied for plaque instability using ultrasound strain imaging and multiple cognitive domains including executive, language, visuospatial reasoning, and memory function. Correlation and ROC analyses were performed between ultrasound strain indices and cognitive function. Strain indices and cognition scores were also compared between symptomatic and asymptomatic patients to determine whether there are significant group differences. RESULTS: Association of high-strain distributions with dysexecutive function was observed in both asymptomatic and symptomatic patients. For memory, visuospatial, and language functions, the correlations between strain and cognition were weaker for the asymptomatic compared to symptomatic group. CONCLUSIONS: Both asymptomatic and symptomatic patients demonstrate a relationship between vessel strain indices and executive function indicating that silent strokes and micro-emboli could initially contribute to a decline in executive function, whereas strokes and transient ischemic attacks may cause the further decline in other cognitive functions.

Quantification of carotid artery plaque stability with multiple region of interest based ultrasound strain indices and relationship with cognition.

Vulnerability and instability in carotid artery plaque has been assessed based on strain variations using noninvasive ultrasound imaging. We previously demonstrated that carotid plaques with higher strain indices in a region of interest (ROI) correlated to patients with lower cognition, probably due to cerebrovascular emboli arising from these unstable plaques. This work attempts to characterize the strain distribution throughout the entire plaque region instead of being restricted to a single localized ROI. Multiple ROIs are selected within the entire plaque region, based on thresholds determined by the maximum and average strains in the entire plaque, enabling generation of additional relevant strain indices. Ultrasound strain imaging of carotid plaques, was performed on 60 human patients using an 18L6 transducer coupled to a Siemens Acuson S2000 system to acquire radiofrequency data over several cardiac cycles. Patients also underwent a battery of neuropsychological tests under a protocol based on National Institute of Neurological Disorders and Stroke and Canadian Stroke Network guidelines. Correlation of strain indices with composite cognitive index of executive function revealed a negative association relating high strain to poor cognition. Patients grouped into high and low cognition groups were then classified using these additional strain indices. One of our newer indices, namely the average L - 1 norm with plaque (AL1NWP) presented with significantly improved correlation with executive function when compared to our previously reported maximum accumulated strain indices. An optimal combination of three of the new indices generated classifiers of patient cognition with an area under the curve (AUC) of 0.880, 0.921 and 0.905 for all (n = 60), symptomatic (n = 33) and asymptomatic patients (n = 27) whereas classifiers using maximum accumulated strain indices alone provided AUC values of 0.817, 0.815 and 0.813 respectively.

A prospective study of bipolar disorder vulnerability in relation to behavioural activation, behavioural inhibition and dysregulation of the Behavioural Activation System.

BACKGROUND: The weak regulation, or "dysregulation", of the Behavioural Activation System (BAS) is implicated in the development and recurrence of bipolar disorder. However, there has been a lack of prospective studies investigating the predictive role of BAS dysregulation in relation to bipolar-vulnerability. Furthermore, no studies have tested the prospective predictive utility of the DYS self-report measure of BAS dysregulation in an analogue sample. The goal of the current study was to redress this gap. METHODS: Participants (n=127) completed baseline self-report measures of mood symptoms (Internal States Scale [ISS]), the Hypomanic Personality Scale (HPS), behavioural activation, inhibition and dysregulation of BAS (BIS/BAS and DYS), and at six months, the Mood Disorders Questionnaire (MDQ). RESULTS: Linear regression analysis indicated a significant main effect of BAS Dysregulation, and a significant interaction between BIS and BAS Fun Seeking, on prospective MDQ scores whilst controlling for baseline mood symptoms and HPS scores. The interaction effect indicated that the relationship between high BAS Fun Seeking and follow-up MDQ scores was strongest when BIS scores were high, whilst the lowest MDQ scores were observed for a combination of low BAS Fun Seeking and high BIS. However, DYS scores were the stronger predictor of MDQ scores compared to the BAS Fun Seeking and BIS interaction. CONCLUSIONS: Bipolar-vulnerability is prospectively associated with heightened BAS Dysregulation, as measured by the DYS subscale, similar to prior findings in clinical samples. Further research investigating the longer-term associations between BAS Dysregulation with the development of clinically significant bipolar mood symptoms is required.

Personal and perceived peer use and attitudes towards the use of nonmedical prescription stimulants to improve academic performance among university students in seven European countries.

BACKGROUND: Overestimations of non-prescribed stimulant use of peers are well documented in the USA and have also been identified as predictive of personal stimulant consumption. This study aimed to examine whether overestimations of peer use and approval of the use are associated with personal use and attitude towards the use of non-prescribed stimulants among European university students. METHOD: The EU funded 'Social Norms Intervention for the prevention of Polydrug usE (SNIPE)' study was conducted in seven European countries. In a web-based questionnaire, 4482 students were asked about their personal use and their attitude towards non-prescribed stimulant use, as well as the perceived peer use and peer attitude. RESULTS: 59% of students thought that the majority of their peers used non-prescribed stimulants more frequently than themselves, and only 4% thought that the use of the majority was lower than their personal use. The perception that the majority of peers had used non-prescribed stimulants at least once was significantly associated with higher odds for personal use of non-prescribed stimulants (OR: 3.30, 95% CI: 2.32-4.71). In addition, the perception that the majority of peers approved of the non-prescribed use of stimulants was associated with a 4.03 (95% CI: 3.35-4.84) times higher likelihood for personal approval. DISCUSSION: European university students generally perceived the non-prescribed use of stimulants of peers to be higher than their personal use. This perception, as well as a perception of higher approval in the peer group, was associated with a higher likelihood of personal non-prescribed stimulant medication use and approval.

Improved Correlation of Strain Indices with Cognitive Dysfunction with Inclusion of Adventitial Layer with Carotid Plaque.

Plaque instability may lead to chronic embolization, which in turn may contribute to progressive cognitive decline. Accumulated strain tensor indices over a cardiac cycle within a pulsating carotid plaque may be viable biomarkers for the diagnosis of plaque instability. Using plaque-only carotid artery segmentations, we recently demonstrated that impaired cognitive function correlated significantly with maximum axial and lateral strain indices within a localized region of interest in plaque. Inclusion of the adventitial layer focuses our strain or instability measures on the vessel wall-plaque interface hypothesized to be a region with increased shearing forces and measureable instability. A hierarchical block-matching motion tracking algorithm developed in our laboratory was used to estimate accumulated axial, lateral, and shear strain distribution in plaques identified with the plaque-with-adventitia segmentation. Correlations of strain indices to the Repeatable Battery for the Assessment of Neuropsychological Status Total score were performed and compared with previous results. Overall, correlation coefficients (r) and significance (p) values improved for axial, lateral, and shear strain indices. Shear strain indices, however, demonstrated the largest improvement. The Pearson correlation coefficients for maximum shear strain and cognition improved from the previous plaque-only analyses of -0.432 and -0.345 to -0.795 and -0.717 with the plaque-with-adventitia segmentation for the symptomatic group and for all patients combined, respectively. Our results demonstrate the advantage of including adventitia for ultrasound carotid strain imaging providing improved association to parameters assessing cognitive impairment in patients. This supports theories of the importance of the vessel wall plaque interface in the pathophysiology of embolic disease.

Toxicological assessment of kretek cigarettes Part 6: the impact of ingredients added to kretek cigarettes on smoke chemistry and in vitro toxicity.

Mainstream smoke (MS) from experimental kretek cigarettes with three ingredient mixes at low (typical use level) and high (2.5 or 3 times that level) inclusion rates was compared to a control kretek cigarette of identical construction (cloves and humectants), but without the addition of ingredients. 350 ingredients, commonly used in various combinations and in a limited number in a given brand in the manufacture of marketed kretek cigarettes were assessed. The MS composition of the kretek cigarettes was characterized by a comprehensive set of analytes (55 smoke constituents). Furthermore, the smoke was assessed in vitro for its cytotoxicity in the Neutral Red Uptake assay (particle phase and gas/vapor phase separately) in mouse embryo BALB/c 3T3 cells, and for mutagenicity/genotoxicity in the Salmonella typhimurium reverse mutation assay and the mammalian cell mouse lymphoma TK assay in L5178Y cells, the latter with and without metabolic activation. There were some statistically significant differences in the yield of smoke constituents (increases as well as decreases, nearly all of them less than ± 20%) as a result of the addition of the ingredient mixes. However, the addition of the three different mixes of ingredients to the experimental kreteks did not change the in vitro cytotoxicity and mutagenicity/genotoxicity of the smoke, when compared to the control kretek cigarette.

Toxicological assessment of kretek cigarettes: Part 2: kretek and American-blended cigarettes, smoke chemistry and in vitro toxicity.

Two commercial kretek cigarettes typical for the Indonesian market and a reference kretek cigarette were compared to the American-blended reference cigarette 2R4F by smoke chemistry characterization and in vitro cytotoxicity and mutagenicity assessments. Despite the widely diverse designs and deliveries of the selected kretek cigarettes, their smoke composition and in vitro toxicity data present a consistent pattern when data were normalized to total particulate matter (TPM) deliveries. This confirms the applicability of the studies' conclusions to a wide range of kretek cigarette products. After normalization to TPM delivery, nicotine smoke yields of kretek cigarettes were 29-46% lower than that of the 2R4F. The yields of other nitrogenous compounds were also much lower, less than would be expected from the mere substitution of one third of the tobacco filler by clove material. Yields of light molecular weight pyrolytic compounds, notably aldehydes and hydrocarbons, were reduced, while yields of polycyclic aromatic hydrocarbons were unchanged and phenol yield was increased. The normalized in vitro toxicity was lowered accordingly, reflecting the yield reductions in gas-phase cytotoxic compounds and some particulate-phase mutagenic compounds. These results do not support a higher toxicity of the smoke of kretek cigarettes compared to American-blended cigarettes.

Toxicological assessment of kretek cigarettes: Part 1: background, assessment approach, and summary of findings.

This publication introduces a series of six other publications describing the toxicological assessment of kretek cigarettes, i.e., cigarettes characterized primarily by the use of a significant amount of cloves as an ingredient added to the tobacco. This paper presents background information on kretek cigarettes, describes the general approach of the in vitro and in vivo toxicological assessment of mainstream smoke from kretek cigarettes, presents the methodology used, and summarizes the results of the assessment program. In summary, the smoke from kretek cigarettes gives rise to the typical cigarette smoke-related effects known from American-blended cigarettes, does not reveal any novel toxicity, and exhibits an unexpected distinct attenuation of pulmonary inflammation. Based on equal amounts of smoke total particulate matter (TPM), kretek cigarettes deliver less toxicants when compared to American-blended cigarettes; when assessed in vitro, the smoke from kretek cigarettes is less cytotoxic (gas/vapor phase) and less mutagenic (TPM). When assessed in vivo, kretek cigarette smoke shows lower toxicity in the respiratory tract. When based on an equal nicotine basis, several of the toxicity endpoints in kretek cigarettes become equivalent to American-blended cigarettes. The data do not indicate an increased hazard potential of kreteks compared to American-blended cigarettes.

Toxicological assessment of kretek cigarettes. Part 7: the impact of ingredients added to kretek cigarettes on inhalation toxicity.

The biological activity of mainstream smoke from experimental kretek cigarettes with and without three mixes of ingredients was assessed in a 90-day rat inhalation study and in a 4-day in vivo micronucleus assay. 350 ingredients, commonly used in various combinations and in a limited number in a given brand in the manufacture of marketed kretek cigarettes, were applied at a low and a high target level to test cigarettes with a typical Indonesian blend of tobaccos and cloves. In the 90-day inhalation study, effects commonly seen in rat inhalation studies with mainstream smoke were observed. In general, no ingredients-related histopathological changes were found in the respiratory tract. In the 4-day micronucleus assay exposure of male rats to mainstream smoke from the test cigarettes containing any of the three mixes did not increase the proportions of micronucleated cells in peripheral blood and bone marrow over the proportion of micronucleated cells in the control group. Based on the results of these studies, it can be concluded that the addition of ingredients commonly used in the manufacture of kretek cigarettes did not change the overall in vivo toxicity profile of the mainstream smoke.

Toxicological assessment of kretek cigarettes Part 3: kretek and American-blended cigarettes, inhalation toxicity.

A typical Indonesian kretek cigarette brand and an experimental kretek reference cigarette were compared to the reference cigarette 2R4F in two 90-day inhalation studies. Male and female rats were exposed nose-only to mainstream smoke for 6 hours daily, for 90 consecutive days. Biological endpoints were assessed according to OECD guideline 413, with special emphasis on respiratory tract histopathology and on lung inflammation (broncho-alveolar lavage fluid levels of neutrophils, macrophages and lymphocytes). Histopathological alterations included: in the nose, hyperplasia and squamous metaplasia of the respiratory epithelium and squamous metaplasia and atrophy of the olfactory epithelium; in the larynx, epithelial squamous metaplasia and hyperplasia; in the lungs, accumulation of macrophages in alveoli and goblet cell hyperplasia in bronchial epithelium. The findings were qualitatively consistent with observations from previous similar studies on conventional cigarettes. Compared to 2R4F cigarette, however, kretek smoke exposure was associated with a pronounced attenuation of pulmonary inflammation and less severe histopathological changes in the respiratory tract. Neutrophilic inflammation was also significantly lower (>70%). These results are consistent with the observations made on smoke chemistry and in vitro toxicology. They do not support any increased toxicity of the smoke of kretek cigarettes compared to conventional American-blended cigarettes.

Toxicological assessment of kretek cigarettes Part 5: mechanistic investigations, inhalation toxicity.

The biological effects of mainstream smoke (MS) from Indonesian-blended cigarettes with and without added cloves, cloves extracted with hot ethanol, and extracted cloves replenished with eugenol or clove oil were assessed in a 90-day inhalation study in rats. A separate 35-day inhalation study in rats was performed with MS from American-blended cigarettes with 0%, 2.5%, 5% or 10% added eugenol. Effects commonly seen in inhalation studies with MS were observed. These included histopathological changes indicative of irritation in the entire respiratory tract and inflammatory responses in the lung. Adding cloves to American- or Indonesian-blended cigarettes reduced the inflammatory response in the lung but with no difference between the two blend types. When the clove oil was extracted (∼ 75% reduction of eugenol achieved) from cloves, the inflammatory response in the lung was still reduced similarly to whole cloves but the severity of histopathological changes in the upper respiratory tract was less reduced. Add back of clove oil or pure eugenol reduced this response to a level similar to what was seen with whole cloves. When eugenol was added to American-blended cigarettes, similar findings of reduced lung inflammation and severity of histopathological changes in respiratory the tract was confirmed. These studies demonstrate a clear effect of cloves, and in particular eugenol, in explaining these findings.

Toxicological assessment of kretek cigarettes Part 4: mechanistic investigations, smoke chemistry and in vitro toxicity.

The smoke chemistry and in vitro toxicity of mainstream smoke (MS) was investigated in American-blended cigarettes with or without the addition of 2.5%, 5% or 10% eugenol to the tobacco and in Indonesian-blended cigarettes with and without the addition of cloves, cloves extracted with hot ethanol, and extracted cloves replenished with eugenol or clove oil. The addition of eugenol reduced the concentration of nearly all toxicants measured in MS as well as the in vitro cytotoxicity of the gas/vapor phase. Reductions were also seen in bacterial mutagenicity of the total particulate matter (TPM) assessed by the Ames Assay. The addition of extracted cloves led to increases and decreases of toxicant concentrations in MS. Replenishment with eugenol or clove oil decreased the toxicant concentrations; with most smoke constituent concentrations reduced below the concentration found in tobacco-only cigarettes. Cytotoxicity of the TPM was not affected by the clove preparations. However, GVP cytotoxicity was reduced (untreated cloves showing the highest reductions). Mutagenicity of TPM was decreased by the clove preparations. Mechanisms for the reductions, (up to 40%), are most likely due to dilution effects by eugenol, changed burning characteristics of the tobacco, and free radical scavenging by eugenol.

Illicit substance use among university students from seven European countries: a comparison of personal and perceived peer use and attitudes towards illicit substance use.

OBJECTIVE: To compare European students' personal use and approval of illicit substance use with their perceptions of peer behaviours and attitudes, and investigate whether perceptions of peer norms are associated with personal use of illicit substances and attitudes. METHOD: This study used baseline data from the Social Norms Intervention for the prevention of Polydrug usE (SNIPE) project involving 4482 students from seven European countries in 2012. Students completed an online survey which included questions on personal and perceived peer illicit substance use and personal and perceived peer attitude towards illicit substances. RESULTS: 8.3% of students reported having used illicit substances at least once in their life. 49.7% of students perceived that the majority of their peers have used illicit substances more frequently than themselves. The perception was significantly associated with higher odds for personal illicit substance use (OR: 1.97, 95% CI: 1.53-2.54). The perception that the majority of peers approve illicit substance use was significantly associated with higher odds for personal approval of illicit substance use (OR: 3.47, 95% CI: 2.73-4.41). CONCLUSION: Students commonly perceived that their peers used illicit subtances more often than themselves. We found an association between the perceived peer norms/attitudes and reported individual behaviour/attitudes.

Microbial community structure during fluoranthene degradation in the presence of plants.

AIMS: To investigate bacterial and fungal community structure during degradation of varying concentrations (0-5000 mg kg(-1) ) of the polycyclic aromatic hydrocarbon (PAH) fluoranthene in the presence or absence of tomato plants. METHOD AND RESULTS: Fluoranthene amended or unamended growing media, with or without a plant, were incubated in pots in a glasshouse for 30 days. Fluoranthene concentration was quantified using GC-FID, while bacterial and fungal community structure was investigated using trflp and arisa, respectively. The abundance of two ring hydroxylating dioxygenase genes was measured using qPCR. More fluoranthene was degraded in the presence of tomato plants at 500 and 5000 mg fluoranthene kg(-1) (P < 0·001), and it had a toxic effect on plant growth. Bacterial and fungal community composition in the rhizosphere was significantly different from that in nonrhizospheric and unplanted samples. The influence of fluoranthene on bacterial communities overcame that of the plant root such that community composition in rhizosphere and planted nonrhizospheric samples was broadly similar when fluoranthene was present. PAH-RHDα-GP genes were more abundant than PAH-RHDα-GN genes in all treatments. PAH-RHDα-GN abundance was unaffected by either PAH concentration or growing medium type, while the abundance of PAH-RHDα-GP was greatest in the rhizosphere. CONCLUSIONS: Plants promoted microbial growth and diversity and led to increases in abundance of Gram-positive dioxygenase genes, correlated with increased degradation of fluoranthene. SIGNIFICANCE AND IMPACT OF THE STUDY: This work contributes to knowledge in the broad area of biodegradation and also provides useful information for the design of future bioremediation strategies.

Estimation of ultrasound strain indices in carotid plaque and correlation to cognitive dysfunction.

Carotid plaque prone to release emboli may be predicted by increased strain variations within plaque due to arterial pulsation over a cardiac cycle. Non-invasive ultrasound strain imaging may therefore be a viable surrogate to determine the risk of embolic stroke and possible cognitive impairment. Ultrasound strain imaging was performed on 24 human subjects with significant plaque, who also underwent standardized cognitive assessment (Repeatable Battery for the Assessment of Neuropsychological Status (RBANS)) prior to a carotid endarterectomy (CEA) procedure. Radiofrequency signals were acquired using a Siemens Antares with a VFX 13-5 linear array transducer. Plaque regions were segmented by a radiologist at end-diastole using the Medical Imaging Interaction Toolkit. A hierarchical block-matching motion tracking algorithm was utilized to estimate the cumulated axial, lateral, and shear strains within the imaging plane. The maximum strain indices of the plaque, defined as mean accumulated strain over a small region of interest in the plaque with large deformations, were obtained. All the strain indices were then correlated with RBANS Total score. Overall cognitive performance was negatively associated with maximum axial and lateral strains respectively. The results demonstrate a direct relationship between the maximum axial and lateral strain indices in carotid plaque and cognitive impairment.

Ethanol promotes cytotoxic effects of tumor necrosis factor-related apoptosis-inducing ligand through induction of reactive oxygen species in prostate cancer cells.

BACKGROUND: Effective treatment of prostate cancer (PCa) remains a major challenge due to chemoresistance to drugs including tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Ethanol and ethanol extracts are known apoptosis inducers. However, cytotoxic effects of ethanol on PCa cells are unclear. METHODS: In this study we utilized PC3 and LNCaP cell culture models. We used immunohistochemical analysis, western blot analysis, reactive oxygen species (ROS) measurement, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) Cell Proliferation Assay, Annexin-V staining and flow cytometry for quantification of apoptosis. In vitro soft agar colony formation and Boyden chamber invasion assays were used. Tumorigenicity was measured in a xenotransplantation mouse model. RESULTS: Here, we demonstrate that ethanol enhances the apoptosis-inducing potential of TRAIL in androgen-resistant PC3 cells and sensitizes TRAIL-resistant, androgen sensitive LNCaP cells to apoptosis through caspase activation, and a complete cleavage of poly (ADP)-ribose polymerase, which was in association with increased production of ROS. The cytotoxicity of ethanol was suppressed by an antioxidant N-acetyl cystein pretreatment. Furthermore, ethanol in combination with TRAIL increased the expression of cyclin-dependent kinase inhibitor p21 and decreased the levels of Bcl-2 and phosphorylated-AKT. These molecular changes were accompanied by decreased proliferation, anchorage-independent growth and invasive potential of PC3 and LNCaP cells. In vivo studies using a xenotransplantation mouse model with PC3 cells demonstrated significantly increased apoptosis in tumors treated with ethanol and TRAIL in combination. CONCLUSIONS: Taken together, use of ethanol in combination with TRAIL may be an effective strategy to augment sensitivity to TRAIL-induced apoptosis in PCa cells.

Methods for robust in vivo strain estimation in the carotid artery.

A hierarchical block-matching motion tracking algorithm for strain imaging is presented. Displacements are estimated with improved robustness and precision by utilizing a Bayesian regularization algorithm and an unbiased subsample interpolation technique. A modified least-squares strain estimator is proposed to estimate strain images from a noisy displacement input while addressing the motion discontinuity at the wall-lumen boundary. Methods to track deformation over the cardiac cycle incorporate a dynamic frame skip criterion to process data frames with sufficient deformation to produce high signal-to-noise displacement and strain images. Algorithms to accumulate displacement and/or strain on particles in a region of interest over the cardiac cycle are described. New methods to visualize and characterize the deformation measured with the full 2D strain tensor are presented. Initial results from patients imaged prior to carotid endarterectomy suggest that strain imaging detects conditions that are traditionally considered high risk including soft plaque composition, unstable morphology, abnormal hemodynamics and shear of plaque against tethering tissue can be exacerbated by neoangiogenesis. For example, a maximum absolute principal strain exceeding 0.2 is observed near calcified regions adjacent to turbulent flow, protrusion of the plaque into the arterial lumen and regions of low echogenicity associated with soft plaques. Non-invasive carotid strain imaging is therefore a potentially useful tool for detecting unstable carotid plaque.

Ultrasonic attenuation estimation in small plaque samples using a power difference method.

Many studies have shown that atherosclerosis changes the ultrasonic attenuation properties of the vessel wall and plaque. Accurate estimation of the attenuation coefficient slope could therefore provide an early indication of atherosclerosis and the differentiation between low, mild and highly-attenuating plaque within the vessel. However, the traditional reference phantom method that fits the power spectrum in a region of interest fails to accurately estimate the attenuation coefficient for small irregular shaped ex-vivo plaque specimens. This discrepancy was primarily due to partial volume effects and the unknown backscatter coefficient of the plaque sample. We have developed a method based on the reference-phantom method that utilizes the difference in the acoustic power above and below the sample to accurately compute values of the attenuation coefficient ex vivo. Our results demonstrate that this approach overcomes the two drawbacks mentioned earlier and provides accurate estimates of the attenuation coefficient slope for small excised tissue samples.