Quantitative Ultrasound Techniques Research Articles

Abstract 13561: The Emerging Role of Stress Speckle Tracking in Viability World

Introduction: Speckle-tracking echocardiography has recently emerged as a quantitative ultrasound technique for accurately evaluating myocardial function by analyzing the motion of speckles identified. Speckle-tracking obtained under stress may offer an opportunity to improve the detection of dynamic regional abnormalities and myocardial viability. Objective: To evaluate stress speckle tracking as tool to detect myocardial viability in comparison to cardiac MRI in post-STEMI patients. Methods: 71 patients were prospectively enrolled in our 18-month’s study. Dobutamin stress echocardiography was performed 4 days post-infaction accompanied with automated functional imaging (Speckle tracking) analysis of left ventricle during rest and then during low dose stress. All patients underwent a follow up stress echocardiography at 6 weeks with speckle tracking analysis. Cardiac MRI took place concomitantly at 4 days post-infarction and 6 weeks. We carried out an assessment of re-admission with acute coronary syndrome (ACS) after one year of enrollment. Results: Investigating strain rate obtained with stress speckle tracking after revascularization predicted the extent of myocardial scar, determined by contrast-enhanced magnetic resonance imaging. A good correlation was found between the global strain and total infarct size (R 0.75, p< 0.001). Furthermore, a clear inverse relationship was found between the segmental strain and the transmural extent of infarction in each segment. ( R -0.69, p<0.01). Meanwhile it provided 81.82% sensitivity and 82.6% specificity to detect transmural from non-transmural infaction at a cut-off value of -10.15. Global stress strain rate showed 80% sensitivity and 77.5% specificity at a cut-off value of -9.1 to predict hospital re-admission with ACS. A cut-off value of -8.4 had shown a 69.23% sensitivity and 73.5% specificity to predict the re-admission related to other cardiac symptoms . Conclusion: Strain rate obtained from speckle tracking during stress is a novel method of detecting myocardial viability after STEMI .Moreover it carries a promising role in post-myocardial infarction risk stratification with a reasonable prediction of reversible cardiac-related hospital re-admission.

Increased levels of interleukin 31 (IL-31) in osteoporosis.

BackgroundSeveral inflammatory cytokines play a key part in the induction of osteoporosis. Until now, involvement of the Th2 cytokine interleukin-31 (IL-31) in osteoporosis hadn’t yet been studied. IL-31 is a proinflammatory cytokine mediating multiple immune functions, whose involvement in a wide range of diseases, such as atopic dermatitis, inflammatory bowel diseases and cutaneous lymphomas, is now emerging. Given the important role of IL-31 in inflammation, we measured its serum levels in postmenopausal osteoporotic patients.Methods and resultsIn fifty-six postmenopausal females with osteoporosis and 26 healthy controls, bone mineral density (BMD) measurements were performed by using calcaneal quantitative ultrasound (QUS) technique, confirmed at the lumbar spine and hip by dual energy X-ray absorptiometry (DXA). Both patients and controls were divided according to age (less or more than 65 years) and disease severity (T-score levels and presence of fractures). Serum IL-31 levels were measured by ELISA technique. Osteoporotic patients exhibited elevated levels of serum IL-31 compared with healthy controls (43.12 ± 6.97 vs 29.58 ± 6.09 pg/ml; p < 0.049). IL-31 expression was higher in over 65 years old patients compared to age-matched controls (45 ± 11.05 vs. 17.92 ± 5.92; p < 0.01), whereas in younger subjects no statistically significant differences were detected between patients and controls (37.91 ± 6.9 vs 32.08 ± 8.2). No statistically significant differences were found between IL-31 levels in patients affected by mild (T-score > -3) compared to severe (T-score < -3) osteoporosis (59.17 ± 9.22 vs 37.91 ± 10.52), neither between fractured and unfractured osteoporotic women (33.75 ± 9.16 vs 51.25 ± 8.9).ConclusionsWe showed for the first time an increase of IL-31 serum levels in postmenopausal women with decreased BMD. Although they did not reflect the severity of osteoporosis and/or the presence of fractures, they clearly correlated with age, as reflected by the higher levels of this cytokine in aged patients.

Unifying Concepts of Statistical and Spectral Quantitative Ultrasound Techniques.

Quantitative ultrasound (QUS) techniques using radiofrequency (RF) backscattered signals have been used for tissue characterization of numerous organ systems. One approach is to use the magnitude and frequency dependence of backscatter echoes to quantify tissue structures. Another approach is to use first-order statistical properties of the echo envelope as a signature of the tissue microstructure. We propose a unification of these QUS concepts. For this purpose, a mixture of homodyned K-distributions is introduced to model the echo envelope, together with an estimation method and a physical interpretation of its parameters based on the echo signal spectrum. In particular, the total, coherent and diffuse signal powers related to the proposed mixture model are expressed explicitly in terms of the structure factor previously studied to describe the backscatter coefficient (BSC). Then, this approach is illustrated in the context of red blood cell (RBC) aggregation. It is experimentally shown that the total, coherent and diffuse signal powers are determined by a structural parameter of the spectral Structure Factor Size and Attenuation Estimator. A two-way repeated measures ANOVA test showed that attenuation (p-value of 0.077) and attenuation compensation (p-value of 0.527) had no significant effect on the diffuse to total power ratio. These results constitute a further step in understanding the physical meaning of first-order statistics of ultrasound images and their relations to QUS techniques. The proposed unifying concepts should be applicable to other biological tissues than blood considering that the structure factor can theoretically model any spatial distribution of scatterers.

Ultrasonographic Median Nerve Changes After Repeated Wheelchair Transfers in Persons With Paraplegia: Relationship With Subject Characteristics and Transfer Skills

BackgroundWheelchair users with spinal cord injuries are susceptible to peripheral neuropathies from overuse, yet no studies have established a relationship between median neuropathy and wheelchair transfers. A more thorough understanding of how transfers and technique contribute to pathologic conditions may guide interventions that curtail its development. ObjectiveTo evaluate the effects of repeated transfers on ultrasound markers for carpal tunnel syndrome (CTS) in people with spinal cord injuries and to relate changes to subject characteristics and transfer skills. DesignCross-sectional, repeated measures. SettingResearch laboratory and national wheelchair sporting events. ParticipantsA convenience sample of 30 wheelchair users with nonprogressive paraplegia were recruited via research registries and at the 2013 National Veterans Wheelchair Games and 2014 Paralyzed Veterans of America Buckeye Games. Participants were older than 18 years and could complete transfers independently within 30 seconds without use of their leg muscles. MethodsDemographic questionnaires and physical examinations for CTS were completed. Quantitative ultrasound techniques were used to measure changes in the median nerve after a repeated-transfers protocol. The Transfer Assessment Instrument (TAI) was completed to quantify transfer ability. Main Outcome MeasurementsMedian nerve cross-sectional area at the level of the pisiform (PCSA) and swelling ratio (SR), transfer quality, and skills via the TAI. ResultsPCSA increased after repeated transfers (P < .025). Participants who used safe hand positions had a lower baseline SR (β = −0.728; P < .01). Participants with a higher body weight had a lower baseline SR provided they performed higher quality transfers. Participants who scooted to the front of the seat prior to transferring (TAI item 7; β = 0.144; P < .05) and who weighed more (β = 0.142; P < .05) exhibited greater increases in PCSA in response to transfers. ConclusionsAn acute increase was observed in median nerve CSA at the pisiform after repeated wheelchair transfers. Changes were greater in persons with higher body weight and in persons who did not perform certain transfer skills correctly (according to the TAI). It is possible that these factors contribute to chronic injury and possibly CTS.

Abstract CT317: Quantitative ultrasound for personalized chemotherapy in locally advanced breast cancer: Clinical trial results

Abstract Many cancer therapies are intended to induce cell death within a target tumour. A substantial body of research using in vitro and in vivo models has demonstrated that cell death can be detected via quantitative ultrasound techniques. This study investigated the potential to quantify tumour responses to therapy in patients, using quantitative spectral and textural biomarkers extracted from low-frequency ultrasound data (4-10 MHz). Results demonstrate for the first time in a large cohort of patients the ability to predict clinical responders from non-responders as early as one week after the start of chemotherapy with over 95% sensitivity and 95% specificity. A clinical study was undertaken investigating the efficacy of ultrasound to quantify cell death in tumor responses with cancer treatment. Patients (n = 100) with locally advanced breast cancer received anthracyline and taxane-based chemotherapy treatments over four to six months. Data collection consisted of acquiring tumor images and radiofrequency data prior to treatment onset and at 4 times during neoadjuvant chemotherapy (weeks 0, 1, 4, 8 and pre-operatively). Data collection was carried out using an Ultrasonix-RP and an L15-5 6cm transducer pulsed at frequencies of ∼5 and ∼7 MHz, respectively. The majority of patients went on to have a modified radical mastectomy and correlative whole mount histopathology. Results obtained from both ∼5 and ∼7 MHz data indicated considerable increases in ultrasound spectral backscatter power in patients who clinically responded to treatment within one week of starting their chemotherapy. This was accompanied by significant increases in quantitative ultrasound spectral parameters such as mid-band-fit (up to 9.1 ± 1.2 dBr) and 0-MHz intercept (up to 10.8 ± 2.4 dBr). Patients categorized as poor responders clinically demonstrated significantly lower increases (1.9 ± 1.1 dBr and 1.4 ± 2.7 dBr for mid-band-fit and 0-MHz intercept, respectively). Textural biomarkers extracted from quantitative ultrasound spectral parametric maps also demonstrated considerable differences in trend between treatment responding and non-responding patients early after the treatment initiation. Statistically significant differences were found between treatment responding and non-responding patient populations using quantitative ultrasound spectral biomarkers 4 and 8 weeks after treatment initiation. Applying quantitative ultrasound textural biomarkers in order to incorporate response heterogeneities resulted in statistically significant differences between these two populations only one week after the start of chemotherapy. There were also associated survival differences between the two groups of patients. Patients with ultrasound-detected responses at week 1 had an over 90+/-5% 3 year survival whereas patients with no ultrasound-detected response at the same time had a 30+/10% survival (p&amp;lt;0.05). This study demonstrates the potential of ultrasound to quantify changes in tumours in response to cancer treatment administration in a clinical setting. The results indicate that such responses can be detected early during a course of chemotherapy. This can potentially permit ineffective treatments to be changed to more efficacious ones potentially leading to improved treatment outcomes within a framework of personalized medicine. Citation Format: Gregory Jan Czarnota, Ali Sadeghi-Naini, Hadi Tadayyon, Lakshmanan Sannachi, Mehrdad Gangeh, William Tran, Frances Wright, Sonal Gandhi, Kathleen Pritchard, Sunil Verma, Maureen Trudeau. Quantitative ultrasound for personalized chemotherapy in locally advanced breast cancer: Clinical trial results. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr CT317. doi:10.1158/1538-7445.AM2015-CT317

WE‐EF‐210‐05: Diagnosis and Quantification of Liver Steatosis with Quantitative Ultrasound Backscatter Technique

Purpose:Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in the United States, affects 30% of adult Americans and may progress to more serious diseases. Liver biopsy is the standard method for diagnosing NAFLD. MRI can accurately diagnose and quantify hepatic steatosis but is expensive. Sonography with qualitative interpretation by radiologists is lower cost, more accessible but less sensitive for detection. The objective of this study, using MRI proton density fat fraction (PDFF) as reference, is to assess the accuracy for diagnosing and quantifying steatosis with two quantitative US parameters‐‐ backscatter coefficient (BSC) and attenuation coefficient (AC)‐‐derived from RF signals using the calibration phantom technique.Methods:We performed a prospective, cross‐sectional analysis of a cohort of adults (n=204) with NAFLD (MRI‐PDFF≥5%) and without NAFLD (controls). Subjects underwent MRI‐PDFF and BSC and AC US analyses of the liver on the same day. Patients were randomly assigned to training (n=102, mean age 51±17 years, mean body mass index 31±7 kg/m2) and validation (n=102, mean age 49±17 years, body mass index 30±6 kg/m2) groups; 69% of patients in each group had NAFLD.Results:BSC provided AUC 0.98 (95% CI 0.95–1.00, p&lt;0.0001) for diagnosis of NAFLD; the optimal BSC cut‐off provided sensitivity, specificity, positive and negative predictive values (PPV, NPV) of 87%, 91%, 95%, and 76%, respectively. AC provided AUC 0.89 (95% CI 0.81–0.96, p&lt;0.0001) for diagnosis of steatosis; the optimal AC cut‐off provided sensitivity, specificity, PPV, NPV of 80%, 84%, 92%, and 66%, respectively. BSC and AC both correlated significantly with MRI‐PDFF (P&lt;0.0001).Conclusion:QUS BSC and AC can accurately diagnose and quantify hepatic steatosis, using MRI‐PDFF as reference. With further validation, QUS may emerge as an inexpensive, widely available tool for NAFLD assessment.General support: NIH R01 CA111289, K23 ‐DK090303, AmerGastroAssoc Found, TF Williams Scholarship, S3000 scanner loaned by Siemens, Sucampo, JA Hartford Found, Atlantic Philanthropies Amer Gastroenterological Assoc. Agencies had no role in design/conduct of study, collection, management, analysis or interpretation of the data; preparation, review, or approval of the manuscript.

Accuracy of quantitative ultrasound technique and osteoporosis self-assessment tool in comparison to DXA in detecting low bone density in post-menopausal women in Riyadh, Saudi Arabia

Accuracy of quantitative ultrasound technique and osteoporosis self-assessment tool in comparison to DXA in detecting low bone density in post-menopausal women in Riyadh, Saudi Arabia

Ultrasound backscattering from cancellous bone in vivo

Osteoporosis is a musculoskeletal disease characterized by a loss of bone mass and a deterioration of trabecular bone microarchitecture. In recent years, significant progress has been made in the quantitative ultrasound technique, and it has become well established as a noninvasive tool for the assessment of bone status. This report will show the ultrasonic backscatter theory in cancellous bone, analyze the ultrasonic backscattering signals, and to investigate correlations among backscatter parameters and bone mineral density (BMD) in vivo. Ultrasonic backscattering measurements were performed on 1226 subjects (601 males and 625 females) at the right calcaneus in vivo using the novel ultrasonic backscatter bone system. Then, the subjects underwent DXA for the BMD at sites located on the lumbar spine (sBMD) and left hip (hBMD). Spectral centroid shift (SCS), mean trabecular bone spacing (Tb.Sp), backscatter coefficient (BC), and apparent integral backscatter coefficient (AIB) were calculated at the central frequencies of 3.5 and 5.0 MHz. Linear regression showed that the SCS at 3.5 MHz exhibited negative correlations with the sBMD (R=−0.66) and hBMD (R=−0.64). The SCS at 5.0 MHz was also found to be closely related to the sBMD (R=−0.68) and hBMD (R=−0.66). Tb.Sp at 3.5 MHz and 5.0 MHz exhibited negative correlations with the sBMD (R=−0.74) and hBMD (R=−0.66).The correlations between backscatter parameters and BMD were found to be statistically significant in both the male and female groups.

Two-dimensional global and segmental longitudinal strain: are the results from software in different high-end ultrasound systems comparable?

To compare the peak global longitudinal myocardial strain (PGLS) and peak segmental longitudinal myocardial strain (PSLS) values by speckle-tracking echocardiography (STE) obtained using two different echocardiography devices. STE is an emerging quantitative ultrasound technique that allows an accurate evaluation of global and segmental myocardial function. However, there is a lack of standardization of the acquired data among different manufacturers. Sixty-three subjects, mean age 56.2±10.4 years, underwent complete echocardiographic studies with two different devices (Philips IE33 and General Electric VIVID E9) performed by the same operator. Thirty-one of them had known cardiac disease, with estimated left ventricular ejection fraction <50%, while 32 were free of any cardiovascular disease (control subjects). All images were digitally stored and analyzed using off-line post processing with QLAB 9 and EchoPAC 11 Software packages. PSLS and PGLS were calculated. A strong relationship between QLAB and EchoPAC was found for PGLS (r=0.91, P<0.001), PSLS-4 chamber (CH; r=0.79, P<0.001), PSLS-2CH (r=0.73, P<0.001), and PSLS-3CH (r=0.78, P<0.001) QLAB. Bland–Altman analysis showed absolute differences vs average of −0.16, −0.37, −0.21, and −0.16 for PGLS, PSLS-4CH, PSLS-2CH, and PSLS-apical long-axis views respectively. Segmental analysis showed a good agreement between the apical segments, whereas poor correlations were found for the basal segments. Receiver operating characteristic curve analysis showed that cutoff values for PGLS of −17.5 and −17.75% with Philips or GE systems gave a sensitivity and specificity of 93.5 and 87.5%, and 90 and 87.5%, respectively, in the discrimination of the patients from the controls. Both Philips and GE echo stations were found to give comparable results for PGLS, with approximately the same cutoff values, suggesting that their PGLS results may be interchangeable.

The Best of Quantitative Ultrasound

The objective of these studies was to demonstrate that quantitative ultrasound (QUS) techniques could be used to improve diagnostic ultrasound imaging. Specifically, QUS techniques were applied to improving detection of breast and thyroid cancer, early detection of preterm birth, quantification of fatty liver and thermometry. QUS techniques were employed that utilized parameterization of the frequency-dependent backscatter coefficient, the attenuation coefficient and/or envelope statistics. The backscatter coefficient was parameterized through the effective scatterer diameter (ESD) and the effective acoustic concentration (EAC). Backscattered ultrasound data were acquired from tissue samples using clinical ultrasound scanners providing the RF signal and from laboratory systems utilizing single-element focused transducers. The data spanned frequency ranges from 2 to 50 MHz. Combinations of the ESD, EAC and envelope statistics were successful in differentiating malignant from benign tumors in rodent models of breast cancer. Similarly, the ESD combined with envelope statistics provided differentiation of malignant from benign nodules in mouse models of thyroid cancer. Cervical attenuation was an early predictor of preterm birth in rat models and in humans. Attenuation and the slope and magnitude of the backscatter coefficient were observed to predict the degree of fatty liver in mouse models and in humans. The EAC was observed to track temperature when using thermal therapies in different tissues. QUS techniques have continued to mature and have demonstrated new sources of contrast leading to improved diagnostic capabilities and the ability to monitor and assess therapy.

Material Characterization of in Vivo and in Vitro Porcine Brain Using Shear Wave Elasticity

Realistic computer simulation of closed head trauma requires accurate mechanical properties of brain tissue, ideally in vivo. A substantive deficiency of most existing experimental brain data is that properties were identified through in vitro mechanical testing. This study develops a novel application of shear wave elasticity imaging to assess porcine brain tissue shear modulus in vivo. Shear wave elasticity imaging is a quantitative ultrasound technique that has been used here to examine changes in brain tissue shear modulus as a function of several experimental and physiologic parameters. Animal studies were performed using two different ultrasound transducers to explore the differences in physical response between closed skull and open skull arrangements. In vivo intracranial pressure in four animals was varied over a relevant physiologic range (2–40 mmHg) and was correlated with shear wave speed and stiffness estimates in brain tissue. We found that stiffness does not vary with modulation of intracranial pressure. Additional in vitro porcine specimens (n = 14) were used to investigate variation in brain tissue stiffness with temperature, confinement, spatial location and transducer orientation. We observed a statistically significant decrease in stiffness with increased temperature (23%) and an increase in stiffness with decreasing external confinement (22–37%). This study determined the feasibility of using shear wave elasticity imaging to characterize porcine brain tissue both in vitro and in vivo. Our results underline the importance of temperature- and skull-derived boundary conditions to brain stiffness and suggest that physiologic ranges of intracranial pressure do not significantly affect in situ brain tissue properties. Shear wave elasticity imaging allowed for brain material properties to be experimentally characterized in a physiologic setting and provides a stronger basis for assessing brain injury in computational models.

Noninvasive Diagnosis of Nonalcoholic Fatty Liver Disease and Quantification of Liver Fat Using a New Quantitative Ultrasound Technique

Liver biopsy analysis is the standard method used to diagnose nonalcoholic fatty liver disease (NAFLD). Advanced magnetic resonance imaging is a noninvasive procedure that can accurately diagnose and quantify steatosis, but is expensive. Conventional ultrasound is more accessible but identifies steatosis with low levels of sensitivity, specificity, and quantitative accuracy, and results vary among technicians. A new quantitative ultrasound (QUS) technique can identify steatosis in animal models. We assessed the accuracy of QUS in the diagnosis and quantification of hepatic steatosis, comparing findings with those from magnetic resonance imaging proton density fat fraction (MRI-PDFF) analysis as a reference. We performed a prospective, cross-sectional analysis of a cohort of adults (N = 204) with NAFLD (MRI-PDFF, ≥5%) and without NAFLD (controls). Subjects underwent MRI-PDFF and QUS analyses of the liver on the same day at the University of California, San Diego, from February 2012 through March 2014. QUS parameters and backscatter coefficient (BSC) values were calculated. Patients were assigned randomly to training (n = 102; mean age, 51 ± 17 y; mean body mass index, 31 ± 7 kg/m(2)) and validation (n = 102; mean age, 49 ± 17 y; body mass index, 30 ± 6 kg/m(2)) groups; 69% of patients in each group had NAFLD. BSC (range, 0.00005-0.25 1/cm-sr) correlated with MRI-PDFF (Spearman ρ = 0.80; P < .0001). In the training group, the BSC analysis identified patients with NAFLD with an area under the curve value of 0.98 (95% confidence interval, 0.95-1.00; P < .0001). The optimal BSC cut-off value identified patients with NAFLD in the training and validation groups with 93% and 87% sensitivity, 97% and 91% specificity, 86% and 76% negative predictive values, and 99% and 95% positive predictive values, respectively. QUS measurements of BSC can accurately diagnose and quantify hepatic steatosis, based on a cross-sectional analysis that used MRI-PDFF as the reference. With further validation, QUS could be an inexpensive, widely available method to screen the general or at-risk population for NAFLD.

Assessment of In Vitro Dental Implant Primary Stability Using an Ultrasonic Method

Dental implants are used for oral rehabilitation. However, there remain risks of failure that depend on the implant stability. The objective of this study is to investigate whether quantitative ultrasound technique can be used to assess the amount of bone in contact with dental implants. Ten implants are first inserted in the bone samples. The 10 MHz ultrasonic response of each implant is measured using a dedicated device and an indicator I is derived based on the amplitude of the signal. Then, the implant is unscrewed by 2 π radians and the measurement is realized again. A statistical analysis of variance was carried out and revealed a significant effect of the amount of bone in contact with the implant on the values of I (p value < 10−5). The results indicates the feasibility of quantitative ultrasound techniques to assess implant primary stability in vitro.

Quantitative ultrasound imaging to monitor in vivo high-intensity ultrasound treatment

The success of any minimally invasive treatment procedure can be enhanced significantly if combined with a robust noninvasive quantitative imaging modality. Quantitative ultrasound (QUS) imaging has been widely investigated for monitoring various treatment responses such as chemotherapy and thermal therapy. Previously we have shown the feasibility of using spectral based quantitative ultrasound parameters to monitor high-intensity focused ultrasound (HIFU) treatment of in situ tumors [Ultrasonic Imaging, 2014]. In the present study we examined the use the various QUS parameters to monitor HIFU treatment of an in vivo mouse mammary adenocarcinoma model. Spectral parameters in terms of the backscatter coefficient, integrated backscattered energy, attenuation coefficient, and effective scatterer size and concentration were estimated from radiofrequency signals during the treatment. The characteristic of each parameter was compared to the temperature profile recorded by needle thermocouple inserted into the tumor a few millimeters away from the focal zone of the intersecting HIFU and the imaging transducer beams. The changes in the QUS parameters during the HIFU treatment followed similar trends observed in the temperature readings recorded from the thermocouple. These results suggest that QUS techniques have the potential to be used for non-invasive monitoring of HIFU exposure.

Quantitative Ultrasound Imaging for Monitoring In Situ High-Intensity Focused Ultrasound Exposure

Quantitative ultrasound (QUS) imaging is hypothesized to map temperature elevations induced in tissue with high spatial and temporal resolution. To test this hypothesis, QUS techniques were examined to monitor high-intensity focused ultrasound (HIFU) exposure of tissue. In situ experiments were conducted on mammary adenocarcinoma tumors grown in rats and lesions were formed using a HIFU system. A thermocouple was inserted into the tumor to provide estimates of temperature at one location. Backscattered time-domain waveforms from the tissue during exposure were recorded using a clinical ultrasonic imaging system. Backscatter coefficients were estimated using a reference phantom technique. Two parameters were estimated from the backscatter coefficient (effective scatterer diameter (ESD) and effective acoustic concentration (EAC). The changes in the average parameters in the regions corresponding to the HIFU focus over time were correlated to the temperature readings from the thermocouple. The changes in the EAC parameter were consistently correlated to temperature during both heating and cooling of the tumors. The changes in the ESD did not have a consistent trend with temperature. The mean ESD and EAC before exposure were 120 ± 16 μm and 32 ± 3 dB/cm3, respectively, and changed to 144 ± 9 μm and 51 ± 7 dB/cm3, respectively, just before the last HIFU pulse was delivered to the tissue. After the tissue cooled down to 37 °C, the mean ESD and EAC were 126 ± 8 μm and 35 ± 4 dB/cm3, respectively. Peak temperature in the range of 50-60 °C was recorded by a thermocouple placed just behind the tumor. These results suggest that QUS techniques have the potential to be used for non-invasive monitoring of HIFU exposure.

Categorizing extent of tumor cell death response to cancer therapy using quantitative ultrasound spectroscopy and maximum mean discrepancy.

Quantitative ultrasound (QUS) spectroscopic techniques in conjunction with maximum mean discrepancy (MMD) have been proposed to detect, and to classify noninvasively the levels of cell death in response to cancer therapy administration in tumor models. Evaluation of xenograft tumor responses to cancer treatments were carried out using conventional-frequency ultrasound at different times after chemotherapy exposure. Ultrasound data were analyzed using spectroscopic techniques and multi-parametric QUS spectral maps were generated. MMD was applied as a distance criterion, measuring alterations in each tumor in response to chemotherapy, and the extent of cell death was classified into less/more than 20% and 40% categories. Statistically significant differences were observed between "pre-" and "post-treatment" groups at different times after chemotherapy exposure, suggesting a high capability of proposed framework for detecting tumor response noninvasively. Promising results were also obtained for categorizing the extent of cell death response in each tumor using the proposed framework, with gold standard histological quantification of cell death as ground truth. The best classification results were obtained using MMD when applied on histograms of QUS parametric maps. In this case, classification accuracies of 84.7% and 88.2% were achieved for categorizing extent of tumor cell death into less/more than 20% and 40%, respectively.

Ultrasound method applied to characterize healthy femoral diaphysis of Wistar rats in vivo.

A simple experimental protocol applying a quantitative ultrasound (QUS) pulse-echo technique was used to measure the acoustic parameters of healthy femoral diaphyses of Wistar rats in vivo. Five quantitative parameters [apparent integrated backscatter (AIB), frequency slope of apparent backscatter (FSAB), time slope of apparent backscatter (TSAB), integrated reflection coefficient (IRC), and frequency slope of integrated reflection (FSIR)] were calculated using the echoes from cortical and trabecular bone in the femurs of 14 Wistar rats. Signal acquisition was performed three times in each rat, with the ultrasound signal acquired along the femur's central region from three positions 1 mm apart from each other. The parameters estimated for the three positions were averaged to represent the femur diaphysis. The results showed that AIB, FSAB, TSAB, and IRC values were statistically similar, but the FSIR values from Experiments 1 and 3 were different. Furthermore, Pearson's correlation coefficient showed, in general, strong correlations among the parameters. The proposed protocol and calculated parameters demonstrated the potential to characterize the femur diaphysis of rats in vivo. The results are relevant because rats have a bone structure very similar to humans, and thus are an important step toward preclinical trials and subsequent application of QUS in humans.

Estimating Cell Concentration in Three-Dimensional Engineered Tissues Using High Frequency Quantitative Ultrasound

Histology and biochemical assays are standard techniques for estimating cell concentration in engineered tissues. However, these techniques are destructive and cannot be used for longitudinal monitoring of engineered tissues during fabrication processes. The goal of this study was to develop high-frequency quantitative ultrasound techniques to nondestructively estimate cell concentration in three-dimensional (3-D) engineered tissue constructs. High-frequency ultrasound backscatter measurements were obtained from cell-embedded, 3-D agarose hydrogels. Two broadband single-element transducers (center frequencies of 30 and 38MHz) were employed over the frequency range of 13-47MHz. Agarose gels with cell concentrations ranging from 1×10(4) to 1×10(6)cellsmL(-1) were investigated. The integrated backscatter coefficient (IBC), a quantitative ultrasound spectral parameter, was calculated and used to estimate cell concentration. Accuracy and precision of this technique were analyzed by calculating the percent error and coefficient of variation of cell concentration estimates. The IBC increased linearly with increasing cell concentration. Axial and lateral dimensions of regions of interest that resulted in errors of less than 20% were determined. Images of cell concentration estimates were employed to visualize quantitatively regional differences in cell concentrations. This ultrasound technique provides the capability to rapidly quantify cell concentration within 3-D tissue constructs noninvasively and nondestructively.

Prevalence and factors associated with low bone mineral density in Saudi women: a community based survey

BackgroundLow bone mineral density (BMD) is a public health issue in Saudi Arabia. This study measured the prevalence and factors associated with low BMD in Saudi women in Riyadh, Saudi Arabia.MethodsA cross sectional study using two stage cluster sampling technique was conducted in Riyadh, 2009. Thirty clusters, each comprising of 300 houses were randomly chosen and from each cluster 38–40 households were selected to identify 1150 women of >40 years. Women were invited to primary health care center for filling of self-administered questionnaire (n = 1069) comprising of sociodemographic, health, diet and physical activity variables. 1008 women underwent screening for low BMD using the quantitative ultrasound technique. 535 (53%) women with positive screening test were referred to King Khalid Hospital for Dual X-ray Energy absorptiometry (DXA).Results362 women underwent DXA and 212 (39.6%) were screened low BMD either at lumbar spine or femur neck. Mean age of women was 55.26(±8.84) years. Multivariate logistic analysis found; being aged 61 to 70 years (OR 2.75, 95% CI: 1.32-1.48), no literacy (OR 2.97, 95% CI:1.44 - 6.12) or primary education (OR 4.12, 95% CI:2.05-8.29), history of fractures (OR 2.20, 95% CI:1.03- 4.69) and not drinking laban(diluted yogurt) (OR 2.81, 95% CI:1.47- 5.37) significantly associated with low BMD.ConclusionsWomen with low level of education, who do not drink laban and had history of fractures were at high risk of low BMD.

To Determine the Risk Factors and Prevalence of Osteoporosis among Adult Pakistani Population Residing in Karachi Using Quantitative Ultrasound Technique

our country too. The purpose of our study was to determine the prevalence of osteoporosis, and also to establish the risk factors associated with it in Pakistan. Method: It was a cross sectional study that was conducted in the primary care setting in different areas of Karachi. Bone mineral density assessment was done by the speed of sound using the quantitative ultrasound technique at the right Calcaneus. A structured questionnaire was prepared, to evaluate the risk factors associated with osteoporosis Results: Out of 500 participants 21.6% were male and 78.4% were female. The overall prevalence of osteoporosis was 30.7% (24% male and 32.6% females). The prevalence of osteopenia was 44.5% (51% being male and 42.6% being female). Factors that were statistically (p value <0.05) associated with low bone mineral density were increasing age, female gender for osteoporosis, normal to heavy weight, office work in both male and female, inadequate physical activity, inadequate sun exposure, inadequate intake of calcium, smoking in males and smokeless tobacco in both male and female, intake of steroids. Past history of fracture among the participants and the history of fracture in the parents, diabetes and depression also showed positive association, balanced diet and educational status and hypertension could not provide any significant statistical association with low bone mineral density. Conclusion: The prevalence of osteoporosis is high among the adult population of Karachi and it is associated with modifiable risk factors. Non-communicable diseases like, diabetes and depression, also gave a positive association, which needs further prospective studies to confirm this association.