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Tissue mimicking materials for the detection of prostate cancer using shear wave elastography: a validation study.

ABSTRACT: Quantification of stiffness changes may provide important diagnostic information and aid in the early detection of cancers. Shear wave elastography is an imaging technique that assesses tissue stiffness using acoustic radiation force as an alternate to manual palpation reported previously with quasistatic elastography. In this study, the elastic properties of tissue mimicking materials, including agar, polyacrylamide (PAA), and silicone, are evaluated with an objective to determine material characteristics which resemble normal and cancerous prostate tissue.Acoustic properties and stiffness of tissue mimicking phantoms were measured using compressional mechanical testing and shear wave elastography using supersonic shear imaging. The latter is based on the principles of shear waves generated using acoustic radiation force. The evaluation included tissue mimicking materials (TMMs) within the prostate at different positions and sizes that could mimic cancerous and normal prostate tissue. Patient data on normal and prostate cancer tissues quantified using biopsy histopathology were used to validate the findings. Pathologist reports on histopathology were blinded to mechanical testing and elastographic findings.Young's modulus values of 86.2 ± 4.5 and 271.5 ± 25.7 kPa were obtained for PAA mixed with 2% Al(2)O(3) particles and silicone, respectively. Young's modulus of TMMs from mechanical compression testing showed a clear trend of increasing stiffness with an increasing percentage of agar. The silicone material had higher stiffness values when compared with PAA with Al(2)O(3). The mean Young's modulus value in cancerous tissue was 90.5 ± 4.5 kPa as compared to 93.8 ± 4.4 and 86.2 ± 4.5 kPa obtained with PAA with 2% Al(2)O(3) phantom at a depth of 52.4 and 36.6 mm, respectively.PAA mixed with Al(2)O(3) provides the most suitable tissue mimicking material for prostate cancer tumor material, while agar could form the surrounding background to simulate normal prostate tissue.

SUBMITTER: Cao R

PROVIDER: S-EPMC3562344 | biostudies-other | 2013 Feb

REPOSITORIES: biostudies-other

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Project description:Objectives:The aim of the study was to compare elastographic means in parathyroid adenomas, using shear wave elastography and strain elastography. Methods:This prospective study examined 20 consecutive patients diagnosed with primary hyperparathyroidism and parathyroid adenoma, confirmed by biochemical assay, technetium-99 sestamibi scintigraphy, and pathology report, after parathyroid surgery. All patients were examined on conventional 2B ultrasound, 2D shear wave elastography, and strain elastography. We determined using 2D shear wave elastography (SWE) the elasticity index (EI) in parathyroid adenoma, thyroid parenchyma, and surrounding muscle and examined using strain elastography the parathyroid adenoma, and determined the strain ratio with the thyroid tissue and muscle tissue. Results:All patients had positive sestamibi scintigraphy and underwent surgery, with confirmation of parathyroid adenoma in all cases. The mean parathormone (PTH) value before surgery was 153.29?pg/ml (36.5, 464.8) and serum calcium concentration was 10.5?mg/dl (9, 11.5). We compared using 2D-SWE and strain elastography parathyroid adenoma with thyroid tissue and with surrounding muscle. The mean EI measured by SWE in parathyroid adenoma was 4.74?±?2.74?kPa and in thyroid parenchyma was 11.718?±?4.206?kPa (mean difference?=?6.978?kPa, p < 0.001), and the mean EI value in muscle tissue was 16.362?±?3.829?kPa (mean difference?=?11.622, p < 0.001). Using ROC analysis, we found that an EI below 7?kPa correctly identifies parathyroid tissue. We evaluated parathyroid adenomas using strain elastography by color mapping and strain ratio as a semiquantitative measurement; however, we could not find any statistical correlation comparing the strain ratio obtained from the parathyroid adenoma with the thyroid tissue (p=0.485). Conclusion:Ultrasound elastography is a helpful tool in identifying parathyroid adenomas. A cutoff value below 7?kPa can be used in 2D-SWE. Color maps in strain elastography without adding strain ratio can be used, parathyroid adenoma being identified as score 1 in the Rago criteria.

Project description:Thromboembolism in a cerebral blood vessel is associated with high morbidity and mortality. Mechanical thrombectomy (MT) is one of the emergenc proceduresperformed to remove emboli. However, the interventional approaches such as aspiration catheters or stent retriever are empirically selected. An inappropriate selection of surgical devices can influence the success rate during embolectomy, which can lead to an increase in brain damage. There has been growing interest in the study of clot composition and using a priori knowledge of clot composition to provide guidance for an appropriate treatment strategy for interventional physicians. Developing imaging tools which can allow interventionalists to understand clot composition could affect management and device strategy. In this study, we investigated how clots of different compositions can be characterized by using acoustic radiation force optical coherence elastography (ARF-OCE) and compared with ultrasound shear wave elastography (SWE). Five different clots compositions using human blood were fabricated into cylindrical forms from fibrin-rich (21% red blood cells, RBCs) to RBC-rich (95% RBCs). Using the ARF-OCE and SWE, we characterized the wave velocities measured in the time-domain. In addition, the semi-analytical finite element model was used to explore the relationship between the phase velocities with various frequency ranges and diameters of the clots. The study demonstrated that the wave group velocities generally decrease as RBC content increases in ARF-OCE and SWE. The correlation of the group velocities from the OCE and SWE methods represented a good agreement as RBC composition is larger than 39%. Using the phase velocity dispersion analysis applied to ARF-OCE data, we estimated the shear wave velocities decoupling the effects of the geometry and material properties of the clots. The study demonstrated that the composition of the clots can be characterized by elastographic methods using ARF-OCE and SWE, and OCE demonstrated better ability to discriminate between clots of different RBC compositions, compared to the ultrasound-based approach, especially in clots with low RBC compositions.

Project description:This study aims to evaluate the feasibility and clinical interest of shear wave elastography, by quantitatively estimating the baseline stiffness of the myometrium before and after placental expulsion. We conducted a prospective cohort study of women at term, without known risk factors for postpartum hemorrhage, who gave birth via spontaneous labor in our tertiary center. Myometrium tonicity was evaluated based on measurements of shear wave speed (SWS) in the anterior uterine corpus. All data points were collected by a single operator. Measurements were carried out at three different time points: after fetal delivery (T1), after placental delivery (T2) and 30 min after placental delivery (T3). Our primary objective was to assess the feasibility of this new imaging technique. Ten valid SWS measurements obtained at each of the three different time points were considered as a positive primary outcome. Our secondary objectives were to evaluate the difference in median myometrial shear wave velocity between each time point, as well as to determine the correlation between myometrial shear wave velocity and patients' characteristics. 38 women were recruited during the study period, of whom 34 met the study criteria. 1017 SWS measurements were obtained. The median time to perform measurements was 16 s for one value, and 2 min 56 s for ten. For 11 women (32%) it was not possible to achieve ten SWS at T1 as placental expulsion immediately followed the birth of the newborn. One patient experienced placental retention and only measurements at T1 were performed. For all other patients, we were successfully able to obtain all measures as intended. There was no difference in the mean shear wave speed between the three time points. After adjustments for confounders, we observed a significant correlation for total blood loss (correlation coefficient = - 0.26, p < 0.001, units of oxytocin (correlation coefficient = - 0.34, p = 0.03), and newborn weight (correlation coefficient = - 0.08, p = 0.001). It is feasible to assess uterine tonicity by shear wave imaging, after placental expulsion. We did not observe a variance in uterine tonicity between the three time points. Women who had higher blood loss, received more units of oxytocin and/or those with newborns of a higher weight exhibited lower shear wave speed measures.

Project description:Background Elastography is a promising way to evaluate tissue differences regarding stiffness, and the stiffness of the malignant breast lesions increased at the lesion margin. However, there is a lack of data on the value of the shear wave elastography (SWE) parameters of the surrounding tissue (shell) of different diameter on the diagnosis of benign and malignant breast lesions. Therefore, the purpose of our study was to evaluate the diagnostic performance of shell elasticity in the diagnosis of benign and malignant breast lesions using SWE. Methods Between September 2016 and June 2017, women with breast lesions underwent both conventional ultrasound (US) and SWE. Elastic values of the lesions peripheral tissue were determined according to the shell size, which was automatically drawn along the edge of the lesion using the following software guidelines: (1): 1?mm; (2): 2?mm; and (3): 3?mm. Quantitative elastographic features of the inner lesions and shell, including the elasticity mean (Emean), elasticity maximum (Emax), and elasticity minimum (Emin), were calculated using an online-available software. The receiver operating characteristic curves (ROCs) of the elastographic features was analyzed to assess the diagnostic performance, and the area under curve (AUC) of each elastographic feature was obtained. Logistic regression analysis was used to predict significant factors of malignancy, permitting the design of predictive models. Results This prospective study included 63 breast lesions of 63 women. Of the 63 lesions, 33 were malignant and 30 were benign. The diagnostic performance of Emax-3shell was the highest (AUC?=?0.76) with a sensitivity of 60.6% and a specificity of 83.3%. According to stepwise logistic regression analysis, the Emax-3shell and the Emin-3shell were significant predictors of malignancy (p?<?0.05). The AUC of the predictive equation was 0.86. Conclusions SWE features, particularly the combination of Emax-3shell and Emin-3shell can improve the diagnosis of breast lesions.

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Tissue mimicking materials for the detection of prostate cancer using shear wave elastography: a validation study.

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