Non-invasive imaging of mechanical properties of cancers in vivo based on transformations of the Eshelby's tensor using compression elastography.

Knowledge of the mechanical properties is of great clinical significance for diagnosis, prognosis and treatment of cancers. Recently, a new method based on Eshelby's theory to simultaneously assess Young's modulus (YM) and Poisson's ratio (PR) in tissues has been proposed. A significant limitation of this method is that accuracy of the reconstructed YM and PR is affected by the orientation/alignment of the tumor with the applied stress. In this paper, we propose a new method to reconstruct YM and PR in cancers that is invariant to the 3D orientation of the tumor with respect to the axis of applied stress. The novelty of the proposed method resides on the use of a tensor transformation to improve the robustness of Eshelby's theory and reconstruct YM and PR of tumors with high accuracy and in realistic experimental conditions. The method is validated using finite element simulations and controlled experiments using phantoms with known mechanical properties. The in vivo feasibility of the developed method is demonstrated in an orthotopic mouse model of breast cancer. Our results show that the proposed technique can estimate the YM and PR with overall accuracy of (97.06 ± 2.42) % under all tested tumor orientations. Animal experimental data demonstrate the potential of the proposed methodology in vivo. The proposed method can significantly expand the range of applicability of the Eshelby's theory to tumors and provide new means to accurately image and quantify mechanical parameters of cancers in clinical conditions.

Non-invasive imaging of interstitial fluid transport parameters in solid tumors in vivo.

In this paper, new and non-invasive imaging methods to assess interstitial fluid transport parameters in tumors in vivo are developed, analyzed and experimentally validated. These parameters include extracellular volume fraction (EVF), interstitial fluid volume fraction (IFVF) and interstitial hydraulic conductivity (IHC), and they are known to have a critical role in cancer progression and drug delivery effectiveness. EVF is defined as the volume of extracellular matrix per unit volume of the tumor, while IFVF refers to the volume of interstitial fluid per unit bulk volume of the tumor. There are currently no established imaging methods to assess interstitial fluid transport parameters in cancers in vivo. We develop and test new theoretical models and imaging techniques to assess fluid transport parameters in cancers using non-invasive ultrasound methods. EVF is estimated via the composite/mixture theory with the tumor being modeled as a biphasic (cellular phase and extracellular phase) composite material. IFVF is estimated by modeling the tumor as a biphasic poroelastic material with fully saturated solid phase. Finally, IHC is estimated from IFVF using the well-known Kozeny-Carman method inspired by soil mechanics theory. The proposed methods are tested using both controlled experiments and in vivo experiments on cancers. The controlled experiments were performed on tissue mimic polyacrylamide samples and validated using scanning electron microscopy (SEM). In vivo applicability of the proposed methods was demonstrated using a breast cancer model implanted in mice. Based on the controlled experimental validation, the proposed methods can estimate interstitial fluid transport parameters with an error below 10% with respect to benchmark SEM data. In vivo results demonstrate that EVF, IFVF and IHC increase in untreated tumors whereas these parameters are observed to decrease over time in treated tumors. The proposed non-invasive imaging methods may provide new and cost-effective diagnostic and prognostic tools to assess clinically relevant fluid transport parameters in cancers in vivo.

Estimation of Mechanical and Transport Parameters in Cancers Using Short Time Poroelastography.

Mechanical and transport properties of cancers such as Young's modulus (YM), Poisson's ratio (PR), and vascular permeability (VP) have great clinical importance in cancer diagnosis, prognosis, and treatment. However, non-invasive estimation of these parameters in vivo is challenged by many practical factors. Elasticity imaging methods, such as "poroelastography", require prolonged data acquisition, which can limit their clinical applicability. In this paper, we investigate a new method to perform poroelastography experiments, which results in shorter temporal acquisition windows. This method is referred to as "short-time poroelastography" (STPE). Finite element (FE) and ultrasound simulations demonstrate that, using STPE, it is possible to accurately estimate YM, PR (within 10% error) using windows of observation (WoOs) of length as short as 1 underlying strain Time Constant (TC). The error was found to be almost negligible (< 3%) when using WoOs longer than 2 strain TCs. In the case of VP estimation, WoOs of at least 2 strain TCs are required to obtain an error < 8% (in simulations). The stricter requirement for the estimation of VP with respect to YM and PR is due its reliance on the transient strain behavior while YM and PR depend on the steady state strain values only. In vivo experimental data are used as a proof-of-principle of the potential applicability of the proposed methodology in vivo. The use of STPE may provide a means to efficiently perform poroelastography experiments without compromising the accuracy of the estimated tissue properties.

Scaling up contraceptives use in the division with lowest contraceptives use in Bangladesh: sources, methods, and determinants.

BACKGROUND: Total fertility rate (TFR) is high and at a static level for the last two decades in Bangladesh. Reduction of fertility by increasing contraceptives use could reduce maternal and neonatal mortality. To achieve the targeted contraceptive prevalence rate (CPR) of Family Planning 2020 (FP2020) Initiative, it is important to increase CPR in all regions of the country. However, it is lower in Sylhet Division compared to other divisions in Bangladesh. This study looked into the methods, source and determinants of contraceptives use in this division. METHODS: Data from the Bangladesh Demographic and Health Survey 2014 (BDHS 2014) were analyzed. After reporting the sources of obtaining contraceptives and choice of methods, distributions of contraceptives use were reported by selected characteristics. Logistic regression was applied to calculate the odds ratios. RESULTS: A total of 599 women were analyzed. CPR was lower in rural areas compared to urban areas, 45.4% and 58.5%, respectively. The majority of the women received services from governmental sectors. The birth control pill was the most common contraceptive method. The proportion of women using long-acting permanent methods was low (<10%) in both urban and rural areas. In the multivariate analyses, number of alive children (adjusted odds ratio (AOR) of ≥5 children: 1.6, 95% confidence interval (CI): 1.1-2.2), presence of a male child (AOR: 1.7; 95% CI: 1.1-2.6), higher education level of the husband (AOR: 1.7; 95% CI: 1.1-2.6), receiving a visit from a family planning worker (AOR: 2.4; 95% CI: 1.6-3.4) and membership in a non-governmental organization (AOR:1.4, 95% CI: 1.1-1.8) were positively associated with contraceptives use in Sylhet after controlling for age, education level and other contextual factors. Conversely, rural women had the lower likelihood of using contraceptives (AOR: 0.6; 95% CI: 0.4-0.8) than urban women. Women's education level and religion were not statistically significant. CONCLUSIONS: A comprehensive strategy is required for this division to address multiple factors which simultaneously influence contraceptives use. In addition to more awareness programs to increase contraceptives use, providing contraceptive distribution services through family planning workers, involving women with non-governmental organizations and prioritizing rural areas could increase contraceptives use in Sylhet Division.