Emerging photoacoustic and thermoacoustic imaging technologies for detecting primary and metastatic cancer and guiding therapy.

In recent years, there has been a progressive trend towards less invasive technologies for detecting metastatic cancer and guiding therapy with the goal of lower morbidity, better outcomes, and superior cosmetic appearance than traditional methods. This mini-review examines three emerging noninvasive hybrid technologies for detecting primary cancer, metastasis and guiding thermal therapy. Real-time thermoacoustic imaging and thermometry potentially provides valuable and critical feedback for guiding focused microwave ablation therapy. Label-free photoacoustic monitoring of cancer cells is a promising clinical diagnostic and theranostic tool for detecting metastatic disease and monitoring the response to therapy. Finally, immunologically targeted gold nanoparticles combined with photoacoustic imaging is able to detect lymph node micrometastasis in mouse models of breast cancer. These emerging techniques have the potential to improve the decision to biopsy, provide more accurate prognosis, and enhance the efficacy of therapy for early and late stage cancers.

Real-time 3D thermoacoustic imaging and thermometry using a self-calibration technique.

Thermoacoustic (TA) imaging is a modality where pulsed microwaves are used to generate ultrasound waves in tissue, which are highly correlated with temperature. This study uses a self-calibration approach to improve the estimation of temperature using 3D real-time TA thermometry in porcine tissue during localized heating. The self-calibration method estimated temperatures at eight embedded thermocouple locations with a normalized root-mean-square error of 3.25±2.08%. The results demonstrate that the method has the suitable accuracy and resolution to provide feedback control for breast cancer ablation therapy.

Computationally Optimizing the Compliance of Multilayered Biomimetic Tissue Engineered Vascular Grafts.

Coronary artery bypass grafts used to treat coronary artery disease (CAD) often fail due to compliance mismatch. In this study, we have developed an experimental/computational approach to fabricate an acellular biomimetic hybrid tissue engineered vascular graft (TEVG) composed of alternating layers of electrospun porcine gelatin/polycaprolactone (PCL) and human tropoelastin/PCL blends with the goal of compliance-matching to rat abdominal aorta, while maintaining specific geometrical constraints. Polymeric blends at three different gelatin:PCL (G:PCL) and tropoelastin:PCL (T:PCL) ratios (80:20, 50:50, and 20:80) were mechanically characterized. The stress-strain data were used to develop predictive models, which were used as part of an optimization scheme that was implemented to determine the ratios of G:PCL and T:PCL and the thickness of the individual layers within a TEVG that would compliance match a target compliance value. The hypocompliant, isocompliant, and hypercompliant grafts had target compliance values of 0.000256, 0.000568, and 0.000880 mmHg-1, respectively. Experimental validation of the optimization demonstrated that the hypercompliant and isocompliant grafts were not statistically significant from their respective target compliance values (p-value = 0.37 and 0.89, respectively). The experimental compliance values of the hypocompliant graft were statistically significant than their target compliance value (p-value = 0.047). We have successfully demonstrated a design optimization scheme that can be used to fabricate multilayered and biomimetic vascular grafts with targeted geometry and compliance.

Racioethnic Differences in Human Posterior Scleral and Optic Nerve Stump Deformation.

Purpose: The purpose of this study was to quantify the biomechanical response of human posterior ocular tissues from donors of various racioethnic groups to better understand how differences in these properties may play a role in the racioethnic health disparities known to exist in glaucoma. Methods: Sequential digital image correlation (S-DIC) was used to measure the pressure-induced surface deformations of 23 normal human posterior poles from three racioethnic groups: African descent (AD), European descent (ED), and Hispanic ethnicity (HIS). Regional in-plane principal strains were compared across three zones: the optic nerve stump (ONS), the peripapillary (PP) sclera, and non-PP sclera. Results: The PP scleral tensile strains were found to be lower for ED eyes compared with AD and HIS eyes at 15 mm Hg (P = 0.024 and 0.039, respectively). The mean compressive strains were significantly higher for AD eyes compared with ED eyes at 15 mm Hg (P = 0.018). We also found that the relationship between tensile strain and pressure was significant for those of ED and HIS eyes (P < 0.001 and P = 0.004, respectively), whereas it was not significant for those of AD (P = 0.392). Conclusions: Our results suggest that, assuming glaucomatous nerve loss is caused by mechanical strains in the vicinity of the optic nerve head, the mechanism of increased glaucoma prevalence may be different in those of AD versus HIS. Our ONS strain analysis also suggested that it may be important to account for ONS geometry and material properties in future scleral biomechanical analysis.