Effects of Lithotripter Fields on Biological Tissues

Abstract: Biological effects resulting from exposure to lithotripter fields include hemorrhage in soft tissues, such as the kidney, lung and intestine, the production of premature cardiac contractions, malformations in the chicken embryo and killing of Drosophila larvae, Pulsed ultrasound can produce similar bioeffects at comparable pressure thresholds. Tissues that contain gas bodies, either naturally or after the addition of ultrasound contrast agents, are particularly susceptible to damage from low ampfitude Iithotripter fields. Lung and intestine contain gas naturally and are hemorrhaged by exposure to lithotripter fields on the order of 1 MPa. After the introduction of an ultrasound contrast agent into the vasculature, many organs and tissues, such as the bladder, kidney, fat, muscle and mesentery, show extensive hemorrhage after exposure to Iithotripter pressures less than 2 MPa. Tissues near developing bone are also selectively susceptible to damage from exposure to low amplitude lithotripter fields. The thresholds for hemorrhage in tissues near developing bone, such as the fetal head, limbs and ribs, are all less than 1 ma for exposures with a piezoelectric Iithotripter. Cavitation and purely mechanical forces have been investigated as possible mechanisms for these biological effects of Iithotripter fields

Diagnostic Ultrasound Safety Review for Point-of-Care Ultrasound Practitioners

Potential ultrasound exposure safety issues are reviewed, with guidance for prudent use of point‐of‐care ultrasound (POCUS). Safety assurance begins with the training of POCUS practitioners in the generation and interpretation of diagnostically valid and clinically relevant images. Sonographers themselves should minimize patient exposure in accordance with the as‐low‐as‐reasonably‐achievable principle, particularly for the safety of the eye, lung, and fetus. This practice entails the reduction of output indices or the exposure duration, consistent with the acquisition of diagnostically definitive images. Informed adoption of POCUS worldwide promises a reduction of ionizing radiation risks, enhanced cost‐effectiveness, and prompt diagnoses for optimal patient care

The role of extracellular matrix fibronectin and collagen in cell proliferation and cellular self-assembly

Thesis (Ph. D.)--University of Rochester. Dept. of Biomedical Engineering, 2013.Biomimetic approaches in tissue engineering aim to fabricate tissues and organs by emulating the process of tissue formation in development. Fibronectin is a principal component of the extracellular matrix (ECM) and plays an important role in regulating tissue formation in development. ECM fibronectin can serve a passive role, maintaining tissue structure, or a signaling role, instructing cell behaviors. Understanding how fibronectin transitions from passive to signaling roles may permit the engineering of biomimetic biomaterials that promote tissue and organ formation through inductive and instructive ECM environments. ECM fibronectin function can be regulated by the composition of the surrounding ECM and the organization of ECM fibronectin. The goal of this thesis was to determine how the organization of ECM fibronectin and the composition of the ECM affect cell proliferation and the assembly of cells into 3-dimensional (3D) structures. To investigate the role of fibronectin in tissue formation, a model of self-assembling 3D microtissues was developed that combined compliant, low adhesive polymerized collagen I substrates with the cell-mediated assembly of fibronectin matrix fibrils. The data presented in this thesis demonstrate the existence of two functional forms of ECM fibronectin: a growth-promoting collagen-associated fibronectin matrix and a pericellular fibronectin matrix capable of providing structural support for assembly of cells into 3D structures. Thus, the data presented in this thesis demonstrate that the composition and organization of the ECM can be used as instructive signals in the formation of tissues and organs using biomimetic tissue engineering approaches

Regional fibronectin and collagen fibril co-assembly directs cell proliferation and microtissue morphology.

The extracellular matrix protein, fibronectin stimulates cells to self-assemble into three-dimensional multicellular structures by a mechanism that requires the cell-dependent conversion of soluble fibronectin molecules into insoluble fibrils. Fibronectin also binds to collagen type I and mediates the co-assembly of collagen fibrils into the extracellular matrix. Here, the role of collagen-fibronectin binding in fibronectin-induced cellular self-assembly was investigated using fibronectin-null fibroblasts in an in vitro model of tissue formation. High resolution, two-photon immunofluorescence microscopy was combined with second harmonic generation imaging to examine spatial and temporal relationships among fibronectin and collagen fibrils, actin organization, cell proliferation, and microtissue morphology. Time course studies coupled with simultaneous 4-channel multiphoton imaging identified regional differences in fibronectin fibril conformation, collagen fibril remodeling, actin organization, and cell proliferation during three-dimensional cellular self-assembly. Regional differences in cell proliferation and fibronectin structure were dependent on both soluble fibronectin concentration and fibronectin-collagen interactions. Fibronectin-collagen binding was not necessary for either fibronectin matrix formation or intercellular cohesion. However, inhibiting fibronectin binding to collagen reduced collagen fibril remodeling, decreased fibronectin fibril extension, blocked fibronectin-induced cell proliferation, and altered microtissue morphology. Furthermore, continual fibronectin-collagen binding was necessary to maintain both cell proliferation and microtissue morphology. Collectively, these data suggest that the complex changes in extracellular matrix and cytoskeletal remodeling that mediate tissue assembly are driven, in part, by regional variations in cell-mediated fibronectin-collagen co-assembly

Ultrasound standing wave field technology for cell patterning and microvessel network formation in vitro and in situ

Thesis (Ph. D.)--University of Rochester. Department of Biomedical Engineering, 2017.The field of tissue engineering holds great promise to regenerate or repair diseased and damaged tissues. However, the fabrication of thick, three-dimensional (3D) tissues is currently limited by the need for perfused microvascular networks to volumetrically supply tissues with nutrients and oxygen. Current efforts to engineer microvascular networks have drawbacks including the inability to control vessel morphology, a limited potential for volumetric scale up, or incompatibility for translation in vivo. The research reported in this thesis developed ultrasound standing wave field (USWF) technologies to volumetrically pattern cells in 3D collagen gels for the fabrication of microvascular networks in vitro and in situ. USWF cell patterning parameters were shown to influence initial 3D endothelial cell patterning, and subsequently, the resultant microvascular network morphology in vitro. USWFs were also employed to co-pattern endothelial and smooth muscle cell types to direct microvascular network morphology, enhance network viability, and promote the formation of mural cell-invested microvessels. Furthermore, novel USWF exposure systems were constructed to demonstrate the feasibility of patterning particles and cells for tissue engineering and regenerative medicine applications in vivo. USWF cell patterning has great capacity to generate vascularized microphysiological systems in vitro, as well as promote tissue regeneration in vivo. Further development of USWF cell patterning technologies would provide noninvasive, rapid, and transformative procedures for the field of tissue engineering

Ultrasound technologies for the spatial patterning of cells and extracellular matrix proteins and the vascularization of engineered tissue

Thesis (Ph. D.)--University of Rochester. Dept. of Biomedical Engineering, 2013.Technological advancements in the field of tissue engineering could save the lives of thousands of organ transplant patients who die each year while waiting for donor organs. Currently, two of the primary challenges preventing tissue engineers from developing functional replacement tissues and organs are the need to recreate complex cell and extracellular microenvironments and to vascularize the tissue to maintain cell viability and function. Ultrasound is a form of mechanical energy that can noninvasively and nondestructively interact with tissues at the cell and protein level. In this thesis, novel ultrasound-based technologies were developed for the spatial patterning of cells and extracellular matrix proteins and the vascularization of three-dimensional engineered tissue constructs. Acoustic radiation forces associated with ultrasound standing wave fields were utilized to noninvasively control the spatial organization of cells and cell-bound extracellular matrix proteins within collagen-based engineered tissue. Additionally, ultrasound-induced thermal mechanisms were exploited to site specifically pattern various extracellular matrix collagen microstructures within a single engineered tissue construct. Finally, ultrasound standing wave field technology was used to promote the rapid and extensive vascularization of three-dimensional tissue constructs. As such, the ultrasound technologies developed in these studies have the potential to provide the field of tissue engineering with novel strategies to spatially pattern cells and extracellular matrix components and to vascularize engineered tissue, and thus, could advance the fabrication of functional replacement tissues and organs in the field of tissue engineering

Rochester Center for Biomedical Ultrasound 20th Anniversary Retrospective

The Rochester Center for Biomedical Ultrasound (RCBU) is celebrating 20 years of ultrasound research at the University of Rochester. This special publication includes reflections from the current directors, Kevin Parker and Deborah Rubens, highlights of the past 20 years from Edwin Carstensen, founding director, and a look to the future from Diane Dalecki, Associate Professor of Biomedical Engineering

Spatial and temporal analysis of fibronectin-induced cell proliferation.

<p>Collagen-adherent FN-null MEFs were treated with 25 nM or 100 nM fibronectin (FN) for either 2 or 4 days, and then processed for immunofluorescence microscopy. Four channel images of fibronectin, actin, BrdU, and DAPI staining were obtained and processed to quantify the spatial distribution of proliferating cells in microtissues. (A) The relative distance of all BrdU-positive cells from the centroid (r _a/r_b) was calculated. Data are grouped to display the frequency of occurrence of proliferating cells from the centroid (r _a/r_b = 0) to the periphery (r_a/r_b = 1). Data are presented as the mean percent of BrdU-positive cells ± SEM of 3 independent experiments. (B) Representative x-y projections showing BrdU (red) and DAPI (blue) staining on day 4. (C) Total numbers of proliferating and non-proliferating cells were determined from BrdU and DAPI staining. Data are presented as mean percent BrdU-positive cells <u>+</u> SEM of 3 experiments performed in triplicate.</p