Methodologies for Quantifying and Characterizing Strain Fields Resulting from Focused Ultrasound Therapies in Mouse Achilles Tendon using Ultrasound Imaging and Digital Image Correlation
Abstract
Tendinopathy is a common pathology of tendons characterized by pain and a decrease in function resulting from changes in the tissue's structure and/or composition due to injury. Diagnosis of tendinopathy is determined by the qualitative analysis of a trained physician usually with assistance from an imaging modality. Although physicians can often identify tendinopathy, there are no quantitative metrics to evaluate tendon fatigue, damage, or healing. Physical therapy (PT) is a common treatment for patients with tendinopathy, and recent studies have investigated Focused Ultrasound (FUS) for its treatment of tendons. Developments in the use of FUS as a therapeutic have led to studies of the underlying mechanisms by which it operates.
Digital Image Correlation (DIC) is a non-contact method of quantifying tissue displacements and strains of a deforming material using high resolution imaging DIC programs can evaluate and interpolate strain data by applying statistical image processing algorithms and solid continuum mechanics principles using a set of sequential image frames capturing the mechanical deformation of the specimen during testing.
The studies presented in this thesis investigate methodologies for using DIC with ultrasound imaging of mouse Achilles tendons to characterize strains resulting from FUS therapies. The first method is based upon an orthogonal configuration of therapy and imaging transducers while the second investigates a coaxial experimental configuration. This work explores DIC as a viable means of quantifying the mechanical stimulation caused by FUS therapies on tendon tissue through ultrasound imaging to better understand the underlying mechanisms of FUS therapy.
General Audience Abstract
Tendinopathy is a common injury that many people will experience in their lifetime. Pain and swelling are common symptoms and can make daily actions uncomfortable to perform. Physical therapy (PT) is one of the most common ways to help relieve the symptoms of this condition. A therapy being investigated to help treat tendinopathy utilizes Focused Ultrasound (FUS) technology to help the healing process. PT can be difficult and painful for those experiencing tendinopathy, but if a therapeutic like FUS could mimic the effects of PT, then some patients would not need to perform these physically demanding tasks. To understand if this treatment is viable, we need to better understand the underlying mechanisms by which it operates. Therefore, we are investigating the mechanical stimulation that FUS imparts on tendons because it is believed that the mechanical stimulations from exercise are a primary contributor to healing. Specifically, we want to evaluate the kind of strains applied by FUS therapies to inform decisions about dosage. One method uses Digital Image Correlation (DIC). DIC is a method of evaluating displacements and strains using non-contact high resolution imaging. DIC works using statistically motivated algorithms to calculate the deformation between subsequent video frames in a given material undergoing a state of stress. Using this technology along with ultrasound imaging, this work gives a preliminary exploration of using DIC as a means of quantifying strain to better understand the underlying mechanisms of the mechanical stimulations caused by FUS therapy.
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