Between Dec 19, 2024 and Jan 2, 2025, datasets can be submitted to DRUM but will not be processed until after the break. Staff will not be available to answer email during this period, and will not be able to provide DOIs until after Jan 2. If you are in need of a DOI during this period, consider Dryad or OpenICPSR. Submission responses to the UDC may also be delayed during this time.

Browsing by Subject "Bioimpedance"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Assessment of Body Composition and Nutritional Status in Individuals with Obesity Before and in the Long-Term After Bariatric Surgery
    (2015-06) Cole, Abigail
    One of the most successful treatments for obesity is bariatric surgery. The Roux-en-Y gastric bypass (RYGB), in particular has been the most commonly performed bariatric surgery over the past decade. It is not well known how time will influence the broader inflammatory-related health outcomes of bariatric surgery, which may depend on complex inter-relationships between nutritional status and body fat mass (FM). This dissertation focuses on the long-term changes in nutritional status and body composition after RYGB with a particular focus on vitamins and minerals that have potential inflammatory action and the development of improved methods to assess changes in body composition in obese individuals. In Chapter 3 we report the results of a pilot study to assess long-term changes in body composition and nutritional and inflammatory status after RYGB. From the assessment of 5 women who were monitored over an 8.5-year period after RYGB we found that improvements in vitamin D status and potential improvements in inflammatory status can occur over time. However, continued loss of lean soft tissue (LST) occur on the background of weight regain between 1-year and 8.5-years post-RYGB. Losses of LST were correlated with decreased handgrip strength. In Chapter 4 we report the results of a validation study to compare the results of a new application of BIS based on multicomponent physiologic models with existing body composition data from DXA in a large NHANES dataset with 5470 observations and in a longitudinal dataset of 25 women for the first-year after RYGB. We found that the BIS method was in relatively good agreement with DXA for the assessment of FM and lean tissue, and that the BIS method was equally as good as DXA for assessing changes in FM in particular after RYGB, over the period from 6-months to 1-year. In the coming years, bariatric surgery is sure to remain a popular treatment for obesity and it is clear that we need better methods to assess changes in body composition in a more comprehensive way, in order to better understand the ramifications of these changes in light of long-term nutritionally relevant health outcomes, including inflammation. This dissertation could serve to inform future studies that should aim to tease apart the factors contributing to long-term FM gain, but more importantly loss of LST and muscle strength, to establish evidence based guidelines.
  • Thumbnail Image
    Item
    Magnetoacoustic tomography with magnetic induction for electrical conductivity imaging of biological tissue.
    (2010-09) Li, Xu
    Electrical properties of biological tissue including conductivity and permittivity play important roles in many biomedical and clinical researches such as modeling neural or cardiac electrical activities and management of electromagnetic energy delivery to the body during clinical diagnosis and treatment. More importantly, these electrical properties may serve as an intrinsic contrast for anatomical or functional imaging. It is therefore of great value to noninvasively image the electrical properties of biological tissue with good accuracy and high spatial resolution. This dissertation research aims at developing and evaluating a new modality i.e. magnetoacoustic tomography with magnetic induction (MAT-MI), for imaging electrical conductivity distribution of biological tissue. In MAT-MI, a conductive object is placed in a static magnetic field and a time-varying magnetic stimulation is applied to induce eddy current inside the object volume. Within the static magnetic field, the Lorentz force acting on the induced eddy current causes mechanical movement of those charged particles in the object and leads to detectable ultrasound signals. These ultrasound signals can be acquired by ultrasound probes and used to reconstruct a high spatial resolution image that indicates the object's electrical conductivity contrast. We have proposed and investigated two types of MAT-MI approaches i.e. single-excitation MAT-MI and multi-excitation MAT-MI. The corresponding image reconstruction algorithms, simulation protocols and experiment systems have been developed for feasibility testing and performance evaluation. It is shown in our computer simulation and experiment studies that using the single-excitation MAT-MI we are able to image the conductivity boundaries of the object with several millimeter spatial resolution. In addition, we have also demonstrated that the multi-excitation MAT-MI approach allows us to further extract the internal information and reconstruct more completely the conductivity contrast of the object. For both approaches, two-dimensional (2D) and three-dimensional (3D) images of physical or tissue phantoms have been acquired and showed promising agreement with the target conductivity distribution. All the results we have collected so far from simulations and experiments suggest that the MAT-MI approach is potential to become an important noninvasive modality for electrical conductivity imaging of biological tissue.