Skip to main content
eScholarship
Open Access Publications from the University of California

Scholarly Works (3 results)

  • Thesis
  • Peer Reviewed
UC Berkeley Electronic Theses and Dissertations (2011)

In MRI, a powerful and uniform static B0 field is responsible for image signal and contrast. However, regions of different magnetic susceptibilities in the static field give rise to field inhomogeneities that cause image artifacts. For example, air and tissue interfaces for a patient in a MRI study induce up to ±5 ppm static B0 field perturbations within the patient. Unfortunately shim coils are too large to compensate for the very steep field variations found near the breast, cervical spine, shoulders, occipital lobe, and other regions of the body. Many MRI applications are vulnerable to B0 inhomogeneity, including robust fat suppression, which requires better than ±1 ppm homogeneity.

To address this challenge, we have developed a flexible, conforming composite foam with magnetic susceptibility matched to human tissue. We surround the region with enough matching material to move the field gradients outside of the body where they cannot cause MRI artifacts. Our matching material is a pyrolytic graphite (PG) composite foam. It has many advantages over existing matching agents: it is lightweight; it adds no noise; and it is safe to embed receiver coils within the PG foam.

In this thesis, we propose theory that describes the magnetic susceptibility matching properties of composite PG foam. We show experimental proof of concept susceptibility matching and safety in phantom experiments. We also experimentally demonstrate that PG foam cushions improve the B0 field uniformity to the critical threshold of ±1 ppm in both phantoms and in the neck of 6 normal volunteers at 3T. The tissue susceptibility matched PG foams consistently mitigate signal drop out, improve image SNR, and enable far more robust frequency selective fat suppression in T1-weighted FLASH images in volunteers. PG foam has many practical applications in MR applications that require a pristine B0 field.

    Cover page: Tissue Magnetic Susceptibility Matched Pyrolytic Graphite Foam for Improved MRI
    • Article
    • Peer Reviewed
    UC Davis Previously Published Works (2021)

    Background

    Lymphocytic neoplasms with frequent reactive lymphocytes are uncommonly reported in dogs, and can pose a diagnostic challenge. Different diagnostic modalities such as cytology, flow cytometry, histopathology, immunohistochemistry, and clonality testing, are sometimes required for a diagnosis. This report illustrates the value of using a multi-modal diagnostic approach to decipher a complex lymphocytic tumor, and introduces immune repertoire sequencing as a diagnostic adjunct.

    Case presentation

    A 10-month-old Great Dane was referred for marked ascites. Cytologic analysis of abdominal fluid and hepatic aspirates revealed a mixed lymphocyte population including numerous large lymphocytes, yielding a diagnosis of lymphoma. Flow cytometrically, abdominal fluid lymphocytes were highly positive for CD4, CD5, CD18, CD45, and MHC II, consistent with T cell lymphoma. Due to a rapidly deteriorating clinical condition, the dog was euthanized. Post mortem histologic evaluation showed effacement of the liver by aggregates of B cells surrounded by T cells, suggestive of hepatic T cell-rich large B cell lymphoma. Immune repertoire sequencing confirmed the presence of clonal B cells in the liver but not the abdominal fluid, whereas reactive T cells with shared, polyclonal immune repertoires were found in both locations.

    Conclusions

    T cell-rich large B cell lymphoma is a rare neoplasm in dogs that may be challenging to diagnose and classify due to mixed lymphocyte populations. In this case, the results of histopathology, immunohistochemistry and immune repertoire sequencing were most consistent with a hepatic B cell neoplasm and reactive T cells exfoliating into the abdominal fluid. Immune repertoire sequencing was helpful in delineating neoplastic from reactive lymphocytes and characterizing repertoire overlap in both compartments. The potential pitfalls of equating atypical cytomorphology and monotypic marker expression in neoplasia are highlighted.
      Cover page: Use of immune repertoire sequencing to resolve discordant microscopic and immunochemical findings in a case of T cell-rich large B cell lymphoma in a young dog
      • Article
      • Peer Reviewed
      UC Berkeley Previously Published Works (2018)

      Purpose

      To independently validate the performance of the University of North Carolina Optical Coherence Tomography (UNC OCT) Index in diagnosing and predicting early glaucoma.

      Methods

      Data of 118 normal subjects (118 eyes) and 96 subjects (96 eyes) with early glaucoma defined as visual field mean deviation (MD) greater than -4 decibels (dB), aged 40 to 80 years, and who were enrolled in the Full-Threshold Testing Size III, V, VI comparison study were used in this study. CIRRUS OCT average and quadrants' retinal nerve fiber layer (RNFL); optic disc vertical cup-to-disc ratio (VCDR), cup-to-disc area ratio, and rim area; and average, minimum, and six sectoral ganglion cell-inner plexiform layer (GCIPL) measurements were run through the UNC OCT Index algorithm. Area under the receiver operating characteristic curve (AUC) and sensitivities at 95% and 99% specificity were calculated and compared between single parameters and the UNC OCT Index.

      Results

      Mean age was 60.1 ± 11.0 years for normal subjects and 66.5 ± 8.1 years for glaucoma patients (P < 0.001). MD was 0.29 ± 1.04 dB and -1.30 ± 1.35 dB in normal and glaucomatous eyes (P < 0.001), respectively. The AUC of the UNC OCT Index was 0.96. The best single metrics when compared to the UNC OCT Index were VCDR (0.93, P = 0.054), average RNFL (0.92, P = 0.014), and minimum GCIPL (0.91, P = 0.009). The sensitivities at 95% and 99% specificity were 85.4% and 76.0% (UNC OCT Index), 71.9% and 62.5% (VCDR, all P < 0.001), 64.6% and 53.1% (average RNFL, all P < 0.001), and 66.7% and 58.3% (minimum GCIPL, all P < 0.001), respectively.

      Conclusions

      The findings confirm that the UNC OCT Index may provide improved diagnostic perforce over that of single OCT parameters and may be a good tool for detection of early glaucoma.

      Translational relevance

      The UNC OCT Index algorithm may be incorporated easily into routine clinical practice and be useful for detecting early glaucoma.
        Cover page: Validation of the UNC OCT Index for the Diagnosis of Early Glaucoma
        Top