Browsing by Subject "Medical imaging"
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Item Clinical photoacoustic imaging for detection and characterization of metal implants(2011-08) Su, Jimmy Li-Shin; Emelianov, Stanislav Y.; Dunn, Andrew; Karpiouk, Andrei; Smalling, Richard; Sokolov, KonstantinAccurate insertion and monitoring of metal implants in-vivo is essential for clinical diagnosis and therapy of various diseases. Clinical studies and examples have demonstrated that the misplacement errors of these metal devices can have dramatic consequences. This thesis focuses on three main metal devices that are in widespread use today: needles, coronary stents and brachytherapy seeds. Each application requires proper image-guidance for correct usage. For needles, image guidance is required to ensure correct local injection delivery or needle aspiration biopsy. Fine needle aspiration biopsies are performed in order to avoid major surgical excisions when obtaining tissue biopsy procedures. However, because of the small biopsy sample, the risk is that the sample is collected outside of the tumorigenic region, resulting in a false negative result. Implantation of stents requires that confirmation that proper stent apposition has been achieved due to balloon inflation. Furthermore, it is important to guide the stent to shield the vulnerable region of an atherosclerotic plaque. With prostate brachytherapy seeds, the ability to monitor seed placement is crucial because needle deflections or tissue deformation can result in seed misplacement errors, decreasing the efficacy of the pre-established treatment plan. For the described applications and other possible clinical practices involving the use of metallic implants, an imaging technology that can accurately depict the location of the metal objects, relative to their respective backgrounds, in real-time, is necessary to improve the safety and the efficacy of these procedures. Currently, ultrasound is used because of its real-time capabilities, non-ionizing radiation, and soft tissue contrast. However, due to high acoustic scattering from tissue, the contrast of metal implants can be low. Photoacoustic imaging can be used as an alternative, or complementary, imaging method to ultrasound for imaging metal. This thesis focuses on the benefits and the pitfalls of using photoacoustic imaging for detecting three different metal implants, each having unique requirements. Overall, the goal of this work is to develop a framework for clinical applications using combined ultrasound and photoacoustic imaging to help guide, detect and follow-up on clinical metal implants introduced in-vivo.Item Clinical, non-invasive in vivo diagnosis of skin cancer using multimodal Spectral Diagnosis(2013-12) Lim, Liang; Tunnell, James W.The goal of this thesis is to study the potential of optical spectroscopy as a clinical diagnostic tool for melanoma and nonmelanoma skin cancer. Skin cancer is the most common cancer in the United States. Like most cancers, early diagnosis and treatment improves patient prognosis for both melanoma and nonmelanoma skin cancer. However, current “gold standard” for diagnosis is invasive, costly and time-consuming. A diagnostic procedure consists of a clinical examination of the suspicious lesion, followed by biopsy and histopathology, with an additional turnaround time of approximately one week. There is a need for an accurate, objective, noninvasive, and faster method to aid physician in diagnosing cancerous lesions, increasing diagnosis accuracy while preventing unnecessary biopsies. We propose Spectral Diagnosis, a system capable of noninvasive in vivo spectroscopic examination of human skin. The research objectives are: (1) Probe pressure effects on in vivo spectroscopy measurements of human skin, (2) Clinical trial of Spectral Diagnosis, (3) Design, construction, and characterization of a confocal Raman microspectroscope. Spectral Diagnosis utilizes an optical fiber probe that transmits and collects optical spectra in contact with the suspected lesion. We identified short term and light probe pressure effects to be minimal on diagnostic parameters, and should not negatively influence diagnostic performance. We conducted a clinical trial at the University of Texas MD Anderson Cancer Center, and our results show that principal components from three spectroscopy modalities (diffuse reflectance spectroscopy, laser induced fluorescence spectroscopy, and Raman spectroscopy) provide excellent melanoma and nonmelanoma skin cancer diagnosis. We also constructed and characterized a Raman microspectroscope, with the goal of developing a physiological-based fitting model to better understand the analysis of in vivo Raman spectroscopy data from human skin tissue.Item Combining multiple mammographic views for computer aided diagnosis(2004-05-22) Gupta, Shalini; Ghosh, Joydeep; Markey, Mia KathleenThe agreement in mammographic lesion features from two projections of the breast was studied for human extracted BI-RADS" and computer extracted image texture features and cases with low agreement were identified. Factors affecting agreement between the two views were isolated and agreement for the two types of features was compared. Agreement in BI-RADS" features was higher than that for texture features, however agreement for both types of features was affected by the institutional source of data. Statistical classifiers for distinguishing benign from malignant lesions were designed using BI-RADS" features from multiple views and the effect of including patient age was investigated. The highest AUC ± SD value of 0.927 ± 0.026 was obtained for a classifier that used features from both the MLO and CC views as well as patient age as features.Item Compressed sensing recovery with unlearned neural networks(2019-07-01) Van Veen, David Michael; Dimakis, Alexandros G.; Vishwanath, SriramThis report investigates methods for solving the problem of compressed sensing, in which the goal is to recover a signal from noisy, linear measurements. Compressed sensing techniques enable signal recovery with far fewer measurements than required by traditional methods such as Nyquist sampling. Signal recovery is an incredibly important area in application domains such as consumer electronics, medical imaging, and many others. While classical methods for compressed sensing recovery are well established, recent developments in machine learning have created wide opportunity for improvement. In this report I first discuss pre-existing approaches, both classical and modern. I then present my own contribution to this field: creating a method using untrained machine learning models. This approach has several advantages which enable its use in complex domains such as medical imagingItem First results from the Time-of-Flight PET for proton therapy(2023-08) Klein, Kyle Thomas (master of arts in physics); Lang, Karol, 1955-There is a clear and distinct need in the field of proton and ion radio-therapies to accurately monitor the location of the Bragg Peak produced by the therapy in the patient. To this end, the Time-of-Flight PET for Proton Therapy (TPPT) consortium has constructed and partially commissioned an in-line Positron Emission Tomography (PET) scanner to monitor the activity of Positron Emitting Species (PES) produced as a result of Proton Beam interactions within the patient. The scanner has a timing resolution near 200 picoseconds that will allow it to successfully reconstruct an image of PES activity to ensure the proton beam is not depositing significant amounts of energy in healthy tissue. First, the motivation behind the scanner is discussed, then the components of the scanner and their capabilities are described. The commissioning process of the scanner is detailed and finally some preliminary results in the form of reconstructed images and next steps for the consortium are discussed.Item Histogram - Based Algorithm for Semiautomated Three-Dimensional Craniofacial Modeling(1994) Levy, Richard A.Volume averaging artifacts in medical imaging result from voxel occupancy by more than one tissue type and, with anisotropic voxels, may be decreased by changing the imaging plane orientation relative to the target tissue and/or by decreasing slice thickness.1 In craniofacial CT imaging, volume averaging artifact becomes significant in areas ofthin bone such as the orbital walls and auditory ossicles. These regions are customarily imaged using multiple scan planes and the thinnest slices possible to reduce such artifacts. In three-dimensional craniofacial imaging, these same parameters may be controlled to reduce partial volume averaging, but areas of bone "drop-out" (also called pseudoforamina) are commonly present secondary to a paradoxical inability to lower thresholds without including unwanted background tissues. At present, the optimal solution to this problem is achieved by manually (and often painstakingly) drawing a region of interest around tissues presumed to contain volume averaged target density voxels and lowering thresholds to include these voxels in the 3D reconstruction, one CT slice at a time. Recently, anatomic modeling technologies have demonstrated the feasibility of assembling particulate hydroxyapatite (SYnthetic bone) into detailed craniofacial models of high anatomic accuracy, theoretically suitable for in vivo implantation (work in progress with the Department of Mechanical Engineering, University of Texas at Austin.) These modeling systems, such as stereolithography and selective laser sintering, operate as do 3D imaging workstations, using thresholds to 198 include/exclude pixels from CT data sets in the modeling process. However, the user interactive capabilities ofsuch technologies may be limited such that manual tracing ofregions of volume averaged thin bone is not possible. Drop-out artifacts in models so generated would be potentially larger than on corresponding 3D images where user input could reduce these artifacts. To circumvent this inability to manually correct volume averaging artifacts on anatomic modeling systems, and to relieve the intensive oPerator input required to otherwise achieve this goal on 3D imaging software, a histogram-based algorithm for semiautomated threedimensional craniofacial modeling was develoPed.Item Knowledge graph applications in medical imaging analysis : a scoping review(2021-12-03) Wang, Song, M.S. in Engineering; Ghosh, Joydeep; Ding, YingThere is an increasing trend to represent domain knowledge in structured graphs, which provide efficient knowledge representations for many downstream tasks. Knowledge graphs are widely used to model prior knowledge in the form of nodes and edges to represent semantically connected knowledge entities, which several works have adopted into different medical imaging applications. We systematically search over five databases to find relevant articles that apply knowledge graphs to medical imaging analysis. After screening, evaluating, and reviewing the selected articles, we performed a systematic analysis. We look at four applications in medical imaging analysis, including disease classification, disease localization and segmentation, report generation, and image retrieval. We also identify limitations of current work, such as the limited amount of available annotated data and weak generalizability to other tasks. We further identify the potential future directions according to the identified limitations, including employing semi-supervised frameworks to alleviate the need for annotated data and exploring task-agnostic models to provide better generalizability. We hope that our article will provide the readers with aggregated documentation of the state-of-the-art knowledge graph applications for medical imaging.Item What lies beneath : medical imaging and the erotic in public culture(2012-08) Wise, Rebecca Louise; Wojciehowski, Hannah Chapelle, 1957-; Browne, Simone A.The anatomic human body is increasingly visible in public culture. Representations of the body sourced from or imitative of the images produced by medical imaging technology are bloodless depictions that highlight the body’s internal structures and elide its viscerality. Despite the deliberate exclusion of the flesh, many of these images are saturated in erotic potential, both implicitly and explicitly. These images emerge in a culture preoccupied with the visualization and control of women’s bodies and sexualities. Feminist scholars have long been critical of the ways in which popular media constructs the body as an object for erotic consumption;; the anatomic images I consider here go one step further. The mainstream gaze has previously been limited to the exterior surfaces of the body, with the penetrating gaze into the body’s interior restricted to the medical and legal establishments. The penetrating gaze is increasingly democratized as x-ray and other interior views of the body become more prevalent.The texts under discussion in this thesis traverse the opaque barrier of the skin and serve to construct the totality of the human body as an object to be examined and consumed. While X-rated x-rays can, sometimes, offer a potential site of resistance to gen- dered surveillance of the anatomic body, their increasing ubiquity demonstrates the escalation of a dominating surveillant regime intent on penetrating and controlling the anatomic body. The images’ uncritical public consumption provides an insidious route by which that regime may be normalized, furthered and even glorified.