Browsing by Author "Curtis, Charlotte"
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- ItemOpen AccessEstimation of Three-Dimensional Breast Features from Standard Two View Mammograms(2010) Curtis, Charlotte; Fear, Elise; Frayne, Richard
- ItemOpen AccessFactors Affecting Image Quality in Near-field Ultra-wideband Radar Imaging for Biomedical Applications(2015-09-01) Curtis, Charlotte; Fear, EliseNear-field ultra-wideband radar imaging has potential as a new breast imaging modality. While a number of reconstruction algorithms have been published with the goal of reducing undesired responses or clutter, an in-depth analysis of the dominant sources of clutter has not been conducted. In this thesis, time domain radar image reconstruction is demonstrated to be equivalent to frequency domain synthetic aperture radar. This reveals several assumptions inherent to the reconstruction algorithm related to radial spreading, point source antennas, and the independent summation of point scatterers. Each of these assumptions is examined in turn to determine which has the greatest impact on the resulting image quality and interpretation. In addition, issues related to heterogeneous and dispersive media are addressed. Variations in imaging parameters are tested by observing their influence on the system point spread function. Results are then confirmed by testing on simple and detailed simulation models, followed by data acquired from human volunteers. Recommended parameters are combined into a new imaging operator that is demonstrated to generate results comparable to a more accurate signal model, but with a 50 fold improvement in computational efficiency. Finally, the most significant factor affecting image quality is determined to be the estimate of tissue properties used to form the image.
- ItemOpen AccessSemiautomated Multimodal Breast Image Registration(Hindawi Publishing Corporation, 2011-10-20) Curtis, Charlotte; Frayne, Richard; Fear, Elise
- ItemOpen AccessSemiautomated Multimodal Breast Image Registration(2012-02-01) Curtis, Charlotte; Frayne, Richard; Fear, EliseConsideration of information from multiple modalities has been shown to have increased diagnostic power inbreast imaging. As a result, new techniques such as microwave imaging continue to be developed. Interpreting these novel image modalities is a challenge, requiring comparison to established techniques such as the gold standard X-ray mammography.However, due to the highly deformable nature of breast tissues, comparison of 3D and 2D modalities is a challenge. To enable this comparison, a registration technique was developed to map features from 2D mammograms to locations in the 3D image space. This technique was developed and tested using magnetic resonance (MR) images as a reference 3D modality, as MR breast imaging is an established technique in clinical practice. The algorithm was validated using a numerical phantom then successfully tested on twenty-four image pairs. Dice's coefficient was used to measure the external goodness of fit, resulting in an excellent overall average of 0.94. Internal agreement was evaluated by examining internal features in consultation with a radiologist, and subjective assessment concludes that reasonable alignment was achieved.
- ItemOpen AccessUsing X-Ray Mammograms to Assist in Microwave Breast Image Interpretation(Hindawi Publishing Corporation, 2011-12-28) Curtis, Charlotte; Frayne, Richard; Fear, Elise
- ItemOpen AccessUsing X-Ray Mammograms to Assist in Microwave Breast Image Interpretation(2012-03-22) Curtis, Charlotte; Frayne, Richard; Fear, EliseCurrent clinical breast imaging modalities include ultrasound, magnetic resonance (MR) imaging, and the ubiquitous X-ray mammography. Microwave imaging, which takes advantage of differing electromagnetic properties to obtain image contrast, shows potential as a complementary imaging technique. As an emerging modality, interpretation of 3D microwave images poses a significant challenge. MR images are often used to assist in this task, and X-ray mammograms are readily available. However, X-ray mammograms provide 2D images of a breast under compression, resulting in significant geometric distortion. This paper presents a method to estimate the 3D shape of the breast and locations of regions of interest from standard clinical mammograms. The technique was developed using MR images as the reference 3D shape with the future intention of using microwave images. Twelve breast shapes were estimated and compared to ground truth MR images, resulting in a skin surface estimation accurate to within an average Euclidean distance of 10 mm. The 3D locations of regions of interest were estimated to be within the same clinical area of the breast as corresponding regions seen on MR imaging. These results encourage investigation into the use of mammography as a source of information to assist with microwave image interpretation as well as validation of microwave imaging techniques.