Browsing by Subject "Breast imaging"

The different patient orientations in breast PET/CT and breast MR imaging, supine versus prone, respectively, cause difficulty in integrating and interpreting the data acquired from these two types of imaging protocols. Prone breast PET/CT could be possible provided the assistance of a suitable support. The main purpose of this project is to evaluate the feasibility of prone breast PET/CT imaging using phantoms and to compare this protocol with the standard supine protocol from an image quality perspective. In this project, a rigid, weight-bearing, radiolucent foam support based on the dimensions and layout of the MRI breast coil for prone-pendant clinical breast imaging was devised for prone PET/CT imaging purposes. In order to scan the same test object in various configurations (prone versus supine), breast phantoms were investigated and tested to develop the most suitable combination of materials that can simulate breast morphology. Water-filled intravenous bags were determined to be the best choice for breast phantom development. The breasts containing lesions, along with a torso phantom, were scanned using a clinical PET/CT scanner in both prone and supine orientations. The acquired PET images were quantitatively evaluated in both orientations. Several image quality metrics such as signal-to-noise ratio, local contrast, contrast uniformity, and quantitative repeatability were assessed from the acquired PET data. As a result, prone PET images present better image quality than supine PETv images in terms of SNR and contrast uniformity. However, the uniformity of the signal intensity is worse in prone orientation, and there are several unexpected image artifacts. The paired t-test statistical results suggest that there are significant differences between prone and supine in terms of signal intensity and SNR. It can be concluded that prone PET/CT imaging is geometrically feasible with the assistance of the developed torso support. Prone PET/CT imaging holds advantages over supine PET/CT imaging considering registration with MRI.

Purpose: To assess the quantitative potential of breast tomosynthesis by estimating the percent density of voxelized anthropomorphic breast phantoms.

Methods and Materials:A Siemens breast tomosynthesis system was modeled using Monte Carlo methods and a voxelized anthropomorphic breast phantom. The images generated by the simulation were reconstructed using Siemens filtered back-projection software. The non-uniform background due to scatter, heel effect, and limited angular sampling was estimated by simulating and subtracting images of a uniform 100% fatty breast phantom. To estimate the density of each slice, the total number of fatty and glandular voxels was calculated both before and after applying a thresholding algorithm to classify voxels as fat vs. glandular. Finally, the estimated density of the reconstructed slice was compared to the known percent density of the corresponding slice from the voxelized phantom. This percent density estimation comparison was done for a 35%- and a 60%-dense 5cm breast phantom.

Results: Without thresholding, overall density estimation errors for the central eleven slices were 4.97% and 2.55% for the 35% and 60% dense phantoms, respectively. After thresholding to classify voxels as fat vs. glandular, errors for central eleven were 7.99% and 6.26%, respectively. Voxel to voxel matching of the phantom vs. reconstructed slice demonstrated 75.69% and 75.25% respectively of voxels were correctly classified.

Conclusion: The errors in slice density estimation were <8% for both the phantoms thus implying that quantification of breast density using tomosynthesis is possible. However, limitations of the acquisition and reconstruction process continue to pose challenges in density estimation leading to potential voxel to voxel errors that warrant further investigation.

This work investigates phantom and subject positioning as well as collecting data with a variety of angular sampling and acquisition trajectories. The overall goal of this work has been to utilize the dedicated, breast SPECT-CT system to acquire the best possible images. A large portion of this work has been to apply corrections to the system for quantitative imaging. The system has been shown to provide high quality images with minimal out-of-field signal contribution. Additionally, the quantification procedure has been shown to be within 10% of the known activity concentration present at the time of imaging for both VAOR and PROJSINE trajectories.

Physical phantoms are an important tool in clinical system evaluation. There exists a lack of suitable anthropomorphic physical phantoms that vary as much as a typical patient population. The lack in diversity in anthropomorphic physical phantoms makes generalizing results found using these phantoms difficult. In order to address this issue, a diverse selection of breast phantoms were 3D printed on a Stratasys Objet350 Connex printer using tissue-approximate photopolymers. These cases were then evaluated on a clinical Hologic Selenia Dimensions Digital Breast Tomosynthesis system. The evaluation consisted of a 4-alternative-forced-choice task printed on a contrast insert with silver-doped ink of concentration 200 mg/mL. The disks ranged in size from 350um-770um and a range of signal intensities was achieved by repeatedly overprinting, layering the ink. Each ink pass corresponded to an increase in signal of 1.4%. The contrast insert was imaged in 8 different orientations, at a fixed kVp of 36, and varied mAs for indicated AGD of 1.4, 2.8, and 4.2 mGy. A channelized-Hotelling observer with Gabor channels was used for evaluation and a percent correct was determined. Detection performance increased as dose increased for all cases. The most dense breast case had the worst detection performance as is had the most overlapping structures to obscure the signal. The approximately average density breast and the fatty, thinner breast performed similarly, however this may be due to the beam filtering used to avoid overexposing the detector with the high kVp and mAs used for this experiment. These results indicate that system performance is dependent on the anatomy being imaged. Further investigations with more phantom cases is needed to better evaluate the anatomical dependence of the system performance.

It is essential that breast cancer be detected at its earliest stages for better prognosis. Advanced imaging techniques and systems are constantly under development and study to improve the screening and detection of breast cancer. Like every technological advancement in medical care, these techniques and systems need to be tested and verified before their clinical translation. What are currently considered the gold standard for justification of clinical translation are randomized clinical trials. Clinical trials are time-consuming, costly, and expose the population to extra irradiation in the case of x-ray imaging. Given the recent advances in computation and modeling, virtual clinical trials can be carefully designed and carried out to inform, orient, or potentially replace clinical trials given adequate validation and credibility. This dissertation elaborates on the design, implementation, and performance analysis of virtual clinical trials, which is made possible through the employment and advancement of sophisticated tools and models.

This study intends to validate the sensitivity and specificity of coded aperture coherent scatter spectral imaging (CACSSI) by comparison to clinical histological preparation and pathologic analysis methods currently used for the differentiation of normal and neoplastic breast tissues. A composite overlay of the CACSSI rendered image and pathologist interpreted, stained sections validate the ability of coherent scatter imaging to differentiate cancerous tissues from normal, healthy breast structures ex-vivo. Via comparison to the pathologist annotated slides, the CACSSI system may be further optimized to maximized sensitivity and specificity for differentiation of breast carcinomas.