Low-Dose 3D Quantitative Vascular X-ray Imaging of the Breast

Background: Worldwide, breast cancer is the most common cancer and second deadliest cancer in women. Diagnostic imaging techniques are a critical part for screening, diagnosis, tumor staging and cancer therapy of the breast. Contrast-Enhanced Magnetic Resonance Imaging (CE-MRI) is the current standard imaging technique allowing detection of abnormal vascular development and lesion contrast uptake. CE-MRI is however very costly and not widely available. Moreover, its spatial resolution might not be sufficient to depict certain types of lesions including microcalcifications. The development of Contrast-Enhanced Spectral Mammography (CESM) has made the clinical use of intravenous contrast enhancement with conventional mammography possible. However, CESM is a 2D projection technique and therefore presents limitations to depict the 3D internal structures of lesions and to provide accurate quantitative 3D functional information.Contrast-Enhanced Digital Breast Tomosynthesis (CE-DBT) and dedicated Contrast-Enhanced Breast CT (CE-bCT) are two breast imaging modalities currently under investigation by academic and industrial research groups. It is however anticipated that the quantitative potential of CE-DBT is limited, due to the inherent low depth-resolution of limited opening angle DBT modality. CE-bCT with quasi-isotropic spatial resolution and voxel signal intensity proportional to the linear attenuation coefficient is believed to offer more accurate quantitative information, though a low-dose operation is still a challenge.Objectives: The purpose of this thesis has been to study the technical feasibility of CE-bCT and its potential to accurately depict and localize tumors, as well as to provide accurate quantitative morphological and functional imaging information about tumors, at low radiation dose levels. To understand the incremental value of CE-bCT over CE-DBT, the quantitative potential of both technologies have been compared. This investigation has been performed through computer simulations.Methods: At first, a simulation platform capable of modeling various X-ray breast imaging techniques and providing radiographic images of simple and complex computational phantoms was developed and validated. Secondly, an optimization study of a CE-bCT technique based on a dual-energy approach was performed, aiming to maximize image quality of iodine-enhanced and morphological images. Finally, the quantitative potential of CE-bCT and CE-DBT was compared through the assessment of iodine-enhanced lesion detectability, characterization, localization and 3D extent measurement. In a human observer study, depiction and characterization of iodine-enhanced lesions of different sizes, shapes and iodine uptakes was compared between CE-bCT and CE-DBT using a mesh-based anthropomorphic breast phantom.Conclusions: The simulation studies in this PhD thesis suggest that dual-energy iodine-injected CE-bCT could be a feasible technique for breast tumor depiction, localization and characterization, with dose levels comparable to standard mammography. While preliminary comparisons with CE-DBT suggests comparable depiction and characterization performance, the fully 3D information combined with high spatial resolution confirms CE-bCT as an interesting low-dose evolution of CESM toward 3D quantitative assessment of contrast uptakes and potential alternative to