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In current dedicated breast computed tomography (mammotomography) systems, comfortable patient positioning on a
stationary bed restricts the practicable range of source-detector trajectories, thus compromising the system's ability to
adequately image the patient's anterior chest wall. This study examines the effect on detecting small, low-contrast
lesion-like-spheres using limited angle x-ray source-detector trajectories and trajectories that intentionally raise the
tomographic imaging system mid-acquisition. These modified acquisition paths may increase chest wall visualization,
simplify the design of the imaging system and increase patient comfort by allowing the design of an improved patient
bed. Thin walled balloons of various volumes filled with iodine act as surrogate high contrast lesions to initially
investigate the effect of these novel trajectories. Then, stacks of 5mm acrylic spheres regularly spaced in concentric
circles are placed in water to simulate a low contrast environment in a uniform scatter medium. 360° azimuthal scans are
acquired at various bed heights with contiguous projections subsequently removed to create limited angle acquisitions
from 240-360°. Projections from the different bed heights are interwoven to form trajectories that mimic discontinuously
raising the imaging system mid-acquisition. The resulting iteratively reconstructed volumes are evaluated with an
observer study. Initial images suggest that using limited angles and raising the system is possible while increasing the
observer's ability to visualize objects near the chest wall. Based on the results of this study, an improved patient bed to
facilitate chest wall imaging will be designed, and the feasibility of vertical system motion to increase imaged breast
volume explored.
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