| Tomosynthesis is a 3-D x-ray imaging technique that enables the reconstruction of any arbitrary set of planes from a single set of projection radiographs, acquired by varying the x-ray source angle, typically over a range of less than 40°. Conventional backprojection tomosynthesis produces reconstructions obscured by substantial tomographic blur. Matrix inversion tomosynthesis (MITS) uses linear systems theory, along with a priori knowledge of the imaging geometry, to deterministically distinguish between true structure and overlying tomographic blur.;This dissertation presents the optimization and clinical implementation of MITS for the detection of subtle pulmonary nodules.;A prototype motion apparatus was constructed and integrated with an existing commercial prototype rapid-acquisition flat-panel detector and x-ray source. An acquisition strategy was devised which allowed a large number of projection images to be acquired during a single breath-hold by the imaging subject. In vivo MITS scans of 20 human subjects were collected in an IRB-approved pilot study to illustrate proof of concept.;An optimum MITS scan angle (ANG), number of projections (N), and number of reconstructed planes (NP) for chest imaging on our prototype system was selected according to the MITS deterministic impulse response (IR) and modulation transfer function (MTF) characteristics, which were determined by simulation. Stochastic noise in MITS reconstructions was characterized by measuring noise power spectra in MITS planes created while varying ANG, N, and NP , and a final optimum MITS technique was selected according to both deterministic and stochastic considerations.;Additionally, a method was devised for suppressing low-contrast artifacts which arise from partial-pixel sharing of digital image data during the creation of MITS planes.;The optimum MITS technique for chest imaging using our system was found to be ANG = 20°, N = 71, NP = 69, and PSEP ≈ 5 mm. Partial-pixel artifacts are shown to be effectively ameliorated by the averaging of 7 adjacent MITS planes to form MITS slabs. Finally, a comparison of 7-plane MITS slabs and radiographs from 8 human subjects show that the optimized MITS approach is clinically feasible, substantially improves the visibility of thoracic anatomy, and will likely enhance the detectability of subtle pulmonary nodules. |
