Showing papers by "Michael W. Vannier published in 2005"
TL;DR: This work presents a systematic method of designing the transmission measurements to reduce the mathematical instability of spectrum estimation, and applies the expectation-maximization (EM) method, which is known to yield robust solutions to positive, linear integral equations such as the one that describes spectrum estimation from transmission data.
Abstract: Knowledge of the x-ray spectrum in diagnostic imaging is important for dose calculations, correction for beam-hardening artifacts, and dual-energy computed tomography. One way to determine the x-ray source spectrum is to estimate it from transmission data of a known phantom. Although such an approach is experimentally simple, spectrum estimation from transmission data is known to be an ill-conditioned problem. The contribution of this work is twofold. First, we present a systematic method of designing the transmission measurements to reduce the mathematical instability of spectrum estimation. Second, we apply the expectation-maximization (EM) method, which is known to yield robust solutions to positive, linear integral equations such as the one that describes spectrum estimation from transmission data. The proposed EM method is compared to other algorithms in the literature on simulated data from x-ray spectra typical to mammography and computed tomography. The EM method appears to outperform existing alg...
141 citations
TL;DR: PC-based MPR CT images of the face using routine scanning CT protocols can be used to accurately measure soft tissue thickness in the facial region, however, for more fine and accurate data collection, scanning protocols with slice thicknesses less than 5mm, and a spiral/helical mode pitch less than 2:1 are recommended.
98 citations
Patent•
29 Aug 2005TL;DR: In this article, a method of utilizing bolus propagation and control for contrast enhancement comprises measuring with an imaging device a position of a bolus moving along a path in a biological structure.
Abstract: A method of utilizing bolus propagation and control for contrast enhancement comprises measuring with an imaging device a position of a bolus moving along a path in a biological structure. The method further comprises predicting a future position of the bolus using a simplified target model and comparing the predicted future position of the bolus with the measured position of the bolus. A control action is determined to eliminate a discrepancy, if any, between the predicted position of the bolus and the measured position of the bolus and the relative position of the imaging device and the biological structure is adaptively adjusted according to the control action to chase the motion of the bolus.
41 citations
23 Oct 2005
TL;DR: This panel assembles end-users from well-known medical facilities and research institutions who have a background in visualization but primarily are experts using this technology for practical diagnostic applications.
Abstract: The objective of this panel is to reflect on the advances that volume rendering has brought to the medical community and, even more important, to discuss its current short-comings and future needs. This direct feedback from the medical community will hopefully inspire the IEEE Visualization audience and help to focus on new research areas that will further advance the state of the art in medical visualization. The panel assembles end-users from well-known medical facilities and research institutions who have a background in visualization but primarily are experts using this technology for practical diagnostic applications.
6 citations
TL;DR: In this article, an adaptive scheme is proposed for a next generation CT scanner, where the purpose of the control is to estimate the contract bolus position so its variations can be compensated by moving the patient table.