PubMed Health⌕ Search

Biomedical subjects

Michael Vannier

Publications and source records attributed to Michael Vannier.

5 recordsLinked to original sources
PubMed2006

Bolus characteristics based on Magnetic Resonance Angiography.

BACKGROUND: A detailed contrast bolus propagation model is essential for optimizing bolus-chasing Computed Tomography Angiography (CTA). Bolus characteristics were studied using bolus-timing datasets from Magnetic Resonance Angiography (MRA) for adaptive controller design and validation. METHODS: MRA bolus-timing datasets of the aorta in thirty patients were analyzed by a program developed with MATLAB. Bolus characteristics, such as peak position, dispersion and bolus velocity, were studied. The bolus profile was fit to a convolution function, which would serve as a mathematical model of bolus propagation in future controller design. RESULTS: The maximum speed of the bolus in the aorta ranged from 5-13 cm/s and the dwell time ranged from 7-13 seconds. Bolus characteristics were well described by the proposed propagation model, which included the exact functional relationships between the parameters and aortic location. CONCLUSION: The convolution function describes bolus dynamics reasonably well and could be used to implement the adaptive controller design.

Computer Simulation↗
PubMed2003

Spatial variation of resolution and noise in multi-detector row spiral CT.

RATIONALE AND OBJECTIVES: The authors performed this study to evaluate an approach for measuring the variations of three-dimensional spatial resolution and image noise throughout a field of view imaged with multi-detector row spiral computed tomographic (CT) scanners. MATERIALS AND METHODS: The authors designed a phantom (diameter, 320 mm) that contained 37 metallic spheres (diameter, approximately 0.8 mm) positioned between two disks made of a material with attenuation being that of water. One sphere was located at the isocenter of the phantom, and the rest were evenly spaced in three concentric rings with diameters of 100, 200, and 300 mm, respectively. The phantom was imaged with two widely used multi-detector row CT scanners by using a standard protocol and four variations of that protocol. Because a recently developed theory holds that image resolution should be proportional to the square root of the trace of the covariance matrix of a point spread function, the authors developed a software package to segment high-attenuation spheres from the CT image volume and compute point spread functions from blurred images of the spheres. Three-dimensional spatial resolution and image noise were calculated as a function of radial distance within the field of view. RESULTS: Resolution and noise were quantified in the resultant CT image volumes and found to be nonisotropic, with worse resolution and less noise occurring at the periphery of the field of view. CONCLUSION: The method enabled measurement of variations in spatial resolution and of their distribution on images obtained with multi-detector row CT scanners. These findings may contribute to the development of an improved algorithm for image reconstruction.

Humans↗
PubMedDate not supplied

Projection-based bolus detection for computed tomographic angiography.

Computed tomographic (CT) angiography is important for imaging studies on cardiovascular structures, peripheral vessels, and solid organs. In practice, a CT angiography scan is triggered by the bolus arrival at a prespecified anatomical location, which is determined using CT fluoroscopy. In this article, we propose a projection-based method adapted from the Grangeat formula to detect the bolus arrival. Then, we evaluate our new method in numerical and animal studies. Our results indicate that this method allows significantly better temporal resolution and is computationally more efficient, as compared with the image-based methods.

Algorithms↗