Brian Edward Nett BS, Presenter: Nothing to Disclose

Charles Anthony Mistretta PhD, Abstract Co-Author: Nothing to Disclose

Guang-Hong Chen PhD, Abstract Co-Author: Nothing to Disclose

To numerically study the necessary number of views of X-ray projections needed for a clinically acceptable angiogram in the context of background subtracted CT angiography.

In background-subtracted angiography, the major sources of streaking artifacts are the contrast-enhanced vessels. This fact potentially enables one to use significantly fewer views to generate clinically acceptable angiograms. This has been demonstrated through significant time speed-up factors achievable in MRA when an undersampled projection based acquisition scheme called VIPR is used. Based on this experience we have proposed a new volumetric CT method called Z-scan CT where multiple pulsed X-ray sources will be used for full acquisition in the Z (S/I) direction within 10 milliseconds. Computer simulations were performed in order to assess the relationship between view sampling and image quality. In the case of parallel beam acquisition the central slice theorem provides a direct relationship between projection acquisition and the frequency space information acquired; thus, volumetric reconstruction from a complete data set of parallel projections provides an ideal tool to test the concept of undersampling the frequency content in CT.

The simulations were performed using numerous mathematical phantoms, including a phantom with significant high frequency content similar to that observed for CT angiography. Using a simulated detector of 512*512 elements 200~300 views of three-dimensional X-ray parallel-beam projections are sufficient to adequately visualize vessel-like structures.

Numeric simulations indicate that 200~300 views of X-ray projections will be sufficient to generate a clinically acceptable angiogram in contrast-enhanced CT angiography. This fact demonstrates the feasibility of the proposed Z-scan CT method in which the full Z (S/I) direction is covered within a 10 millisecond cardiac phase and angular information is acquired over multiple heart beats using a single slow gantry rotation. This acquisition eliminates the need for a precise relationship between the heart beat and the rapid gantry rotation speed that is required for segmented spiral cardiac CT.

Nett, B, Mistretta, C, Chen, G, Numerical Investigation of View Sampling Criterion in CT Image Reconstruction from Three-dimensional Parallel-beam Projections.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4414335.html