Grant M. Stevens PhD, Presenter: Employee, General Electric Company

Roy A. Nilsen, Abstract Co-Author: Employee, General Electric Company

With the emergence of advanced CT reconstruction techniques, acquisition parameters can be adjusted to leverage the improved image quality in order to achieve the optimal radiation dose. While this can be estimated using phantom data, and fine-tuned after a period of clinical scanning, it is preferable to obtain feedback on clinical images without subjecting any additional patients to [sub-optimal] exposure. One approach to achieve this is the use of noise insertion techniques to retrospectively modify the noise content of existing scan data. In particular, the use of a projection domain-based approach makes this method viable for advanced reconstruction techniques.

A clinical CT scanner (GE CT750HD) has been used to evaluate a projection domain-based noise insertion technique. Phantom scans were performed to compare image quality metrics between actual and emulated CT scans, including noise level and noise power spectrum. Human subject scans, obtained at multiple dose levels, were used to evaluate noise insertion performance over a range of acquisition techniques. Human observer studies were performed to evaluate the ability of the noise insertion approach to emulate scans with a lower tube current. Evaluations were performed for both filtered backprojection and advanced reconstruction techniques.

Both the quantitative image quality metric analysis and the human observer studies indicate the ability of the projection domain-based noise insertion approach to emulate scans with a lower tube current. This performance holds even with substantial reductions in the radiation output of the scanner.

Based on this work, noise insertion techniques can be used to emulate scans with a lower tube current. This approach allows existing clinical scans to be used to obtain feedback of desired image quality, in order to optimize protocols for advanced CT reconstruction techniques.

This study can be used as the basis for determining how to use clinical scans to optimize protocols for advanced CT reconstruction techniques, without the additional exposure of patients.

Stevens, G, Nilsen, R, Clinical Protocol Optimization for Advanced Reconstruction Techniques.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12043901.html