098-004: Method & Apparatus for Processing Data from a Tomographic Imaging System

This invention relates to the field of computer tomographic (CT) imaging and constitutes a new method and apparatus capable of reducing the amount of radiation exposure to a patient by using almost completely local data.

As a corollary, this method allows for greatly improved CT resolution of the subject without altering the amount of radiation exposure. This method reconstructs a region of radius 16 pixels in a 256x256 image to within 1 % average error using 22% of the data, and to within 1 % maximum error using 30% of the data.

The basis of this invention is an algorithm that reconstructs the wavelet coefficients of an image from localized Radon transform data. The reduction of radiation on the patient results from the smaller region of exposure. In scanning a subject to construct its CT image, one can go straight to the wavelet transform without the step of reconstructing the image first achieving local image reconstruction with superior definition in a shorter time frame. This ability to reconstruct a localized image directly from its projections equates to fewer projections overall and greater computational efficiency.
Additionally, the algorithm of the invention allows computation of the actual value of densities verses "estimates of jumps" in relative densities providing more accurate information for diagnostic purposes.

- Reduces radiation dosage - Improved resolution requiring a smaller region of exposure - Computationally more efficient yielding faster image output - Uniform exposure at all angles for easier hardware implementation - Reconstructs centered, off-centered, and multiple regions - Application in non-separable wavelet bases - Effective reconstruction in both the parallel and fan-beam geometries

Market Significance:

With the acceptance of CT into the mainstream concerns about the radiation dosage it imposes on the body come into play. Conventional tomography constitutes a global procedure in that the recovery of an image at any fixed point requires the knowledge of all projections of the image meaning that a patient needs to be exposed to relatively large amount of X-rays even to view only a small part of the patient's body. This invention can be used control this exposure and improve the results. Commercial application can be approached from a hardware perspective - the design an entirely new CT system, or it can be incorporated as part of an existing CT control system as a front-end software control program.