Circle Plus Partial Helical Scan Scheme for a Flat Panel Detector-Based Cone Beam Breast X-Ray CT

Dong Yang,Ruola Ning,Weixing Cai

doi:10.1155/2009/637867

Abstract

Flat panel detector-based cone beam breast CT (CBBCT) can provide 3D image of the scanned breast with 3D isotropic spatial resolution, overcoming the disadvantage of the structure superimposition associated with X-ray projection mammography. It is very difficult for Mammography to detect a small carcinoma (a few millimeters in size) when the tumor is occult or in dense breast. CBBCT featured with circular scan might be the most desirable mode in breast imaging due to its simple geometrical configuration and potential applications in functional imaging. An inherited large cone angle in CBBCT, however, will yield artifacts in the reconstruction images when only a single circular scan is employed. These artifacts usually manifest themselves as density drop and object geometrical distortion that are more noticeable in the reconstructed image areas that are further away from the circular scanning plane. In order to combat this drawback, a circle plus partial helical scan scheme is proposed. An exact circle plus straight line scan scheme is also conducted in computer simulation for the purpose of comparison. Computer simulations using a numerical breast phantom demonstrated the practical feasibility of this new scheme and correction to those artifacts to a certain degree.

Highlights

Breast cancer imaging has improved over the last decade with higher and more uniform quality standards for mammography as well as through the increasing use of sonography and magnetic resonance imaging as the adjunct tools
In order to overcome these cone beam artifacts, we propose the circle plus partial helical (CH) scan scheme based on the idea that by partially filling the object support in the Radon domain where the circular scan does not touch through the additional scanning trajectory, we can acquire more information than from just a single circular scan
Partial helical scan with different sampling intervals showed that the number of X-ray shootings between 32 and 64 could provide acceptable reconstructed images in terms of correction to the intensity drop along the scanning axis and geometrical distortion

Summary

Introduction

Breast cancer imaging has improved over the last decade with higher and more uniform quality standards for mammography as well as through the increasing use of sonography and magnetic resonance imaging as the adjunct tools. Katsevich and Kapralov [10] proposed a circle plus general curve scan algorithm for exact reconstruction, which is of FBP type; it is an exact shiftinvariant algorithm and very computationally efficient The requirements for this additional scan are that, first, this additional general curve has to be a piecewise smooth curve (i.e., a straight line or helix); second, during this additional scan the circle trajectory must find its projection on the detector as it is seen from the X-ray source. The second requirement with respect to the aforementioned Katsevich algorithm is hard to meet Based on this special geometric requirement of CBBCT, the proposed partial helical scan part will be reconstructed using a shift-variant filtered-backprojection [11]. Computer simulations based on the numerical breast phantom verified that the proposed CH scheme outperforms the FDK-based single circular scan scheme

Methods and Materials

Radon shell C

FBP Reconstruction Algorithm Associated with Different Scan Schemes

Computer Simulation

Results

Conclusion and Discussion