Reduced partial volume artifacts using spiral computed tomography and an integrating interpolator

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Abstract
A technique is described for obtaining computed tomography (CT) head images with significantly reduced partial volume artifacts while retaining excellent low contrast resolution. Partial volume artifacts could be reduced by narrowing the collimation and summing thin slices. However, in axial scans, the acquisition and reconstruction time required for generating all the thin slices would prove clinically impractical. In addition, image artifacts could occur due to patient motion during the scans, particularly in trauma cases. In the case of spiral CT, a narrow collimation along with a small pitch can be used to reduce partial volume artifacts. However, the time required to reconstruct and sum the thin slices is still prohibitive. In this paper, we present a spiral technique using an integrating spiral interpolator (ISI) that allows a head study to be performed in less time without the partial volume artifacts normally seen. Using this interpolator, thick slices can be prospectively reconstructed from a spiral scan with a narrow collimation. The slice sensitivity profile for this interpolator was obtained and the full width at half-maximum and full width at tenth-maximum values were compared with both axial and predicted values. Noise values were also measured and compared to axial and theoretical predictions. Using this ISI interpolator, high quality head images were obtained with significantly reduced partial volume artifacts compared to standard axial and spiral scans. Total acquisition time is less than that of standard contiguous axial head scans.