Maximum volume coverage in spiral computed tomography scanning
1Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
Rationale And Objectives:
Given a slice thickness and an image noise level, volume coverage in spiral computed tomography (CT) scanning was maximized with respect to detector collimation and table increment.
Methods:
The maximization was analytically performed on the basis of the following relationships: (1) With the half-scan interpolation method, the slice sensitivity profile (SSP) in spiral CT scanning is the convolution of a rectangular detector response function (the width is equal to the detector collimation) and a triangular table motion function (the base is equal to the table increment); (2) the SSP variance is equal to the sum of squared detector collimation divided by 12 and squared table increment divided by 24; (3) the image noise variance is inversely proportional to tube current and detector collimation; and (4) the maximum continuous scanning time is inversely proportional to tube current.
Results:
Given a limited tube heat capability, a slice thickness, and an image noise level, we proved that the maximum volume coverage is reached with a pitch of square root of 2.
Conclusion:
With a heat-limited tube and for a specified image quality in terms of slice thickness and image noise, a pitch of 1.4 should be used for maximum volume coverage in spiral CT scanning.
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