Spatial variation of section sensitivity profile in spiral computed tomography

Area of Science:

• Medical Imaging
• Radiological Physics
• Image Reconstruction

Background:

• The section sensitivity profile (SSP) characterizes longitudinal image resolution in computed tomography (CT).
• Spiral CT interpolation introduces asymmetry, causing SSP to vary with transverse position.
• Previous research has not explored the spatial variation of SSP in spiral CT.

Purpose of the Study:

• To investigate and quantify the spatial variation of the SSP across the scan field in spiral CT.
• To formulate the SSP for the half-scan interpolation method concerning transverse position.
• To analyze the impact of this variation on image reconstruction.

Main Methods:

• Formulation of the SSP for half-scan interpolation based on transverse position.
• Mathematical analysis and numerical simulations of the SSP.
• Moment analysis of the SSP up to the third order.

Main Results:

• The SSP exhibits antisymmetry with respect to a specific axis in the transverse slice.
• Normalized SSP ensures approximate mass conservation during reconstruction.
• For a 50-degree fan angle, slice thickness variation is within 10%, and skewness is around 0.15.
• Smaller fan angles lead to reduced SSP spatial variation.

Conclusions:

• The spatial variation of SSP in spiral CT is quantifiable and dependent on the fan angle.
• The SSP along the longitudinal axis can serve as a representative for the SSP family in spiral CT.
• Understanding SSP variation is crucial for accurate image resolution assessment in spiral CT.