An effective method to verify line and point spread functions measured in computed tomography

Area of Science:

• Medical Imaging
• Radiology
• Image Quality Assessment

Background:

• Spatial resolution characterization is vital for computed tomography (CT) performance evaluation.
• Line Spread Function (LSF) and Point Spread Function (PSF) are key metrics for assessing CT spatial resolution.
• Accurate measurement of LSF and PSF is essential for reliable image quality assessment.

Purpose of the Study:

• To develop and validate an effective method for verifying measured LSF and PSF in CT imaging.
• To confirm the accuracy of LSF and PSF by comparing computed images with phantom-scanned images.
• To establish a simple, clinically applicable phantom-based approach for LSF and PSF verification.

Main Methods:

• Measured LSF and derived 2D PSF from scanner data.
• Scanned a phantom with uniform cylindrical objects parallel to the z-axis.
• Calculated CT images by convolving the object function with the derived PSF.
• Compared computed images with scanned phantom images using normalized standard deviation (SD).

Main Results:

• Good agreement was found between computed and measured images, with normalized SDs below 5.0% for validated LSF/PSF.
• Inaccurate LSF/PSF measurements resulted in normalized SDs of 6.0% or more.
• Demonstrated differences in Modulation Transfer Functions (MTFs) derived from validated versus inaccurate LSFs.
• The proposed method uses a simple phantom suitable for clinical scanning.

Conclusions:

• The developed method effectively verifies the accuracy of measured LSF and PSF in CT.
• The technique provides a reliable and quantitative assessment of spatial resolution.
• This simple phantom-based verification method is recommended for routine CT quality control and validation of new measurement techniques.