Proceedings Article | 15 March 2007
KEYWORDS: Computed tomography, Point spread functions, Scanners, Image quality standards, Manufacturing, Image quality, Lung, CT reconstruction, Bone, Zoom lenses
This study discusses a method of CT image quality standardization that uses a point-spread function (PSF) in MDCT.
CT image I(x,y,z) is represented by the following formula: I(x,y,z) = O(x,y,z)***PSF(x,y,z). Standardization was
performed by measuring the three-dimensional (3-D) PSFs of two CT images with different image qualities. The image
conversion method was constructed and tested using the 3-D PSFs and CT images of the CT scanners of three different
manufacturers. The CT scanners used were Lightspeed QX/i, Somatom Volume Zoom, and Brilliance-40. To obtain the
PSF(x,y) of these CT scanners, the line spread functions of the respective reconstruction kernels were measured using a
phantom described by J.M. Boone. The kernels for each scanner were: soft, standard, lung, bone, and bone plus (GE);
B20f, B40f, B41f, B50f, and B60f (Siemens); and B, C, D, E, and L (Philips). Slice sensitivity profile (SSP) were
measured using a micro-disk phantom (50 μm* φ1 mm) with 5 mm slice thickness and beam pitch of 1.5 (GE, Siemens)
and 0.626 (Philips). 3-D PSF was verified using an MDCT QA phantom. Real chest CT images were converted to
images with contrasting standard image quality. Comparison between the converted CT image and the original standard
image showed good agreement. The usefulness of the image conversion method is discussed using clinical CT images
acquired by CT scanners produced by different manufacturers.
