A method of accuracy evaluation of line spread function (LSF) and point spread function (PSF) measured in computed tomography

Shinichi Wada; Masaki Ohkubo; Toru Matsumoto; Kanae Nishizawa

doi:10.1117/12.654087

2 March 2006 A method of accuracy evaluation of line spread function (LSF) and point spread function (PSF) measured in computed tomography

Shinichi Wada, Masaki Ohkubo, Toru Matsumoto, Kanae Nishizawa

Author Affiliations +

Proceedings Volume 6142, Medical Imaging 2006: Physics of Medical Imaging; 61423I (2006) https://doi.org/10.1117/12.654087
Event: Medical Imaging, 2006, San Diego, California, United States

Abstract

This study describes an effective method for verifying the line spread function (LSF) and point spread function (PSF) measured in computed tomography (CT). The CT image of an assumed object-function was calculated using LSF or PSF based on a model to understand spatial resolution in the imaging system. Validities of LSF and PSF were confirmed by comparing the calculated image with the scanned image of the phantom corresponding to the object-function. Differences between the scanned and calculated images depended on accuracies of LSF and PSF used in the calculations. First, we measured LSF in our scanner, and derived the two-dimensional PSF in the scan-plane from LSF. Second, we scanned the phantom including uniform cylindrical objects parallel to the long axis of a patient's body (z-direction). Scanned images of such a phantom were characterized according to spatial resolution in the scan-plane, and didn't depend on spatial resolution in the z-direction. Third, images were calculated by two-dimensionally convolving the object-function with PSF, which object-function was determined to correspond to the phantom. Calculated images agreed with scanned images, confirming validities of PSF and LSF. On the other hand, we obtained another LSF with an inappropriate manner, and calculated images as mentioned above. On this case, the calculated images did not agree with the scanned images, indicating the inaccuracy of LSF. We could verify LSFs and PSFs for three types of reconstruction kernels. When one obtains LSF, PSF or MTF, verification using the proposed method is recommended.

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Shinichi Wada, Masaki Ohkubo, Toru Matsumoto, and Kanae Nishizawa "A method of accuracy evaluation of line spread function (LSF) and point spread function (PSF) measured in computed tomography", Proc. SPIE 6142, Medical Imaging 2006: Physics of Medical Imaging, 61423I (2 March 2006); https://doi.org/10.1117/12.654087

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KEYWORDS

Point spread functions

Computed tomography

Titanium

Aluminum

Spatial resolution

Modulation transfer functions

Scanners

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