Open AccessAn algorithm for automated modulation transfer function measurement using an edge of a PMMA phantom: Impact of field of view on spatial resolution of CT images
Author(s) -
Anam Choirul,
Fujibuchi Toshioh,
Budi Wahyu Setia,
Haryanto Freddy,
Dougherty Geoff
Publication year - 2018
Publication title -
journal of applied clinical medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.83
H-Index - 48
ISSN - 1526-9914
DOI - 10.1002/acm2.12476
Subject(s) - imaging phantom , optical transfer function , point spread function , image resolution , field of view , optics , scanner , computer science , filter (signal processing) , enhanced data rates for gsm evolution , computer vision , physics , algorithm , region of interest , point (geometry) , mathematics , geometry
Purpose The purpose of this study was to introduce a new algorithm for automated measurement of the modulation transfer function ( MTF ) using an edge of a readily available phantom and to evaluate the effect of reconstruction filter and field of view ( FOV ) on the spatial resolution in the CT images. Methods Our automated MTF measurement consisted of several steps. The center of the image was established and an appropriate region of interest ( ROI ) designated. The edge spread function ( ESF ) was determined, and a suitably interpolated ESF curve was differentiated to obtain the line spread function ( LSF ). The LSF was Fourier transformed to obtain the MTF . All these steps were accomplished automatically without user intervention. The results of the automated MTF from the edge phantom were validated by comparing them with a point image, and the results of the automated calculation were validated by the standard fitting method. The automated MTF calculation was then applied to the images of two polymethyl methacrylate ( PMMA ) phantoms and a wire phantom which had been scanned by a Toshiba Alexion 4‐slice CT scanner and reconstructed with various filter types and FOV s. Results The difference in the 50% MTF values obtained from the edge and point phantoms were within ±4%. The values from the automated and fitted methods agreed to within ±2%, indicating that the automated MTF calculation was accurate. The automated MTF calculation was able to differentiate MTF curves for various filters. The spatial resolution values were 0.37 ± 0.00, 0.71 ± 0.01, and 0.78 ± 0.01 cycles/mm for FC 13, FC 30 and FC 52 filters, respectively. The spatial resolution of the images decrease linearly ( R 2 > 0.98) with increasing FOV s. Conclusion An automated MTF method was successfully developed using an edge phantom, the PMMA phantom. The method is easy to implement in a clinical environment and is not influenced by user experience.