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Simple computation of the approximated modulation transfer function (MTF) using spreadsheet-software: method and evaluation in five maxillofacial CBCT-devices

2019; Oxford University Press; Volume: 48; Issue: 4 Linguagem: Inglês

10.1259/dmfr.20180350

1476-542X

Ralf Schulze, Clara I Doering,

Radiation Dose and Imaging

To develop a simple way to compute the approximated modulation transfer function (MTF) manually using conventional spreadsheet software.Basing on an edge-image a method was developed, facilitating computation of the edge spread and line spread function in open-source spreadsheet software (Gnumeric; http://projects.gnome.org/gnumeric/downloads.shtml ). By means of the integrated fast Fourier transformation Fourier coefficients are obtained from the line spread function which can then be plotted vs spatial frequency to obtain MTF-plots. For the experimental evaluation an edge test object was exposed in five commercial CBCT devices for maxillofacial applications.The MTF as obtained from the above-described manual method at 10% modulation ranged between 1.6 and 2.3 cycles/mm. Reproducibility as expressed as relative differences between single assessments ranging between 3% and 11%. The computed MTF-values compare well with results from the literature.The method introduced can be used to manually and reliably estimate a CBCTs' MTF as one central parameter for the imaging systems' performance.