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Heri Sutanto
Diponegoro University

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Computational phantoms for investigating impact of noise magnitude on modulation transfer function Choirul Anam; Ariij Naufal; Heri Sutanto; Geoff Dougherty
Indonesian Journal of Electrical Engineering and Computer Science Vol 27, No 3: September 2022
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/ijeecs.v27.i3.pp1428-1437

Abstract

Accurate measurement of spatial resolution in terms of modulation transfer function (MTF) is essential in computed tomography (CT) images. The purpose of this study was to developed a computational phantom that can be used to evaluate the effect of noise on the MTF in CT images. Our computational phantoms for measuring MTF in CT were developed with MATLAB software. The phantom image was blurred by a point spread function of a certain standard deviation. Subsequently, different noise levels were added to the phantoms. Next, an automatic MTF calculation was implemented. The first step of the MTF calculation was to determine the region of interest (ROI). Profile was generated from the ROI, and a line spread function (LSF) curve was formed. The LSF curve was Fourier transformed to produce a MTF curve. Greater noise added to phantom image, it yields greater effect of standard deviation on the measured MTF. The greater noise makes the MTF curve increases differently than MTF with 0 HU noise. The 10% MTF values at the 25% noise reach more than 2.0 cycle/mm. By the developed computational phantoms, the spatial resolution and the amount of noise can be determined independently.
An improvement of the computational effective diameter measurement in thoracic computed tomography examinations Choirul Anam; Riska Amilia; Wahyu S. Budi; Heri Sutanto; Zaenul Muhlisin; Ariij Naufal; Geoff Dougherty
Indonesian Journal of Electrical Engineering and Computer Science Vol 31, No 1: July 2023
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/ijeecs.v31.i1.pp189-196

Abstract

A method to calculate a corrected effective diameter (DMIL) to more accurately estimate the dose received by a patient in chest computed tomography (CT) examination had been previously proposed. However, the discrepancy between DMIL and water-equivalent diameter (Dw) is still relatively high (i.e. about 6%). Furthermore, the method is still performed manually, so it is laborious and time-consuming. This study aims to improve the corrected effective diameter with bone correction (Deffcorr) and to automatically calculate it. The automated Deffcorr was calculated as the square root of the product of these corrected AP and LAT diameters. The approach was implemented on 30 patients who had undergone chest CT examination with the standard protocol. The results show that the correlation between the Deffcorr and Dw is R2=0.93 with no statistical difference (p>0.05). The automated Deffcorr is 3.1% lower than Dw. While the DMIL is 10.5% higher than Dw and both are statistically different (p<0.05). In conclusion, the new Deffcorr was introduced and the result obtained was closer to Dw than DMIL. This method is simple enough to be used as an alternative method to accurately estimate Dw for radiation dose estimation in clinical chest CT scanning.
Rectangular and radial region of interests on the edge of cylindrical phantom for spatial resolution measurement Choirul Anam; Nazil Ainurrofik; Heri Sutanto; Ariij Naufal; Mohammad Haekal
Indonesian Journal of Electrical Engineering and Computer Science Vol 31, No 2: August 2023
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/ijeecs.v31.i2.pp747-754

Abstract

The purpose of this study was to evaluate the effect of rectangular region of interest (ROI) size on modulation transfer function (MTF), to develop the radial ROI, and to compare both ROIs performances for MTF measurement using a cylindrical polymethyl methacrylate (PMMA) phantom. The PMMA phantom used in this study was rotated 45°. Four rectangular ROIs and a radial ROI were created to measure the MTF value. The rectangular ROI sizes were 3×41, 21×41, 41×41, and 61×41 pixels; each was placed at upper phantom edge. The radial ROI’s length was 41 pixels and placed at several points in phantom edge. The MTF calculation was automatically conducted using MATLAB. The MTFs from rectangular ROIs and radial ROI were then compared. The comparison of the MTF measurement was also conducted using three different filters. The MTF which used radial ROI was smoother than those of rectangular ROI for all filters. This indicated that radial ROI was more resistant to noise than rectangular ROI. Rectangular ROI with the 41×41 pixels had similar 50% and 10% MTF values with the radial ROI. The MTF value which was obtained using radial ROI is more accurate and robust than those obtained using rectangular ROI.
Co-Authors Ariij Naufal Choirul Anam AM Diponegoro Geoff Dougherty Mohammad Haekal Nazil Ainurrofik Riska Amilia Wahyu S. Budi Zaenul Muhlisin