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CC BY-NC-ND 4.0 · Indian J Radiol Imaging 2019; 29(01): 53-60
DOI: 10.4103/ijri.IJRI_124_18
Radiophysics

The investigation of dose and image quality of chest computed tomography using different combinations of noise index and adaptive statistic iterative reconstruction level

Supawitoo Sookpeng
Department of Radiological Technology, Faculty of Allied Health Sciences, Naresuan University, Phitsanulok, Thailand
,
Colin J Martin
Department of Clinical Physics, University of Glasgow, Glasgow, UK
,
Chitsanupong Butdee
Department of Radiological Technology, Faculty of Allied Health Sciences, Naresuan University, Phitsanulok, Thailand
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Subject Editor: Financial support and sponsorship Nil.
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Abstract

Background: Computed tomography (CT) automatic tube current modulation (ATCM) systems and iterative reconstruction (IR) play an important role in CT radiation dose optimization. How the two can best be used together is one of the challenges faced by radiology professionals. Aim: To determine optimum settings of ATCM noise index (NI) together with adaptive statistic iterative reconstruction (ASIR) for a general electric (GE) scanner that aims to achieve similar image quality to the standard protocol used in the hospital (Smart mA technique with NI of 11.57 and 30% ASIR reconstruction) with a lower dose. Methods: Different NI and ASIR levels were set for scans of a phantom. Objective image quality assessments in terms of noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), low-contrast detectability (LCD), and modulation transfer function (MTF) were carried out in an anthropomorphic chest and a Catphan 700 phantom. Subjective image quality assessment was also performed with five readers to confirm whether the image quality of the new protocols was adequate. Result and Conclusion: SNR and CNR increased with the strength of ASIR, and decreased with higher NI settings. The MTF improved slightly for higher dose levels and from filtered back projection (FBP) to higher strength of ASIR. LCD improved with ASIR compared to FBP and with higher strengths of ASIR. Qualitative scoring ranged between 3.0 and 4.6. A moderate degree of reliability was found between scoring. Use of NI 15.04 with 70% ASIR can reduce dose by 41% compared to the standard protocol of NI 11.57 with 30% ASIR without degradation of image quality.

Keywords

Adaptive statistic iterative reconstruction - automatic tube current modulation - computed tomography optimization


Publication History

Article published online:
23 July 2021

© 2019. Indian Radiological Association. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial-License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/).

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