Spatial Distribution of Noise Reduction in Four Iterative Reconstruction Algorithms in CT-A Technical Evaluation.

Anette Guleng,Daniel Aadnevik,Kirsten Bolstad,Silje Flatabø,Ingvild Dalehaug,Helge E S Pettersen

doi:10.3390/diagnostics10090647

Anette Guleng, Daniel Aadnevik + Show 4 more

Open Access

https://doi.org/10.3390/diagnostics10090647

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Abstract

Iterative reconstruction (IR) is a computed tomgraphy (CT) reconstruction algorithm aiming at improving image quality by reducing noise in the image. During this process, IR also changes the noise properties in the images. To assess how IR algorithms from four vendors affect the noise properties in CT images, an anthropomorphic phantom was scanned and images reconstructed with filtered back projection (FBP), and a medium and high level of IR. Each image acquisition was performed 30 times at the same slice position, to create noise maps showing the inter-image pixel standard deviation through the 30 images. We observed that IR changed the noise properties in the CT images by reducing noise more in homogeneous areas than at anatomical edges between structures of different densities. This difference increased with increasing IR level, and with increasing difference in density between two adjacent structures. Each vendor’s IR algorithm showed slightly different noise reduction properties in how much noise was reduced at different positions in the phantom. Users need to be aware of these differences when working with optimization of protocols using IR across scanners from different vendors.

Highlights

Since computed tomography (CT) was introduced in the 1970s, it has become an indispensable tool in diagnostic medicine
Our study extends their work by including four Iterative reconstruction (IR) algorithms from different vendors, which to our knowledge has not been attempted in any previous studies
IR more noise is reduced in homogeneous areas and less at anatomical edges, making the spatial distribution of the noise more heterogeneous compared to filtered back projection (FBP)

Summary

Introduction

Since computed tomography (CT) was introduced in the 1970s, it has become an indispensable tool in diagnostic medicine. While a CT scan gives life saving diagnostic information, there is a small risk associated with the X-ray radiation exposure involved in the procedure [1,2] For this reason, several technological advancements have focused on reducing the radiation dose necessary to obtain the desired image quality, like improvements in detector technology, the use of automatic tube current modulation and improvements in image reconstruction algorithms [3]. IR methods were re-introduced into daily clinical routine as faster computer technology made it practical to use, and today all CT vendors have developed their own IR algorithms. They are often used in addition to conventional

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