Performance of three model-based iterative reconstruction algorithms using a CT task-based image quality metric

TL;DR

This study compares the task-based image quality of three CT scanners using different model-based iterative reconstruction levels, showing how detectability varies with reconstruction method and dose, aiding protocol optimization.

Contribution

It introduces a comprehensive evaluation of CT image quality using task-based metrics across different vendors and MBIR levels, highlighting differences in detectability.

Findings

Advanced MBIR yields higher detectability index (d')

Different CT systems show varying noise power spectrum behaviors

Detectability index can guide dose reduction and protocol optimization

Abstract

In this study we evaluated the task-based image quality of a low contrast clinical task for the abdomen protocol (e.g., pancreatic tumour) of three different CT vendors, exploiting three model-based iterative reconstruction (MBIR) levels. We used three CT systems equipped with a full, partial, advanced MBIR algorithms. Acquisitions were performed on a phantom at three dose levels. Acquisitions were reconstructed with a standard kernel, using filtered back projection algorithm (FBP) and three levels of the MBIR. The noise power spectrum (NPS), the normalized one (nNPS) and the task-based transfer function (TTF) were computed following the method proposed by the American Association of Physicists in Medicine task group report-233 (AAPM TG-233). Detectability index (d') of a small lesion (small feature; 100 HU and 5-mm diameter) was calculated using non-prewhitening with eye-filter model observer (NPWE).The nNPS, NPS and TTF changed differently depending on CT system. Higher values of d' were obtained with advanced-MBIR, followed by full-MBIR and partial-MBIR.Task-based image quality was assessed for three CT scanners of different vendors, considering a clinical question. Detectability can be a tool for protocol optimisation and dose reduction since the same dose levels on different scanners correspond to different d' values.