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Effects of different levels of CT iterative reconstruction on low-contrast detectability and radiation dose in patients of different sizes: an anthropomorphic phantom study

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Abstract

Purpose

The purpose of this study was to verify the maintenance of low-contrast detectability at different CT dose reduction levels, in patients of different sizes, as a consequence of the application of iterative reconstruction at different strengths combined with tube current modulation.

Methods

Anthropomorphic abdominal phantoms of two sizes (small and large) were imaged at a fixed noise with iterative algorithm ASIR-V percentages in the range between 0 and 70% and corresponding dose reductions in the range of 0–83%. A total of 1400 images with and without liver low-contrast simulated lesions were evaluated by five radiologists, using the receiver operating characteristics (ROC) paradigm and evaluating the area under the ROC curve (AUC). The human observer results were then compared with AUC obtained with a channelized Hotelling observer (CHO). CNR values were also calculated.

Results

For the small phantom, the AUC values lie between 0.90 and 0.93 for human evaluations of images acquired without iterative reconstruction, with 30% ASIR-V and with 50% ASIR-V. The AUC decreased significantly to 0.81 (p = 0.0001) at 70% ASIR-V. The CHO results were in coherence with human observer scores. Also, similar results were observed for the large size phantom. CNR values were stable for the different ASIR-V percentages.

Conclusions

The iterative algorithm maintained the low-contrast detectability up to a dose reduction of about 70%, following application of a 50% ASIR-V combined with automatic tube current modulation, regardless of the phantom size. At further dose reductions using greater iterative percentages, a significant decrease in detectability was observed.

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Abbreviations

AUC:

Area under the curve

AFC:

Alternative force choice

CHO:

Channelized Hotelling observer

CNR:

Contrast–noise ratio

DR:

Dose reduction

FBP:

Filtered back projection

FD:

Full dose

IR:

Iterative reconstruction

LCD:

Low-contrast detectability

NI:

Noise index

ROC:

Receiver operating characteristics

TCM:

Tube current modulation

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Acknowledgements

This work was supported, in part, by grant from the project “Procedure radiologiche: informazione della dose al paziente” Compagnia San Paolo Torino.

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Authors and Affiliations

  1. Medical Physics Unit, S.C. Fisica Sanitaria, A.O.U. Città della Salute e della Scienza di Torino, Corso Bramante 88, 10126, Turin, Italy

    Osvaldo Rampado & Roberto Ropolo

  2. University Radiodiagnostic Unit, A.O.U. Città della Salute e della Scienza di Torino, Corso Bramante 88, 10126, Turin, Italy

    Alessandro Depaoli, Filippo Marchisio, Marco Gatti, Valeria Ruggeri, Irene Ruggirello, Fatemeh Darvizeh & Paolo Fonio

  3. Institute of Radiation Physics, Lausanne University Hospital, Rue du Grand-Pré 1, 1007, Lausanne, Switzerland

    Damien Racine

Authors
  1. Osvaldo Rampado
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  2. Alessandro Depaoli
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  3. Filippo Marchisio
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  4. Marco Gatti
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  5. Damien Racine
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  6. Valeria Ruggeri
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  7. Irene Ruggirello
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  8. Fatemeh Darvizeh
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  9. Paolo Fonio
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  10. Roberto Ropolo
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Corresponding author

Correspondence to Osvaldo Rampado.

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The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Research involving human participants and/or animals

This is a phantom study without involving human or animals.

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Not needed being a phantom study.

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Rampado, O., Depaoli, A., Marchisio, F. et al. Effects of different levels of CT iterative reconstruction on low-contrast detectability and radiation dose in patients of different sizes: an anthropomorphic phantom study. Radiol med 126, 55–62 (2021). https://doi.org/10.1007/s11547-020-01228-5

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  • DOI: https://doi.org/10.1007/s11547-020-01228-5

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