European Radiology

, Volume 30, Issue 2, pp 1075–1078 | Cite as

Optimization of radiation dose for CT detection of lytic and sclerotic bone lesions: a phantom study

  • J. GreffierEmail author
  • J. Frandon
  • F. Pereira
  • A. Hamard
  • J. P. Beregi
  • A. Larbi
  • P. Omoumi
Computed Tomography



To determine the best compromise between low radiation dose and suitable image quality for the detection of lytic and sclerotic bone lesions of the lumbar spine and pelvis.


A phantom was scanned using the routine protocol (STD, 13 mGy) and six decreasing dose levels. Raw data were reconstructed using level 3 of iterative reconstruction (IR3) with 1-mm slice thickness for the STD protocol and highest IR levels with 3-mm slice thickness for the others. CTDIvol was used for radiation dose assessment. Quantitative criteria (noise power spectrum [NPS], task-based transfer function [TTF], and the detectability index [d′]), as well as qualitative analysis, were used to compare protocols. NPS and TTF were computed using specific software (imQuest). d′ was computed for two imaging tasks: lytic and sclerotic bone lesions. A subjective analysis was performed to validate the image quality obtained on the anthropomorphic phantom with the different dose values.


Similar d′ values were found for CTDIvol from 3 to 4 mGy with IR4 and from 1 to 2 mGy for IR5 compared with d′ values using the STD protocol. Image quality was validated subjectively for IR4 but rejected for IR5 (image smoothing). Finally, for the same d′, the dose was reduced by 74% compared with the STD protocol, with the CTDIvol being 3.4 mGy for the lumbar spine and for the pelvis.


A dose level as low as 3.4 mGy, in association with high levels of IR, provides suitable image quality for the detection of lytic and sclerotic bone lesions of the lumbar spine and pelvis.

Key Points

• A CTDI vol of 3.4 mGy, in association with high iterative reconstruction level, provides suitable image quality for the detection of lytic and sclerotic bone lesions, both at objective and subjective analysis.

• Compared with the standard protocol, radiation dose can be reduced up to 74% for the lumbar spine and pelvis.

• A task-based image quality assessment using  the detectability index represents an objective method for the assessment of image quality and bridges the gap between complex physical metrics and subjective image analysis.


Multidetector computed tomography Image enhancement Image reconstruction Spine 



Computed tomography


Volume-computed tomography dose index


Detectability index


Dose length product


Effective dose


Edge-spread function


Filtered back projection


Iterative reconstruction


Line-spread function


Noise power spectrum


Nonprewhitening observer model with eye filter


Region of interest


Sinogram-affirmed iterative reconstruction


Standard protocol


Task-based transfer function



We are deeply grateful to Dr. J. Solomon for support regarding the use of the imQuest software.

Funding information

The authors state that this work has not received any funding.

Compliance with ethical standards


The scientific guarantor of this publication is Jean Paul Beregi.

Conflict of interest

The authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article.

Statistics and biometry

No complex statistical methods were necessary for this paper.

Informed consent

Written informed consent was not required for this study because this is a phantom study.

Ethical approval

Institutional Review Board approval was not required because this is a phantom study.


• experimental

• Performed at one institution

Supplementary material

330_2019_6425_MOESM1_ESM.docx (11.7 mb)
ESM 1 (DOCX 11.6 MB)


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Copyright information

© European Society of Radiology 2019

Authors and Affiliations

  1. 1.Service d’imagerie medicale, CHU NimesUniv Montpellier, Medical Imaging Group NimesNîmes Cedex 9France
  2. 2.Department of Diagnostic and Interventional RadiologyLausanne University Hospital and University of LausanneLausanneSwitzerland

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