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European Radiology
Published in: European Radiology 10/2014

01-10-2014 | Physics

Automatic exposure control in CT: the effect of patient size, anatomical region and prescribed modulation strength on tube current and image quality

Authors: Antonios E. Papadakis, Kostas Perisinakis, John Damilakis

Published in: European Radiology | Issue 10/2014

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Abstract

Objectives

To study the effect of patient size, body region and modulation strength on tube current and image quality on CT examinations that use automatic tube current modulation (ATCM).

Methods

Ten physical anthropomorphic phantoms that simulate an individual as neonate, 1-, 5-, 10-year-old and adult at various body habitus were employed. CT acquisition of head, neck, thorax and abdomen/pelvis was performed with ATCM activated at weak, average and strong modulation strength. The mean modulated mAs (mAsmod) values were recorded. Image noise was measured at selected anatomical sites.

Results

The mAsmod recorded for neonate compared to 10-year-old increased by 30 %, 14 %, 6 % and 53 % for head, neck, thorax and abdomen/pelvis, respectively, (P < 0.05). The mAsmod was lower than the preselected mAs with the exception of the 10-year-old phantom. In paediatric and adult phantoms, the mAsmod ranged from 44 and 53 for weak to 117 and 93 for strong modulation strength, respectively. At the same exposure parameters image noise increased with body size (P < 0.05).

Conclusions

The ATCM system studied here may affect dose differently for different patient habitus. Dose may decrease for overweight adults but increase for children older than 5 years old. Care should be taken when implementing ATCM protocols to ensure that image quality is maintained.

Key Points

• ATCM efficiency is related to the size of the patient’s body.
• ATCM should be activated without caution in overweight adult individuals.
• ATCM may increase radiation dose in children older than 5 years old.
• ATCM efficiency depends on the protocol selected for a specific anatomical region.
• Modulation strength may be appropriately tuned to enhance ATCM efficiency.
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Metadata
Title
Automatic exposure control in CT: the effect of patient size, anatomical region and prescribed modulation strength on tube current and image quality
Authors
Antonios E. Papadakis
Kostas Perisinakis
John Damilakis
Publication date
01-10-2014
Publisher
Springer Berlin Heidelberg
Published in
European Radiology / Issue 10/2014
Print ISSN: 0938-7994
Electronic ISSN: 1432-1084
DOI
https://doi.org/10.1007/s00330-014-3309-4

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