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European Radiology

, Volume 29, Issue 12, pp 6790–6793 | Cite as

How patient off-centering impacts organ dose and image noise in pediatric head and thoracoabdominal CT

  • André EulerEmail author
  • Natalia Saltybaeva
  • Hatem Alkadhi
Paediatric

Abstract

Objectives

To assess the impact of patient off-centering on organ dose and image noise for head and thoracoabdominal CT in a pediatric phantom.

Methods

An anthropomorphic phantom simulating a 5-year-old child was used. Semiconductor dosimeters were placed in various cranial and thoracoabdominal organs. Head and thoracoabdominal CT were performed using automatic tube current modulation (ATCM) and default bowtie filters. The phantom was imaged repeatedly at vertical table positions ranging from − 6 to + 6 cm from the 0-position. Tube current time products (TCTP), organ doses, and image noise were recorded. Scatter radiation was measured in the thyroid for head CT. The effect of ATCM and bowtie filters was assessed.

Results

Depending on patient position, organ doses differed up to 22% for the supratentorial brain, 34% for the infratentorial brain, 19% for the eyes, 28% for the lungs, 25% for the stomach, and 22% for the liver compared with those in the 0-position. The relation between position and dose was linear and mainly affected by the bowtie filter in head CT, while it was quadratic and affected by ATCM and bowtie filter in thoracoabdominal CT. It further depended on the relative position of each organ to the isocenter. An inverse relation was found between position and image noise. Scatter radiation was not significantly related to patient positioning (p = 0.21).

Conclusions

In pediatric CT, vertical patient positioning had a substantial impact on radiation dose with differences of up to 34%, depending on the body region and location of each individual organ.

Key Points

• Patient off-centering has a substantial impact on organ radiation dose and image noise in pediatric CT.

• Impact of patient off-centering on radiation dose and noise differs between head and thoracoabdominal CT.

• Differences are caused by both ATCM and bowtie filter in thoracoabdominal CT, but mainly by bowtie filter in head CT.

Keywords

Child Multidetector computed tomography Radiation exposure Radiation dosimeters Phantoms, imaging 

Abbreviations

ATCM

Automatic tube current modulation

TCTP

Tube current time product

Notes

Funding

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

Compliance with ethical standards

Guarantor

The scientific guarantor of this publication is André Euler.

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

One of the authors has significant statistical expertise.

Informed consent

Not needed because of the design as a phantom study.

Ethical approval

Institutional Review Board approval was not required because of the design as a phantom study.

Methodology

• prospective

• experimental

• performed at one institution

Supplementary material

330_2019_6330_MOESM1_ESM.docx (670 kb)
ESM 1 (DOCX 669 kb)

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Copyright information

© European Society of Radiology 2019

Authors and Affiliations

  1. 1.Institute for Diagnostic and Interventional RadiologyUniversity Hospital Zurich, University of ZurichZurichSwitzerland

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