How patient off-centering impacts organ dose and image noise in pediatric head and thoracoabdominal CT
To assess the impact of patient off-centering on organ dose and image noise for head and thoracoabdominal CT in a pediatric phantom.
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.
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).
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.
• 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.
KeywordsChild Multidetector computed tomography Radiation exposure Radiation dosimeters Phantoms, imaging
Automatic tube current modulation
Tube current time product
The authors state that this work has not received any funding.
Compliance with ethical standards
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.
Not needed because of the design as a phantom study.
Institutional Review Board approval was not required because of the design as a phantom study.
• performed at one institution