The relationship between CT scout landmarks and lung boundaries on chest CT: guidelines for minimizing excess z-axis scan length
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As the relationship between CT scout landmarks and chest CT boundaries is not known, the selected scan length is often greater than necessary for the CT scan, resulting in increased radiation dose to the neck and upper abdomen. The purpose of this study is to establish the relationship between CT scout landmarks with the superior and inferior boundaries of the lungs on chest CT.
Retrospective comparison of the location of the top of the first rib on frontal scout and the most inferior costophrenic angle on lateral scout to the chest CT slice just above and below the lungs. The percent of scans that would exclude part of the lung based on CT initiated at several distances above or below these landmarks was calculated.
There was 2.7 times greater variability between scout landmarks and lung boundaries inferiorly than superiorly on chest CT (p < 0.001). Initiating CT at the top of the first rib on scout did not exclude any lung on CT. Initiating CT 0, 1, 2, 3, and 4 cm inferior to the CPA on lateral scout excluded part of the lung in 45.7%, 12.9%, 4.3%, 1.9%, and 0.8% of CTs.
Chest CT to include the lungs should be performed from the top of the first rib to 3 or 4 cm below the costophrenic angle on lateral topogram.
• There is a greater motion at the inferior lung than at the superior lung.
• Chest CT acquisition from the top of the first rib on scout would not exclude the lung.
• Chest CT acquisition from CPA on lateral scout would exclude the lung 46% of time.
KeywordsThorax Radiation dosage Tomography X-ray computed
Picture archiving and communication system
The authors state that this work has not received any funding.
Compliance with ethical standards
The scientific guarantor of this publication is Stuart Cohen.
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.
Written informed consent was waived by the Institutional Review Board.
Institutional Review Board approval was obtained.
• performed at one institution
- 3.O’Connor GT, Hatabu H (2012) Lung cancer screening, radiation, risks, benefits, and uncertainty. JAMA 307:2434–2435Google Scholar
- 9.(2002) The ALARA (as low as reasonably achievable) concept in pediatric CT intelligent dose reduction. Multidisciplinary conference organized by the Society of Pediatric Radiology. August 18-19, 2001. Pediatr Radiol 32:217–313Google Scholar
- 10.Strauss KJ, Kaste SC (2006) The ALARA (as low as reasonably achievable) concept in pediatric interventional and fluoroscopic imaging: striving to keep radiation doses as low as possible during fluoroscopy of pediatric patients—a white paper executive summary. Pediatr Radiol 36:110–112CrossRefGoogle Scholar
- 20.Cohen SL, Ward TJ, Jacobi AH, Cham M (2019) Institutional impact of a personalized technologist feedback program on scan length and radiation dose. J Am Coll Radiol. https://doi.org/10.1016/j.jacr.2019.02.001
- 21.Schwartz F, Stieltjes B, Szucs-Farkas Z, Euler A (2018) Over-scanning in chest CT: comparison of practice among six hospitals and its impact on radiation dose. Eur J Radiol 102:49–54Google Scholar
- 22.Noh DK, Lee JJ, You JH (2014) Diaphragm breathing movement measurement using ultrasound and radiographic imaging: a concurrent validity. Biomed Mater Eng 24:947–952Google Scholar
- 24.R Development Core Team (2010) R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, AustriaGoogle Scholar
- 25.Frank EL, Bruce Smith, Barbara. (2013) Merrill’s atlas of radiographic positioning and procedures - E-Book: Volume 3. Elsevier Mosby, St. LouisGoogle Scholar
- 27.Shepard JA (2019) Thoracic imaging the requisites (requisites in radiology), 3rd edn. Elsevier, PhiladelphiaGoogle Scholar
- 29.Kalra MK, Sodickson AD, Mayo-Smith WW (2015) CT radiation: key concepts for gentle and wise use. Radiographics 35:1706–1721Google Scholar