Statistical analysis for obtaining optimum number of CT scanners in patient dose surveys for determining national diagnostic reference levels
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To statistically determine an ‘optimum number of CT scanners’ for obtaining ‘diagnostic reference levels’ (DRLs) in CT examinations as close as possible to ‘ideal DRLs’ when all available CT scanners are considered.
First, six ‘ideal DRLs’ (CTDIVol and DLP) were determined for head, chest and abdomen/pelvis examinations by using patient-dose survey data of 100 CT scanners of different models in Tehran. Then, a ‘random sampling method’ was applied to different percent fractions of patient dose data of 100 CT scanners. The percent differences (PD) of the DRLs obtained from ‘ideal DRLs’ and their coefficients of variation (CVs) were calculated. The ‘optimum number of CT scanners’ determined met those of ‘ideal DRL’ criteria; i.e. precision (CV ≤ 10%) and accuracy (PD ≤ 10%).
‘Optimum number of CT scanners’ for determining DRLs as close as possible to ‘ideal DRLs’, fulfilling the stated criteria, is 43 instead of using 100.
‘Optimum number of CT scanners’ for obtaining DRLs as close as possible to ‘ideal DRLs’ was determined. This optimum number can be effectively applied in patient-dose survey situations with limited resources in a time- and cost-effective manner.
• Ideal DRLs were determined by a CT patient-dose survey applied to available scanners.
• ‘Optimum number of CT scanners’ statistically determined for DRLs is 43%.
• Optimum number can be used for DRLs as if ‘ideal DRLs’ were determined by all scanners.
KeywordsSurveys and questionnaires Radiation protection Statistics Radiation dosage Tomography scanners, X-ray computed
Volume computed tomography dose index
Coefficient of variation
Dose length product
Diagnostic reference level
The authors state that this work has been carried out under the current budget of the Amirkabir University of Technology with partial support from the Iranian National Science Foundation through Grant No. 96006106.
Compliance with ethical standards
The scientific guarantor of this publication is Prof. Mehdi Sohrabi from the Amirkabir University of Technology.
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 (Dr. Sanaz Hariri Tabrizi) has significant statistical expertise.
No complex statistical methods were necessary for this paper.
Written informed consent was not required for this study because the study was based on the ‘QC-based dose-survey method’, which required no information about the CT institutes or any particular patients.
Institutional Review Board approval was not required because the study is based on CT scanner models, which do not involve ethical issues.
• multicentre study
- 1.United Nations Scientific Committee on the Effects of Atomic Radiation (2008) Report Vol. I. Sources and effects of ionizing radiation. United Nations Sales Publications, New YorkGoogle Scholar
- 2.National Council on Radiation Protection and Measurements (2009) Report No. 160. Ionizing radiation exposure of the population of the United States. NCRP, BethesdaGoogle Scholar
- 3.European Commission (2008) European guidance on estimating population doses from medical X-ray procedures. Report Radiation Protection 154 (with Annexes)Google Scholar
- 4.International Commission on Radiological Protection (2000) ICRP Publication 87. Managing patient dose in computed tomography. Ann ICRP 30(4)Google Scholar
- 5.International Commission on Radiological Protection (1991) ICRP Publication 60. 1990 recommendations of the International Commission on Radiological Protection. Ann ICRP 21(1–3)Google Scholar
- 6.International Commission on Radiological Protection (1996) ICRP Publication 73. Radiological protection and safety in medicine. Ann ICRP 26(2)Google Scholar
- 7.European Commission (1999) European guidelines on quality criteria for computed tomography. Report EUR 16262. Brussels, BelgiumGoogle Scholar
- 8.International Commission on Radiological Protection (2007) ICRP Publication 102. Managing Patient Dose in Multi-Detector Computed Tomography (MDCT). Ann ICRP 37(1)Google Scholar
- 9.International Commission on Radiological Protection (2007) ICRP Publication 105. Radiological protection in medicine. Ann ICRP 37(6)Google Scholar
- 10.International Commission on Radiological Protection (2017) ICRP Publication 135. Diagnostic reference levels in medical imaging. Ann ICRP 46(1)Google Scholar
- 14.Sohrabi M, Parsi M, Mianji F (2017) Determination of national diagnostic reference levels in Computed Tomography examinations of Iran by a new quality control-based dose survey method. Radiat Prot Dosimetry 10:1–10Google Scholar
- 15.International Commission on Radiological Protection (2002) Supporting guidance 2. Diagnostic reference levels in medical imaging: review and additional advice. Annals ICRP 31(Suppl. 4):33–52Google Scholar