Implementation of Size-Dependent Local Diagnostic Reference Levels for CT Angiography

Hub Boere, Nienke G. Eijsvoogel, Anna M. Sailer, Joachim E. Wildberger, Michiel W. de Haan, Marco Das, Cecile R. L. P. N. Jeukens*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


OBJECTIVE. Diagnostic reference levels (DRLs) are established for standard-sized patients; however, patient dose in CT depends on patient size. The purpose of this study was to introduce a method for setting size-dependent local diagnostic reference levels (LDRLs) and to evaluate these LDRLs in comparison with size-independent LDRLs and with respect to image quality. MATERIALS AND METHODS. One hundred eighty-four aortic CT angiography (CTA) examinations performed on either a second-generation or third-generation dual-source CT scanner were included; we refer to the second-generation dual-source CT scanner as "CT1" and the third-generation dual-source CT scanner as "CT2." The volume CT dose index (CTDI(vo)l) and patient diameter (i.e., the water-equivalent diameter) were retrieved by dose-monitoring software. Size-dependent DRLs based on a linear regression of the CTDIvol versus patient size were set by scanner type. Size-independent DRLs were set by the 5th and 95th percentiles of the CTDIvol values. Objective image quality was assessed using the signalto- noise ratio (SNR), and subjective image quality was assessed using a 4-point Likert scale. RESULTS. The CTDIvol depended on patient size and scanner type (R-2 = 0.72 and 0.78, respectively; slope = 0.05 and 0.02 mGy/mm; p < 0.001). Of the outliers identified by size-independent DRLs, 30% (CT1) and 67% (CT2) were adequately dosed when considering patient size. Alternatively, 30% (CT1) and 70% (CT2) of the outliers found with size-dependent DRLs were not identified using size-independent DRLs. A negative correlation was found between SNR and CTDIvol (R-2 = 0.36 for CT1 and 0.45 for CT2). However, all outliers had a subjective image quality score of sufficient or better. CONCLUSION. We introduce a method for setting size-dependent LDRLs in CTA. Size-dependent LDRLs are relevant for assessing the appropriateness of the radiation dose for an individual patient on a specific CT scanner.
Original languageEnglish
Pages (from-to)W226-W233
Number of pages8
JournalAmerican Journal of Roentgenology
Issue number5
Publication statusPublished - 1 May 2018


  • CT angiography
  • image quality
  • local diagnostic reference levels
  • radiation dose
  • size-dependent diagnostic reference levels
  • volume CT dose index (CTDI (vol))

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