Implementation of Institutional Size-Specific Diagnostic Reference Levels for CT Angiography

Yan Klosterkemper; Christoph Thomas; Oliver T Bethge; Elisabeth Appel; Joel Aissa; Judith Boeven; Gerald Antoch; Johannes Boos

doi:10.1016/j.acra.2019.01.019

Implementation of Institutional Size-Specific Diagnostic Reference Levels for CT Angiography

Acad Radiol. 2019 Dec;26(12):1661-1667. doi: 10.1016/j.acra.2019.01.019. Epub 2019 Feb 22.

Authors

Yan Klosterkemper¹, Christoph Thomas¹, Oliver T Bethge¹, Elisabeth Appel², Joel Aissa¹, Judith Boeven¹, Gerald Antoch¹, Johannes Boos¹

Affiliations

¹ University Duesseldorf, Department of Diagnostic and Interventional Radiology, Moorenstraße 5, 40225 Duesseldorf, Germany.
² University Duesseldorf, Department of Diagnostic and Interventional Radiology, Moorenstraße 5, 40225 Duesseldorf, Germany; Division of Abdominal Imaging, Department of Radiology, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Harvard Medical School, Boston, Massachusetts. Electronic address: elisabeth.appel@med.uni-duesseldorf.de.

PMID: 30803896
DOI: 10.1016/j.acra.2019.01.019

Abstract

Rationale and objectives: To generate institutional size-specific diagnostic reference levels (DRLs) for computed tomography angiography (CTA) examinations and assess the potential for dose optimization compared to size-independent DRLs.

Materials and methods: CTA examinations of the aorta, the pulmonary arteries and of the pelvis/lower extremity performed between January 2016 and January 2017 were included in our retrospective study. Water equivalent diameter (Dw) was automatically calculated for each patient. The relationship between Dw and computed tomography dose index (CTDI_vol) was analyzed and the 75th percentile was chosen as the upper limit for institutional DRLs. Size-specific institutional DRLs were compared to national size-independent DRLs from Germany and the UK.

Results: A total of 1344 examinations were included in our study (n = 733 aortic CTA, n = 406 pulmonary CTA, n = 205 pelvic/lower extremity CTA). Mean Dw was 26 ± 9 cm and mean CTDI_vol was 7.0 ± 4.6 mGy. For all CTA protocols, there was a linear progression of CTDI_vol with increasing Dw with an R² = 0.95 in aortic CTA, R² = 0.94 in pulmonary CTA and R² = 0.93 in pelvic/lower extremity CTA. Median CTDI_vol increased by 0.57 mGy per additional cm Dw in aortic CTA, by 1.1 mGy in pulmonary CTA and by 0.31 mGy in pelvic/lower extremity CTA. Institutional DRLs were lower than national DRLs for average size patients (aortic CTA: Dw 28.2 cm, CTDI_vol 7.6 mGy; pulmonary CTA, Dw 27.9 cm, CTDI_vol 11.8 mGy; pelvic/lower extremity CTA, Dw 20.0 cm, CTDI_vol 6.4 mGy). More dose outliers in small patients were detected with size-specific DRLs compared to national size-independent DRLs (56.4% vs 16.2%).

Conclusion: We implemented institutional size-specific DRLs for CTA examinations which enabled a more precise analysis compared to national sizeindependent DRLs.

Keywords: Dose monitoring; computed tomography angiography; radiation protection; size-specific diagnostic reference levels.

MeSH terms

Aged
Aorta / diagnostic imaging*
Computed Tomography Angiography / methods*
Feasibility Studies
Female
Humans
Lower Extremity / blood supply*
Lower Extremity / diagnostic imaging
Male
Pelvis / blood supply*
Pelvis / diagnostic imaging
Pulmonary Artery / diagnostic imaging*
Radiation Dosage
Reference Values
Reproducibility of Results