Radiation Dose Optimization in Pediatric Chest CT: Major Indicators of Dose Exposure in 1695 CT Scans over Seven Years

Abstract

Purpose To analyze possible influencing factors on radiation exposure in pediatric chest CT using different approaches for radiation dose optimization and to determine major indicators for dose development.

Materials and Methods In this retrospective study at a clinic with maximum care facilities including pediatric radiology, 1695 chest CT examinations in 768 patients (median age: 10 years; range: 2 days to 17.9 years) were analyzed. Volume CT dose indices, effective dose, size-specific dose estimate, automatic dose modulation (AEC), and high-pitch protocols (pitch ≥ 3.0) were evaluated by univariate analysis. The image quality of low-dose examinations was compared to higher dose protocols by non-inferiority testing.

Results Median dose-specific values annually decreased by an average of 12 %. High-pitch mode (n = 414) resulted in lower dose parameters (p < 0.001). In unenhanced CT, AEC delivered higher dose values compared to scans with fixed parameters (p < 0.001). In contrast-enhanced CT, the use of AEC yielded a significantly lower radiation dose only in patients older than 16 years (p = 0.04). In the age group 6 to 15 years, the values were higher (p < 0.001). The diagnostic image quality of low-dose scans was non-inferior to high-dose scans (2.18 vs. 2.14).

Conclusion Radiation dose of chest CT was reduced without loss of image quality in the last decade. High-pitch scanning was an independent factor in this context. Dose reduction by AEC was limited and only relevant for patients over 16 years.

Key Points

• The radiation dose of pediatric chest CT was reduced in the last decade.

• High-pitch scanning is an independent factor of dose optimization.

• Dose reduction by AEC is limited and only relevant for older children.

Citation Format

• Esser M, Hess S, Teufel M et al. Radiation Dose Optimization in Pediatric Chest CT: Major Indicators of Dose Exposure in 1695 CT Scans over Seven Years. Fortschr Röntgenstr 2018; 190: 1131 – 1140

Zusammenfassung

Ziel Analyse möglicher Einflussfaktoren auf die Strahlenexposition bei der Thorax-CT des Kindes unter Anwendung verschiedener Methoden der Dosisoptimierung und Bestimmung von Kenngrößen für die Dosisentwicklung.

Material und Methoden In dieser retrospektiven Studie an einer Klinik der Maximalversorgung einschließlich einer Abteilung für Kinderradiologie wurden 1695 Thorax-CTs von 768 Patienten (mittleres Alter, 10 Jahre; Spannweite, zwei Tage bis 17,9 Jahre) analysiert. Volumen-CT-Dosisindex, effektive Dosis und size-specific dose estimate, automatische Dosismodulation (AEC), sowie High-Pitch-Protokolle (Pitch ≥ 3,0) wurden mittels univariater Analyse ausgewertet. Die Bildqualität von Niedrigdosis-Untersuchungen wurde zu Protokollen mit höherer Dosis mittels „Non-Inferiority“-Analyse verglichen.

Ergebnisse Die medianen Dosiswerte sanken pro Jahr um durchschnittlich 12 %. Untersuchungen mit High-Pitch-Modus (n = 414) lieferten geringere Dosiswerte (p < 0,001). In nativen Untersuchungen mit AEC ergaben sich höhere Dosiswerte im Vergleich zu Untersuchungen mit manuell festgelegten Parametern (p < 0,001). In kontrastangehobenen CTs erzielte die AEC nur bei Patienten über 16 Jahren signifikant niedrigere Dosiswerte (p = 0,04). Im Alter von 6 bis 15 Jahren waren die Dosiswerte mit AEC höher (p < 0,001). Die diagnostische Bildqualität von Niedrigdosis-Untersuchungen war den CTs mit höherer Dosis nicht unterlegen (2,18 vs. 2,14).

Schlussfolgerung Im letzen Jahrzehnt wurden die Dosiswerte der Thorax-CT ohne Verlust der Bildqualität reduziert. High-Pitch-Protokolle sind in diesem Zusammenhang ein unabhängiger Einflussfaktor. Die Dosisreduktion mittels AEC war beschränkt und nur für Patienten über 16 Jahren relevant.

Kernaussagen

• Im letzten Jahrzehnt konnte die Strahlendosis der Thorax-CT bei Kindern reduziert werden.

• Die Untersuchung mit hohen Pitch-Werten ist ein unabhängiger Faktor der Dosisoptimierung.

• Die Dosisreduktion der AEC ist beschränkt und nur für ältere Kinder relevant.

Key words

thorax - CT-spiral - radiation safety

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