[Results of the Austrian CT dose study 2010: typical effective doses of the most frequent CT examinations]

Abstract

Purpose: To determine typical doses from common CT examinations of standard sized adult patients and their variability between CT operators for common CT indications.

Materials and methods: In a nationwide Austrian CT dose survey doses from approx. 10,000 common CT examinations of adults during 2009 and 2010 were collected and "typical" radiation doses to the "average patient", which turned out to have 75.6kg body mass, calculated. Conversion coefficients from DLP to effective dose were determined and effective doses calculated according to ICRP 103. Variations of typically applied doses to the "average patient" were expressed as ratios between 90(th) and 10(th) percentile (inter-percentile width, IPW90/10), 1(st) and 3(rd) quartile (IPW75/25), and Maximum/Minimum.

Results: Median effective doses to the average patients for standard head and neck scans were 1.8 mSv (cervical spine), 1.9 mSv (brain: trauma/bleeding, stroke) to 2.2 mSv (brain: masses) with typical variation between facilities of a factor 2.5 (IPW90/10) and 1.7 (IPW75/25). In the thorax region doses were 6.4 to 6.8 mSv (pulmonary embolism, pneumonia and inflammation, oncologic scans), the variation between facilities was by a factor of 2.1 (IPW90/10) and 1.5 (IPW75/25), respectively. In the abdominal region median effective doses from 6.5 mSv (kidney stone search) to 22 mSv (liver lesions) were found (acute abdomen, staging/metastases, lumbar spine: 9-12 mSv; oncologic abdomen plus chest 16 mSv; renal tumor 20 mSv). Variation factors between facilities were on average for abdominal scans 2.7 (IPW90/10) and 1.8 (IPW75/25).

Conclusion: Variations between CT operators are generally moderate for most operators, but in some indications the ratio between the minimum and the maximum of average dose to the typical standard patients exceeds a factor of 4 or even 5. Therefore, comparing average doses to Diagnostic Reference Levels (DRLs) and optimizing protocols need to be encouraged.

Keywords: CT; Diagnostic Reference Values; Optimierung; Patientendosis; Strahlenschutz; diagnostische Referenzwerte; effective dose; effektive Dosis; optimization; patient dose; radiation protection.