Arnold Schilham PhD, Presenter: Nothing to Disclose

Aart J. Van Der Molen MD, Abstract Co-Author: Nothing to Disclose

Paul Stoop PhD, Abstract Co-Author: Nothing to Disclose

Ischa de Waard-Schalkx, Abstract Co-Author: Nothing to Disclose

Jacob Geleijns PhD, Abstract Co-Author: Nothing to Disclose

Mathias Prokop MD, PhD, Abstract Co-Author: Nothing to Disclose

To characterize CT practice in Dutch hospitals and to test a web survey for determination of the annual radiation dose to the Dutch population due to CT.

First, an inventory of CT practice was performed: a representative group of 21 academic and non-academic hospitals tallied all CT exams for a period of 2 weeks. From the data the relative contributions of protocols to annual CT dose was estimated. A Top 23 of protocols contributing most to CT dose was made (representing > 90% of the total annual CT dose and > 80% of the number of exams done in the Netherlands) and a web survey was designed. Second, the same 21 hospitals participated in a pilot study and completed the web survey for the 23 types of CT exams. For each scanner in the facility detailed dose-relevant questions about scan protocol for a real standard patient (73±3 kg, 176±4 cm) were filled in for each CT protocol. Effective dose per CT protocol was calculated using the ImPACT CT dose calculator, which was extended with data from current scanners and experimentally determined relations for tube current modulation and overranging. Dose levels for these 23 exams were compared to reported values of other countries. The contribution of overranging to patient dose was calculated.

Mean effective dose ranged from 0.2 mSv for sinus CT to 26.0 mSv for multi-phase liver CT protocol. The calculated dose levels in the Netherlands are lower than those of the German survey of 2001 but higher than the UK survey of 2003. Our pilot revealed 5-50% differences in dose between hospitals for most CT protocols, but for 5 protocols (thorax/abdomen, CTU, coronary CTA, abdominal aorta CTA, kidney tumor) the difference between hospitals exceeded 100%. Excess dose due to overranging caused more than 25% of patient dose in 23% of exams and more than 10% of dose in 80% of exams. A nationwide survey in all hospitals is currently underway.

The pilot study showed large differences between hospitals in patient dose for the most common CT protocols. A substantial part of the patient dose is excess dose due to overranging. 

Dose surveys contribute to dose-awareness. Our data can be used to select nation-wide best practice protocols and provides hospitals with means to benchmark and optimize their protocols.

Schilham, A, Van Der Molen, A, Stoop, P, de Waard-Schalkx, I, Geleijns, J, Prokop, M, Design and Pilot Results of the Dutch National Survey on CT Dose.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11005579.html