Martin Hupfer PhD, Presenter: Employee, CT Imaging GmbH

Natalia Saltybaeva, Abstract Co-Author: Nothing to Disclose

Daniel Kolditz PhD, Abstract Co-Author: Employee, CT Imaging GmbH

Bernhard Schmidt PhD, Abstract Co-Author: Employee, Siemens AG

Willi A. Kalender PhD, Abstract Co-Author: Consultant, Siemens AG Consultant, Bayer AG Founder, CT Imaging GmbH Scientific Advisor, CT Imaging GmbH CEO, CT Imaging GmbH

Dose from localizer radiographs was considered negligible compared to dose from the CT examination itself. Due to recent technical improvements, dose from CT examinations has decreased substantially and therefore dose from localizer radiographs, which previously was not adding a relevant contribution to the effective dose, now may have to be taken into account. The aim of this work was to include and test dose calculations for localizer radiographs in a software package based on pre-calculated dose tables for estimates of effective dose.

Localizer functionality was integrated into the software package ImpactDose2.1 (CT Imaging GmbH, Erlangen, Germany), which estimates organ and effective dose in CT depending on patient size, scan region and scan protocol. It is based on pre-tabulated dose values calculated by Monte Carlo (MC) simulations performed on the ORNL family of phantoms as well as on the ICRP110 standard adult male and female phantoms. The validity of the MC software used for table generation was evaluated by point-by-point comparison of MC dose results with measurements performed by using a set of thermoluminescent dosimeters (TLD) in a Rando-Alderson phantom. New dose tables were generated for AP, PA and LAT localizer radiographs and added to the software tool.

The MC tool was successfully validated for localizer radiographs. The mean difference between TLD measurements and simulations was about 14 %. Effective dose values varied strongly depending on the type of localizer radiograph, for example, for males’ abdomen-pelvis region effective doses were 0.4 mSv and 0.2 mSv for AP and LAT localizer, respectively.

The optimal choice of the localizer direction (AP, PA, LAT) has a significant impact on dose and offers potential dose savings. Software based on MC pre-calculated tables provides within a few seconds accurate dose estimates for arbitrary CT examinations and localizer radiographs.

Dose from localizer radiographs may contribute significantly to total effective dose. Software tools allow fast and accurate patient dose calculations taking localizer radiograph dose into account.

Hupfer, M, Saltybaeva, N, Kolditz, D, Schmidt, B, Kalender, W, Fast and Easy Estimates of Dose from Localizer Radiographs in Clinical CT Based on Pre-calculated Monte Carlo Tables.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14017329.html