Andreas Christe, Presenter: Nothing to Disclose

Alain Brönnimann, Abstract Co-Author: Nothing to Disclose

Peter Vock MD, Abstract Co-Author: Nothing to Disclose

To compare two different post-processing software algorithms (LMS Lung, Median technologies and LungCARE, Siemens) in CT-volumetric measurement and to analyze the effect of soft (B30) and hard reconstruction filter (B70) on automated volume measurement.

Fifty-two patients with a total of 167 pulmonary nodules were included to compare the algorithms for soft reconstruction filters. In addition, five patients with a total of 13 nodules were recruited to compare the algorithms for hard reconstruction filters and study the influence of the filters on each algorithm. The CT-exam was performed on a 64 row multi-detector CT scanner (Somatom Sensation, Siemens, Erlangen, Germany) with a collimation of 24x1.2mm, a pitch of 1.15, 120 kVp voltage and reference tube current-time of 100 mAs. Automated volumetric measurement of each lung nodule was performed with the two different post-processing algorithms based on two reconstruction filters (B30 and B70).

At soft reconstruction filters the LMS system produced mean nodule volumes that were larger than those by LungCARE system: the mean relative volume measurement error (VME%) was 40% with a limit of agreement (LA) between -60% and 140%. The volume measurement with soft filters (B30) was significantly larger than with hard filters (B70): for LMS the volume measurement error was 20.5% (LA between -7.9% and 49%) and 5.9% (-9.8% to 21.6%) for LungCARE, respectively (both with p-values <0.05). LMS measured higher volumes for both filters with a VME of 20.3% for soft and 5.6% for hard filters, respectively (p<0.01 and p=0.17).

There is big inter-software (LMS/LungCARE) as well as intra-software variability (B30/B70) in lung nodule volume measurement: LMS and soft reconstruction filters showed significantly higher volumes. An increase of nodule volume of over 140% is more likely to be real nodule growth than inter-software variability, changing from LungCARE to a hypothetical LMS follow up exam. Therefore, it is mandatory to use the same equipment with the same reconstruction filter for the follow up of lung nodule volume.

There is significant variability among different volume measurement algorithms and reconstruction filters, that it is mandatory to use the same equipment for follow-up of lung nodules. 

Christe, A, Brönnimann, A, Vock, P, Volumetric Analysis of Lung Nodules in Computed Tomography (CT): Comparison of Two Different Segmentation Algorithm Softwares and Two Different Reconstruction Filters on Automated Volume Calculation.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11004711.html