David F. Yankelevitz MD, Presenter: Research grant, OSI Pharmaceuticals, Inc Research grant, Carestream Health, Inc Research grant, GlaxoSmithKline plc Research grant, AstraZeneca PLC Royalties, patent Cornell Research Foundation licensed to General Electric Company

Helen Mann MSC, MS, Abstract Co-Author: Nothing to Disclose

Marietta Scott MS, PhD, Abstract Co-Author: Employee, AstraZeneca PLC, United Kingdom

Dana Cici Ghiorghiu, Abstract Co-Author: Employee, AstraZeneca PLC, United Kingdom

Alberto M. Biancardi PhD, Abstract Co-Author: Nothing to Disclose

Anthony P. Reeves PhD, Abstract Co-Author: Stockholder, VisionGate, Inc Patent agreement, General Electric Company Research grant, AstraZeneca PLC Research grant, GlaxoSmithKline plc Research grant, Carestream Health, Inc

To assess the influence of Computer Assisted Marking (CAM) and side by side viewing in measuring components of variability in volumetric assessment of lung nodules.

12 nodules ranging in volume from 29.1 mm3 to 27,700 mm3 on thin section CT images were presented in a random order to 8 readers. Volume was measured in two ways; by manually outlining the boundary on each slice and by using a novel method that allowed the reader to choose seed points on each slice with the computer completing the outline. Each reading was repeated for each method, and additional readings were also performed where the readers saw their original markings (side by side viewing). Manual and CAM intra and inter-reader components of variability (COV) were obtained using linear mixed effects models, incorporating random effects for reader and nodule.

The inter-reader variability was greater for manual reads (COV=11.2%) compared to the CAM method (COV=3.5%). The intra-reader variability was also greater for manual reads (COV=10.1%) compared with the CAM method (COV=6.7%). When readers were allowed to concurrently view their prior read, the between reader variability increased for the manual method (COV of side by side read=13.9%, COVs for non side by side reads=10.4%, 12.1%) and decreased for the CAM method (COV of side by side read=1.4%, COVs for non side by side reads=2.9%, 3.5%). The residual (unexplained) component of variability decreased for the CAM method (COV of side by side read=5.5%, COVs for non side by side reads=6.6%, 7.5%) and one of the manual read sessions (COV of side by side read=8.1%, COVs for non side by side reads=7.1%, 12.7%).

The CAM approach allows for improved repeatability. Side by side reading decreased the inter-reader and residual variability for the CAM method, while decreases were not consistently seen for the manual method. These findings suggest that each reader has a bias when manually determining the boundary and that when viewing side by side, the bias between readers is enhanced whereas it is minimized when using the CAM techniques.

Biases in measuring change in nodule volumes can be minimized by use of CAM and side by side viewing

Yankelevitz, D, Mann, H, Scott, M, Ghiorghiu, D, Biancardi, A, Reeves, A, Quantifying Variability in Nodule Volume Measurements.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9015952.html