title: 3D Assessment of Lymph Nodes vs. RECIST 1.1.
abstract: OBJECTIVE
  In today's clinical practice, the size of lymph nodes is assessed by measuring the long and the short axis in the axial plane. This study compares this approach with three-dimensional (3D) assessment.
  
  
  METHODS
  For a representative set of 49 lymph nodes, the axes in the axial plane have been measured and a 3D model has been created manually. Based on the 3D model, the real axial long and short axis as well as the three 3D axes and the volume have been computed and compared to the measured axial axes.
  
  
  RESULTS
  The inter-observer variability is around 10% for all measured lengths and almost 16% for the computed volume. The average relative error of the measured long (short) axial axis is 9.73% (24.57%) to the computed axial axis and 25.05% (19.97%) to the computed 3D axis, respectively. The product of the axial long axis and the square of the axial short axis provides best correlation to the volume.
  
  
  CONCLUSIONS
  This study confirms Response Evaluation Criteria In Solid Tumours 1.1 that measuring the short axis is more robust than measuring the long axis because of less impact of the node's spatial orientation. Nonetheless it is shown that considering both axes is a better prognostic factor for the volume than measuring the short axis only.
authors.affiliation: Competence Center Medical Imaging, Fraunhofer IGD, Fraunhoferstrasse 5, 64283 Darmstadt, Germany. sebastian.steger@igd.fraunhofer.de
authors.forename: Sebastian
authors.initials: S
authors.lastname: Steger
authors.forename: Fabio
authors.initials: F
authors.lastname: Franco
authors.forename: Nicola
authors.initials: N
authors.lastname: Sverzellati
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Chiari
authors.forename: Ramon
authors.initials: R
authors.lastname: Colomer
mesh_terms: D000328:Adult; D000369:Aged, 80 and over; D000465:Algorithms; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008198:Lymph Nodes / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*