Target Volume Delineation for Preoperative Radiotherapy of Rectal Cancer: Inter-Observer Variability and Potential Impact of FDG-PET/CT Imaging

Abstract

To analyze the inter-observer variability and the potential impact of

Critical discussion of evaluation parameters for inter-observer variability in target definition for radiation therapy

“…The magnitude of this uncertainty is determined by several factors such as images used for delineation (image modality, resolution, contrast, and windowing), human factors (experience of observers, their professional background), and the presence of the guidelines or atlases for contouring [3,4,11,32,35,43,50,52]. The introduction of multimodality imaging in planning and delivery process (CT, MR, PET-CT) gives further promise of better target definition [16,19,26,30,34,38,44,45,47].…”

“…The first group is based on descriptive statistics and contains parameters describing the distribution of volumes, such as mean, standard deviation, standard error, range, ratio of the largest drawn volume to the smallest one, and dispersion of the distribution, i.e., coefficient of variation (COV). COV is a popular parameter [2,13,19,25,26,43,51] as it provides the measure of dispersion of the distribution in a single number and can be easily correlated with other parameters of interest.…”

“…Due to the variety of used metrics (common to encompassing volume ratio, Jaccard index, or Dice similarity coefficient, etc. ), it represents the domain where harmonization in reporting is lacking [2,5,6,8,10,19,22,24,25,26,29,32,34,37,38,41,42,44,45,46,48,51,52,53]. When moving to 3D representation, metrics such as variation of the center of mass (COM) allow the evaluation of the volume displacement in space [3,10,25,37,46,47,52,53].…”

Delineation of the larynx as organ at risk in radiotherapy: a contouring course within “Rete Oncologica Piemonte-Valle d’Aosta” network to reduce inter- and intraobserver variability

“…Some studies evaluated the variability in target volume delineation using descriptive statistics and parameters describing the distribution of volumes and diameters, such as mean, standard deviation, range, and dispersion of the distribution, such as COV [21][22][23][24][25][26][27][28]. The majority of studies deal with approaches that describe the overlapping area between contoured volumes, using metrics, such as CI and DC [22][23][24][26][27][28][29][30][31]. Moreover, when moving to 3D representation, metrics, such as variation of the COM, allow to evaluate the volume displacements in space [27,32,33].…”

Clinical application of multimodality imaging in radiotherapy treatment planning for rectal cancer

“…This contouring process significantly reduces the interobserver variability in the interpretation of images, as it eliminates the human factor, increases consistency, and diminishes interobserver variability [ 42 , 43 ] . Krengli et al [ 44 ] analyzed the interobserver variation for target volume delineation in preoperative radiotherapy of rectal cancer, and concluded that PET/CT may allow a reduced interobserver variation in GTV delineation in comparison with CT. Buijsen et al [ 45 ] analyzed the effect of the use of PET/CT on the interobserver variation in GTV definition in rectal cancer. Forty-two patients diagnosed with rectal cancer underwent PET/CT for radiotherapy planning.…”