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. 2024 Oct 4;58(4):580-587.
doi: 10.2478/raon-2024-0043. eCollection 2024 Dec 1.

Inter-observer variation in gross tumour volume delineation of oesophageal cancer on MR, CT and PET/CT

Ajra Secerov-Ermenc  1   2 , Primoz Peterlin  1 , Franc Anderluh  1 , Jasna But-Hadzic  1   2 , Ana Jeromen-Peressutti  1 , Vaneja Velenik  1   2 , Barbara Segedin  1   2
Affiliations

Inter-observer variation in gross tumour volume delineation of oesophageal cancer on MR, CT and PET/CT

Ajra Secerov-Ermenc et al. Radiol Oncol. .

Abstract

Background: The aim of our study was to assess the inter-observer variability in delineation of the gross tumour volume (GTV) of oesophageal cancer on magnetic resonance (MR) in comparison to computed tomography (CT) and positron emission tomography and CT (PET/CT).

Patients and methods: Twenty-three consecutive patients with oesophageal cancer treated with chemo-radiotherapy were enrolled. All patients had PET/CT and MR imaging in treatment position. Five observers independently delineated the GTV on CT alone, MR alone, CT with co-registered MR, PET/CT alone and MR with co-registered PET/CT. Volumes of GTV were measured per patient and imaging modality. Inter-observer agreement, expressed in generalized conformity index (CIgen), volumetric conformity index (VCI), planar conformity index (PCI) and inter-delineation distance (IDD) were calculated per patient and imaging modality. Linear mixed models were used for statistical analysis.

Results: GTV volume was significantly lower on MR (33.03 cm3) compared to CT (37.1 cm3; p = 0.002) and on PET/CT MR (35.2 cm3; p = 0.018) compared to PET/CT (39.1 cm3). The CIgen was lowest on CT (0.56) and highest on PET/CT MR (0.67). The difference in CIgen between MR (0.61) and CT was borderline significant (p = 0.048). The VCI was significantly higher on MR (0.71; p = 0.007) and on CT MR (0.71; p = 0.004) compared to CT (0.67). The PCI was significantly higher on CT MR (0.67; p = 0.031) compared to CT (0.64). The largest differences were observed in the cranio-caudal direction.

Conclusions: The highest inter-observer agreement was found for PET/CT MR and the lowest for CT. MR could reduce the difference in delineation between observers and provide additional information about the local extent of the tumour.

Keywords: gross tumour volume; magnetic resonance; oesophageal cancer; positron emission tomography.

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Figures

FIGURE 1.
FIGURE 1.
The coordinate system for spatial assessment of inter-delineation distances is projected on a single slice of imaging modality containing an example of GTV and divided in 12 angular segments (6 on the left and 6 on the right). Green line represents the reference contour, red line is the test contour.
FIGURE 2.
FIGURE 2.
Mean planar conformity index (PCI) for the GTV as a function of slice number for all imaging modalities for case 22. Blue = computed tomography (CT); Green = fusion of PET/CT and MR; Red = magnetic resonance imaging (MR); Violet = positron emission tomography and CT (PET/CT); Yellow = fusion of CT and MR (CT MR); 1= most caudal slice; 33= most cranial slice.
FIGURE 3.
FIGURE 3.
Delineation of the gross tumour volume (GTV) of all five observers of case 22, sagittal view. The variation in cranial border is highest on computed tomography (CT) and lowest on positron emission tomography (PET/CT) magnetic resonance (MR). (A) CT; (B) PET/CT; (C) fusion of CT and MR; (D) fusion of PET/CT and MR.
FIGURE 4.
FIGURE 4.
Mean inter-delineation distance (IDD) curves of the gross tumour volume (GTV) delineated on different imaging modalities as a function of the angle. The IDD is largest in tumours of the lower third and similar in upper and thirds. (A) Upper third of the oesophagus; (B) Middle third of the oesophagus; (C) Lower third of the oesophagus. Blue = computed tomography; Green = fusion of PET CT and MR. Red = magnetic resonance imaging; Violet = positron emission tomography and CT; Yellow = fusion of CT and MR
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