Interobserver variation in parotid gland delineation: a study of its impact on intensity-modulated radiotherapy solutions with a systematic review of the literature

Loo, Suat; Martin, W.M.C.; Smith, Paula Marincola; Cherian, Sheen; Roques, Tom

doi:10.1259/bjr/32038456

Cited by 35 publications

(19 citation statements)

References 73 publications

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“…Manual target volume and OAR delineation are affected by clinician variability [3]. Minimising interobserver variability will improve the accuracy of the dose delivered, maximise tumour control, limit toxicities and increase knowledge of organ at risk (OAR) dose [4][5][6]. Methods to standardise OAR volumes have been developed including superior imaging techniques, peer review and the development of contouring atlases [7].…”

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confidence: 99%

Use of a novel atlas for muscles of mastication to reduce inter observer variability in head and neck radiotherapy contouring

Hague

Beasley

Dixon

et al. 2019

Radiotherapy and Oncology

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Trismus is caused by injury to the masticatory muscles resulting from cancer or its treatment. Contouring these muscles to reduce dose and radiation related trismus can be problematic due to interobserver variability. This study aimed to evaluate the reduction in interobserver variability achievable with a new contouring atlas. Materials/methods: The atlas included: medial and lateral pterygoids (MP, LP), masseter (M) and temporalis (T) muscles, and the temporo-mandibular joint (TMJ). Seven clinicians delineated five paired structures on CT scans from 5 patients without the atlas. After 5 weeks, contouring was repeated using the atlas. Using contours generated by the clinicians on the same 5 CT scans as reference, dice similarity coefficient (DSC), mean distance-to-agreement (DTA) and centre of mass (COM) difference were compared with and without the atlas. Comparison was also performed split by training grade. Mean and standard deviation (SD) values were measured. Results: The atlas reduced interobserver variability for all structures. Mean DTA significantly improved for MP (p = 0.01), M (p < 0.01), T (p < 0.01) and TMJ (p < 0.01). Mean DTA improved using the atlas for the trainees across all muscles, with the largest reduction in variability observed for the T (4.3 ± 7.1 v 1.2 ± 0.4 mm, p = 0.06) and TMJ (2.1 ± 0.7 v 0.8 ± 0.3 mm, p < 0.01). Distance between the COM and interobserver variability reduced in all directions for MP and T. Conclusion: A new atlas for contouring masticatory muscles during radiotherapy planning for head and neck cancer reduces interobserver variability and could be used as an educational tool.

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mentioning

confidence: 99%

Use of a novel atlas for muscles of mastication to reduce inter observer variability in head and neck radiotherapy contouring

Hague

Beasley

Dixon

et al. 2019

Radiotherapy and Oncology

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“…Therefore, DW-MRI should always be used as an addition to high quality anatomical images. Other delineation studies in the head-and-neck area [28,29] show lower or similar CI gen Fig. 3.…”

Section: Discussionmentioning

confidence: 62%

Evaluation of diffusion weighted imaging for tumor delineation in head-and-neck radiotherapy by comparison with automatically segmented 18F-fluorodeoxyglucose positron emission tomography

Schäkel

Peltenburg

Dankbaar

et al. 2018

Physics and Imaging in Radiation Oncology

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Background and purpose: Diffusion weighted (DW) MRI may facilitate target volume delineation for head-andneck (HN) radiation treatment planning. In this study we assessed the use of a dedicated, geometrically accurate, DW-MRI sequence for target volume delineation. The delineations were compared with semi-automatic segmentations on 18 F-fluorodeoxyglucose (FDG) positron emission tomography (PET) images and evaluated for interobserver variation. Methods and materials: Fifteen HN cancer patients underwent both DW-MRI and FDG-PET for RT treatment planning. Target delineation on DW-MRI was performed by three observers, while for PET a semi-automatic segmentation was performed using a Gaussian mixture model. For interobserver variation and intermodality variation, volumes, overlap metrics and Hausdorff distances were calculated from the delineations. Results: The median volumes delineated by the three observers on DW-MRI were 10.8, 10.5 and 9.0 cm 3 respectively, and was larger than the median PET volume (8.0 cm 3). The median conformity index of DW-MRI for interobserver variation was 0.73 (range 0.38-0.80). Compared to PET, the delineations on DW-MRI by the three observers showed a median dice similarity coefficient of 0.71, 0.69 and 0.72 respectively. The mean Hausdorff distance was small with median (range) distances between PET and DW-MRI of 2.3 (1.5-6.8), 2.5 (1.6-6.9) and 2.0 (1.35-7.6) mm respectively. Over all patients, the median 95th percentile distances were 6.0 (3.0-13.4), 6.6 (4.0-24.0) and 5.3 (3.4-26.0) mm. Conclusion: Using a dedicated DW-MRI sequence, target volumes could be defined with good interobserver agreement and a good overlap with PET. Target volume delineation using DW-MRI is promising in head-andneck radiotherapy, combined with other modalities, it can lead to more precise target volume delineation.

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“…Also, some uncertainties in estimating the delivered doses, due to uncertainties in estimates of the deformation aligning the daily CBCT image with the planning CT, likely existed in our as well as other studies of delivered doses [15, 16]. Additional limitations in our, as well as other related studies, include using weekly rather than daily CBCTs, and parotid contouring reproducibility uncertainties (22). …”

Section: Discussionmentioning

confidence: 88%

Parotid Glands Dose–Effect Relationships Based on Their Actually Delivered Doses: Implications for Adaptive Replanning in Radiation Therapy of Head-and-Neck Cancer

Hunter

Fernandes

Vineberg

et al. 2013

International Journal of Radiation Oncology*Biology*Physics

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Purpose Doses actually delivered to the parotid glands during radiotherapy often exceed planned doses. We hypothesized that the delivered doses correlate better with parotid salivary output than the planned doses, used in all previous studies, and that determining these correlations will help decisions regarding adaptive re-planning (ART) aimed at reducing the delivered doses. Methods and Materials Prospective study: oropharyngeal cancer patients treated definitively with chemo-irradiation underwent daily cone beam CT (CBCT) with clinical set-up alignment based on C2 posterior edge. Parotid glands in the CBCTs were aligned by deformable registration to calculate cumulative delivered doses. Stimulated salivary flow rates were measured separately from each parotid gland pretherapy and periodically posttherapy. Results 36 parotid glands of 18 patients were analyzed. Average mean planned doses was 32 Gy and differences from planned to delivered mean gland doses were −4.9 to +8.4 Gy, median difference +2.2 Gy in glands whose delivered doses increased relative to planned. Both planned and delivered mean doses were significantly correlated with post-treatment salivary outputs at almost all post-therapy time points, without statistically significant differences in the correlations. Large dispersions [on average, standard deviation (SD) 3.6 Gy] characterized the dose/effect relationships for both. The differences between the cumulative delivered doses and planned doses were evident already at first fraction (r=0.92, p<0.0001) due to complex set-up deviations, e.g. rotations and neck articulations, uncorrected by the translational clinical alignments. Conclusions After daily translational set-up corrections, differences between planned and delivered doses in most glands were small relative to the SDs of the dose/saliva data, suggesting that ART is not likely to gain measurable salivary output improvement in most cases. These differences were observed already at first treatment, indicating potential benefit for more complex set-up corrections or adaptive interventions in the minority of patients with large deviations detected very early by CBCT.

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Interobserver variation in parotid gland delineation: a study of its impact on intensity-modulated radiotherapy solutions with a systematic review of the literature

Cited by 35 publications

References 73 publications

Use of a novel atlas for muscles of mastication to reduce inter observer variability in head and neck radiotherapy contouring

Use of a novel atlas for muscles of mastication to reduce inter observer variability in head and neck radiotherapy contouring

Evaluation of diffusion weighted imaging for tumor delineation in head-and-neck radiotherapy by comparison with automatically segmented 18F-fluorodeoxyglucose positron emission tomography

Parotid Glands Dose–Effect Relationships Based on Their Actually Delivered Doses: Implications for Adaptive Replanning in Radiation Therapy of Head-and-Neck Cancer

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