The Reasons for Discrepancies in Target Volume Delineation

Jeanneret‐Sozzi, Wendy; Moeckli, Raphaël; Valley, J.-F.; Zouhair, Abderrahim; Özşahin, Esat Mahmut; Mirimanoff, René-Olivier

doi:10.1007/s00066-006-1463-6

Cited by 52 publications

(20 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Before implementing commercial AS tools, potential relative time savings and software accuracy need to be rigorously investigated, as plan optimization (and thus OAR sparing and target coverage) is predicated on accurate ROI segmentation [21,22]. AS algorithms have been shown to be quite reliable in appropriately delineating OARs [5].…”

Section: Discussionmentioning

confidence: 99%

Prospective randomized double-blind study of atlas-based organ-at-risk autosegmentation-assisted radiation planning in head and neck cancer

Walker

Awan

Tao

et al. 2014

Radiotherapy and Oncology

112

115

View full text Add to dashboard Cite

Background and purpose Target volumes and organs-at-risk (OARs) for radiotherapy (RT) planning are manually defined, which is a tedious and inaccurate process. We sought to assess the feasibility, time reduction, and acceptability of an atlas-based autosegmentation (AS) compared to manual segmentation (MS) of OARs. Materials and methods A commercial platform generated 16 OARs. Resident physicians were randomly assigned to modify AS OAR (AS + R) or to draw MS OAR followed by attending physician correction. Dice similarity coefficient (DSC) was used to measure overlap between groups compared with attending approved OARs (DSC = 1 means perfect overlap). 40 cases were segmented. Results Mean ± SD segmentation time in the AS + R group was 19.7 ± 8.0 min, compared to 28.5 ± 8.0 min in the MS cohort, amounting to a 30.9% time reduction (Wilcoxon p < 0.01). For each OAR, AS DSC was statistically different from both AS + R and MS ROIs (all Steel–Dwass p < 0.01) except the spinal cord and the mandible, suggesting oversight of AS/MS processes is required; AS + R and MS DSCs were non-different. AS compared to attending approved OAR DSCs varied considerably, with a chiasm mean ± SD DSC of 0.37 ± 0.32 and brainstem of 0.97 ± 0.03. Conclusions Autosegmentation provides a time savings in head and neck regions of interest generation. However, attending physician approval remains vital.

show abstract

Section: Discussionmentioning

confidence: 99%

Prospective randomized double-blind study of atlas-based organ-at-risk autosegmentation-assisted radiation planning in head and neck cancer

Walker

Awan

Tao

et al. 2014

Radiotherapy and Oncology

112

115

View full text Add to dashboard Cite

show abstract

“…Accurate target delineation is extremely important to make sure that the CTV is not under-treated and to limit the dose to surrounding normal tissue. Despite the well-known consequences of geometric inaccuracy in target volume delineation [11-13], variability in target delineation has been demonstrated in several studies and for various anatomic tumor sites [13]. In the case of non-small cell lung cancer, for example, Steenbakkers et al .…”

Section: Discussionmentioning

confidence: 99%

Dosimetric impact of inter-observer variability for 3D conformal radiotherapy and volumetric modulated arc therapy: the rectal tumor target definition case

et al. 2013

View full text Add to dashboard Cite

BackgroundTo assess the dosimetric effect induced by inter-observer variability in target definition for 3D-conformal RT (3DCRT) and volumetric modulated arc therapy by RapidArc (RA) techniques for rectal cancer treatment.MethodsTen patients with rectal cancer subjected to neo-adjuvant RT were randomly selected from the internal database. Four radiation oncologists independently contoured the clinical target volume (CTV) in blind mode. Planning target volume (PTV) was defined as CTV + 7 mm in the three directions. Afterwards, shared guidelines between radiation oncologists were introduced to give general criteria for the contouring of rectal target and the four radiation oncologists defined new CTV following the guidelines. For each patient, six intersections (I) and unions (U) volumes were calculated coupling the contours of the various oncologists. This was repeated for the contours drawn after the guidelines. Agreement Index (AI = I/U) was calculated pre and post guidelines. Two RT plans (one with 3DCRT technique using 3–4 fields and one with RA using a single modulated arc) were optimized on each radiation oncologist’s PTV. For each plan the PTV volume receiving at least 95% of the prescribed dose (PTV V95%) was calculated for both target and non-target PTVs.ResultsThe inter-operator AI pre-guidelines was 0.57 and was increased up to 0.69 post-guidelines. The maximum volume difference between the various CTV couples, drawn for each patient, passed from 380 ± 147 cm3 to 137 ± 83 cm3 after the introduction of guidelines. The mean percentage for the non-target PTV V95% was 93.7 ± 9.2% before and 96.6 ± 4.9%after the introduction of guidelines for the 3DCRT, for RA the increase was more relevant, passing from 86.5 ± 13.8% (pre) to 94.5 ± 7.5% (post). The OARs were maximally spared with VMAT technique while the variability between pre and post guidelines was not relevant in both techniques.ConclusionsThe contouring inter-observer variability has dosimetric effects in the PTV coverage. The introduction of guidelines increases the dosimetric consistency for both techniques, with greater improvements for RA technique.

show abstract

“…Intensity modulated RT (IMRT) further allows for an improved therapeutic ratio through the use of “inverse planning” to optimize dose to the tumor while preferentially sparing organs at risk (11). However, target volumes and organs-at-risk for treatment planning are necessarily defined by human users, introducing possible geometric variability due to variation in target delineation (12). Under -contouring can lead to local relapse, and over -contouring can lead to unnecessary normal tissue toxicity.…”

Section: Introductionmentioning

confidence: 99%

Quantitative assessment of target delineation variability for thymic cancers: agreement evaluation of a prospective segmentation challenge

et al. 2015

View full text Add to dashboard Cite

Objectives We sought to quantitatively determine the inter-observer variability of expert radiotherapy target-volume delineation for thymic cancers, as part of a larger effort to develop an expert-consensus contouring atlas. Methods A pilot dataset was created consisting of a standardized case presentation with pre- and post-operative DICOM CT image sets from a single patient with Masaoka-Koga Stage III thymoma. Expert thoracic radiation oncologists delineated tumor targets on the pre- and post-operative scans as they would for a definitive and adjuvant case, respectively. Respondents completed a survey including recommended dose prescription and target volume margins for definitive and post-operative scenarios. Inter-observer variability was analyzed quantitatively with Warfield's simultaneous truth, performance level estimation (STAPLE) algorithm and Dice similarity coefficient (DSC). Results Seven users completed contouring for definitive and adjuvant cases; of these, 5 completed online surveys. Segmentation performance was assessed, with high mean±SD STAPLE-estimated segmentation sensitivity for definitive case GTV and CTV at 0.77 and 0.80, respectively, and post-operative CTV sensitivity of 0.55; all volumes had specificity of ≥0.99. Inter-observer agreement was markedly higher for the definitive target volumes, with mean±SD DSC of 0.88±0.03 and 0.89±0.04 for GTV and CTV respectively, compared to post-op CTV DSC of 0.69±0.06 (Kruskal-Wallis p<0.01. Conclusion Expert agreement for definitive case volumes was exceptionally high, though significantly lower agreement was noted post-operatively. Technique and dose prescription between experts was substantively consistent, and these preliminary results will be utilized to create an expert-consensus contouring atlas to aid the non-expert radiation oncologist in the planning of these challenging, rare tumors.

show abstract

The Reasons for Discrepancies in Target Volume Delineation

Cited by 52 publications

References 27 publications

Prospective randomized double-blind study of atlas-based organ-at-risk autosegmentation-assisted radiation planning in head and neck cancer

Prospective randomized double-blind study of atlas-based organ-at-risk autosegmentation-assisted radiation planning in head and neck cancer

Dosimetric impact of inter-observer variability for 3D conformal radiotherapy and volumetric modulated arc therapy: the rectal tumor target definition case

Quantitative assessment of target delineation variability for thymic cancers: agreement evaluation of a prospective segmentation challenge

Contact Info

Product

Resources

About