Variations in inter-observer contouring and its impact on dosimetric and radiobiological parameters for intensity-modulated radiotherapy planning in treatment of localised prostate cancer

Bhardwaj, Anup Kumar; Kehwar, Than S.; Chakarvarti, S. K.; Sastri, Goda Jayant; Oinam, Arun S; Goswami, Pradeep; Kumar, Vinay; Mallick, Indranil; Sharma, Suresh C.

doi:10.1017/s1460396908006316

Cited by 12 publications

(14 citation statements)

References 35 publications

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“…Therefore, the model can be easily shared by creating pseudo-structures at each institute. It was also reported that inter-observer contouring variations have a signi cant impact on dosimetric and radiobiological outcomes in intensity modulated radiation therapy planning [36]. Reducing the number of structures is useful as a means of homogenizing treatment plan quality across institutions.…”

Section: Discussionmentioning

confidence: 99%

Knowledge-based Planning using Pseudo-structures for Volumetric Modulated arc Therapy (VMAT) of Postoperative Uterine Cervical Cancer: A Multi-Institutional Study

Kamima

Ueda

Fukunaga

et al. 2020

Preprint

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Background: The aim of this study was to investigate the performance of the RapidPlan knowledge-based treatment planning system using models including registered pseudo-structures, and to determine how many structures are required for automatic optimization of volumetric modulated arc therapy (VMAT) for postoperative uterine cervical cancer. Methods: Pseudo-structures were retrospectively contoured for patients who had completed treatment at one of five institutions. For 22 patients, RPs were generated with a single optimization for models with two (RP_2), four (RP_4), or five (RP_5) registered structures, and the dosimetric parameters of these models were compared with a clinical plan with several optimizations. The total times for pseudo-structure creation and optimization were also measured.Results: Most dosimetric parameters showed no major differences between each RP. In particular, the rectum Dmax, V50Gy, and V40Gy with RP_2, RP_4, and RP_5 were not significantly different, and were lower than those of the clinical plan. In addition, the average proportions of plans achieving acceptable criteria for all dosimetric parameters were 98%, 99%, 98%, and 98% for the clinical plan, RP_2, RP_4, and RP_5, respectively. The average times for the creation and optimization of pseudo-structures were 105, 17, 21, and 29 minutes, for the clinical plan, RP_2, RP_4, and RP_5, respectively. Conclusions: The RapidPlan model with two registered pseudo-structures could generate clinically acceptable plans while saving time. This modeling approach using pseudo-structures could possibility be used for the VMAT planning process.

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Section: Discussionmentioning

confidence: 99%

Knowledge-based Planning using Pseudo-structures for Volumetric Modulated arc Therapy (VMAT) of Postoperative Uterine Cervical Cancer: A Multi-Institutional Study

Kamima

Ueda

Fukunaga

et al. 2020

Preprint

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“…DV can stem from multiple sources, including inter-observer variability (i.e. multiple delineators will not generate precisely the same structures) (Bhardwaj et al 2008, Caravatta et al 2014, Xu et al 2016, intra-observer variability (i.e. the same delineator will not generate precisely the same structures in two different sessions) (Fiorino et al 1998, Petric et al 2008, Xu et al 2016, and methodological variability (i.e.…”

Section: Introductionmentioning

confidence: 99%

Quantifying the dosimetric impact of organ-at-risk delineation variability in head and neck radiation therapy in the context of patient setup uncertainty

Aliotta¹,

Nourzadeh²,

Siebers³

2019

Phys. Med. Biol.

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The purpose of this study was to quantify the potential dosimetric impact of delineation variability (DV) in head and neck radiation therapy (RT) when inherent patient setup variability (SV) is also considered.The impact of DV was assessed by generating plans with multiple structure sets, cross-evaluating them, including SV, across sets, and determining P PQM : the probability of achieving organ-specific plan quality metrics (PQM). DV was incorporated by: (1) using multiple organ at risk (OAR) structure sets delineated by independent manual observers; and (2) randomly perturbing manually generated OARs to generate alternatives with varying levels of uncertainty (low, medium, and high DV). For each structure set, independent VMAT plans were auto-generated to meet clinical PQMs. Each plan was cross-evaluated using OARs from multiple structure sets with simulated SV including per-fraction random (σ s ) and per-treatment-course systematic (Σ s ) setup errors. The dosimetric impact of DV was assessed by examining P PQM with and without SV/DV. Clinically significant differences were defined by those that exceeded differences caused by a +2% output variation.Without including SV, simulated DV at the medium level reduced P PQM by an average of 5.5% for all OARs with D max PQMs. This reduction decreased to 2.8% for SV = 2 mm and 2.4% for SV = 4 mm (the average P PQM reduction due to 2% output errors was 2.7%). For OARs with D mean PQMs, the average P PQM reduction was 0.9% for SV = 0 and ⩽0.1% for SV ⩾ 2 mm. The effect of DV was larger for OARs that directly abutted a target volume than for those that did not. These trends were also observed with real DV from multi-observer delineations.The dosimetric impact of DV appeared to decrease when random and systematic SV was considered. Sensitivity to DV was affected by OAR objective type (i.e. D mean versus D max objectives) as well as distance from the target volume.

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“…Currently, ROIs are mostly segmented manually by physicians or dosimetrists prior to their use in treatment planning. While manual contouring is the clinical standard for structure delineation during treatment planning, it is both time consuming and prone to inter‐ and intraobserver contour variability …”

Section: Introductionmentioning

confidence: 99%

“…Intrinsic and extrinsic factors can limit the ability to delineate anatomical regions for different imaging modalities due to poor soft tissue contrast, noise, and image artifacts. In addition, manual contours have interobserver delineation variability (due to different perception of observers), and intraobserver delineation variability (rooted in different interpretations/perception of the same observer in different trials). Observer variability is one of the dominant geometric uncertainties in radiation therapy, nonetheless, manual contours are considered the gold standard.…”

Section: Introductionmentioning

confidence: 99%

Clinical adequacy assessment of autocontours for prostate IMRT with meaningful endpoints

et al. 2017

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Purpose: To determine if radiation treatment plans created based on autosegmented (AS) regionsof-interest (ROI)s are clinically equivalent to plans created based on manually segmented ROIs, where equivalence is evaluated using probabilistic dosimetric metrics and probabilistic biological endpoints for prostate IMRT. Method and materials: Manually drawn contours and autosegmented ROIs were created for 167 CT image sets acquired from 19 prostate patients. Autosegmentation was performed utilizing Pinnacle's Smart Probabilistic Image Contouring Engine. For each CT set, 78 Gy/39 fraction 7-beam IMRT treatment plans with 1 cm CTV-to-PTV margins were created for each of the three contour scenarios; P MD using manually delineated (MD) ROIs, P AS using autosegmented ROIs, and P AM using autosegmented organ-at-risks (OAR)s and the manually drawn target. For each plan, 1000 virtual treatment simulations with different systematic errors for each simulation and a different random error for each fraction were performed. The statistical probability of achieving dose-volume metrics (coverage probability (CP)), expectation values for normal tissue complication probability (NTCP), and tumor control probability (TCP) metrics for all possible cross-evaluation pairs of ROI types and planning scenarios were reported. In evaluation scenarios, the root mean square loss (RMSL) and maximum absolute loss (MAL) of coverage probability of dose-volume objectives, E[TCP], and E [NTCP] were compared with respect to the base plan created and evaluated with manually drawn contours. Results: Femoral head dose objectives were satisfied in all situations, as well as the maximum dose objectives for all ROIs. Bladder metrics were within the clinical coverage tolerances except D 35Gy for the autosegmented plan evaluated with the manual contours. Dosimetric indices for CTV and rectum could be highly compromised when the definition of the ROIs switched from manually delineated to autosegmented. Seventy-two percent of CT image sets satisfied the worst-case CP thresholds for all dosimetric objectives in all scenarios, the percentage dropped to 50% if biological indices were taken into account. Among evaluation scenarios, (MD,P AM ) bore the highest resemblance to (MD,P MD ) where 99% and 88% of cases met all CP thresholds for bladder and rectum, respectively. Conclusions: When including daily setup variations in prostate IMRT, the dose-volume metric CP, and biological indices of ROIs were approximately equivalent for the plans created based on manually drawn targets and autosegmented OARs in 88% of cases. The accuracy of autosegmented prostates and rectums are impediment to attain statistically equivalent plans created based on manually drawn ROIs.

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Variations in inter-observer contouring and its impact on dosimetric and radiobiological parameters for intensity-modulated radiotherapy planning in treatment of localised prostate cancer

Cited by 12 publications

References 35 publications

Knowledge-based Planning using Pseudo-structures for Volumetric Modulated arc Therapy (VMAT) of Postoperative Uterine Cervical Cancer: A Multi-Institutional Study

Knowledge-based Planning using Pseudo-structures for Volumetric Modulated arc Therapy (VMAT) of Postoperative Uterine Cervical Cancer: A Multi-Institutional Study

Quantifying the dosimetric impact of organ-at-risk delineation variability in head and neck radiation therapy in the context of patient setup uncertainty

Clinical adequacy assessment of autocontours for prostate IMRT with meaningful endpoints

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