Abstract
AimsTo compare the contouring of organs at risk (OAR) between a clinical specialist radiation therapist (CSRT) and radiation oncologists (ROs) with different levels of expertise (senior–SRO, junior–JRO, fellow–FRO).MethodsOn ten planning computed tomography (CT) image sets of patients undergoing breast radiotherapy (RT), the observers independently contoured the contralateral breast, heart, left anterior descending artery (LAD), oesophagus, kidney, liver, spinal cord, stomach and trachea. The CSRT was instructed by the JRO e SRO. The inter-observer variability of contoured volumes was measured using the Dice similarity coefficient (DSC) (threshold of ≥ 0.7 for good concordance) and the centre of mass distance (CMD). The analysis of variance (ANOVA) was performed and a p-value < 0.01 was considered statistically significant.ResultsGood overlaps (DSC > 0.7) were obtained for all OARs, except for LAD (DSC = 0.34 ± 0.17, mean ± standard deviation) and oesophagus (DSC = 0.66 ± 0.06, mean ± SD). The mean CMD < 1 cm was achieved for all the OARs, but spinal cord (CMD = 1.22 cm). By pairing the observers, mean DSC > 0.7 and mean CMD < 1 cm were achieved in all cases. The best overlaps were seen for the pairs JRO-CSRT(DSC = 0.82; CMD = 0.49 cm) and SRO-JRO (DSC = 0.80; CMD = 0.51 cm).ConclusionsOverall, good concordance was found for all the observers. Despite the short training in contouring, CSRT obtained good concordance with his tutor (JRO). Great variability was seen in contouring the LAD, due to its difficult visualization and identification of CT scans without contrast.
Highlights
Conformal radiotherapy (RT), based on three-dimensional technique and, more recently, on intensity-modulated RT (IMRT), is widely used as a modern approach to postoperative treatments for breast cancer
The best overlaps were seen for the pairs junior RO (JRO)-clinical specialist radiation therapist (CSRT)(DSC = 0.82; centre of mass distance (CMD) = 0.49 cm) and senior RO (SRO)-JRO (DSC = 0.80; CMD = 0.51 cm)
Conformal RT is based on complex procedures which start from the accurate delineation of the clinical target volume (CTV) and organs at risk (OAR) [3, 4]
Summary
Conformal radiotherapy (RT), based on three-dimensional technique and, more recently, on intensity-modulated RT (IMRT), is widely used as a modern approach to postoperative treatments for breast cancer. Conformal RT allows for dosimetric optimization and increases organs at risk (OAR) sparing, which represents major goals of treatment planning [1], and more tailored dose distributions to the target volume are obtained with IMRT [2]. The accuracy of dose delivery is provided by means of image-guided RT, which ensures the reproducibility of patient positioning at each treatment fraction. Conformal RT is based on complex procedures which start from the accurate delineation of the clinical target volume (CTV) and OARs [3, 4]. The contouring task is a fundamental pre-requisite for high-quality plans and a source of potential inaccuracy. Great efforts are spent to lower the inter-observer variability by using atlases, auto-contouring software, and attending live contouring workshops [5]
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