Elsevier

Radiotherapy and Oncology

Volume 150, September 2020, Pages 121-127
Radiotherapy and Oncology

Original Article
Delineation of whole heart and substructures in thoracic radiation therapy: National guidelines and contouring atlas by the Danish Multidisciplinary Cancer Groups

https://doi.org/10.1016/j.radonc.2020.06.015Get rights and content

Highlights

  • National guidelines for whole heart and cardiac substructures were established.

  • Inter-observer contour overlap was 78–96% for the heart and four chambers.

  • The median distance between centers of left main coronary artery was 2–4 mm.

  • Variance measure for OAR ready for use in auto segmentation.

Abstract

Background and purpose

This study presents Danish consensus guidelines for delineation of the heart and cardiac substructures across relevant Danish Multidisciplinary Cancer Groups.

Material and methods

Consensus guidelines for the heart and cardiac substructures were reached among 15 observers representing the radiotherapy (RT) committees of four Danish Multidisciplinary Cancer Groups. The guidelines were validated on CT scans of 12 patients, each with five independent contour sets. The Sørensen-Dice similarity coefficient (DSC), the distance between the centers of the arteries and the mean surface distance were used to evaluate the inter-observer variation.

Results

National guidelines for contouring the heart and cardiac substructures were achieved. The median DSC was 0.78–0.96 for the heart and the four cardiac chambers. For the four substructures of the left ventricle, the median DSC was 0.35–0.57. The coronary arteries were contoured in ten segments, with the best agreement for the left anterior descending coronary artery segments, with a median distance between the arteries ranging from 2.4–4.4 mm. The median variation was 3.7–12.8 mm for the right coronary artery segments and 3.7–6.2 mm for the left circumflex coronary artery segments, with the most pronounced inter-observer variation in the distal segment for all three coronary arteries.

Conclusion

National guidelines for contouring the heart and cardiac substructures were developed across relevant Danish Multidisciplinary Cancer Groups, where RT dose to the heart is of concern. The inter-observer contour overlap was best for the heart and chambers and decreased for smaller structures.

Section snippets

Guideline and cardiac contouring

One oncologist (MLHM) performed contouring of the heart and cardiac substructures on randomly selected non-contrast enhanced, planning CT scans of ten breast cancer patients. Based on existing cardiac contouring guidelines, preliminary guidelines detailing the delineation of the heart and 24 cardiac substructures were developed: the four cardiac chambers, the four segments of the left ventricle wall, ten coronary artery segments and six help-structures (aorta, inferior and superior vena cava,

Results

Based on existing cardiac contouring guidelines, the preliminary guidelines and preliminary atlas, final consensus regarding the guidelines of the heart and cardiac substructures was reached [16], [17]. The anatomical borders were defined from an axial CT scan. For atlas contouring, see Fig B.1.

The base of the heart emerges caudally to the right and the left main pulmonary artery, just after the split from the pulmonary trunk [16]. Caudally, the heart blends with the diaphragm. The coronary

Discussion

The majority of patients with thoracic cancer receive adjuvant or curative RT and, in Denmark, contouring of the heart is clinical practice. However, no consensus guidelines for cardiac delineation across different diagnoses were available. In this study, we present national guidelines for delineation of the whole heart and cardiac substructures for RT planning, obtained by the four DMCGs. These guidelines were intended for ensuring a standardized way to report RT dose to cardiac substructures

Disclosure of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Acknowledgements

The workshop was funded by the DCCC Radiotherapy – The Danish National Research Center.

BVO was supported by the Danish Cancer Society and the DCCC Radiotherapy – The Danish National Research Center.

MLHM was supported by the Danish Cancer Society, the DCCC Radiotherapy – The Danish National Research Center and Aarhus University.

References (23)

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