Alexandra Moignier1, David Broggio2, Sylvie Derreumaux3, Fida El Baf2, Anne-Marie Mandin4, Théodore Girinsky5, Jean-François Paul6, Michel Chea4, Catherine Jenny4, Didier Franck2, Bernard Aubert3, Jean-Jacques Mazeron4. 1. Institut de Radioprotection et de Sûreté Nucléaire, PRP-HOM/SDI/LEDI, Laboratoire d'Evaluation de la Dose Interne, Fontenay-aux-Roses, France. Electronic address: alexandra.moignier@gmail.com. 2. Institut de Radioprotection et de Sûreté Nucléaire, PRP-HOM/SDI/LEDI, Laboratoire d'Evaluation de la Dose Interne, Fontenay-aux-Roses, France. 3. Institut de Radioprotection et de Sûreté Nucléaire, PRP-HOM/SER/UEM, Unité d'Expertise en radioprotection Médicale, Fontenay-aux-Roses, France. 4. Groupe Hospitalier Pitié-Salpêtrière, Assistance Publique - Hôpitaux de Paris, Service de Radiothérapie Oncologique, Paris, France. 5. Institut Gustave Roussy, Service de Radiothérapie Oncologique, Villejuif, France. 6. Centre Chirurgical Marie-Lannelongue, Service de Radiologie, Le Plessis-Robinson, France.
Abstract
PURPOSE: In left-side breast radiation therapy (RT), doses to the left main (LM) and left anterior descending (LAD) coronary arteries are usually assessed after delineation by prior anatomic knowledge on the treatment planning computed tomography (CT) scan. In this study, dose sensitivity due to interindividual coronary topology variation was assessed, and hot spots were located. METHODS AND MATERIALS: Twenty-two detailed heart models, created from heart computed tomography angiographies, were fitted into a single representative female thorax. Two breast RT protocols were then simulated into a treatment planning system: the first protocol comprised tangential and tumoral bed beams (TGs_TB) at 50 + 16 Gy, the second protocol added internal mammary chain beams at 50 Gy to TGs_TB (TGs_TB_IMC). For the heart, the LAD, and the LM, several dose indicators were calculated: dose-volume histograms, mean dose (Dmean), minimal dose received by the most irradiated 2% of the volume (D2%), and 3-dimensional (3D) dose maps. Variations of these indicators with anatomies were studied. RESULTS: For the LM, the intermodel dispersion of Dmean and D2% was 10% and 11%, respectively, with TGs_TB and 40% and 80%, respectively, with TGs_TB_IMC. For the LAD, these dispersions were 19% (Dmean) and 49% (D2%) with TGs_TB and 35% (Dmean) and 76% (D2%) with TGs_TB_IMC. The 3D dose maps revealed that the internal mammary chain beams induced hot spots between 20 and 30 Gy on the LM and the proximal LAD for some coronary topologies. Without IMC beams, hot spots between 5 and 26 Gy are located on the middle and distal LAD. CONCLUSIONS: Coronary dose distributions with hot spot location and dose level can change significantly depending on coronary topology, as highlighted by 3D coronary dose maps. In clinical practice, coronary imaging may be required for a relevant coronary dose assessment, especially in cases of internal mammary chain irradiation.
PURPOSE: In left-side breast radiation therapy (RT), doses to the left main (LM) and left anterior descending (LAD) coronary arteries are usually assessed after delineation by prior anatomic knowledge on the treatment planning computed tomography (CT) scan. In this study, dose sensitivity due to interindividual coronary topology variation was assessed, and hot spots were located. METHODS AND MATERIALS: Twenty-two detailed heart models, created from heart computed tomography angiographies, were fitted into a single representative female thorax. Two breast RT protocols were then simulated into a treatment planning system: the first protocol comprised tangential and tumoral bed beams (TGs_TB) at 50 + 16 Gy, the second protocol added internal mammary chain beams at 50 Gy to TGs_TB (TGs_TB_IMC). For the heart, the LAD, and the LM, several dose indicators were calculated: dose-volume histograms, mean dose (Dmean), minimal dose received by the most irradiated 2% of the volume (D2%), and 3-dimensional (3D) dose maps. Variations of these indicators with anatomies were studied. RESULTS: For the LM, the intermodel dispersion of Dmean and D2% was 10% and 11%, respectively, with TGs_TB and 40% and 80%, respectively, with TGs_TB_IMC. For the LAD, these dispersions were 19% (Dmean) and 49% (D2%) with TGs_TB and 35% (Dmean) and 76% (D2%) with TGs_TB_IMC. The 3D dose maps revealed that the internal mammary chain beams induced hot spots between 20 and 30 Gy on the LM and the proximal LAD for some coronary topologies. Without IMC beams, hot spots between 5 and 26 Gy are located on the middle and distal LAD. CONCLUSIONS: Coronary dose distributions with hot spot location and dose level can change significantly depending on coronary topology, as highlighted by 3D coronary dose maps. In clinical practice, coronary imaging may be required for a relevant coronary dose assessment, especially in cases of internal mammary chain irradiation.
Authors: Frances K Duane; Paul McGale; Dorthe Brønnum; David J Cutter; Sarah C Darby; Marianne Ewertz; Sara Hackett; Per Hall; Ebbe L Lorenzen; Kazem Rahimi; Zhe Wang; Samantha Warren; Carolyn W Taylor Journal: Pract Radiat Oncol Date: 2019-01-26