**9. Conclusion**

**Substructure Definition Note**

inferior to the left pulmonary artery Caudal: The heart blends with the

Pericardium [34] The whole heart Cardiac vessels run in the fatty tissue within the

Right atrium [34] No Starts to the right of the aortic root superiorly Right ventricle [34] No Lies directly beneath the sternum and connects to

–

the pulmonary trunk

left ventricles

section on axial CT

section on axial CT

shared

shared

No Cannot be seen on CT. It is located on the basal

therapy

–

Aortic valve [34] No Found within the ascending aorta and seen in cross

Pulmonic valve [34] No Found within the pulmonary trunk and seen in cross

Tricuspid valve [34] No Located between the right atrium and ventricle. It

Mitral valve [34] No Located between the left atrium and ventricle. It is

If contrast is administered, the superior vena cava (SVC) can generally be separately contoured from the whole heart. In a noncontrast scan, the SVC can be included for simplification and consistency

pericardium and should be included in the contours

Typically, anterior and to the left of the left atrium

Originates from the left side of the ascending aorta,

Originates from the right side of the ascending aorta

Originates from the left coronary artery and runs in the interventricular groove between the right and

Originates from the left coronary artery and runs

is difficult to see, but it is defined as the area where the blood pool between the atrium and ventricle is

difficult to see, but it is defined as the area where the blood pool between the atrium and ventricle is

portion of the interventricular septum and extends

It is an imaged subregion in the anterior port of the heart as a high-risk region for breast cancer radiation

between the right atrium and ventricle

inferior to the right pulmonary artery

between the left atrium and ventricle

Heart [16, 34, 70] Cranial: The whole heart starts just

diaphragm

Left ventricle [16, 34] The visible heart according to both

pulmonary artery

CT images and heart anatomy

Defined from its origin in the aortic sinus to the first branches

Defined from where they branched at the left or right main coronary artery to the caudal edge of the endocardial

surface of the left ventricle

Comprises the myocardium from the anterior surface of the heart up to 1.0 cm posteriorly and the main branches of the coronary arteries at the anterior portion of the heart

**Table 1**. Recommended delineations of the heart and substructures.

Left atrium [34] Begins just inferior to the left

Left main coronary artery [34, 70]

Right coronary artery

Left circumflex artery

Right marginal artery

Atrioventricular node

Anterior myocardial territory [16, 17, 70]

[34]

[34, 70]

202 Radiotherapy

[34, 70]

[34, 70]

[70]

Left anterior descending artery As a significant radiation-induced toxicity, RRHD should not be neglected during clinical decision-making, especially for patients who could be cured by modern anticancer modalities. RRHD includes radiation-induced death from heart diseases, as well as clinical and subclinical heart disease. Advanced RT techniques including breath control, IMRT, and imaging-guided RT might be used to avoid or spare cardiac doses and/or volume, which might translate into decreased incidence of RRHD. Furthermore, the significance and implications of RRHD differ depending on the clinical scenario; therefore, a consensus has not yet been reached regarding the recommended dose-volume limits. It is prudent to minimize the cardiac dose/volume and optimize the patient cardiovascular risk profiles. The recognition, prevention and prediction, and treatment of RRHD should be within the domain of oncocardiology, which requires close collaboration between oncologists and cardiologists [14, 63].
