Table 1.

Measurement Indices of Various Breast Treatment Parameters [7]

Parameter	Definition
Maximum heart distance (MHD)	The maximum distance of the cardiac silhouette perpendicular to the longitudinal edge of the treatment field.
Central lung distance (CLD)	The perpendicular distance from the edge of the tangential field to the posterior part of the anterior chest wall in the middle of the field.
Chest wall separation (CWS)	Defined as the non-divergent posterior field edge from the sternum to the lateral exterior aspect of the chest wall.
Haller index	Defined as the ratio between transverse diameter of the chest and shortest distance between sternum and vertebrae. The Haller index is measured at the deepest aspect of the thoracic curve, with a normal Haller index ratio calculated as 2 or less.
Conformity index (CI)	Conformity index (CI)= VI/TV, where, VI = Reference isodose volume and TV = Target volume.
Homogeneity index (HI)	HI = D2-D98/Dmean, where D2 and D98 are the doses received by 2% and 98% of the planned target volumes (PTV) respectively.