Adaptations to level III borders indicated on patient CT scan taken in PCP. The figure shows the first cranial slice where the axillary/subclavian artery first crosses both the lateral border of the first rib and the clavicle. In the most cranial slices of level III, the minor pectoral muscle can still be located (very laterally) close to its insertion on the coracoid process of the scapula. To spare the (up to 30 mm) margin indicated by the double arrow, the lateral border is taken at the lateral edge of the axillary artery until the artery crosses the medial edge of the minor pectoral muscle. Also note that the CTV excludes the subclavius muscle. Turquoise (SA) = serratus anterior muscle, red (A) = common carotid artery, or axillary/subclavian artery, yellow (3) = level III, blue (V) = subclavian vein, brown (*) = subclavius muscle, orange (MiP) = minor pectoral muscle, dark green (B/C) = biceps/coracobrachial muscle bundle, pink (MaP) = major pectoral muscle.