Anatomic texts books and radiologic data were reviewed for descriptions of the brachial plexus within the neck, supraclavicular fossa, and axilla As limited information was available on the identification of the brachial plexus using axial computed tomography (CT), sagittal and coronal magnetic resonance imaging (MRI)-based descriptions were used to identify the course of the brachial plexus through the neck and supraclavicular region on 3-mm axial computed tomography (CT) images. A board-certified neuroradiologist (A.D.) assisted with identification of the brachial plexus, as well as adjacent structures, including the anterior and middle scalene muscles, the subclavian and axillary arteries and veins, and relevant cervical and thoracic vertebrae using noncontrast axial CT. The following step-by-step technique for contouring the brachial plexus on axial noncontrast CT was devised:

1.Identify and contour C5, T1, and T2.
2.Identify and contour the subclavian and axillary neurovascular bundle.
3.Identify and contour anterior and middle scalene muscles from C5 to insertion onto the first rib.
4.To contour the brachial plexus OAR use a 5-mm diameter paint tool.
5.Start at the neural foramina from C5 to T1; this should extend from the lateral aspect of the spinal canal to the small space between the anterior and middle scalene muscles.
6.For CT slices, where no neural foramen is present, contour only the space between the anterior and middle scalene muscles.
7.Continue to contour the space between the anterior and middle scalene muscles; eventually the middle scalene will end in the region of the subclavian neurovascular bundle
8.Contour the brachial plexus as the posterior aspect of the neurovascular bundle inferiorly and laterally to one to two CT slices below the clavicular head.
9.The first and second ribs serve as the medial limit of the OAR contour.