RANZCR Rad Onc Anatomy cheat sheet
RANZCR Rad Onc Anatomy · Keep the key ideas within reach.
Anatomy as Applied to Radiation Oncology Practice
Spinal cord tolerance is conventionally expressed as a maximum dose (Dmax) to the thecal sac surface; cord contouring should include the true cord plus a small margin, and dose is reported to 0.03–1.2 cm³ depending on protocol.
Brachial plexus lies in the posterior cervical triangle between anterior and middle scalene muscles, lateral to the carotid sheath and medial to the humeral head; it is at risk in apical lung and supraclavicular nodal irradiation.
Lumbosacral plexus is formed by ventral rami L1–S4; the lumbosacral trunk (L4–L5) crosses the pelvic brim medial to the psoas, placing it at risk in pelvic node irradiation.
Cauda equina occupies the lumbar cistern below the conus medullaris (typically L1–L2 in adults); tolerance is higher than spinal cord and is usually specified as a maximum dose to the cauda equina.
Optic chiasm lies above the sella turcica and is best localized on coronal T1 post-contrast MRI; chiasm and optic nerves are serial organs, so maximum dose governs tolerance rather than volume.
Parotid glands: superficial lobe lies lateral to the retromandibular vein and masseter, deep lobe medial to the vein; mean dose to each gland correlates with xerostomia, and the submandibular gland lies medial to the mandible body.
Waldeyer's ring comprises nasopharynx, palatine tonsils, base of tongue, and oropharynx; involved-node radiotherapy for head and neck cancer uses the neck node levels I–VII defined by consensus boundaries.
For breast tangent radiotherapy, the heart (left anterior descending artery) and lung are the dose-limiting structures; the internal mammary chain lies parasternal, 1–2 cm lateral to the sternal edge, deep to the costal cartilages.
Prostate target definition relies on zonal anatomy: peripheral zone posterior/lateral, transition zone central; the rectum lies posterior and the neurovascular bundles posterolateral, and the membranous urethra is the dose-limiting structure at the apex.