Radiology Anatomy Key Points

Overview

This lecture covers 100 key radiological anatomy questions, emphasizing scan identification, anatomical structures, variants, and clinical relevance, with concise explanations and exam-focused takeaways.

Neuroanatomy & Head

• CT and MRI scans are distinguished by bone and tissue brightness; gray matter is denser and brighter than white matter on CT.
• The lentiform nucleus (putamen + globus pallidus) is a basal nucleus made of gray matter.
• Basal nuclei are CNS collections of cell bodies; correct term is "nuclei" (not "ganglia").
• The internal capsule (white matter) separates basal nuclei and carries afferent/efferent fibers.
• Coronal bone windowed CT is used to visualize bone detail, e.g., hypoglossal canal in the occipital bone (C0).
• The hypoglossal nerve (CN XII) passes through the hypoglossal canal and originates in the medulla.

Paranasal Sinuses & Vasculature

• The maxillary ostium drains the maxillary sinus into the middle meatus; frontal and anterior ethmoidal sinuses also drain here.
• 3D CT angiograms display major arteries: the first branch of the aortic arch is the brachiocephalic trunk, dividing into right subclavian and right common carotid arteries.
• "Bovine arch" describes a common variant where the left common carotid shares an origin with the brachiocephalic.
• Coronary arteries (right and left) arise from the aortic root as the first aortic branches.

Brain & Circle of Willis

• T1 MRI: gray matter darker than white, CSF dark; the cerebral aqueduct connects the 3rd and 4th ventricles.
• Cisterns around the midbrain: interpeduncular, ambient, quadrigeminal.
• The anterior communicating artery is the only unpaired artery in the Circle of Willis.
• Basilar artery forms from vertebral arteries and travels in the pre-pontine cistern.

Musculoskeletal Anatomy

• Proton density (PD) weighted MRI shows bright fat and fluid, dark tendons/cartilage, good for MSK imaging.
• Supraspinatus tendon inserts on the greater tubercle, inferior to the acromion; magic angle artifact can mimic pathology.
• Patella is within the quadriceps tendon; medial/lateral orientation is determined by facet size.
• The trochlear groove and medial retinaculum prevent lateral patellar dislocation.

Abdominal Anatomy

• Celiac trunk branches: splenic, left gastric, and common hepatic arteries; supplies the foregut, originates at T12.
• Liver segments (Quino classification): segments labeled clockwise; hepatic veins drain to IVC.
• Portal venous phase CT shows enhanced portal and hepatic veins; segmental anatomy is essential for localizing pathology.

Thoracic Anatomy

• Axial CT lung window visualizes airways; right main bronchus gives off upper lobe bronchus, then bronchus intermedius.
• A "tracheal bronchus" variant can occur.

Head & Neck Spaces

• T1 axial MRIs distinguish deep neck spaces; parapharyngeal space is deep and filled with fat.
• Superficial layer of deep cervical fascia defines lateral border; above hyoid is "suprahyoid" neck.

Radiographs & Ossification

• "Radiograph" is correct term for x-ray images; e.g., lateral elbow view shows radial head (lateral).
• Elbow ossification centers: CRITOE mnemonic; capitellum appears first, followed by radial head, medial epicondyle.

GI Tract, Retroperitoneum & Pancreas

• D1 (first part) of duodenum is intraperitoneal; rest are retroperitoneal.
• Major duodenal papilla is in D2; jejunum starts at the ligament of Treitz (DJ flexure).
• Pancreas is in the anterior pararenal space, bordered posteriorly by Gerota's fascia; supplied by branches of the splenic, superior and inferior pancreaticoduodenal arteries.

Wrist & Spine Anatomy

• Triangular fibrocartilage complex stabilizes wrist above ulna; flexor retinaculum forms carpal tunnel floor.
• Pisiform is a sesamoid bone within the flexor carpi ulnaris tendon.
• C7 vertebral body is identified on lateral cervical films; C8 nerve root exits below C7.

Pelvis & Neck

• Anterior superior iliac spine (ASIS) is attachment for sartorius muscle and inguinal ligament; pelvic bone formed from ilium, ischium, pubis.
• Axial CT of neck shows vallecula (separated by median glossoepiglottic fold), with epiglottis posterior; supraglottic space is above true vocal cords.
• Inferior border of larynx is defined by the cricoid cartilage.

Key Terms & Definitions

• Lentiform nucleus — lens-shaped basal nucleus (putamen + globus pallidus).
• Internal capsule — white matter tract separating basal nuclei.
• Ostium — anatomical opening (e.g., sinus drainage).
• Bovine arch — variant aortic arch branching pattern.
• Proton density MRI — MRI sequence with minimized T1/T2 differences, highlights fat and fluid.
• Magic angle artifact — MRI artifact causing tendon hyperintensity at 54.7°.
• Quino segments — liver segmentation system.
• Triangular fibrocartilage complex — cartilage stabilizing ulnar side of wrist.
• CRITOE — elbow ossification mnemonic: Capitellum, Radial head, Internal epicondyle, Trochlea, Olecranon, External epicondyle.

Action Items / Next Steps

• Review original anatomy videos for unclear topics.
• Practice identifying scan types (CT, MRI, radiograph) and anatomical variants.
• Study liver segmental anatomy and abdominal vascular branches.
• Memorize the CRITOE mnemonic for elbow ossification centers.
• Review deep neck spaces, wrist complexes, and laryngeal anatomy.