Skull & Paranasal Sinuses Radiographic Anatomy & Projections

Vocabulary flashcards covering skull and paranasal sinus anatomy, cranial sutures, infant fontanelles, positioning reference lines, and primary/supplementary radiographic projections.

Bregma

The junction point at the anterior end of the sagittal suture where it meets the coronal suture.

Lambda

The junction point at the posterior end of the sagittal suture where it meets the lambdoid suture.

Pterion

The bilateral suture junction where the parietal, temporal, and sphenoid bones meet.

Asterion

The bilateral suture junction located at the intersection of the squamous and lambdoid sutures.

Sagittal Suture

An immovable fibrous joint located along the midline between the right and left parietal bones.

Coronal Suture

An immovable fibrous joint located between the frontal bone and the two parietal bones.

Lambdoid Suture

An immovable fibrous joint located between the parietal bones and the occipital bone.

Squamous Suture

An immovable fibrous joint located between the temporal bone and the parietal bone on each side of the skull.

Adult Cranial Sutures

Immovable fibrous joints that articulate the individual bones of the adult cranial vault.

Infant Fontanelles

Fibrous soft spots (anterior, posterior, sphenoid, and mastoid) in a newborn skull that allow bone overlap (moulding) during birth, rapid brain expansion, and clinical assessment of intracranial pressure.

Petrous Ridges

Dense bony ridges located between the sphenoid and occipital bones that form the densest portion of the skull base, serving as a primary symmetry landmark on radiographic projections.

Radiographic Positioning Lines

Specific surface anatomy baselines (such as OML and IOML) used to establish consistent head angulation and central ray orientation during skull radiography.

AP Axial Towne Method

A routine skull projection angled $30^\text{o}$ caudad to the OML (or $37^\text{o}$ if unable to flex the neck) to visualize the posterior fossa, occipital bone, and dorsum sellae within the foramen magnum.

PA Axial Caldwell's Method

A routine skull projection using a $15^\text{o}$ caudad Central Ray angle to evaluate anterior cranial structures and position the petrous ridges in the lower $\frac{1}{3}$ of the orbits.

PA Skull Projection ($0^\text{o}$)

A skull projection performed with a perpendicular ($0^\text{o}$) Central Ray angle, causing the petrous ridges to completely fill the orbits for evaluation of intracranial structures and the crista galli.

Submentovertical (SMV) Projection

A supplementary projection requiring full neck extension with the Central Ray perpendicular to the IOML to demonstrate the skull base, sphenoid sinus, foramen magnum, foramen ovale, foramen spinosum, and zygomatic arches.

Stenver's Projection

A supplementary projection using a $45^\text{o}$ anterior oblique position and a $12^\text{o}$ cephalad Central Ray angle, used almost exclusively to profile the petrous temporal bone and evaluate cochlear implant electrode arrays.

Water's Projection (Parietoacanthial)

A sinus projection performed with the mentomeatal line (MML) perpendicular to the Image Receptor, demonstrating the maxillary sinuses free of superimposition and showing air-fluid levels when acquired erect.

Paranasal Sinuses

Air-filled cavities lined with mucous membrane surrounding the nasal cavity, categorized into frontal, ethmoid, sphenoid, and maxillary sinuses.

Frontal Sinuses

Asymmetrical paired paranasal sinuses located superior to the orbits within the frontal bone, prone to infection due to poor drainage.

Maxillary Sinuses

The largest of the paranasal sinuses, pyramid-shaped and located in the maxilla, characterized by poor drainage owing to their anatomical shape.

Ethmoid Sinuses

A complex collection of multiple air cells located within the ethmoid bone between the orbits and the nasal cavity.

Sphenoid Sinus

A paranasal sinus situated deep within the body of the sphenoid bone posterior to the ethmoid sinuses, making infections difficult to detect.