The Skull Dr Mohamed El Safwany, MD. 1

Intended Learning Outcome The student should be able to recognize technological principles of radiographic imaging of the skull.

TECHNICAL ASPECTS Sitting erect positions are preferred to exclude any air-fluid levels within the cranial cavities or sinuses. Patient comfort and skull immobilization are necessary. Exposure factors range between 75 kVp and 85 kVp. A small focus is to be used with short times and high mA. A high lattice grid (40 lines/inch) must be used. Good collimation (Narrow cone for small parts) and non-repeats helps in minimizing the radiation exposure to the patient. A contact shield should be used over the neck and chest to reduce the exposure to the thyroid and female breast in the AP projection.

PA Skull (0 Occipital-frontal) projection B For frontal bone #s and neoplastic processes of the cranium, Paget’s disease, orbits (obscured by petrous temporals), I.A.M, frontal and ethmoidal sinuses, dorsum sellae. Patient nose and forehead against the couch center, neck flexed so that OML is 90 to the couch, MSP 90 to couch center, head not rotated, EAMS equidistant from the couch top. Film: HD 24x30 cm CP: Exits the glabella CR: 0 (that is 90) to film center NB/ AP is not recommended as it produces 200 times eyes absorbed dose produced in the PA position.

PA Axial Skull (Caldwell projection for sinuses ) B Good for sinuses (frontal and anterior ethmoidal sinuses). Also shows other inflammatory conditions (secondary osteomyelitis, sinus polyps). Patient’s nose and forehead against film, neck extended so that OML is 15 from the horizontal Film: HD 18x24 cm CP: Naison (to occiput to exit at level of lower orbital margins). CR: 90 horizontal to film center (or 15 caudal with OML 90 to the film).

AP Axial (Towne’s projection) B For occipital bone, cranial #s, neoplasms, and Paget’s disease. Also for AP dorsum sellae, and advanced pathology of the temporal bone (advanced acoustic neuroma), anterior clinoids, foramen magnum, mastoids, foramen magnum. Patient supine, or in erect AP sitting, chin is depressed (OML 90 to film), no rotation of the head Film: HD 24x30 cm CP: 6 cm above the glabella (2 cm superior to level of EAMs). CR: 30 caudal (30 caudal for the posterior clinoids).

AP Axial (Towne’s projection – for mandible) B For #s, neoplastic or inflammatory processes of the condyloid processes of the mandible. Same position as for Towne AP (OML 90 to couch top. Film: HD 18x24 cm CP: Glabella (midway between EAMs and angles of the mandible). A CP at one inch anterior to level of TMJs will show TMJs. CR: 35- 40 caudal.

Lateral Skull (general) B Same indication as for PA (0). A horizontal beam is used for trauma cases Patient in a semiprone (Sim’s position), recumbent or erect sitting, head in a true lateral (required side close to the film), MSP parallel to couch, IPL 90 to couch top. Film: HD 18x24 cm CP: 5 cm superior to EAM . CR: 90 to film center .

Lateral Skull (for lateral Sella Turcica) B To show evidence of pituitary adenomas. Same position as for the lateral skull (as in Sim’s position), IOML 90 to couch top. Film: HD 18x24 cm CP: 2 cm anterior and 2 cm superior to EAM. CR: 90 to film center

Lateral Skull (for nasal bones) B For nasal bone fractures. Head in true lateral (same position as for lateral skull as in Sim’s position) or erect, chin adjusted so that both IPL and IOML are 90 to couch top. Film: HD 18x24 cm CP: 1.25 cm inferior to naison CR: 90 to film center

Lateral Skull (for sinuses) B For inflammatory conditions: Secondary osteomyelitis, sinusitis, and sinus polyps (good for sphenoid, frontal, ethmoid, and maxillary sinuses). Patient erect sitting, head in true lateral (IPL 90 to film) Film: HD 18x24 cm CP: Midway between outer canthus and EAM CR: 90 horizontal to film center

Lateral 25 - 30 (Axiolateral) (for mandible) B For #s, neoplastic, or for inflammatory processes of the mandible (both sides are done for comparison) . Head in true lateral with MSP parallel to the film, side of interest placed against the film, mouth closed, head then rotated in oblique 30 (for the body), 45 (for mentum), and 10 - 15 for a (general survey). Film: HD 18x24 cm CP: Mandibular region of interest (body, ramus, ….). CR: 25 cephalic.

Lateral 15 (Modified Law for TMJs) S For advanced bony pathology of the mastoid process. Patient prone or erect, head in lateral, IPL 90 to film, face ( and MSP) then rotated 15 toward the film. Closed and opened mouth. Film: HD 18x24 cm CP: 4 cm superior to upside EAM CR: 15 caudal to pass through the downside TMJ.

Axiolateral (Schüller for mastoids) S For advanced bony pathology of the mastoid air cells. Patient prone or erect, head in the true lateral, IPL 90 to film, MSP parallel to the film. Film: HD 18x24 cm CP: downside mastoid tip (4 cm superior, 4 cm posterior to upside EAM). CR: 25 - 30 caudal.

Axiolateral Oblique (Modified Law for mastoids) B For advanced pathology of mastoids. Patient prone or erect, each auricle taped forward, head in lateral, then rotated 15 oblique toward the film, IPL 90 to couch, side of interest down. Film: HD 18x24 cm CP: Exit downside mastoid tip (1 inch posterior, 2.5 cm posterior, 2.5 cm superior to upside EAM). CR: 15 caudal

Submentovertex (SMV) S For base of the skull (Basilar view), occipital bone, mandible, foramen ovale and foramen magnum, TMJs, orbits, zygomatic arches, sphenoidal, maxillary sinuses and mastoid processes. Patient supine or erect sitting, chin raised, neck hyperextended till IOML is parallel to film, MSP 90 to couch top. A pillow under patient’s back allows for sufficient extension. Film: HD 24x30 cm. CP: Midway between angles of mandible (2 cm anterior to level of EAMs). CR: 90 to IOML.

Submentovertex (SMV) (for mandible) S For #s, neoplastic, or inflammatory processes of the mandible. Patient supine or erect sitting, chin raised, neck hyperextended till IOML is parallel to film, MSP 90 to couch top. A pillow under patient’s back allows for sufficient extension. Film: HD 18x24 cm CP: Midway between angles of mandible (4 cm inferior to mandibular symphysis). CR: 90 to IOML.

ORTHOPANTOMOGRAPHY (tomography of the mandible) S For #s of the mandible and TM joint. Tube and film attached at starting position, chin rest raised to same level as patient’s chin, chin rested on a sterile bite block, patient as close as possible to the tube stand, chin adjusted until IOML is parallel with the floor, occlusal plane declines 10 from posterior to anterior, patient’s lips placed together, tongue on roof of the mouth. Film: HD 23x30 cm, or curved non-grid cassette CP: Fixed CR and FFD.

Parieto-orbital (Rhese View) for optic foramina S For bony abnormalities of the optic foramen. Both sides must be done for comparison. Patient prone or erect, chin, cheek, and nose against couch, head adjusted so that the MSP makes 53 with the couch top, the acanthiomeatal line AML makes 90 to the film, a long narrow cone should be used. Film: HD 18x24 cm CP: Downside orbit (7 cm above and 7 cm behind the up EAM). CR: 90 to IR

Parietoacanthial (OM) (Waters View for sinuses ) B Best for maxillary and frontal sinuses and nasal fossae. Also shows other inflammatory conditions (secondary ostemyelitis, and sinus polyps). Patient erect, neck extended, chin and nose against couch, head adjusted till MML is 90 to the film. Film: HD 18x24 cm CP: At level of lower border of the orbits to exit at the acanthion. CR: 90 horizontal to film center

Parietoacanthial (OM) (Open-Mouth Waters for sinuses ) S Same as for Waters.. Same position as for Waters view, but with open mouth (patient drops his jaw without moving the head). Film: HD 18x24 cm. CP: At level of lower border of the orbits to exit at the acanthion. CR: 90 horizontal to film center

Assignment Two students will be selected for assignment

Suggested Readings Clark’s Radiographic technology

Question Describe radiographic principles of SKULL PA radiogram?

Thank You