Radiographic Technique – II Lecture 2 Prepared By: Ala’a Ali Tayem Abed.

Radiographic Positioning of the Skull

Skull Bones 1. Cranial Bones. 2. Facial Bones. Human Skull consist of 22 Bones: 8 Bones of the Cranium (Occipital Bone, 2 Temporal Bones, 2 Parietal Bones, Sphenoid Bone, Ethmoid Bone, Frontal Bone), and 14 Bones of the Facial (Vomer, 2 Conchae, 2 Nasal Bones, 2 Maxilla, Mandible, 2 Palatine Bones, 2 Zygomatic Bones, 2 Lacrimal Bones). The Skull also contains the Sinus Cavities, which are Air-Filled Cavities. Paranasal sinuses are a group of four paired air-filled spaces that surround the Nasal Cavity. 1. Cranial Bones. 2. Facial Bones.

Patient Preparation Useful Accessories Before undertaking skull radiography, the following specific considerations should be made: • Ensure that all metal objects are removed from the patient, e.g. hair clips and hairpins. • Bunches of hair often produce artifacts and thus should be untied. • If the area of interest includes the mouth, then false teeth containing metal and metal dental bridges should be removed. • The patient should be provided with a clear explanation of any movements and film positions associated with the normal operation of the skull unit. Useful Accessories • The usefulness of foam pads as an aid to immobilization cannot be overstated. The photograph opposite shows a specially designed pad for skull radiography. It is available in a range of sizes to accommodate different age groups. • Forty-five-degree triangular pads are extremely useful for immobilizing children. They can be held by the parent and support the head without the parent placing their hands in the primary beam. • Individual side markers are essential for skull radiography, as the clip-type side markers are easily lost in the collimation, particularly when using a skull unit. • Velcro straps are of great use when immobilizing a patient on a skull unit.

General Image Quality Guidelines and Radiation Protection considerations: • Images should have a visually sharp reproduction of all structures, such as outer and inner lamina of the Cranial Vault (Cranial Cavity), the trabecular structure of the cranium, the various sinuses and sutures where visible, vascular channels, Petrous part of the temporal bone and the pituitary fossa. • Important image details should be visualized. • Whenever possible, use an Occipito-frontal (PA) rather than a fronto-occipital (AP) since this vastly reduces the dose to the eyes. • Exposure Factors: 70 – 85 kVp. 20 mAs. • Cassette (IR) Size: 24 x 30 cm, (10 x 12 inches). • Cassette Orientation: Portrait but in Lateral View Landscape. • FFD / SID: 100cm, (40 in). • Always using Bucky (Grid). • Projections of the skull may be taken with the Patient sitting, standing or Laying depending on the patient's condition. Portrait: Lengthwise. Landscape: Crosswise.

Skull Projections ( Cranium) AP (Fronto occipital). PA (Occipito frontal). Lateral View. Fronto occipital ( AP Axial - TOWNE’S View). Occipito frontal ( PA - CALDWELL’S View). Submentovertex (SMV – Schüller Method). PA Axial (Haas Method).

AP Skull Positioning: Collimation: Outer skin margins of the skull. The patient typically presents in a supine position in trauma cases. Rotate the e Head of Patient to make the Radiographic Baseline (OML) perpendicular to IR. Centering Point: Directed to the Nasion. Central Ray: Perpendicular to the IR / Bucky, Parallel to the radiographic baseline (Orbitomeatal Line). Collimation: Outer skin margins of the skull.

AP Skull Evaluation Criteria No rotation is evidenced by The lateral borders of the orbits to the lateral borders of the skull are equidistant on both sides. No tilt is evidenced by The Petrous ridges are horizontal. Area Covered Collimation: Shutter A: Open to include the lateral skin margins of the skull. Shutter B: Open to include the entire skull superiorly, and the maxilla inferiorly. Exposure: Assess for adequate penetration of the thickest part of the skull, the frontal bone. Bony trabecular patterns and cortical outlines are sharply defined. Soft tissues are visualized.

PA Skull Positioning: Erect Prone Patient is standing or sitting facing the upright Bucky. Forehead and nose are touching the Bucky. The radiographic baseline (Orbitomeatal Line) is perpendicular to the Bucky. Ensure no rotation of the head by checking that the EAMs are the same distance from Bucky. Prone Rest patients nose and forehead against table/ Bucky. Flex neck to align OML perpendicular to IR. Centering Point: Exit at the level of the Glabella. Central Ray: Perpendicular to the IR / Bucky, Parallel to the radiographic baseline (Orbitomeatal Line). Collimation: Outer skin margins of the skull.

PA Skull Evaluation Criteria No rotation is evidenced by The lateral borders of the orbits to the lateral borders of the skull are equidistant on both sides. No tilt is evidenced by The Petrous ridges are horizontal and will be seen within the orbits. Area Covered Collimation: Shutter A: Open to include the lateral skin margins of the skull. Shutter B: Open to include the entire skull superiorly, and the maxilla inferiorly. Exposure: Assess for adequate penetration of the thickest part of the skull, the frontal bone. Bony trabecular patterns and cortical outlines are sharply defined. Soft tissues are visualized.

Cassette Orientation: Landscape. Lateral Skull Positioning: Patient standing or sitting facing the Bucky, Supine or Prone. Place the side of interest of the skull closest to the Bucky. Oblique the body slightly to assist with positioning and patient comfort. Interpupillary line perpendicular to Bucky. The midsagittal plane is parallel to the Bucky. Centering Point: Center to a point 2 inches (5 cm) superior to EAM. Central Ray: Perpendicular to the IR / Bucky. Collimation: Outer skin margins of the skull. Note: Cassette Orientation: Landscape.

Erect Supine Prone

Lateral Skull Evaluation Criteria No tilt is evidenced by There is superimposition of the superior orbital plates of the frontal bone. Area Covered Collimation: Shutter A: Open to include the skin margins of the top of skull superiorly, and the base of the Occipito inferiorly Shutter B: Open to include the skin margins of the anterior and posterior skull Exposure: Assess for adequate penetration of the thickest part of the skull, the frontal bone. Bony trabecular patterns and cortical outlines are sharply defined. Soft tissues are visualized. Lateral Skull

Skull - Townes (also called Skull - AP Axial) Positioning: Patient is in an erect position, either standing or sitting or Supine. Position the patient so that their back and posterior skull are touching the Bucky. Bring the patients chin down until the radiographic baseline Orbitomeatal line (OML) is perpendicular the Bucky. If the patient is not able to do this, the central ray angle may have to be increased caudally so that there is a 30 degree angle between the radiographic baseline (OML) and the central ray. Centering Point: Directed to 6 cm superior to the Glabella (this is typically the hairline). Central Ray: CR 30° caudal. Collimation: Outer skin margins of the skull.

Skull - Townes Evaluation Criteria No rotation is evidenced by The lateral borders of the foramen magnum are equidistant from the lateral borders of the skull. No tilt is evidenced by The Petrous ridges are horizontal. The central ray is at 30 degrees to the radiographic baseline, evidenced by The dorsum sellae & posterior clinoid processes are seen in the foramen magnum. Collimation Shutter A: Open to include the outer skin margins of the skull laterally Shutter B: Open to include the superior aspect of the skull Exposure Assess for adequate penetration of the thickest part of the skull The dorsum sellae and posterior clinoid processes are seen in the foramen magnum Bony trabecular patterns and cortical outlines are sharply defined Soft tissues are visualized. Skull - Townes

Skull - Caldwell (also called Skull - PA Axial) Positioning: Let the patient's nose and forehead rest the against table or Bucky surface. Slowly flex the patient's neck as needed to align Orbitomeatal Line (OML) perpendicular to Image Receptor. Centering Point: Exit at the level of the Nasion. Central Ray: Angulated Central Ray to 15° caudal. Alternate with CR 25° to 30° caudal. Collimation: Outer skin margins of the skull. Note: For patients who are unable to be positioned for a PA projection (e.g., trauma patients), an AP axial projection may be obtained with the use of a 15 ° cephalic angle, with the OML positioned perpendicular to the IR.

Skull - Caldwell Evaluation Criteria No rotation as assessed by equal distance from the midlateral orbital margins to the lateral wall of cranium on each side, superior orbital fissures symmetric within the orbits, correct extension of neck. In 15° caudal: Petrous pyramids are projected into the lower one-third of the orbits. In 25° - 30° caudal: Petrous pyramids are projected at or below the inferior orbital rim to allow visualization of the entire orbital margin. Collimation Shutter A: Open to include the outer skin margins of the skull laterally Shutter B: Open to include the superior aspect of the skull Exposure Assess for adequate penetration of the thickest part of the skull, the frontal bone. Bony trabecular patterns and cortical outlines are sharply defined. Soft tissues are visualized.

Skull - Caldwell PA - 15° Caudal PA - 0° PA / 25° - 30º Caudal

PA Axial (Haas Method) Positioning: Rest patient's nose and forehead against the table/Bucky surface. Flex neck, bringing OML perpendicular to IR. Align midsagittal plane to CR and to the midline of the grid or table/Bucky surface. Centering Point: Entering 1.5 in (3.8cm) inferior to external Occipital Protuberance (Inion) and exiting 1.5 in (3.8 cm) superior to Nasion. Central Ray: Angle CR 25° cephalic. Collimation: Outer skin margins of the skull. Note: For patients who are unable to be positioned for a PA projection (e.g., trauma patients), an AP axial projection may be obtained with the use of a 15 ° cephalic angle, with the OML positioned perpendicular to the IR.

Skull - Haas Evaluation Criteria No rotation is evident, as indicated by bilateral symmetric Petrous ridges. Dorsum sellae and posterior clinoids are visualized in the foramen magnum, which indicates correct CR angle and proper neck flexion and extension. No tilt as evidenced by correct placement of anterior clinoids within the middle of the foramen magnum. Collimation In Haas Method the entire skull is visualized in the image with the vertex near the top and the foramen magnum and mastoid portions near the bottom. Collimation borders are visible to outer margins of skull. Exposure Density and contrast are sufficient to visualize occipital bone and sellar structures within foramen magnum. Sharp bony margins indicate no motion. Skull - Haas

Submentovertex (SMV – Schüller Method) Positioning: The aim is to get the IOML (Infraorbitomeatal Line) parallel to the IR and Bucky. The method used to achieve this will depend on the presentation of the patient. The following description is for patients who are able to tip their head back, hyper extending their neck, and are able to sit. The patient sits in an AP position in front of the upright Bucky. The chin is raised and the head tipped back until the IOML is parallel to the Bucky and the vertex of the skull is centered and resting against the Bucky. If the patient is able to achieve this position then the central ray is perpendicular to both the Bucky and the IOML. If the patient is unable to tip their head back far enough, then angle the central ray so that it is perpendicular to the IOML. Centering Point: Directed at the point midway between the Angles of Mandible. Central Ray: Perpendicular to the IR / Bucky. Collimation: Outer skin margins of the skull.

(SMV – Schüller Method) Submentovertex (SMV – Schüller Method)

Skull – Schüller (SMV) Evaluation Criteria No rotation is evidenced by The lateral borders of the foramen magnum are equidistant from the lateral borders of the skull. No tilt is evidenced by The Vomer and the bony nasal septum are aligned with the long axis of the film. Collimation Shutter A: Open to include the soft tissue and lateral borders of the skull Shutter B: Open to include the mandible superiorly and the Occipito of the skull inferiorly. Exposure Assess for adequate penetration of the thickest part of the skull. Bony trabecular patterns and cortical outlines are sharply defined. Soft tissues are visualized. Skull – Schüller (SMV)

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