What angle of the CR is used for a PA axial Caldwell view of the facial bones?

CALDWELL METHOD | PA AXIAL FOR FACIAL BONE X-RAY

Pathology Demonstrated:

• Fracture and neoplastic or inflammatory processes of the facial bones are shown.

Technical Factors:

• IR size is 24 x 30 cm (10 x12 inches), lengthwise or film size 18 x 24 cm (8 x 10 inches)
• Image receptor size varies depending on the patient.
• Moving or stationary grid.
• 70 to 80 kV range.
• Small focal spot.
• mAs 18

Patient Position:

• Rest patient's nose and forehead against table top.
• Tuck chin, bringing OML perpendicular to image receptor.
• Align MSP perpendicular to middle of grid or table or bucky surface. Ensure no rotation or tilt of head.

Central Ray of Caldwell Method:

• Angle Central Ray 15 degrees caudad, to exit at nasion. If area of interest is the orbital floors, use a 30 degree caudad angle to project the petrous ridges below the inferior orbital margin.
• Central Ray must be centered to IR.
• Ensure minimum SID of 40 inches (100 cm)

Collimation:

• Collimate on all sides to facial bones.

Respiration:

• Suspend respiration.

Radiographic Criteria when performing the Caldwell Method:

Structure Shown:

• Orbital rim, maxillae, nasal septum, zygomatic bones and anterior nasal bone spine.

Position:

• Correct patient position / CR angulation is indicated by petrous ridges projected into the lower 1/3 of orbits with 15 degrees caudad central ray. If the orbit floors are the area of interest, the 30 degree caudad angle projects the petrous ridges below the inferior margins of the orbit.
• No rotation of cranium is indicated by equal distance from midlateral orbital margin to the outer skull margin on each side
• Superior Orbital fissures are symmetric.

Collimation and Central Ray:

• The inferior orbital rim is located at the center of the image.
• The collimated field includes the entire orbital margin and maxillae.

Exposure Criteria:

• Comtrast and density are sufficient to visualize maxillary region and orbital floor.
• Sharp bony margins indicate no motion.

Caldwell's view (or Occipitofrontal view) is a radiographic view of skull, where X-ray plate is perpendicular to the orbitomeatal line. The rays pass from behind the head and are angled at 15-20° to the radiographic plate. It is commonly used to get better view of the ethmoid and frontal sinuses. It is named after the noted American radiologist Eugene W. Caldwell, who described it in 1907.

Structures seen[edit]

Possible observations[edit]

• Different pneumatisation patterns of frontal sinus are observed in population.
• The frontal sinuses can be asymmetric in normal individual.
• Usually, frontal sinus shows radiolucent shadow and individual cells are made out, giving it a scalloping or clove-like appearance.

• Increased frontal sinus opacity.
• Normal scalloping absent.

• Marked radiopacity is seen. (Denser than bone)

References[edit]

The skull is a solid bony structure that encloses and protects the brain and other components of the central nervous system. It consists of 8 cranial bones and 14 facial bones (see our article on radiographic positioning of the face and mandible). The back of the cranium consists of the occipital and right and left parietal bones. The vertex is made up of the paired parietal bones joining the frontal bone at the sagittal suture. The right and left parietal bones and right and left temporal bones make up the sides of the cranium. The front of the cranium consists of the frontal bone. The base of the skull is complex and consists of the paired temporal bones as well as the sphenoid and ethmoid. The base has numerous foramina to allow passage of nerves, veins, and arteries. Radiologists use the images of the skull to assess the size, shape, thickness, and density of skull bones as well as vascular markings and sutures. Due to the complexity of skull anatomy, technologists require an in-depth understanding and attention to detail during radiographic imaging of the face and skull. To this end, we have separate articles, for example, radiographic positioning of the mastoid process, that provide more detailed information.

Major Landmarks in Skull Radiography

• Vertex
• External Occipital Protuberance
• External Auditory Meatus
• Outer Canthus of the Eye
• Infraorbital Point
• Glabella
• Nasion
• Acanthion

Patient Positioning for Skull Radiography

Patients can be imaged either erect or recumbent. In the erect position, a standard X-ray table and upright Bucky are used. This allows easy and quick positioning and use of a horizontal beam, which is necessary to demonstrate any air-fluid levels in the cranium or sinuses. The patient’s head needs to be positioned precisely during skull radiography, but techs should remember to keep the body in a comfortable position, using aids such as pillows and sponges if necessary. In general, respiration is suspended during exposure to prevent artifacts due to breathing movements, although this may not be possible in patients with severe trauma. RTs must remember to perform appropriate handwashing and hygiene measures as well disinfection of surfaces since radiographic positioning of the skull frequently requires direct contact between the patient’s face and the technologist’s hands and table/Bucky surface.

Imaging Planes for Skull Radiography

In order to produce accurate images and reproducing positioning, technologists must understand the planes used in skull radiography. For example, the median sagittal plane is a vertical plane perpendicular to the ground that separates the skull into equal right and left halves when viewed from the front of the patient. The coronal plane (auricular plane) is a vertical plane that divides the skull into anterior and posterior parts along the auricular line. The transverse plane (anthropological plane) is a horizontal plane that splits the skull into upper and lower halves.

Baselines Used in Skull Radiography

• The orbitomeatal line (OML) runs from the nasion through the outer canthus of the eye to the center of the external auditory meatus.
• The infraorbitomeatal line (IOML) runs from the inferior orbital margin to the upper border of the external auditory meatus.
• The meatomental line (MML) runs from the external auditory meatus to the mental point (tip of chin).
• Other lines used in skull radiography include the glabellomeatal (GML), acanthomeatal (AML), and lipsmeatal (LML).

Skull PA Occipito-Frontal

Purpose and Structures Shown To get a clear posteroanterior image of the skull and demonstrate pathology such as skull fractures with medial and lateral displacement. This projection demonstrates the frontal bone, crista galli, internal auditory canals, anterior ethmoid and frontal sinuses, greater and lesser wings of the sphenoid, and petrous ridges.

Position of patient Prone with the vertical beam angled at 20 degrees. This position should never be used if there is a possibility of facial bone fractures or in unconscious patients.

Position of part Remove dentures, hair grips, ear clips, and anything from the hair. Provide a mattress under the body for comfort. The hands should be under the chest. The forehead and nose are on the table.

Skull PA Axial Caldwell Method

Purpose and Structures Shown A caudally angled PA radiograph of the skull to visualize the frontal sinus and other paranasal sinuses. This projection demonstrates skull fractures with medial and lateral displacement. Structures shown include the greater and lesser sphenoid wings, superior orbital fissures, frontal bone, anterior ethmoid and frontal sinuses, superior orbital margins, and crista galli.

Position of patient Standing erect with the tube angled at 15 degrees caudal. The patient’s nose and forehead are placed against the IR. Keeping the orbitomeatal line perpendicular to the IR ensures no tilt or rotation. Centering is at the nasion. The midsagittal plane is perpendicular to the IR to ensure no tilt.

Position of part Remove dentures, hair grips, ear clips, and anything from the hair. The patient should be asked to suspend respiration during exposure. In a properly positioned Caldwell image, the petrous ridges are symmetric and project into the lower third of the orbits. The medial and lateral orbital margins are equidistant from the lateral cranium on either side indicating no rotation.

Purpose and Structures Shown A PA projection of the skull to visualize the sellar structures projecting into the foramen magnum in patients who cannot be positioned for the AP axial projection. Structures demonstrated include the occipital bone, foramen magnum, and petrous pyramids along with the posterior clinoids and dorsum sellae in the shadow of the foramen magnum.

Position of patient Prone with the central ray directed cephalad at an angle of 25 degrees. The angulation can be varied to demonstrate other anatomy as needed. The midsagittal plane is centered to the midline of the grid. The elbows are flexed and the arms are placed in a comfortable position. The shoulders are adjusted to lie flat against the table in the same horizontal plane.

Position of part Remove dentures, hair grips, ear clips, and anything from the hair. The patient’s nose and forehead rest on the table. Neck flexion is adjusted to ensure the orbitomeatal line is perpendicular. The head is immobilized. The patient should be asked to suspend respiration during exposure. The image shows the occipital region of the skull with symmetric petrous pyramids. The dorsum sellae are projected into the foramen magnum. The entire cranium is visualized with a symmetric distance between the lateral border of the skull and the lateral margin of the foramen magnum on both sides.

Video Credit : ela drozd

Skull AP Fronto-Occipital

Purpose and Structures Shown To get a clear anteroposterior image of the skull. Anatomy seen includes the frontal bone, crista galli, internal auditory canals, ethmoid and frontal sinuses, and greater and lesser wings of the sphenoid.

Position of patient Supine with the vertical beam angled at 20 degrees. This position is used for patients who cannot be imaged in the prone position.

Position of part Remove dentures, hair grips, ear clips, and anything from the hair.  The chin is extended fully. The head is immobilized. The patient should be asked to suspend respiration during exposure. The VSM projection is useful to evaluate the anterior cranial base and sphenoid sinuses. In a properly positioned VSM projection, the petrosae are symmetric and the lateral margin of the skull is equidistant on both sides from the mandibular condyles. Structures of the cranial base are visualized and the mandibular symphysis is superimposed on the anterior frontal bone.

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