Skull Planes and Positioning Terminology

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Questions and Answers

What does the median sagittal plane divide the skull into?

Superior and inferior halves

Right and left halves (correct)

Coronal and axial halves

Anterior and posterior halves

What is the method for describing a skull projection not dependent on?

The angle of the central ray

Centring point within the X-ray beam

The size of the image receptor (correct)

The relative positions of the skull planes

In which plane does the auricular plane run?

Perpendicular to the median sagittal plane (correct)

At an angle to the coronal plane

Dividing the skull into top and bottom halves

Parallel to the anthropological plane

When describing beam angulation, what does a cranial angulation indicate?

Beam directed towards the head Signup and view all the answers

What happens in an occipto-frontal projection?

The central ray enters through the occipital bone Signup and view all the answers

Which of these projections would involve a central ray angling towards the feet?

FO30°↓ projection Signup and view all the answers

Which anatomical landmark is located at the posterior end of the median sagittal plane?

External occipital protuberance Signup and view all the answers

Which statement is true regarding the coronal planes?

They run at right angles to the median sagittal plane. Signup and view all the answers

What is the significance of landmarks in skull radiography?

They assist in properly positioning the patient for accurate imaging. Signup and view all the answers

Which of the following correctly describes the nasion?

The articulation between the nasal and frontal bones. Signup and view all the answers

What anatomical structure is referred to as the 'glabella'?

A bony prominence on the frontal bone. Signup and view all the answers

Which line in skull radiography connects the outer canthus of the eye to the center of the external auditory meatus?

Orbito-meatal baseline Signup and view all the answers

What is the position of the vertex in relation to the skull?

The highest point of the skull in the median sagittal plane. Signup and view all the answers

Where is the external occipital protuberance located?

On the occipital bone at the median sagittal plane. Signup and view all the answers

What does the infraorbital margin refer to?

The lowest point of the inferior rim of the orbit. Signup and view all the answers

Which landmark is located at the posterior border of the lower border of the ramus of the mandible?

Angle of the mandible Signup and view all the answers

What defines a lateral projection in radiography?

The central ray passes through the coronal plane. Signup and view all the answers

How is an oblique projection primarily named?

According to the contact of either anterior or posterior portion of the head. Signup and view all the answers

What does a 40 degree left anterior oblique projection indicate about the head's position?

The median sagittal plane is 40° to the image receptor. Signup and view all the answers

What additional element complicates oblique projections?

Adding caudal or cranial angulation. Signup and view all the answers

In the given complex projection of 55°RAO with 35° caudal angulation, what is the significance of the median sagittal plane's angle?

It specifies the angle of the head in relation to the receptor. Signup and view all the answers

When creating the combination projection with a 20° raised plane and a 15° caudal angulation, what is the resulting total beam angulation?

Total beam angulation sums up to 35°. Signup and view all the answers

In a lateral projection where the beam enters from the left side and exits on the right, how is this defined?

As a right lateral projection. Signup and view all the answers

Why might both tube angling and chin raising be used in complex projections?

To compensate for patient mobility limitations. Signup and view all the answers

Study Notes

Skull Planes

Median Sagittal Plane: Divides the skull into right and left halves. The nasion (anterior) and external occipital protuberance/inion (posterior) are landmarks.
Coronal Planes: Perpendicular to the median sagittal plane. They divide the head into anterior and posterior sections.
Anthropological plane: Horizontal plane containing the two anthropological baselines and the infraorbital line.
Auricular Plane: Perpendicular to the anthropological plane and passes through the center of the two external auditory meatuses (EAM).
Median Sagittal, Anthropological, and Coronal Planes are all at right angles to each other.

Positioning Terminology

Skull Projections: Require specifying:
- Skull plane relative to image receptor
- Central ray relative to skull planes/image receptor
- Centring point or area for collimated X-ray beam
Occipto-frontal (OF) projection: Central ray enters the skull through the occipital bone and exits through the frontal bone.
Frontal-Occipital (FO) projection: Central ray enters the skull through the frontal bone and exits through the occipital bone.

Beam Angulation

OF, FO, or Lateral Projections: Often require central ray to pass along the sagittal plane, angled to the orbital-meatal plane.
Cranial Angulation: Beam directed up the body towards the head (↑).
Caudal Angulation: Beam angled toward the feet (↓).
Example: (FO30°↓) indicates a fronto-occipital projection with 30 degrees of caudal angulation.

Lateral Projections:

Collimated Central Ray: Passes along a coronal plane, perpendicular to the median sagittal plane.
Naming: Based on the side of the head closest to the image receptor.
Example: Right lateral projection: beam enters the skull on the left side, exits on the right side where the image receptor is located.

Oblique Projections

Central Ray: At an angle to both the median sagittal plane and the coronal plane.
Naming: Based on:
- Whether the anterior or posterior portion of the head is in contact with the receptor
- Whether the left or right side of the head is in contact with the receptor
Example: Forty degree left anterior oblique (40°LAO): head rotated to the left, median sagittal plane 40° to the image receptor, left side of the head in contact with receptor.

Complex Oblique Projections

Caudal or Cranial Angulation: Added in relation to a specified baseline (often achieved by raising or lowering the chin).
Example: Fifty-five degree right anterior oblique with 35°caudal angulation (55°RAO35°↓): right side of face in contact with receptor, median sagittal plane at a 55° angle, 35° caudal beam angulation.

Skull Landmarks

Outer Canthus of the Eye: Lateral point where the upper and lower eyelids meet.
Infraorbital Margin/Point: Lowest point on the inferior rim of the orbit.
Nasion: Articulation between the nasal and frontal bones.
Glabella: Bony prominence on the frontal bone superior to the nasion.
Vertex: Highest point of the skull in the median sagittal plane.
External Occipital Protuberance (Inion): Bony prominence on the occipital bone, usually coincident with the median sagittal plane.
External Auditory Meatus (EAM): Opening within the ear that leads into the external auditory canal.
Angle of the Mandible (Gonial Angle): Posterior border at the junction of the lower border of the ramus of the mandible.

Skull Lines

Interpupillary (Interorbital) Line: Joins the centers of the two orbits or the centers of the two pupils when the eyes are looking straight forward.
Infraorbital Line: Joins the two inferior infraorbital points.
Anthropological Baseline: Passes from the infraorbital point to the upper border of the EAM.
Orbito-meatal Baseline (Radiographic Baseline): Extends from the outer canthus of the eye to the center of the EAM.

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Description

Explore the various skull planes such as the median sagittal, coronal, and anthropological planes. Understand their positions, landmarks, and relevance in skull projections and X-ray imaging techniques. This quiz will test your knowledge on the terminology and concepts related to skull anatomy.