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Questions and Answers
What is the correct position of the patient when imaging occurs supine?
What is the angle at which the central ray should be directed to the orbito-meatal plane for imaging?
Which anatomical feature should be centrally projected within the foramen magnum in the X-ray image?
How should the median sagittal plane be positioned in relation to the image receptor?
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What is the recommended position for an unsteady patient during X-ray imaging?
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What should be ensured about the skull during the imaging process to avoid rotation?
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How should the top of the cassette be positioned to ensure appropriate beam angulation?
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What adjustment should be made to the orbito-meatal baseline relative to the image receptor?
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What is the correct positioning of the patient when undertaking a skull radiographic technique?
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Which anatomical landmarks should be aligned perpendicular to the image receptor during a basic skull radiographic technique?
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Which describes the proper angulation of the collimated beam in skull radiography?
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What is the consequence of improper elevation of the head during skull imaging?
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What common fault occurs when the lateral portions of the cranial fossa are not superimposed?
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What is the purpose of using a non-opaque skull pad during the imaging process?
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What must be ensured to avoid common faults in skull radiography positioning?
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What does a true lateral view in skull imaging result in?
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What is the correct positioning of the petrous ridges in an OF projection?
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Why should fronto-occipital projections only be performed when a patient cannot be moved?
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What must be ensured regarding the patient's position for accurate imaging?
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What is the primary direction for angulations in FO projections?
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What happens to the image resolution of skull structures during FO projections?
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Which of the following statements about the collimated vertical X-ray beam is correct?
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What is one advantage of maintaining the correct alignment of the image receptor?
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What should be included in the collimated field for FO projection?
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Study Notes
Basic Skull Technique
- The patient should lie supine with the head raised and stabilized using a non-opaque skull pad.
- The median sagittal plane should be perpendicular to the table/trolley, while the interpupillary line is perpendicular to the image receptor.
- The image receptor should be positioned vertically against the lateral aspect of the head, parallel to the median sagittal plane, with its edge 5 cm above the vertex of the skull.
- The beam should be directed parallel to the interpupillary line, at right-angles to the median sagittal plane.
- The centring point is midway between the glabella and the external occipital protuberance, approximately 5 cm superior and posterior to the EAM.
- The long axis of the image receptor should align with the long axis of the skull.
- The image should capture all cranial bones and the 1st cervical vertebrae.
- A true lateral view will show superimposition of the lateral portions of the anterior and posterior cranial fossa floors.
- The clinoid processes of the sella turcica should also be superimposed.
Common Faults and Solutions
- If the occipital region is not included, adjust the head to ensure it is elevated properly.
- For poor superimposition of cranial fossa floors, ensure the interobital line is perpendicular to the cassette/receptor, and the median sagittal plane is perpendicular to the trolley surface.
Lateral Skull Technique
- The patient should sit facing the erect Bucky/receptor.
- The head should be rotated so the median sagittal plane is parallel to the Bucky/receptor, and the interpupillary line is perpendicular to the Bucky/receptor.
- The shoulders may need to be rotated for proper positioning.
- The patient may grip the Bucky inferiorly for stability.
- The degree of beam angulation is determined by the position of the petrous ridges within the orbits:
- OF - petrous ridges are completely superimposed within the orbit, with upper borders coincident with the upper 1/3 of the orbit.
- OF10°↓ - petrous ridges are in the middle 1/3 of the orbit.
- OF15°↓ - petrous ridges are in the lower 1/3 of the orbit.
- OF20°↓ - petrous ridges are just below the inferior orbital margin.
Fronto-Occipital (FO) Projections
- FO projections demonstrate the same anatomy as OF projections.
- Orbits and the frontal bone are magnified due to their increased distance to the image receptor.
- FO projections are only used for patients who cannot be moved and must be imaged supine.
- These projections increase radiation dose to the orbits and result in some loss of resolution in anterior skull structures due to increased object-to-receptor distance.
FO Projections - Positioning and Beam Direction
- The patient should lie supine with the posterior aspect of the skull resting on the image receptor/gridded CR cassette.
- The head should be adjusted to bring the median sagittal plane at right-angles to the image receptor and coincident with its midline.
- The EAMs should be equidistant from the image receptor to avoid rotation.
- The orbito-meatal baseline should be perpendicular to the image receptor.
- All angulations are made cranially for FO projections.
- The collimated vertical X-ray beam is directed perpendicular to the image receptor along the median sagittal plane.
- The collimated field should include the vertex of the skull superiorly, the base of the occipital bone inferiorly, and the lateral skin margins.
- FO10°↑, FO15°↑, FO20°↑: These projections employ the same technique as OF, but use cranial angulation. The degree of angulation varies based on the projection required.
- The image receptor must be moved superiorly to accommodate the tube angulation.
Townes Projection - Positioning and Beam Direction
- Patient lies supine on the trolley/X-ray table with the posterior aspect of the skull resting on the image receptor/gridded CR cassette.
- The head should be adjusted to ensure the median sagittal plane is at right-angles to the image receptor and coincident with its midline.
- The orbito-meatal baseline should be perpendicular to the image receptor.
- The central ray is angled caudally, forming a 30-degree angle to the orbito-meatal plane.
- Center the beam midway between the external auditory meatuses, approximately 5 cm above the glabella.
- The top of the cassette should be positioned adjacent to the vertex of the skull to prevent the area of interest projecting off the bottom of the image.
Townes Projection - Essential Image Characteristics
- The sella turcica of the sphenoid bone should appear within the foramen magnum.
- The image should include all of the occipital bone and the posterior parts of the parietal bone.
- The lambdoidal suture should be clearly visualized.
- The skull should not be rotated - this can be assessed by ensuring the sella turcica appears centrally in the foramen magnum.
Basal Skull View
- The patient can be imaged erect or supine.
- Supine technique is advisable if the patient is unsteady.
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Supine Technique:
- The patient's shoulders are raised and neck is hyperextended so that the vertex of the skull touches the image receptor/gridded CR cassette.
- The head should be adjusted to bring the EAMs equidistant from the image receptor.
- The median sagittal plane should be at right-angles to the image receptor, along its midline.
- The orbito-meatal plane should be as close to parallel as possible to the image receptor.
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Erect Technique:
- The patient sits facing the X-ray tube a short distance away from the vertical Bucky/receptor.
- The neck is hyperextended, allowing the head to fall back until the vertex of the skull makes contact with the center of the vertical image receptor.
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Description
Test your understanding of the basic skull technique in radiography. This quiz covers positioning, alignment, and capturing essential views of cranial bones and vertebrae. Ideal for students and professionals in medical imaging.
