Image Criteria Skull

IMAGE CRITERIATHE SKULL

BY: MS NORFARIHA BT CHE MOHAMED

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• Patient Preparations• Positioning Considerations

- skull morphology- surface markings and reference lines and planes- positioning modifications

• Breathing Instructions• Exposure Factors• Radiation Protections

1. Patient preparation• Basic psychological preparation with reassurance and

explanation of technique.

• Patients referred for skull radiography may be worried and anxious about the outcome.

• Some will be mentally disturbed, unconscious or unable to co-operate; the assistance of a nurse or other competent person may be required

1. Patient preparation

• Before starting any examination, the identity of the patient must be checked by the radiographer; a patient may answer to a name not his/her own and this is particularly true for some disorientated patients attending for skull imaging.

• Metallic objects are removed from neck and head area – e.g eye glasses, dental appliances, hairpins, elastic bands, buttons and zippers.

• Wash hands or wear disposable gloves.

2. Positioning Considerations

Erect vs recumbent• Examination can be done erect or recumbent• Advantages of erect: – easier for the patient and– allows visualization of fluid levels

• Before attempting erect position assess patient conditions – not all patients are suitable for the erect

• For recumbent position, consider patient body type and comfort when positioning is made and give enough support to get accurate positions

Skull Morphology

Surface Markings

Positioning Modifications for Various Body Types

3. Breathing Instructions

• In order to help minimize movement and unsharpness on the film, exposure should be made on suspended respiration where possible.

• Alert the patient that the exposure is going to be made.

4. Technical Factors

• Small focal spot when possible – to get sharper image (high resolution)

• Tight collimation – improves image quality – how?• kVp ranges from 65-85 kVp

: 65-70 – lateral,: 80-85 – AP/PA/Axial

• mAs depends on film/screen speed, type of grid, and pathologic condition

5. Radiation Protection

• The most radiosensitive organs involved are the eyes and thyroid gland Use PA instead of AP projection

• The use of beam limiting cones and diaphragms is adequate in most cases.

• Direct lead rubber gonad protection when the central ray is directed towards the gonads is probably not necessary but may be considered good practice.

• The most effective method of dose reduction is careful technique to avoid the need for repeat radiographs.

Skull Projections (Cranium)

• Lateral• PA (OF) • PA axial (Caldwell) • AP axial 30°/37° (Towne)

Lateral Skull• Shows the detail of the side

adjacent to the IR• Entire cranium without

rotation or tilt• Superimposed orbital roofs

and greater wings of sphenoid• Superimposed mastoid

regions and EAMs• Superimposed TMJs• Sella turcica seen in profile• No overlap of cervical spine

by mandible

PA (OF) - 0°

• The orbits are filled by the margins of the petrous portions.

• The posterior ethmoidal air cells, crista galli, frontal bone, and frontal sinuses also seen.

• The dorsum sellae is seen as a curved line extending between the orbits, just above the ethmoidal air cells.

PA axial (Caldwell) - 15°

• Many of the same structures that appear in the direct PA projection are seen.

• However, the petrous ridges are projected into the lower third of the orbits.

AP axial 30°/37° (Towne)

• Equal distance from the lateral border of skull to lateral margin of foramen magnum on both sides, indicating no rotation

• Symmetric petrous pyramids• Dorsum sellae and posterior

clinoid processes visible within foramen magnum

• Penetration of occipital bone without excessive density at lateral borders of skull

Skull Projections (Cranial Base)

Cranial Base Submentovertical (SMV) – Shuller Method

Sella Turcica (coned view) Lateral AP Axial 30° and 37°

Optic canal and foramen Parietorbital oblique – Rhese Method Orbitoparietal oblique – Rhese Method

SMV Cranial base• Clearly visible structures of the

cranial base• Equal distance from lateral

border of skull to mandibular condyles on both sides, indicating no tilt

• Superimposition of mental protuberance over anterior frontal bone, indicating full extension of neck

• Mandibular condyles anterior to petrous pyramids

• Symmetric petrosae

Lateral sella turcica

• No rotation or distortion of sella turcica

• Superimposed anterior clinoid processes

• Superimposition of posterior clinoid processes

• Sella turcica centered on radiograph

• Close beam restriction of sellar region

AP axial (Towne) sella turcica

• Sellar structures witin foramen magnum with a 37° angle

• Sellar structures through occipital bone with a 30° angle

• No rotation of cranium• Symmetric petrous

pyramids• Close beam restriction

of sellar region

Parieto-Orbital Oblique (Rhese) Optic Canal/Foramen

• Optic canal and foramen visible at end of sphenoid ridge in inferior and lateral quadrant of orbit

• Entire orbital rim• Supraorbital margins lying

in same horizontal line• Close beam restriction to

the orbital region

Orbitoparietal Oblique (Rhese) Optic Canal/Foramen

• Optic canal and foramen visible at end of sphenoid ridge in inferior and lateral quadrant of orbit

• Entire orbital rim• Close beam restriction to

the orbital region• Supraorbital margins lying

on same horizontal plane

POP QUIZ!!

THANK YOU..