NEET MDS Lessons
Radiology
1. Postero-Anterior (PA) View of Skull
- Head Position: Centered in front of the cassette; canthomeatal line parallel to the floor. For cephalometric applications, the canthomeatal line is 10° above the horizontal, and the Frankfort plane is perpendicular to the film.
- Projection of Central Ray: Passes posterior to anterior, perpendicular to the film.
- Important Features:
- Used to examine the skull for disease, trauma, and sinuses.
- Best for viewing the coronoid process; a PA view with a 10° tilt is called the Caldwell projection.
2. Lateral Skull or Cephalometric View
- Head Position: Left side of the face near the cassette; midsagittal plane parallel to the film.
- Projection of Central Ray: Directed towards the external auditory meatus, perpendicular to the film and midsagittal plane.
- Important Features:
- Assesses facial growth.
- Reveals soft tissue profile.
- Surveys skull and facial bones for disease and trauma.
3. Water's Projection
- Head Position: Sagittal plane perpendicular to the film; chin raised so the canthomeatal line is 37° above horizontal.
- Projection of Central Ray: Passes through the maxillary sinus.
- Important Features:
- Also known as Occipito-mental projection (variation of PA view).
- Best for demonstrating zygoma fractures, paranasal sinuses, and nasal cavity.
- Shows the position of the coronoid process between the maxilla and zygomatic arch.
4. Submentovertex (SMV) View
- Head Position: Head and neck extended backward; vertex of the skull at the center of the cassette.
- Projection of Central Ray: Directed towards the vertex of the skull.
- Important Features:
- Also called BASE, FULL AXIAL, or JUG HANDLE VIEW.
- Best for viewing the base of the skull and zygomatic arch fractures.
- Contraindicated in patients with cervical spondylitis.
- For viewing zygomatic arches, exposure time is reduced to one-third of that used for the skull.
5. Reverse Towne's View
- Head Position: Canthomeatal line oriented 25-30° downward.
- Projection of Central Ray: Directed towards the occipital bone.
- Important Features:
- Frankfort plane vertically oriented and parallel to the film.
- Best for viewing condylar neck fractures.
- Condyles are better visualized if the patient opens their mouth widely.
6. Lateral Oblique Mandibular Body Projection
- Head Position: Tilted towards the side being examined; mandible protruded.
- Projection of Central Ray: Directed towards the first molar region.
- Important Features:
- Demonstrates the premolar and molar region.
- Best for viewing the inferior border of the mandible.
7. Lateral Oblique Mandibular Ramus Projection
- Head Position: Tilted towards the side being examined; mandible protruded.
- Projection of Central Ray: Directed posteriorly towards the center of the ramus.
- Important Features:
- Often used for examining third molar regions of the maxilla and mandible.
- Provides a view of the ramus from the angle to the condyle.
General guidelines for vertical angulations for common dental radiographs in children:
Anterior Teeth
- Maxillary Central Incisors:
- Vertical Angulation: +40 to +50 degrees
- Maxillary Lateral Incisors:
- Vertical Angulation: +40 to +50 degrees
- Maxillary Canines:
- Vertical Angulation: +45 to +55 degrees
- Mandibular Central Incisors:
- Vertical Angulation: -10 to -20 degrees
- Mandibular Lateral Incisors:
- Vertical Angulation: -10 to -20 degrees
- Mandibular Canines:
- Vertical Angulation: -15 to -25 degrees
Posterior Teeth
- Maxillary Premolars:
- Vertical Angulation: +30 to +40 degrees
- Maxillary Molars:
- Vertical Angulation: +20 to +30 degrees
- Mandibular Premolars:
- Vertical Angulation: -5 to -10 degrees
- Mandibular Molars:
- Vertical Angulation: -5 to -10 degrees