NEET MDS Lessons
Radiology
Fractures of the Zygomatic Arch
- Structures: Zygomatic arch, zygomatic bone.
- Best Views:
- Submento-Vertex View: Provides a clear view of the zygomatic arch and helps assess fractures.
- Waters View: Useful for visualizing the zygomatic bone and maxillary sinus.
- Reverse Townes View: Can also be used to visualize the zygomatic arch.
Base of Skull
- Structures: Base of the skull, cranial fossae.
- Best Views:
- Submento-Vertex View: Effective for assessing the base of the skull and related fractures.
Maxillary Sinus
- Structures: Maxillary sinus, zygomatic bone.
- Best Views:
- Waters View: Excellent for visualizing the maxillary sinus and any associated fractures.
Fractures of Zygoma
- Structures: Zygomatic bone, zygomatic arch.
- Best Views:
- Waters View: Good for assessing zygomatic fractures.
- PA View: Provides a frontal view of the zygomatic bone.
- Reverse Townes View: Useful for visualizing the zygomatic arch.
Nasal Septum
- Structures: Nasal septum, nasal cavity.
- Best Views:
- PA View: Useful for assessing the nasal septum and any associated fractures.
Condylar Neck Fractures
- Structures: Mandibular condyle, neck of the condyle.
- Best Views:
- Lateral Oblique View (15°): Good for visualizing condylar neck fractures.
- Transpharyngeal View: Useful for assessing the condylar region.
Medially Displaced Condylar Fractures
- Structures: Mandibular condyle.
- Best Views:
- Lateral Oblique View (30°): Effective for visualizing medially displaced condylar fractures.
Coronoid Process of Mandible
- Structures: Coronoid process.
- Best Views:
- PA View of Skull: Can help visualize the coronoid process.
Fractures of Ramus and Body of Mandible
- Structures: Mandibular ramus, body of the mandible.
- Best Views:
- Lateral Oblique View (15°): Useful for assessing fractures of the ramus and body of the mandible.
Horizontal Favorable and Unfavorable Fractures of Mandible
- Structures: Mandible.
- Best Views:
- Lateral Oblique View (30°): Effective for evaluating horizontal fractures.
Bony Ankylosis of TMJ
- Structures: Temporomandibular joint.
- Best Views:
- CT Scan: Provides detailed imaging of bony structures and ankylosis.
Fibrous Ankylosis of TMJ
- Structures: Temporomandibular joint.
- Best Views:
- CT Scan: Useful for assessing fibrous ankylosis.
Internal Derangement of the Disk
- Structures: TMJ disk.
- Best Views:
- MRI: The best modality for evaluating soft tissue structures, including the TMJ disk.
Disk Perforation
- Structures: TMJ disk.
- Best Views:
- MRI: Effective for diagnosing disk perforation.
Arthrography
- Structures: TMJ.
- Best Views:
- Arthrography: Can be used to assess the TMJ and visualize the disk and joint space.
Radiation Biology
-X- and g -rays are called sparsely ionizing because along the tracks of the electrons set in motion, primary ionizing events are well separated in space.
Alpha-particles and neutrons are densely ionizing because the tracks consist of dense columns of ionization.
X-rays, gamma rays, electrons, and protons are all low LET forms of radiation in that their density of ionization is sparse. In general, they penetrate tissues deeply and result in less intracellular radiation injury.
High LET forms of radiation, such as heavy nuclear particles (e.g. fast neutrons), penetrate tissues less deeply and cause more radiation injury to biologic material.
Cells are most sensitive to Radiation when:
- they are undifferentiated.
Exceptions to this Law:
- lymphocyte
- Oocyte
X-rays and gamma rays show latent injury that is residual tissue damage even after the initial radiation reaction is subsided.
Proteins tend to be more radiosensitive than carbohydrates and lipids.
Most radiosensitive tissue-small lymphocyte
Most radioresistant tissue- brain
Embryonic, immature or poorly differentiated tissues are more easily injured by radiation, but they also show greater recovery properties.
All cells show increased susceptibility to radiation at the time of mitotic division and if the cells are irradiated during the resting phase, mitosis is delayed or inhibited.
- In general, cells are most radiosensitive in late M and G2 phases and most resistant in late S.
- for cells with a longer cell cycle time and a significantly long G1 phase, there is a second peak of resistance late in G1
- the pattern of resistance and sensitivity correlates with the level of sulfhydryl compounds in the cell. Sulfhydryls are natural radioprotectors and tend to be at their highest levels in S and at their lowest near mitosis.
- To produce its effect. Oxygen must be present during the radiation exposure or at least during the lifetime of the free radicals (10-5 sec).
- Mandible is more ssceptible to radiation injury than maxilla due to the denser structure and poorer blood supply.
- Salivary glands though an organ with a low turnover rate, was unusually sensitive to radiation
- Liposarcoma tumors are the most radiosensitive soft tissue tumors
- Exophytic tumors are usually more easily controlled with radiation while infiltrative and ulcerative lesions are more radioresistant.
The infiltrative and ulcerative lesions are more likely to be larger than clinically apparent and contain a larger proportion of hypoxic cells.