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Skull CT anatomy

The sagittal suture is the line where the right and left parietal bone are in contact.

The coronal suture is the line where the parietal bone frontal bone and are in contact.

The lambdoid suture is a line where the parietal bone occipital bone and are in contact.

The lambda is the point where joins lambdoid sutures and the Sagittal suture.

The bregma is the point where joins coronal suture and sagittal suture.

Images are shown from the vertex to the base of the skull

Image 1. CT Anatomy of skull, axial reconstruction, bone window.
1, Parietal bone. 2, Sagittal suture.

  • Image 1. CT Anatomy of skull, axial reconstruction, bone window.
    1, Parietal bone. 2, Sagittal suture.

  • Image 2. CT Anatomy of skull, axial reconstruction, bone window.
    1, Parietal bone. 2, Lambdoid suture. 3, Lambda.

  • Image 3. CT Anatomy of skull, axial reconstruction, bone window.
    1, Sagittal suture. 2, Parietal bone. 3, Lambdoid suture. 4, Occipital bone.

  • Image 4. CT Anatomy of skull, axial reconstruction, bone window.
    1, Coronal suture. 2, Bregma. 3, Parietal bone. 4, Lambdoid suture. 5, Occipital bone.

  • Image 5. CT Anatomy of skull, axial reconstruction, bone window.
    1, Frontal bone. 2, Coronal suture. 3, Parietal bone. 4, Lambdoid suture. 5, Occipital bone.

  • Image 6. CT Anatomy of skull, axial reconstruction, bone window.
    1, Temporal bone. 2, Frontal bone. 3, Squamosal suture. 4, Mastoid air cells. 5, Lambdoid suture. 6, Occipital bone. 7, Posterior cranial fossa.

  • Image 7. CT Anatomy of skull, axial reconstruction, bone window.
    1, Middle cranial fossa. 2, Greater wing of sphenoid bone. 3, Frontal bone. 4, Anterior cranial fossa. 5, external auditory canal. 6, Petrous temporal bone.

  • Image 8. CT Anatomy of skull, axial reconstruction, bone window.
    1, Mandibular condyle. 2, Sphenosquamosal suture. 3, Frontal bone. 4, Greater wing of sphenoid bone. 5, Temporal bone. 6, Sphenoid sinus. 7, Clivus.

  • Image 9. CT Anatomy of skull, axial reconstruction, bone window.
    1, Mandibular condyle. 2, Zygomatic bone. 3, Ethmoid bone / ethmoid air cells. 4, Zygomatic arch.

  • Image 10. CT Anatomy of skull, axial reconstruction, bone window.
    1, Lateral mass of C1. 2, Zygomatic bone. 3, Globe. 4, Nasal bone. 5, Maxillary sinus. 6, Zygomatic arch. 7, Pterygoid process (sphenoid bone). 8, Mandible. 9, Ondotoid process (C2).

  • Image 11 of 11. CT Anatomy of skull, axial reconstruction, bone window.
    1, C1. 2, Pterygoid process. 3, Maxillary sinus. 4, Zygomatic bone. 5, Mandible. 6, Ondotoid process (C2).

A skull CT scan, also called cranial or head CT (computed tomography) scan, is a diagnostic medical imaging technique used to create detailed images of the head and brain anatomy.

A skull CT scan uses special X-ray equipment to generate a series of cross-sectional and three-dimensional images of the head and neck region(1).

However, unlike X-rays, a CT imaging scan shows the internal organs in greater detail, especially soft tissues and blood vessels(2).

Understanding Skull CT Imaging

In grayscale skull or cranial CT imaging, the black areas denote air pockets or areas filled only with air(3). These areas include the paranasal sinuses (air-filled extensions of the nasal cavity) and mastoid air cells.

The bright white shapes in CT images are structures with calcium content, such as bones of the cranium or skull(4).

Soft tissues and fluids are shown in different shades of gray(5). Among soft tissues in the head and neck region are the brain matter, eyes, and muscles.

Fluids commonly observed in skull CT scans are blood and cerebrospinal fluid or the liquid surrounding the brain and spinal cord.

How Skull CT Images Are Produced

Contrast agents or contrast materials are required for different radiology imaging scans, including CT scans(6).

As the name suggests, contrast materials increase the visual contrast of the different internal body organs. These materials help highlight the areas that need to be examined(7).

Various contrast materials have different purposes and reactions, depending on the radiology imaging technique or tool used.

Contrast agents used in CT scans and X-rays absorb radiation(8). Meanwhile, contrast dyes used in MRI scans have magnetic properties (ability to magnetize). 

In ultrasonography or ultrasound procedure, contrast dyes may help reflect the ultrasound waves, which produces higher contrast in ultrasound images(9)

Radiological contrast material may be administered in three ways(10):

  • Swallowed or taken by mouth
  • Injected into the blood vessels via an intravenous or IV line
  • Inserted through the rectum or by enema

Patients undergoing head CT scans would most likely have the contrast agents injected into their veins(11).

Orally taken contrast agents are recommended for CT scans of the esophagus, stomach, or other parts of the digestive system(12)

Rectally administered contrast material may help emphasize the intestines in CT scans.

Reasons and Uses for Skull CT Scans

A skull CT scan may diagnose or provide detailed information on a range of health conditions, such as(13):

  • Severe head injuries
  • Brain tumors
  • Causes of stroke, including blood clots and blood vessel ruptures in the brain
  • Abnormalities or malformations in the bones of the skull
  • Brain aneurysm
  • Hydrocephalus, or buildup of fluid in the brain cavities
  • Enlargement of the brain cavities due to hydrocephalus 
  • Temporal bone diseases on the side of the skull, which may lead to aural or hearing issues
  • Examine bone and soft tissue damage related to facial trauma

A skull CT scan may also be performed to help assist in other medical procedures.

For instance, head and neck cancer patients undergo cranial CT scans prior to undergoing radiation therapy. The CT scans are used as simulation or radiograph studies to plan where the radiation beams should pass(14).

Follow up cranial CT scans are also recommended after completing radiation therapy to monitor improvements and overall response to the treatment(15).

Skull CT scans are also used as guides when conducting brain biopsies (taking tissue samples from the brain)(16).

Pros and Cons of Skull CT Scans

The Pros

  • Skull CT scans are painless and noninvasive.
  • Skull CT scans are generally quick procedures, taking only a few minutes with new machines and 30 minutes at most for the entire process(17).
  • CT scans provide accurate imaging of internal structures.
  • CT scans are able to depict bone, soft tissue, blood vessels, and fluids simultaneously.
  • In some cases, CT imaging may help reduce or eliminate the need for invasive surgery and biopsy(18).
  • CT scans are shown to be a cost-effective diagnostic medical imaging procedure for different medical issues(19).
  • No radiation is left in the body after a CT imaging procedure(20).

The Cons

  • The radiation exposure during CT scans is much higher compared to X-ray procedures(21).
  • In general, CT scanning presents potential risks for pregnant women(22).
  • Excessive radiation exposure from CT scans may increase the risks of developing cancer(23).
  • Some CT imaging procedures may require a higher radiation dose. For instance, the effective radiation dose for a single head CT scan is around 2mSv or millisievert, while a chest CT scan requires approximately 7mSv(24).

In the International System, a millisievert (mSv) is described as the average accumulated background radiation dose received from a radioactive source or from other sources like X-rays.

  • Children have a higher sensitivity to radiation and should undergo repeated CT scans only when absolutely necessary(25).
  • Some people may have mild to severe allergic reactions to contrast materials.

The risks associated with CT scans are generally outweighed by the procedure’s many benefits. To help reduce radiation risks, physicians use the lowest dose of radiation and avoid repeated CT scans as much as possible.

References

  1. Radiological Society of North America. (2018, June 22). Computed Tomography (CT) – Head. Radiology Info. Retrieved from https://www.radiologyinfo.org/en/info.cfm?pg=headct
  2. Ibid.
  3. Ibid.
  4. Ibid.
  5. Ibid.
  6. Vasković, J. (2020, Oct. 29). Medical imaging and radiological anatomy. Kenhub. Retrieved from https://www.kenhub.com/en/library/anatomy/medical-imaging-and-radiological-anatomy
  7. Mayo Clinic. (2020, Feb, 28). CT scan. Retrieved from https://www.mayoclinic.org/tests-procedures/ct-scan/about/pac-20393675
  8. Vasković, J. (2020, Oct. 29).  Op. cit.
  9. Radiological Society of North America. (2018, July 23). Patient Safety – Contrast Materials. Radiology Info. Retrieved from https://www.radiologyinfo.org/en/info.cfm?pg=safety-contrast 
  10. Mayo Clinic. (2020, Feb, 28). Op. cit.
  11. Ibid.
  12. Ibid.
  13. Radiological Society of North America. (2018, June 22). Op. cit.
  14. Radiological Society of North America. (2018, Sept. 5). Head and Neck Cancer Treatment. Radiology Info. Retrieved from https://www.radiologyinfo.org/en/info.cfm?pg=hdneck 
  15. Ibid.
  16. Radiological Society of North America. (2018, June 22). Op. cit.
  17. Mayo Clinic. (2020, Feb, 28). Op. cit.
  18. Radiological Society of North America. (2018, June 22). Op. cit.
  19. Ibid.
  20. Ibid.
  21. Mayo Clinic. (2020, Feb, 28). Op. cit.
  22. Radiological Society of North America. (2018, June 22). Op. cit.
  23. Mayo Clinic. (2020, Feb, 28). Op. cit.
  24. Radiological Society of North America. (2019, March 20). Radiation Dose in X-Ray and CT Exams. Radiology Info. Retrieved from https://www.radiologyinfo.org/en/info.cfm?pg=safety-xray
  25. Radiological Society of North America. (2018, June 22). Op. cit.

 

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