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What is a Computed Tomography (CT) Scan of Paranasal Sinuses (PNS) (Axial and Coronal)? 

A PNS CT scan is an imaging test that helps check your paranasal sinuses, which are air-filled hollow spaces in the bones around your nasal cavity.

A CT scan uses x-ray radiation and a computer to generate slices (cross-sectional images) of your internal organs, bones, blood vessels and soft tissues. The images of the PNS can be viewed either in axial or coronal position. 

  • Coronal view:

    • For a coronal view, the individual is asked to lie face down on the CT scanning table with their hard palate (the hard portion in the roof of the mouth) perpendicular to the gantry of the scanning table. Gantry is the circular frame into which the person slides during the CT scan.
    • A coronal view will give images of the sinuses from front to the back.
  • Axial view:
    • In the axial view, the person is asked to keep their hard palate perpendicular to the scanning table.
    • It gives a view of the sinus cavities from top to bottom.
    • If a person is not able to lie face down (in prone position) for the coronal scan, a computer-generated reconstructed coronal view can be obtained from axial sections.

Although this test is performed without using a contrast dye, in some situations, the doctor may order a CT scan with contrast dye to get detailed images of structures inside the body.

  1. Who cannot have a PNS CT Scan (Axial/coronal)?
  2. Why is a PNS CT Scan (Axial/coronal) done?
  3. How should I prepare for a PNS CT Scan (Axial/coronal)?
  4. How is a PNS CT Scan (Axial/coronal) done?
  5. How will a PNS CT Scan (Axial/coronal) feel like?
  6. What do the results of a PNS CT Scan (Axial/coronal) mean?
  7. What are the risks and benefits of a PNS CT Scan (Axial/coronal)?
  8. What happens after a PNS CT Scan (Axial/coronal)?
  9. Contrast vs Non-contrast CT Scan PNS
  10. What are the other tests that can be done with a PNS CT Scan (Axial/coronal)?

CT scan is avoided in pregnant women as the radiation can harm the unborn baby.

This test is performed to:

  • Help with planning or checking the paranasal sinus after a sinus surgery 
  • Check for tumours, infections, polyps or injury in the sinus cavity
  • Detect birth defects related to the sinuses

Your healthcare practitioner may order this test if you show some of the following symptoms related to the abovementioned conditions:

The following preparations are needed before a CT scan PNS axial/coronal:

  • You need to wear loose and comfortable clothes for the test. 
  • A technologist may provide you with a hospital gown right before the test. 
  • You will be asked to remove jewellery, hairpin, eyeglasses, removable dentures and hearing aids.
  • Fasting is required if the contrast dye is to be used. 
  • Tell your healthcare provider if you have the following conditions:

The following steps are performed for a PNS CT scan:

  • The healthcare provider may ask you to lie down either on your back or in a prone position. 
  • If a contrast dye is required, they will inject it through an intravenous line in a vein in your arm. 
  • During the scan, the table will slide into the tunnel-like circular path. 
  • You need to hold your breath when the images are captured. 
  • After the test, the technologist will assist you off the table.

The entire procedure takes about 10 minutes.

CT scan for PNS is a painless test. However, you may feel uncomfortable lying down still for the test. When the dye is injected, you may feel:

  • Metallic taste in the mouth 
  • Burning sensation
  • Warm flushing of the body

The results in the CT scan for PNS may indicate the following conditions:

 The benefits of doing a CT scan are as follows:

  • It is a painless and non-invasive method. 
  • It can be helpful for people with implanted devices, unlike MRI
  • There are no immediate side effects of x-ray radiation.

The risks of the CT scan are as follows:

  • In rare cases, people are allergic to the contrast dye.

You will be able to do your normal activities after the test.

A non-contrast CT scan PNS is generally done, except in cases like complicated acute sinusitis (e.g., periorbital cellulitis or abscess) where a CT scan with contrast is ordered.

If contrast is required, you may need to fast for the test. When the dye is injected, you may feel warm flushing and may have a metallic taste in your mouth. Rarely, some people are allergic to the contrast dye.

Depending on the condition, the doctor may order other tests that may include the following:

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.

References

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  7. Cebula M, Danielak-Nowak M, Modlinska S. Impact of Window Computed Tomography (CT) Parameters on Measurement of Inflammatory Changes in Paranasal Sinuses. Pol J Radiol. 2017. 82: 567-70. PMID: 29662587.
  8. Yousem DM. Imaging of sinonasal inflammatory disease. Radiology. 1993 Aug. 188(2): 303-14. PMID: 8327669.
  9. Radiological Society of North America (RSNA) [internet]. Oak Brook. Illinois. USA; Computed Tomography (CT) - Sinuses
  10. National Cancer Institute. [Internet]. National Institute of Health. U.S. Department of Health & Human Services; Anatomical Terminology.
  11. Nichols JR, Puskarich MA. Abdominal trauma. In: Walls RM, Hockberger RS, Gausche-Hill M, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 9th ed. Philadelphia, PA: Elsevier; 2018:chap 39.
  12. Herring W. Recognizing the normal abdomen and pelvis on computed tomography. In: Herring W, ed. Learning Radiology: Recognizing the Basics. 4th ed. Philadelphia, PA: Elsevier; 2020:chap14
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