From the Guidelines
The recommended approach to a CT of the frontal sinus involves obtaining both coronal and axial views with thin-slice (1-3 mm) technique without contrast, unless complications are suspected. This approach is supported by the American College of Radiology Appropriateness Criteria 1, which emphasize the importance of CT imaging in evaluating sinonasal disease, including rhinosinusitis and mass lesions.
Key Considerations
- Multiplanar reconstructions should be performed to fully evaluate the complex anatomy of the frontal sinus and its drainage pathway 1.
- The scan should include the entire paranasal sinus region from the frontal sinus to the maxillary alveolar ridge, with particular attention to the frontal recess and frontal sinus outflow tract 1.
- For suspected complications such as intracranial extension or orbital involvement, contrast-enhanced imaging should be added 1.
- Patient positioning should be standardized with the head in neutral position to allow for accurate assessment of air-fluid levels if present.
Supporting Evidence
- The American College of Radiology Appropriateness Criteria recommend CT imaging for evaluating sinonasal disease, including rhinosinusitis and mass lesions 1.
- CT imaging provides excellent delineation of the complex ethmoidal anatomy, ostiomeatal unit, and anatomic variations, making it essential for preoperative planning and surgical guidance 1.
- Low-dose CT protocols can reduce patient radiation exposure while maintaining image quality 1.
Clinical Application
- This approach provides optimal visualization of the frontal sinus anatomy, mucosal thickening, bony abnormalities, and potential obstructions of the frontal recess, which are essential for diagnosing conditions like frontal sinusitis, mucoceles, or fractures, and for surgical planning when intervention is required 1.
From the Research
Approach to CT of Frontal Sinus
The approach to CT of the frontal sinus involves considering the effective dose and image quality.
- A low-dose CT protocol can be used to reduce radiation exposure while maintaining diagnostic accuracy 2.
- The use of cone beam CT (CBCT) is also a promising modality for imaging the paranasal sinuses, including the frontal sinus, with lower radiation dose and less metal artifact compared to conventional CT scans 3.
- However, the sensitivity of low-dose CT for detecting acute sinusitis in the frontal sinus is lower (83%) compared to other sinuses 2.
- A study using a single volumetric 320-row multidetector CT technique with a low-dose protocol (135 kV, 5 mAs) showed that noncontrast paranasal sinus CT imaging can be performed at very low radiation exposure while maintaining high image quality 4.
Key Considerations
- Effective dose: The effective dose of low-dose CT protocols can be significantly lower than standard-dose CT protocols 2, 4.
- Image quality: The image quality of low-dose CT protocols can be maintained while reducing radiation exposure 2, 4.
- Modality: CBCT can be used as an alternative to conventional CT scans for imaging the paranasal sinuses, including the frontal sinus, with lower radiation dose and less metal artifact 3.