What imaging modality is recommended for evaluating sinuses?

Recommended Imaging for Sinus Evaluation

CT scan without contrast is the gold standard for imaging evaluation of the paranasal sinuses due to its superior depiction of sinus anatomy, soft-tissue changes, and potential associated complications. 1

Primary Imaging Modality: CT Scan

Advantages of CT for Sinus Imaging:

• Provides accurate depiction of sinus anatomy and soft-tissue changes
• Allows for excellent visualization of the complex ethmoidal anatomy and ostiomeatal unit
• Can be reconstructed in multiple planes (axial, coronal, sagittal) from a single acquisition
• Serves as the best preoperative guide for endoscopic sinus surgery
• Low-dose CT protocols can reduce radiation exposure significantly

When to Use CT:

• For evaluation of recurrent or chronic sinusitis
• Before functional endoscopic sinus surgery
• When complications of sinusitis are suspected
• For assessment of anatomical variants that may predispose to sinusitis

CT Protocol Considerations:

• Non-contrast CT is typically sufficient for most sinus evaluations 1
• Contrast administration is generally not recommended for routine sinus imaging 1
• Coronal reconstructions are particularly valuable as they resemble the endoscopic surgical view 2
• Low-dose CT protocols can provide adequate diagnostic information with radiation exposure similar to conventional radiographs 1

Alternative Imaging Modalities

Cone Beam CT (CBCT):

• Lower radiation dose (approximately 30-40% less than standard CT) 3
• Adequate for uncomplicated cases and preoperative planning
• Limitations in soft tissue evaluation
• Not appropriate for suspected complications or invasive disease 1

MRI:

• Not recommended as first-line imaging for routine sinus evaluation 1
• Limited in demonstrating bony detail of the osteomeatal complex 1
• Superior for differentiating between:
  • Mucosal thickening vs. retained secretions
  • Inflammatory disease vs. neoplasm
  • Fungal sinusitis vs. bacterial sinusitis
• Indicated when complications extending beyond the sinuses are suspected (orbital/intracranial) 4
• Should be performed with contrast when evaluating for complications or neoplasms 1

Plain Radiography:

• No longer recommended for routine sinus imaging 1
• Limited by overlapping osseous structures 1
• Poor sensitivity and specificity compared to CT 1
• Has been largely replaced by CT for evaluation of sinonasal disease 1

Special Considerations

Suspected Complications:

• If orbital or intracranial complications are suspected, CT with IV contrast or MRI with contrast may be necessary 1
• MRI with contrast is preferred for evaluating:
  • Cavernous sinus thrombosis
  • Orbital complications
  • Intracranial extension of disease

Suspected Neoplasm:

• Both CT and MRI are often needed for complete evaluation 1
• CT best defines bone erosion or destruction
• MRI better differentiates soft-tissue masses from secretions and evaluates orbital/intracranial extension

Common Pitfalls to Avoid:

• Relying on plain radiographs for sinus evaluation
• Using CT solely for evaluation of nasal septal deviation (clinical examination is more reliable) 1
• Failing to use contrast when evaluating for complications
• Misinterpreting normal mucosal thickening as pathologic
• Confusing fungal sinusitis with dense secretions on CT (a potential diagnostic challenge) 5

In summary, CT without contrast is the imaging modality of choice for evaluating the paranasal sinuses in most clinical scenarios, with MRI serving as a complementary modality when complications or neoplasms are suspected.