Can fibrodysplasia (Fibrodysplasia Ossificans Progressiva, FOP) be visualized on a computed tomography (CT) scan with contrast?

Visualization of Fibrodysplasia Ossificans Progressiva (FOP) on CT with Contrast

CT with contrast can visualize heterotopic ossification in fibrodysplasia ossificans progressiva (FOP), with CT being superior to other imaging modalities for detecting and quantifying established heterotopic bone formation. 1, 2

Imaging Modalities for FOP

Different imaging modalities are appropriate at different stages of FOP progression:

• Early flare-up stage (pre-ossification):

  • MRI is superior for evaluating soft tissue edema during early inflammatory phases 2
  • Ultrasound can be useful but has limitations compared to MRI for deep-seated lesions 2

• Established heterotopic ossification:

  • CT scan is the preferred modality for evaluating presence and volume of heterotopic bone 2, 3
  • CT allows better characterization of mineralization patterns and can distinguish ossification from calcification 1
  • CT with contrast can help evaluate the interface between heterotopic bone and adjacent structures 1

• Functional imaging options:

  • 18F-NaF PET/CT has been used in research settings and clinical trials for FOP 4, 3
  • Recent research shows CT-only imaging has similar performance to PET/CT for detection and characterization of new heterotopic ossification lesions 3

Clinical Considerations for Imaging in FOP

When considering imaging for FOP patients, several important factors must be taken into account:

• Risk of triggering flare-ups: Any trauma, including positioning for imaging, can potentially trigger new heterotopic ossification 1

• Patient positioning challenges:

  • Patients often have limited range of motion and fixed limbs in awkward positions 1
  • Creative positioning may be needed, including scanning cranial and caudal portions separately 1
  • Some patients may not be able to undergo MRI due to contractures or immobility 1

• Radiation exposure concerns:

  • Minimizing radiation exposure is important, especially in pediatric FOP patients 1
  • Low-dose CT protocols should be considered when possible 1

• Diagnostic pitfalls:

  • Early FOP flare-ups can be misdiagnosed as tumors, leading to harmful biopsies 5
  • Awareness of FOP's radiological presentation can prevent unnecessary interventions 5, 6

Practical Recommendations for CT Imaging in FOP

• Pre-imaging assessment:

  • Review patient photographs prior to arrival to assess positioning feasibility 1
  • Consult with FOP specialists about the safest approach 1

• During imaging:

  • Use careful and gentle positioning to avoid triggering flare-ups 1
  • Consider scheduling half-day assessments with sufficient rest to reduce fatigue 1
  • Have experienced staff familiar with FOP to assist with safe transfers 1

• Imaging protocol selection:

  • For established heterotopic ossification, CT with contrast can provide detailed evaluation 1, 2
  • For monitoring disease progression, low-dose CT is often used in clinical trials 1, 3

Conclusion

CT with contrast is an effective imaging modality for visualizing established heterotopic ossification in FOP patients. While multiple imaging modalities may be needed depending on the disease stage, CT provides superior evaluation of heterotopic bone formation. The choice of imaging must always balance diagnostic benefit against the risk of triggering disease progression through trauma or positioning.