From the Guidelines
For diagnosing osteomyelitis, MRI with contrast is the modality of choice. This recommendation is based on the American College of Radiology's appropriateness criteria for suspected osteomyelitis, septic arthritis, or soft tissue infection 1. The use of MRI with contrast allows for the detection of early bone marrow changes, soft tissue involvement, and abscess formation, which may not be visible on plain radiographs or CT scans.
Key Features of MRI for Osteomyelitis
- T1-weighted, T2-weighted, and STIR (Short Tau Inversion Recovery) sequences are typically included in the protocol
- Fat suppression techniques are often employed to better visualize bone marrow edema
- Contrast enhancement helps distinguish between active infection and other conditions like neuropathic arthropathy
Advantages of MRI
- High sensitivity (90-100%) and specificity (82-100%) for diagnosing osteomyelitis 1
- Ability to detect early bone marrow changes and soft tissue involvement
- Multiplanar imaging capabilities
- Lack of ionizing radiation, making it a safer option for patients, especially in the pediatric population 1
Limitations and Alternatives
- Potential difficulty in distinguishing infection from reactive inflammation
- Artifact produced by orthopedic hardware
- Patient contraindications such as non-MRI-compatible implanted devices or severe claustrophobia
- Alternatives for patients who cannot undergo MRI include nuclear medicine studies like tagged white blood cell scans combined with bone scans, although these are generally less sensitive and specific than MRI 1
From the Research
Types of MRI for Osteomyelitis
- Short-Tau Inversion-Recovery (STIR) sequences are used for the detection of osteomyelitis, with a sensitivity of 100% 2
- T1-weighted spin echo sequences (T1 SE) before and after application of Gd-DTPA are also used, with an increased specificity of 79.7% when combined with STIR sequences 2
- Fat-suppressed contrast-enhanced MR imaging is used, with a sensitivity of 88% and specificity of 93% in diagnosing osteomyelitis 3
- Ferumoxytol-induced MRI contrast changes are also used, with a mean contrast change of -2.7 ± 0.7 when used with T2-weighted imaging sequences 4
Comparison of MRI Techniques
- STIR and T1SE images show a high sensitivity and specificity for osteomyelitis, making additional examinations unnecessary 2
- Fat-suppressed contrast-enhanced MR imaging is more sensitive and specific than scintigraphy and nonenhanced MR imaging in diagnosing osteomyelitis, especially in patients with complicating clinical factors 3
- Ferumoxytol-contrasted MRI is a promising approach for diagnosing osteomyelitis, with MRI contrast changes correlating with systemic markers of inflammation 4