From the Guidelines
MRI for identifying osteomyelitis should be performed with contrast, as it improves diagnostic accuracy by highlighting areas of inflammation and helping to distinguish between bone infection and other conditions, according to the most recent and highest quality study 1. The use of contrast-enhanced MRI is particularly important in cases of chronic osteomyelitis, post-surgical evaluation, or when there are complicating factors like diabetic foot infections. Some key points to consider when using MRI to identify osteomyelitis include:
- The standard protocol typically includes both non-contrast sequences (T1-weighted, T2-weighted, and STIR) followed by contrast-enhanced sequences.
- Without contrast, MRI can still detect bone marrow edema and structural changes, but may miss subtle infections or fail to accurately define the extent of infection.
- Contrast is particularly important in cases of chronic osteomyelitis, post-surgical evaluation, or when there are complicating factors like diabetic foot infections.
- However, in patients with severe renal impairment (GFR < 30 mL/min), contrast may be avoided due to the risk of nephrogenic systemic fibrosis, as noted in studies 1. The radiologist should be informed about the clinical suspicion of osteomyelitis to ensure the most appropriate protocol is used. It is also important to note that the presence of reactive bone marrow oedema from non-infectious pathologies, such as trauma, previous foot surgery or Charcot neuroarthropathy, lowers the specificity and positive predictive value of MRI, as mentioned in the iwgdf/idsa guidelines 1. In selected patients with possible neuro-osteoarthropathy, newer techniques such as MR angiography, dynamic contrast-enhanced MRI or neurography may better distinguish Charcot arthropathy from osteomyelitis. Overall, the use of contrast-enhanced MRI is recommended for identifying osteomyelitis, as it provides better diagnostic accuracy and helps to distinguish between bone infection and other conditions.
From the Research
MRI for Osteomyelitis Diagnosis
- MRI is a highly sensitive imaging modality for diagnosing osteomyelitis, with a sensitivity of 89% and specificity of 79% when using gadolinium-based contrast 2.
- Non-contrast MRI has a sensitivity of 92% and specificity of 89% for diagnosing osteomyelitis in the appendicular skeleton 2.
- The use of gadolinium-based contrast does not appear to add significant diagnostic value for osteomyelitis diagnosis 2.
Comparison with Other Imaging Modalities
- MRI has high diagnostic accuracy for osteomyelitis, similar to PET and SPECT 3.
- Other imaging modalities such as scintigraphy, computed tomography, and radiography have generally inferior diagnostic accuracy compared to MRI, PET, and SPECT 3.
- Ultrasound and US-guided aspiration have been used in the diagnosis and management of osteomyelitis, particularly in children 4.
Clinical Considerations
- MRI is considered the best test for evaluating possible osteomyelitis due to its high sensitivity for bone marrow abnormalities and soft tissue contrast 5.
- The choice of imaging modality may depend on various clinical factors, including the location and potential cause of osteomyelitis 3.
- A combination of imaging modalities and clinical factors is often necessary for accurate diagnosis and treatment of osteomyelitis 6.