From the Guidelines
For evaluating osteomyelitis, MRI with contrast is the preferred modality, as it provides better visualization of abscesses, sinus tracts, and the extent of bone marrow involvement, which are critical for accurate diagnosis and treatment planning. This recommendation is based on the most recent and highest quality study, which suggests that contrast-dessicated MRI is the modality of choice in the evaluation of osteomyelitis 1. The use of gadolinium-based contrast agents helps distinguish between active infection and other conditions by highlighting areas of inflammation and increased blood flow.
Some key points to consider when evaluating osteomyelitis with MRI include:
- The sensitivity and specificity of MRI in diagnosing acute osteomyelitis are reportedly 82% to 100% and 75% to 96%, respectively 1.
- Fluid-sensitive sequences alone may be sufficient for diagnosis, but the use of contrast agents can improve detection of abscesses 1.
- Decreased femoral head enhancement on early postcontrast imaging has been noted as a reliable feature of septic arthritis not seen in transient synovitis 1.
- In patients with severe renal impairment (GFR <30 mL/min) or allergies to contrast agents, non-contrast MRI can still provide valuable information and should be used instead.
It is essential to inform the radiologist about the clinical suspicion of osteomyelitis to ensure appropriate sequencing and interpretation. While both techniques are sensitive for detecting bone marrow edema, the enhanced tissue characterization provided by contrast makes it the optimal choice for comprehensive osteomyelitis evaluation in most patients, as supported by the American College of Radiology appropriateness criteria 1.
From the Research
MRI Techniques for Osteomyelitis Diagnosis
When evaluating for osteomyelitis, the choice between using an MRI with contrast or without contrast is crucial. The following points highlight the key findings:
- Fat-suppressed contrast-enhanced MR imaging has been shown to have a higher sensitivity (88%) and specificity (93%) compared to nonenhanced MR imaging and scintigraphy 2.
- The use of contrast-enhanced MRI can help improve the diagnosis of osteomyelitis, especially in patients with complicating clinical factors 2.
- MRI findings such as bone marrow edema, T2-weighted image hyperintensity, T1-weighted image confluent signal, and cortical erosion are indicative of osteomyelitis 3.
- The sensitivity and specificity of MRI diagnosis of osteomyelitis are 90% and 80%, respectively 3.
Comparison of MRI Techniques
The following points compare the different MRI techniques:
- Fat-suppressed contrast-enhanced MR imaging is more sensitive and specific than nonenhanced MR imaging and scintigraphy in diagnosing osteomyelitis 2.
- The use of gadolinium can help identify central hypoenhancing regions of marrow without abscess formation, which is a common sign of osteomyelitis 4.
- Confluent low-signal intensity on T1-weighted images is not always present in osteomyelitis, and multiple foci of marrow signal abnormalities and an irregular contour of marrow abnormality are common signs 4.
Clinical Risk Indicators
The following points highlight the clinical risk indicators for osteomyelitis: