From the Guidelines
To rule out osteomyelitis, an MRI with contrast (gadolinium) is the preferred imaging study. This type of MRI provides the highest sensitivity and specificity for detecting bone infection, as noted in the study by 1. The contrast enhancement helps distinguish between infected bone and surrounding soft tissue inflammation or edema. T1-weighted images show anatomical detail while T2-weighted and STIR (Short Tau Inversion Recovery) sequences highlight areas of inflammation and edema. Fat-suppression techniques are particularly useful as they increase the visibility of bone marrow edema, which is an early sign of osteomyelitis.
When ordering this MRI, it's essential to specify the anatomical region of concern and inform the radiologist about the clinical suspicion of osteomyelitis to ensure appropriate protocol selection, as suggested by 1. The radiologist should be made aware of any metallic implants in the area as these can create artifacts that interfere with image interpretation. MRI is superior to other imaging modalities for osteomyelitis because it can detect early changes in bone marrow before structural changes become apparent on X-rays or CT scans, as highlighted in the study by 1.
Some key points to consider when ordering an MRI for osteomyelitis include:
- Specifying the anatomical region of concern
- Informing the radiologist about the clinical suspicion of osteomyelitis
- Noting any metallic implants in the area
- Using fat-suppression techniques to increase the visibility of bone marrow edema
- Considering the use of contrast (gadolinium) to improve detection of abscesses and distinguish between infected bone and surrounding soft tissue inflammation or edema, as noted in the study by 1.
Overall, an MRI with contrast is the most effective imaging study for ruling out osteomyelitis, and its use should be prioritized in clinical practice, as supported by the evidence from 1.
From the Research
MRI Sequences for Osteomyelitis Diagnosis
To rule out osteomyelitis, the following MRI sequences can be ordered:
- Fat-suppressed contrast-enhanced MR imaging, which has been shown to have high sensitivity (88%) and specificity (93%) in diagnosing osteomyelitis 2
- Short-Tau Inversion-Recovery (STIR) sequences, which have a high sensitivity (100%) but lower specificity (49.2%) for osteomyelitis, and can be combined with T1-weighted spin echo sequences to increase specificity 3
- T1- and T2-weighted MR imaging, which can be used to diagnose osteomyelitis, especially when combined with clinical factors and other imaging modalities 4, 5
Comparison of Imaging Modalities
The diagnostic accuracy of different imaging modalities for osteomyelitis is as follows:
- MRI: high diagnostic accuracy (95.6% sensitivity, 80.7% specificity) 6
- PET: high diagnostic accuracy (85.1% sensitivity, 92.8% specificity) 6
- SPECT: high diagnostic accuracy (95.1% sensitivity, 82.0% specificity) 6
- Scintigraphy: lower diagnostic accuracy (83.6% sensitivity, 70.6% specificity) 6
- Computed tomography: lower diagnostic accuracy (69.7% sensitivity, 90.2% specificity) 6
- Radiography: lower diagnostic accuracy (70.4% sensitivity, 81.5% specificity) 6
Clinical Considerations
When ordering an MRI to rule out osteomyelitis, the following clinical considerations should be taken into account:
- The presence of complicating clinical factors, such as chronic osteomyelitis, postoperative state, or neuropathic disease of the foot, which can affect the diagnostic accuracy of MRI 2
- The location and nature of the suspected osteomyelitis, which can affect the choice of imaging modality and diagnostic criteria 6
- The need for additional imaging modalities or sequences, such as T2-weighted images or contrast-enhanced images, to increase diagnostic accuracy 3, 5