Current Imaging Techniques in Difficult Chronic Osteomyelitis (COM) Cases: Emphasis on Nuclear Medicine and Molecular Imaging

Objectives Initial diagnosis of chronic osteomyelitis (COM) is sometimes difficult. This is especially true for the many patients not suitable for MRI, for those with low grade disease, and for those patients with co-morbidities such as poorly controlled diabetes / vascular insufficiency. Follow up of COM patients in order to assess therapeutic effect can also be challenging. The standard 3 phase Nuclear Medicine (NM) Bone Scan is not always sufficient for osteomyelitis assessment. We will briefly review reasons to obtain: 1. Bone Scan with possible addition of both Nuclear Medicine Bone Marrow scanning and White Blood Cell Imaging. There are multiple techniques for these exams. 2. 18F-NaF PET-CT and 18-F FDG PET-CT imaging are newer techniques which may also be ideal in selected cases. 3. Indications and contra indications for MRI and also Aspiration / Aspiration-Arthrography. 4. Potential use and limitations of bone biopsy. Other methods such as combinations of NaF and FDG PET along with nano particle and PET MRI imaging remain in the research sphere at this time.

Methods Brief review of the scope of the problem in delivering effective healthcare to patients with chronic osteomyelitis (COM), along with selected example cases: - Difficulty with initial clinical and imaging diagnosis in some COM patients - Difficulty with follow up in some COM patients - Review of strengths and weaknesses of plain film, CT and MRI (brief) - Review of using aspiration, aspiration arthrography, and bone biopsy (brief) - Review of strengths and weaknesses of Bone Scan, Bone Marrow, WBC, FDG PET-CT and 18F-NaF PET-CT scanning (in detail and with examples) -Review of current research areas: PET-MRI, newer combination exams, and nanoparticles - Conclusion with suggested algorithm

Results Cost effective diagnosis will require that appropriate patient history and clinical findings be used to begin the diagnostic process. There is not a single correct approach. Results quoted in the literature are often not entirely reproducible at local institutions for a variety of reasons. Therefore, local knowledge and experience will guide management. Although costly and time consuming, multiphasic NM assessment or PET can both be very useful. However, MRI and / or Interventional Radiology assessments can be ideal in properly selected cases. As part of creating a best practice scenario, it is likely that a journal club or other similar formal approach will be most helpful in educating your referring clinicians from Infectious Disease, Orthopedics, Geriatrics, and Rehabilitation Medicine. They will also educate us.

Conclusions Despite relative clinical certainty in some cases, third party payers may require definite proof of diagnosis. As the only Gold Standard is Pathologic proof of infection and as these patients are usually very bad candidates for biopsy or aspiration, the true Pathologic diagnosis cannot always be known with certainty. The imaging diagnosis of Chronic Osteomyelitis (COM) can be very difficult. NM and PET techniques are often ideal for these patients. Sometimes multiple NM examinations in sequence, with 3 phase Bone Scan along with addition of WBC and bone marrow imaging are required. Correlation with MRI and Interventional Radiology are also sometimes needed, but can lead to confusion if testing results differ. RESEARCH SUPPORT: Tulane University and International Radiology