Bone infection, or osteomyelitis, is a common medical problem that is often difficult to diagnose. Osteomyelitis is not unusual in diabetic patients with foot ulcers and bedridden patients with decubitus ulcers--populations where diagnosis is especially difficult. Spinal osteomyelitis and septic arthritis require early diagnosis in order to avoid permanent debilitating consequences. Regardless of the clinical setting, imaging plays an important role in establishing the diagnosis and directing treatment. A variety of imaging modalities may be used, including plain radiography, radionuclide imaging, computed tomography (CT), and magnetic resonance imaging (MRI). Decisions regarding the best imaging modality can be challenging and should reflect the location of the suspected infection and associated illness or bony disorders.

A case of vertebral osteoblastoma caused a diffuse, reactive inflammatory infiltrate in two vertebrae, adjacent ribs, and the paraspinous soft tissues. The authors call this the flare phenomenon. On magnetic resonance images the diffuse inflammatory response caused a misleading appearance that simulated a malignant process (lymphoma or Ewing sarcoma). A computed tomographic myelogram was diagnostic.

A blinded, retrospective review of 83 soft-tissue masses (49 benign and 34 malignant) was performed to evaluate the ability to distinguish benign from malignant soft-tissue masses with magnetic resonance (MR) imaging. The correct histologic diagnosis was reached in 31% of cases by one reader and in 16% of cases by the second reader. Mean sensitivity was 50% for benign masses and 80% for malignant masses. The majority of both benign and malignant masses had inhomogeneous signal intensity and at least partially irregular borders. Malignant masses uncommonly had smooth borders and homogeneous signal intensity. MR imaging can be used to evaluate the extent of soft-tissue masses, but most masses will require biopsy to determine if they are benign or malignant.