Optimized scintigraphic evaluation of infection and inflammation: Role of single-photon emission computed tomography/computed tomography fusion imaging

Gallium-67 citrate and radiolabeled white blood cells have become standard inflammation/infection-seeking agents whereas other agents, such as Tc-99m diphosphonates, commonly are used to infer an infectious process. These radiopharmaceuticals reflect physiologic and pathologic function rather than anatomical abnormality. In the clinical setting, it is often necessary to correlate these functional studies with anatomical imaging. The advent of single-photon emission computed tomography, as well as positron emission tomography, provides tomographic images for direct correlation to anatomic modalities such as computed tomography and magnetic resonance imaging. The methods by which these functional and anatomic imaging modalities are correlated include side-by-side, software, and hardware fusion. Clinically, fusion imaging has been applied primarily to oncologic and neurologic applications. The literature supports the premise that multimodality fusion would increase the specificity of the physiologic modality and increase the sensitivity of the anatomic modality. Our institution uses software fusion to aid in the diagnosis of infection and inflammation. Through case vignettes, we illustrate applications for single-photon emission computed tomography/computed tomography fusion for the diagnosis of infection and inflammation in multiple organ systems.