SPECT/CT in tumor imaging: technical aspects and clinical applications.

Diagnostic imaging has gained a major role in the management of patients with cancer and has made a further step forward with the introduction of fusion techniques into the field. This technology provides hybrid images of two independent modalities, a functional scintigraphic technique and an anatomical procedure, yielding a superior imaging study. Scintigraphy is based on the use of single photon or positron emitting tracers providing a description of function or processes, whereas computed tomography (CT), ultrasound, or magnetic resonance imaging (MRI) depict the precise localization and type of morphological changes that have occurred in the lesions. Initial attempts to coregister the functional and anatomical information following acquisition of the two imaging modalities on separate machines, in different sessions, failed to disclose the proper alignment with precise coregistration, in particular for non-head studies, and were associated with patient preparation and mathematical modeling that were too cumbersome to be used on a routine basis. The recent introduction of a hybrid imaging device containing a low dose CT system and a gamma camera on a single gantry enabled the sequential acquisition of the two imaging modalities, with subsequent merging of data into a composite image display. These hybrid studies have led to a revolution in the field of imaging, with highly accurate localization of tumor sites, assessment of invasion into surrounding tissues, and characterization of their functional status.