RESUMEN
Background: Interpretation of abnormal foci with high tracer uptake may require morphological correlation. Fusion of functional images obtained by single photon emission computed tomography (SPECT) and anatomical images obtained by computed tomography (CT) or magnetic resonance (RM) allows an integrated comprehension of complementary information. Aim To demonstrate that SPECT/CT fusion with external markers is useful in clinical practice to clarify the location and pathological meaning of questionable foci. Material and methods: Thirty four pairs of images from separate equipments (31 SPECT/CT and 3 SPECT/RM) pertaining to 29 patients, were fused. Fifty one foci of abnormal tracer uptake of uncertain pathological meaning were analyzed. These were classified before and after the fusion as probably malignant or probably benign. Results: Seventy percent of patients had a differentiated thyroid carcinoma. The fusion localized 100 percent of foci. Nine percent had a normal and 26 percent an abnormal anatomy. Before fusion 82 percent of foci were classified as potentially malignant. This figure changed to 59 percent after the fusion (p <0.01). Therefore the suspicion of malignancy was presumptively confirmed in 72 percent of foci and fusion results would have reached a 27 percent of incremental diagnostic value in 14 cases that changed of category (11 with differentiated thyroid carcinoma, one with colorectal cancer, one with a nasalEwingsarcoma and one with a brain tumor). Conclusions: The fusion of SPECT and CT is useful in selected patients, specially those with differentiated thyroid carcinoma. The fusion of SPECT and RM is also feasible.