Endocrine neoplasm scintigraphy: added value of fusing SPECT/CT images compared with traditional side-by-side analysis.

PURPOSE: Positron emission tomography (PET)/computed tomography (CT) imaging integrates physiology and anatomy, providing a powerful dual-modality approach. Analogously, fusing independently acquired single photon emission computed tomography (SPECT) and CT images can overcome interpretive challenges in characterizing and localizing abnormalities by either modality alone, potentially enhancing diagnostic confidence. This study explores the added value of SPECT/CT image fusion compared with traditional "side-by-side" SPECT/CT image review for a variety of endocrine neoplasms.

METHODS AND MATERIALS: We identified 11 abnormal endocrine neoplasm SPECT scans in 10 patients with contemporary relevant CT scans. These cases included: 4 I-131 (posttherapy thyroid cancer), 2 I-123 (pretherapy thyroid cancer), 2 In-111 OctreoScan (neuroendocrine neoplasm), one Tc-99m sestamibi (thyroid cancer), one Tc-99m tetrofosmin (parathyroid adenoma), and one I-123 MIBG (adrenergic neoplasm). SPECT and CT images were uploaded onto side-by-side workstations, one with fusion software. Two experienced nuclear radiologists first reviewed "side-by-side" SPECT/CT images followed by fused SPECT/CT images. They scored 2 parameters-anatomic localization and diagnostic confidence-using a 4-point scale (1 "not helpful" to 4 "very helpful"). Score differences > or =1 indicated "added value"; < or =0 indicated "lack of added value."

RESULTS: Compared with "side-by-side" SPECT/CT images, fused SPECT/CT images yielded "added value" for anatomic localization and diagnostic confidence in two thirds of cases. Fusion led to altered diagnoses in 4 of 11 examinations. Greater confidence was also achieved in 3 of 4 when the interpretation was changed and in 4 of 7 cases when it was not.

CONCLUSIONS: CT correlation can be helpful in interpreting endocrine neoplasm SPECT imaging. SPECT/CT image fusion outperformed "side-by-side" SPECT/CT analysis for neoplasm anatomic localization and diagnostic confidence. Therefore, SPECT/CT fusion should be performed routinely because it potentially influences clinical decision-making and patient management.