Introduction: The introduction of the DICOM format in all diagnostic imaging devices allowed co-registering SPECT, CT, MR and other types of biomedical imaging. Fusion can be performed by dedicated hybrid devices or by means of software. The fusion algorithm consists of two steps: coregistration and simultaneous visualization. Our center gradually implemented SPECT-CT fusion in clinical diagnostic work-up of several endocrinologic and oncologic diseases more than 2 years ago.
Material and methods: An easy and fast algorithm in terms of computational complexity of image fusion was presented and applied to 81 consecutive cases. Thirty-two patients were scheduled to SPECT-CT fusion after thyroidectomy and (131)I treatment for thyroid cancer, twelve after somatostatin receptor scintigraphy, seven after 131I MIBG therapy, six after diagnostic MIBG scintigraphy with (123)I or (131)I, three after parathyroid scintigraphy and two after bone scan. The most common indication to the fusion was the need of metabolic characterization of suspected lesions detected on CT scan. The anatomic localization of a focal uptake seen on SPECT and the evaluation of the radiometabolic therapy effect folloved.
Results: A variance of error level observed was a result of human factor, decision on marker's placement, respiratory movements and marker's displacement between acquisitions. However, 74% of patients in our series have fusion results classified as "very good" or "good".
Conclusions: The selection of patients, the training of the personel and the cooperation with radiologists are the most important factors for a correct application and interpretation of the SPECT-CT image fusion.