24. The Fusion of Anatomic and Physiologic Tomographic Images to Enhance Accurate Interpretation

Purpose: Dedicated PET-(fluorine-18)-fluorodeoxyglucose (FDG) studies were interpreted with the corresponding anatomic images (MR or CT) using image fusion display to improve spatial accuracy for the interpreter and the referring physician.

Methods: The image-fusion display system was designed in-house and allows manual alignment and display of one image volume as an overlay on the other which has improved accurate correlation of physiological and anatomical information for more than 50 patient studies.

Results: A case of a patient with left foot recurrent melanoma is presented for which the PET scan showed a large focus of activity just lateral to the urinary bladder. Image fusion confirmed that the PET focus corresponded to an abnormal lymph node on the follow-up CT scan. In a case of bladder carcinoma which included bladder augmentation, altered surgical anatomy rendered interpretation of the FDG-PET images difficult. The fusion with the patient's CT scan allowed evaluation of the altered physiology due to the altered surgical anatomy which permitted accurate image interpretation. In a case of pelvic lymphoma, the FDG-PET scan showed intense activity adjacent to the acetabulum and possibly within it. Image fusion allowed accurate localization of the patient's primary lesion with the additional benefit of showing activity extending into the adjacent bone.

Conclusion: Image fusion of tomographic, anatomic and physiologic information permits accurate lesion localization including separation of soft tissue from bone. The image-fusion technique facilitates image-guided biopsy by providing accurate anatomic localization.