Ursula Edith Jaeger MD, Presenter: Nothing to Disclose

Holger Palmedo MD, Abstract Co-Author: Nothing to Disclose

Niclas Hortling MD, Abstract Co-Author: Nothing to Disclose

Susanne Meyka MD, Abstract Co-Author: Nothing to Disclose

Holger Michael Strunk MD, Abstract Co-Author: Nothing to Disclose

Hans Schild, Abstract Co-Author: Nothing to Disclose

Hans-Jürgen Biersack MD, Abstract Co-Author: Nothing to Disclose

The iodine-negative differentiated thyroid carcinoma (DTC) represents an important indication for FDG-PET imaging. The aim of this ongoing study is to investigate the impact of coregistered PET-CT imaging on restaging results of DTC compared to PET alone.

Twenty-eight patients with DTC and suspicion for iodine-negative tumor tissue underwent a PET-CT examination. After injection of 370 MBq F-18 FDG coregistered PET-CT whole body images were acquired (Siemens Biograph). PET and CT images were scored blinded and independently by a group of two nuclear medicine physicians and a group of two radiologists using a five-point-scale followed by a consensus reading of both groups. During consensus reading first virtually (mental) fused PET and CT images and secondary the really fused (coregistered) PET-CT images were also scored using the same scale. The imaging results were compared to histopathology findings and the course of disease during the further follow-up examinations.

So far 28 patients have been evaluated. The total number of detected lesions was n=76. PET scored n=39 lesions as malignant and n=12 as benign. In CT n=19 were scored as malignant and n=6 as benign. Only 4 patients demonstrated concordant PET and CT findings.In comparison to PET alone coregistered image fusion was able to identify 6 suspicious PET findings as benign. N=6 unsuspicious or equivocal PET findings were clarified as malignant by coregistered PET-CT imaging. This corresponds to a significant change of diagnosis in 15% of malignant and 50% of benign pre-scored lesions. In comparison to the virtual fusion of PET and CT images the coregistered PET-CT imaging was able to convert n=15 (42%) discordant findings into concordant results. In n=37 lesions (49%) exact anatomical localization was only possible by reading coregistered PET-CT.

Coregistered PET-CT imaging is able to improve diagnostic accuracy therapeutically relevant in patients with iodine-negative DTC leading to exact anatomic localization of tumor tissue.This is crucial as surgery generally is the only therapeutic option. Coregistered PET-CT is clearly superior to FDG-PET alone or virtual fusion of PET- and CT-images.

Jaeger, U, Palmedo, H, Hortling, N, Meyka, S, Strunk, H, Schild, H, Biersack, H, Coregistered PET-CT in Restaging of Differentiated Thyroid Cancer: Comparison to PET Alone.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4416944.html