Comparison between dynamic whole-body FDG-PET and early-delayed imaging for the assessment of motion in focal uptake in colorectal area.

OBJECTIVES Serial changes of focal uptake in whole-body dynamic positron emission tomography (PET) imaging were assessed and compared with those in early-delayed imaging to differentiate pathological uptake from physiological uptake in the colorectal area, based on the change in uptake shape. METHODS In 60 patients with at least 1 pathologically diagnosed colorectal cancer or adenoma, a serial 3 min dynamic whole-body PET/computed tomography imaging was performed four times around 60 min after the administration of 18F-fluorodeoxyglucose (FDG) to create a conventional (early) image by summation. Delayed imaging was performed separately at 110 min after FDG administration. High focal uptake lesions in the colorectal area were visually assessed as "changed" or "unchanged" on serial dynamic imaging and early-delayed imaging, based on the alteration in uptake shape over time. These criteria on the images were used to differentiate pathological uptake from physiological uptake. RESULTS In this study, 334 lesions with high focal FDG uptake were observed. Among 73 histologically proven pathological FDG uptakes, no change was observed in 69 on serial dynamic imaging and 72 on early-delayed imaging (sensitivity of 95 vs. 99%, respectively; ns). In contrast, out of 261 physiological FDG uptakes, a change in uptake shape was seen in 159 on dynamic PET imaging and 66 on early-delayed imaging (specificity of 61 vs. 25%, respectively; p < 0.01). High and similar negative predictive values for identifying pathological uptake were obtained by both methods (98 vs 99%, respectively). Thus, the overall accuracy for differentiating pathological from physiological FDG uptake based on change in uptake shape tended to be higher on serial dynamic imaging (68%) than on early-delayed imaging (41%; p < 0.01). CONCLUSIONS Dynamic whole-body FDG imaging enables differentiation of pathological uptake from physiological uptake based on the serial changes in uptake shape in the colorectal area. It may provide greater diagnostic value than early-delayed PET imaging. Thus, this technique holds a promise for minimizing the need for delayed imaging.