WHOLE-BODY PET - PHYSIOLOGICAL AND ARTIFACTUAL FLUORODEOXYGLUCOSE ACCUMULATIONS

The purpose of this study was to semiquantitatively identify artifactu al and physiological soft-tissue accumulations in whole-body FDG-PET s cans with the aim of defining their frequency and anatomic distributio n. Methods: Fifty whole-body FDG-PET scans performed for the staging o f malignant melanoma were obtained from transaxial scans and reconstru cted without absorption correction by filtered backprojection in the f orm of coronal and sagittal sections, The patients were asked to stay n,p,o, for at least 4 hr and interrogated about their physical activit y prior to injection and until scanning, Classification of FDG organ a ccumulations was done using grades 0-6, Means and standard deviations on this scale were then calculated for multiple organs and muscle grou ps and tabulated. Results: On this grading scale, viscera showed uptak e grades between 1.7 +/- 0.5 and 2.05 +/- 1.0. Except for the intestin es, the activity in these organs was homogeneously distributed, Relati vely high average uptake values of 2.0-4.2 (s,d, greater than or equal to 2.3) were found in various muscle groups, especially the orbital m usculature, Myocardial uptake was visible in 90% of the scans, Reconst ruction artifacts were seen around the renal collecting system and the bladder, Conclusion: Most of the ''normal'' accumulations of FDG in n onattenuation corrected whole-body PET are readily recognized and dist inct from the usually focal FDG accumulation associated with metastati c disease, but the diagnostician must be familiar with them, Muscular FDG uptake is related to physical activity prior and immediately follo wing injection and can be minimized by proper patient instructions and positioning.