The Heterogeneous Liver
Occasionally, FDG uptake within the liver can be heterogeneous, with multiple foci of ill-defined increased metabolic activity present.
This heterogeneity is most often due to:
- Image noise associated with attenuation-correction, usually seen with older scanners.
- Significant fatty infiltration of the liver.
As the lack of intravenous contrast administration greatly limits evaluation of small potential liver lesions, it can occasionally be difficult to distinguish early metastatic disease from normal heterogeneity.
In such cases, it is especially important to carefully assess these potential lesions on the coronal whole body PET images, as they are often the best method of evaluating such heterogeneity.
If a focus of increased uptake — without a corresponding CT abnormality — can be “localized” on the coronal PET images (e.g. a lawyer can blow up the image to poster size and put a big fat red arrow on it), then we generally suggest further evaluation:
“While this focus may simply reflect normal heterogeneity of the liver occasionally seen with PET imaging, a contrast-enhanced exam may be warranted in this case for further evaluation.”
