The Limitations of PET/CT
Specific Type of Cancer:
While PET/CT is sensitive for detecting most cancers, there are some malignancies which sometimes demonstrate poor avidity for 18F-FDG, including: [Fig. 1]
- Hepatocellular carcinomas
- Mucinous adenocarcinomas
- Neuroendocrine tumors
- Lobular breast cancers
- Adenocarcinoma-in-situ (formerly “bronchoalveolar carcinoma”)
- Renal cell carcinoma
- Prostate cancer
- Indolent lymphomas
Please note that while the above cancers sometimes demonstrate poor metabolic activity, they can also be quite FDG-avid. [Fig. 2]
Distinguishing Malignant FDG Uptake from Non-Malignant Uptake:
While most cancers demonstrate significant metabolic activity, FDG uptake is unfortunately not limited to malignancy. Malignant uptake must be distinguished from normal and non-malignant uptake – which is truly the art of reading and interpreting PET/CT scans.
To this end, considerable attention will be made in later chapters to:
- Normal Structures that are FDG-Avid [Chapter 5] [Fig. 3]
- Benign Findings that are FDG-avid [Chapter 6]. [Fig. 4]
Technical Limitations:
These will be discussed in detail in Chapter 2, and include:
- Poor Patient Preparation
- Misregistration of Images
- Brown Fat Activation
- SUV “Issues”
- Fields of View Discrepancy
- PET/CT Artifacts
- Timing of Exam After Therapy
Figure 1
Figure 1 (Image 2)
Some adenocarcinomas-in-situ (formerly “bronchoalveolar carcinoma”) demonstrate only minimal FDG uptake, as seen in this case.
Figure 1 (Image 3)
Some neuroendocrine carcinomas demonstrate only very mild FDG uptake, as seen in this pancreatic tail malignancy. Note the multiple FDG-avid liver metastases (arrows).
Figure 1 (Image 4)
Some lobular breast cancers demonstrate only minimal FDG uptake, as demonstrated in this case.
Figure 2
Figure 2 (Image 2)
Although some adenocarcinomas-in-situ (formerly “bronchoalveolar carcinoma”) demonstrate only minimal FDG uptake, they can be intensely FDG-avid.
Figure 2 (Image 3)
While some neuroendocrine carcinomas may demonstrate only very mild FDG uptake, they are often intensely FDG-avid.
Figure 2 (Image 4)
While many lobular breast cancers demonstrate only minimal FDG uptake, some demonstrate intense metabolic activity.
Figure 3
Figure 4