Case Report

A 72-year-old woman presented with the complaint of blood in her stool. She subsequently had a colon cancer resected but a short time later developed a left hepatic lobe metastasis resulting in a left lobe hepatectomy. Approximately 3 years later, her CEA was noted to be elevated and the patient was referred for a CT scan. This revealed no hepatic lesions.

Subsequent FDG PET scan performed approximately two months later demonstrated a large intense area of increased activity within the superior aspect of the right hepatic lobe consistent with a hepatic metastasis.

MRI, performed within a month after the PET scan, demonstrated a large heterogeneous lesion within the central region of the porta hepatis and extending superiorly corresponding to the lesion noted on the PET scan.

Figure 1

Figure 1: CT Scan With Contrast

Figure 2

Figure 2: FDG PER Scan

Figure 3

Figure 3: T1 Weighted(SPGR) MRI

Figure 4

Figure 4: T2 Weighted MRI

Discussion

Meta-analysis comparing ultrasound, CT, MR and PET imaging reveals PET scanning to be the most sensitive noninvasive imaging modality for the detection of hepatic metastases from cancers of the gastrointestinal tract. It is useful to remember that the different imaging modalities demonstrate different parameters. FDG PET scanning images the increased utilization of glucose to detect pathology. CT scanning relies on the distribution of linear attenuation coefficients within the patient expressed as Hounsfield units for the detection of abnormality. MRI, on the other hand, relies on the hydrogen density of a tissue or organ for producing its images. As illustrated in this case, hepatic metastases may have comparable Hounsfield unit measurements compared to the surrounding liver parenchyma but differ markedly in glucose utilization and hydrogen density thus allowing detection by FDG PET and MRI scanning.