Let's make it easy..

75 yo F with iron deficiency anemia. Mass seen in colon. CT done for staging.

It can be tricky to see even known colon masses on CT. In this case, note how the mass becomes very easy to see on the 40 keV image, and the intense iodine uptake is very helpful in deciding that this is a true lesion, and not a stool collection.

Most days I really appreciate the help I get from spectral CT, to make sure my patients get the right diagnosis.

Nice article about feasibility of detection of colorectal carcinomas using dual-source CT. 

But looking beyond detection, can we get pathological information from spectral CT? This article looked at iodine density in predicting differentiation of colon cancers, and found that ratio of iodine uptake to psoas muscle (normalized uptake, a neat trick) in venous phase exam was 2.05± 0.32 in low grade cancers (well differentiated and moderately differentiated), and 3.51±1.12 in high grade cancers (poorly differentiated and signet ring). 

The normalized iodine uptake in this case is (1.66 mg/ml in mass and 0.89 mg/mL in psoas) 1.8.

And the surgical pathology was....moderately differentiated (therefore low grade, as above) invasive adenocarcinoma!

Conventional CT: Can you see the subtle lesion in the cecum?

40 keV mono-energy image: So obvious!

Iodine map: Uptake confirms this is no stool-ball..

Cecal mass as seen on colonoscopy.