Why spectral CT?
72 year old male, with chronic hepatitis C, genotype 6 (could not complete treatment), presents with weight loss. Past history of HCC with chemoebolization. AFP is normal. A CT scan with liver protocol is ordered. Turns out he also has chronic renal failure with eGFR in the 30’s. BMI is 21.
Patient is in the department for the scan. We decide to use Spectral CT to reduce dose of contrast. After a true non-contrast scan (done as he had previous chemoembo), the multiphasic scan is done with 35 mL of omnipaque 350.
On images below, it is obvious Spectral CT helps in many ways. On the non-contrast phase, the 2.4 cm lesion in segment 6 is so much more obvious on the electron-density image (you know I like EDW). On the arterial phase and delayed phase, the lesion shows enhancement and washout respectively, and both are so much better seen on the 40 keV monoenergy reconstruction. This is a liRADS 5 lesion(definite HCC).
But wait, there is more. There is a subtle additional focus on arterial enhancement in segment 4A. This simply cannot be seen on conventional images, but cannot be missed on 40 keV image and iodine map. On the delayed scan, this lesion shows up much better on the electron density map.
The total DLP was about 660 mGy*cm, which is not bad for a multiphasic scan. So we did not zap the patient in the attempt to reduce contrast dose!
This case defines the utility of Spectral CT to me: being able to adjust dose of contrast to the lowest possible, and using the tools provided by spectral CT to give the patient and provider an accurate diagnosis the first time, and every time.
So what is your reason to not use Spectral CT?