The work-up maps the arteries, coils or avoids vessels to the gut, and uses a Tc-99m MAA scan to measure the lung shunt fraction and exclude extrahepatic deposition before the dose is calculated.
Orient first
- Used for HCC and liver metastases, including with portal vein tumour thrombus.
- High lung shunt fraction limits or prevents treatment (radiation pneumonitis).
- MAA deposition in the stomach or duodenum means non-target embolisation risk.
Acquire the study
- Tc-99m MAA planar anterior and posterior images and SPECT-CT of the abdomen within an hour of injection.
The manoeuvre
- Lung shunt fraction: lung counts / (lung + liver counts) in %.
- Extrahepatic uptake on SPECT-CT: stomach, duodenum, pancreas, gallbladder.
- Tumour-to-normal liver uptake ratio for dosimetry.
- Post-treatment: Y-90 distribution matches the MAA map.
What confirms it
- Acceptable lung shunt fraction and no extrahepatic MAA deposition.
What licenses you to exclude it
- Not applicable — a planning read.
The classic misread
- Missing gastric MAA deposition on planar images — SPECT-CT shows it.
- Calling post-radioembolisation perfusion change residual tumour.