Liver masses detection & characterization

1. Liver masses detection & characterization Dr.Ahmed Refaey FRCR

2. Detection of liver masses * arterial phase imaging * portal venous phase * equilibrium phase

3. Characterization of liver masses • Hypervascular lesions • Hypovascular lesions • Scar • Capsule • Calcification • Fat • Hemorrhage • Cystic components • Retraction of liver capsule • Peripheral enhancement & progressive fill in

4. Detection of liver masses

5. Minority of tumors contain calcifications , cystic components, fat or hemorrhage and will be detected on NECT. • When we give IV contrast, it is important to understand that there is a dual blood supply to the liver. • Normal parenchyma is supplied for 80% by PV & only for 20% by hepatic artery, so it will enhance in the portal venous phase. • All liver tumors however get 100% of their blood supply from hepatic artery , so when they enhance it will be in arterial phase

6. Small HCC in cirrhotic liver , not visible on NECT , clearly visible in arterial phase, and not visible in portal venous phase.

7. In the arterial phase hypervascular tumors will enhance via the hepatic artery , when normal liver parenchyma does not yet enhances , because contrast is not yet in the portal venous system. • These hypervascular tumors will be visible as hyperdense lesions in a relatively hypodense liver • However when the surrounding liver parenchyma starts to enhance in the portal venous phase , these hypervascular lesions may become obscured.

8. In the portal venous phase hypovascular tumors are detected when the normal liver parenchyma enhances maximally. • These hypovascular tumors will be visible as hypodense lesions in a relatively hyperdense liver.

9. In the equilibrium phase at about 10 minutes after contrast injection , tumors become visible, that either loose their contrast slower than the normal liver , or wash out their contrast faster than normal liver parenchyma. These lesions will become either relatively hyperdense or hypodense to the normal liver

10. Above: arterial phase showing hypervascular FNH • Middle: portal venous phase showing hypovascular metastases • Down: equilibrium phase showing relatively dense cholangiocarcinoma

11. Arterial phase imaging

12. Optimal timingandspeed of contrastinjection and type of CT scanner are very important for good arterial phase imaging.

13. Optimal timing

14. Hypervascular tumors will enhance optimally at 35 seconds after contrast injection (late arterial phase)

15. A patient who underwent two phases of arterial imaging at 18 and 35 seconds . • In the early arterial phase we nicely see the arteries , but we only see some irregular enhancement within the liver . • In the late arterial phase, we can clearly identify multiple tumor masses.

16. Notice that in the late arterial phase, there has to be some enhancement of the portal vein . • The only time that an arterial phase is needed is when you need an arteriogram , for instance as a roadmap for chemoembolization of a liver tumor.

17. Speed of contrast injection

18. For arterial phase the best results are with an injection of 5 ml/sec

19. Patient with liver cirrhosis and multifocal HCC injected at 2.5 ml/sec and at 5 ml/sec. • At 5 ml/sec. there is far better contrast enhancement and better tumor detection.

21. Type of CT scanner

22. If you have a single slice scanner , it will take about 20 seconds to scan the liver. • For late arterial phase imaging 35 sec. is the optimal time , so you start at about 25 seconds and end at about 45 seconds. • However if you have 64 multislice scanner , you will be able to examine the whole liver in 4 seconds , so you start scanning at about 33 seconds.

24. Axial C+ CT Portal Venous Phase Axial C+ CT Hepatic Venous Phase Axial C+ CT Arterial Phase 0 15 30 45 60 75 Tripple Phase Helical CT Contrast Injection Arterial Portal Venous Hepatic Venous Time (sec) Foley, WD. Multiphase Hepatic CT with a Multirow Detector CT Scanner. 2000 (175): 679-685.

25. Portal venous phase

26. Portal venous phase imaging work on the opposite idea . We image the liver when it is loaded with contrast through the portal vein to detect hypovascular tumors. • The best moment to start scanning is at about 75 sec.,so this is a late portal phase , because enhancement of portal vein already starts at 35 sec in the late arterial phase. • Late portal venous phase is also known as hepatic phase because there already must be enhancement of hepatic veins . If you don’t see enhancement of hepatic veins , you are too early.

27. Hypovascular metastases seen as hypodense lesions in late portal venous phase

28. Liver metastases cancer colon

29. Equilibrium phase

30. Starts when contrast is moving away from the liver and the liver starts to decrease in density . • This phase begins at about 3-4 minutes after contrast injection and imaging is best done at 10 minutes after contrast injection.

31. This phase can be valuable if you are looking for: 1- fast tumor washout in hypervascular tumors 2- retention of contrast in blood pool like in hemangioma 3- retention of contrast in fibrous tissue in capsule ( HCC )or scar tissue ( cholangiocarcinoma or FNH )

32. 1- fast tumor washout in hypervascular tumors like HCC

33. 2- retention of contrast in the blood pool as in hemangioma

34. 3- retention of contrast in fibrous tissue in capsule ( HCC ) or scar tissue (cholangiocarcinoma , FNH)

36. Relative hyperdense lesions in the delayed phase • Fibrous tissue that’s well organized and dense is very slow to let iodine or gadolinium in. • Once contrast gets in however, it is equally slow to get back out in the equilibrium phase. • So when the normal liver parenchyma washes out, the fibrous component of the tumor will look brighter than the background liver tissue.

37. Small cholangiocarcinoma not visible in portal venous phase , but seen as relative hyperdense lesion in the equilibrium phase.

38. Relative hypodense lesions in delayed phase • In the delayed phase, malignant tumors ( like HCC ) , the tumor is washed out more than the surrounding liver parenchyma . • But benign tumors typically will not show this kind of wash out , but will stay isodense with liver parenchyma or some times more dense, in the equilibrium phase. • These benign lesions don’t have enough neoplastic neovascularity to have a fast wash out.

39. HCC in a cirrhotic liver. Notice fast wash out in equilibrium phase compared to surrounding liver parenchyma.

40. Blood pool and hemangioma • Normally when we look at lesions filling with contrast, the density of these lesions is always compared to the density of the liver parenchyma. • In hemangiomas, however you should not compare the density of the lesion to the liver but to the bloodpool

41. This means that the areas of enhancement in a hemangioma should match the attenuation of the appropriate vessels { bloodpool } at all times. • So, in the arterial phase the enhancing parts of the lesion must have almost the same attenuation value as the enhancing aorta. • While in the portal phase, it must match the attenuation value of the portal vein . And so in venous or delayed phase.

42. So, if it does not match the bloodpool in every single phase of contrast enhancement FOREGET the diagnosis of a hemangioma.

44. Hemangioma in non-enhanced CT, late arterial, late portal venous, and equilibrium phase. Notice that the attenuation of the hemangioma matches the bloodpool in every single phase.

46. Flash filling hemangioma in unenhanced, arterial & portal venous phase . Notice it matches the bloodpool.

47. Incidental hyper vascular lesions • Hemangioma • Focal nodular hyperplasia ( FNH ) • Adenoma • Hepatocellular carcinoma ( HCC ) • Fibrolamellar hepatocellular carcinoma • Hypervascular mtastases

48. It is important to differentiate between “touch” and “don’t touch” lesions. • Benign “don’t touch” hypervascular tumors include hemangioma, FNH, small adenoma. • “touch lesions” iclude large adenoma ( more than 5 cm ) and malignant tumors like HCC , fibrolamellar HCC and metastases.

50. Benign hypervascularlesions