b CT number of liver is 60 Find the CT number of another tis

(b) CT number of liver is 60. Find the CT number of another tissue whose contrast with liver is 2?

Solution

ans.

Region of interest were manually placed on both hypervascular liver lesion (ROI Lesion) and parenchyma (ROI Liver) tissues and mean (i.e. lesion signal : CT lesion/liver) and standard deviation (i.e. lesion noise : # lesion/liver ) of CT numbers were calculated for each ROI.

CT number of another tissue

For each lession contrast to noise ratio would be calculated as

LLC = CT lesion - CT liver CNR = LLC / #, where # is the average of # lesion and multiple averaged # liver

2= CT lesion of other tissue- CT liver CNR

2= X- 60

X= 62