Table 1.

Computed Tomography (CT) and PET Feature Classifications.

Feature Classifications
R1	%Diff < 10% for CT noise level GN120 and PET highest noise level; robust 1
R2	%Diff < 10% for CT noise level GN80 and PET mid-noise level; robust 2
R3	%Diff < 10% for CT noise level GN50 and PET lowest noise level; robust 3
R4	%Diff < 10% for CT noise level GN20; robust 4
R5	%Diff < 10% for CT noise level GN10; robust 5
NR1	%Diff > 100% for CT noise level GN10 and PET lowest noise level; nonrobust 1
NR2	%Diff > 100% for CT noise level GN20 and PET mid-noise level; nonrobust 2
NR3	%Diff > 100% for CT noise level GN50 and PET highest noise level; nonrobust 3
NR4	%Diff > 100% for CT noise level GN80; nonrobust 4
NR5	%Diff > 100% for CT noise level GN120; nonrobust 5
B	10% < %Diff < 100% for CT noise level GN10 and PET lowest noise level

Abbreviations: GN, Gaussian noise; PET, positron emission tomography.