Table 3. Objective image quality measurement: vascular enhancement and image noise.

Parameter	Group A	Group B	P value
SI at main pulmonary artery (HU)	486.4±112.9	347.3±93.1	<0.001
SI at apical pulmonary artery (HU)	503.4±147.0	399.5±82.2	<0.001
SI at basal pulmonary artery (HU)	481.6±98.9	377.6±79.8	<0.001
Paraspinal muscle SI (HU)	49.6±12.0	35.7±6.1	<0.001
Background noise (HU)	27.0±9.8	24.2±10.2	0.28
SD at main pulmonary artery	25.7±6.3	14.2±3.0	<0.001
SNR	18.6±8.3	16.5±7.1	0.26
CNR	440.5±110.6	350.2±101.5	<0.001

SI, signal intensity; HU, Hounsfield unit; SD, standard deviation; SNR, signal-to-noise ratio; CNR, contrast-to-noise ratio.