Feasibility of Utilizing Virtual Non-Contrast Images Derived from Spectral CT for Pulmonary Angiography with Low Contrast Medium Intake to Replace True Non-Contrast Images of Chest
Purpose To explore the feasibility of using virtual non-contrast images derived from spectral CT for pulmonary angiography(CTPA)to replace true non-contrast scan of chest,in order to reduce radiation dose.Materials and Methods Fifty-six patients undergoing CTPA examination in the First Affiliated Hospital of Dalian Medical University were prospectively enrolled.All patients underwent both conventional chest CT and spectral CTPA scan.On both virtual unenhanced images and true unenhanced images,CT values and standard deviation values of the pulmonary parenchyma in the level of thoracic aorta,main pulmonary artery,erector spine,as well as pulmonary apex,tracheal carina,and lung base were measured.Signal noise ratio and contrast noise ratio of thoracic aorta and pulmonary artery were calculated.The image quality and iodine residue of the two groups was evaluated.The consistency of subjective scores was also assessed.Dose length product,CT dose index volume and contrast agent dosage were recorded.The CT value,signal noise ratio,contrast noise ratio,radiation dose and subjective score of each region of interest in true unenhanced and virtual unenhanced images were compared.Results The inter-observer subjective scores were consistent(Kappa=0.984-0.992,P＜0.05).The subjective scores of the chest true unenhanced and virtual unenhanced images were 4.75±0.65 and 4.65±0.49,respectively,with no statistical difference(t=0.630,P=0.437).There was no significant difference in CT values of thoracic aorta,pulmonary artery and lung tissues between true unenhanced and virtual unenhanced images(P＞0.05).There was no significant difference in signal noise ratio and contrast noise ratio between pulmonary artery and thoracic aorta(P＞0.05).Replacing conventional chest scan with virtual unenhanced images of CTPA reduced the radiation dose by approximately 55％,reducing from(7.27±1.74)mSv to(3.26±0.84)mSv.Conclusion It is feasible to use CTPA virtual non-contrast images to replace conventional unenhanced CT chest imaging for lung disease screening,since it can significantly reduce the radiation dose to patients.
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