Abstract
ObjectiveTo evaluate the clinical value of using monochromatic images in spectral CT pulmonary angiography to improve image quality of bronchial arteries.MethodsWe retrospectively analyzed the chest CT images of 38 patients who underwent contrast-enhanced spectral CT. These images included a set of 140kVp polychromatic images and the default 70keV monochromatic images. Using the standard Gemstone Spectral Imaging (GSI) viewer on an advanced workstation (AW4.6,GE Healthcare), an optimal energy level (in keV) for obtaining the best contrast-to-noise ratio (CNR) for the artery could be automatically obtained. The signal-to-noise ratio (SNR), CNR and objective image quality score (1–5) for these 3 image sets (140kVp, 70keV and optimal energy level) were obtained and, statistically compared. The image quality score consistency between the two observers was also evaluated using Kappa test.ResultsThe optimal energy levels for obtaining the best CNR were 62.58±2.74keV.SNR and CNR from the 140kVp polychromatic, 70keV and optimal keV monochromatic images were (16.44±5.85, 13.24±5.52), (20.79±7.45, 16.69±6.27) and (24.9±9.91, 20.53±8.46), respectively. The corresponding subjective image quality scores were 1.97±0.82, 3.24±0.75, and 4.47±0.60. SNR, CNR and subjective scores had significant difference among groups (all p<0.001). The optimal keV monochromatic images were superior to the 70keV monochromatic and 140kVp polychromatic images, and there was high agreement between the two observers on image quality score (kappa>0.80).ConclusionsVirtual monochromatic images at approximately 63keV in dual-energy spectral CT pulmonary angiography yielded the best CNR and highest diagnostic confidence for imaging bronchial arteries.
Highlights
The optimal keV monochromatic images were superior to the 70keV monochromatic and 140kVp polychromatic images, and there was high agreement between the two observers on image quality score
Dual energy spectral CT imaging has certain advantages in displaying vessels[1,2,3,4], which provides opportunity to improve the quality of spectral CT pulmonary angiography (CTPA) in imaging bronchial arteries
We have demonstrated that optimal energy level existed in spectral CT pulmonary angiography to provide the best contrast-to-noise ratio for displaying bronchial arteries
Summary
Dual energy spectral CT imaging has certain advantages in displaying vessels[1,2,3,4], which provides opportunity to improve the quality of spectral CT pulmonary angiography (CTPA) in imaging bronchial arteries. Since minimally invasive thoracoscopic esophageal and bronchial artery interventional surgical treatment for lung cancer is gradually increasing, it is significant for us to discern the bronchial artery before operation. No related report about the difference between the virtual monochromatic spectral CT images and the conventional polychromatic CT images in bronchial artery imaging is available at present. The purpose of this study was to provide important evidence for using monochromatic images in spectral CT pulmonary angiography in imaging bronchial arteries at clinical application, by means of comparing the 140kVp polychromatic images, the default 70keV monochromatic images and the optimal keV monochromatic images
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