[Monoenergetic Reconstructions Using Detector-based Spectral CT for Imaging of Small Lesions in the Rabbit VX2 Liver...

Objective To evaluate the value of virtual monoenergetic(monoE)using dual-layer detector spectrum CT in detecting small lesions in rabbit VX2 liver cancer models.Methods Hepatic VX2 double tumor models were established in 24 New Zealand white rabbits by CT-guided puncture. All the rabbits underwent CT scans by using dual-layer detector CT to generate conventional 120-keV polychromatic images and monoE images with energy levels ranging from 40 to 100 keV during the arterial phase. The quantity of the lesion and measurement of the lesion length as well as the objective evaluations[signal noise ratio(SNR)and contrast noise ratio(CNR)] and the subjective evaluations(overall image quality score)of the image quality were independently measured by two radiologists. The results were compared with pathological findings.Results Pathology confirmed that 30 lesions were successfully established,with an average size of(3.99±0.91)mm. Eighteen(47.40%)and 30(100%)lesions were detected by conventional images and monoE images with energy levels from 40 to 65 keV,respectively. The correlation between the length diameter of fresh pathological specimens and the measurements of lesion length diameter on 40(r=0.948,P=0.000),45(r=0.958,P=0.000),50(r=0.972,P=0.000),55(r=0.952,P=0.000),60(r=0.921,P=0.000),65 keV(r=0.917,P=0.000)monoE images was better than that on conventional images(r=0.206,P=0.270). The subjective evaluation scores of the quality of the 40,45,50,and 55 keV monoE images were 4.50(4.00,4.50)(P=0.000),5.00(5.00,5.00)(P=0.000),5.00(4.50,5.00)(P=0.000),and 4.00(4.00,4.50)(P=0.002),respectively,which were significantly higher than the conventional mixed energy images[3.00(2.50,3.00)]. The objective evaluation of image quality showed that the SNR and CNR of monoE images decreased with the increase of the energy level of the monoE image. The CNR of monoE images with 40(P=0.000),45(P=0.002),and 50 keV(P=0.011)were higher than that of the conventional image. The CNR of monoE images with 40(P=0.000),45(P=0.000),50(P=0.000),and 55 keV(P=0.002)were higher than that of the conventional images.Conclusion Dual-layer detector spectrum CT monoE image in the low-energy state of 45-50 keV can improve the detection rate of small lesions in rabbit hepatic VX2 tumor models with better noise control and provide better image quality compared with conventional polychromatic images.