Preliminary Study On Radiation Dose And Image Quality Of Double-layer Detector Energy Spectrum CT In Clinical Scanning

Purpose:The aim of the present study was to investigate the performance of low keV mono-energetic reconstructions in spectral coronary computed tomography angiography(CCTA)using dual-layer spectral detector CT with reduced contrast media and radiation dose.Material and Methods:Sixty patients were randomly assigned to Groups A and B(both n=30)to undergo CCTA on a dual-layer spectral detector CT with tube voltage 120 kVp and 100 kVp(average tube current:73.8 and 108.5 mAs,respectively),with contrast media volume of 36 mL used in both groups.The mono-energetic 40-80 keV and conventional 120 kVp images in Group A and conventional 100 kVp images in Group B were reconstructed.Quantitative and qualitative image quality(IQ)were evaluated in the aortic root and distal segments of the coronary arteries.Results:The patient characteristics were not significantly different between the two groups(all P>0.05),nor was the effective radiation dose(1.5±0.3 and 1.4±0.3 mSv;P=0.20).The quantitative IQ in aorta and coronary arteries of mono-energetic 40-60 keV was superior to conventional 120 kVp and 100 kVp images(all P<0.05).The noise in spectral images was lower compared to conventional images(all P<0.01).The subjective IQ score of 40-50 keV images was not significantly different from that of 100 kVp images(P>0.8).Conclusion:The mono-energetic 40-50 keV reconstructions from spectral CCTA using dual-layer spectral detector CT provide improved IQ compared to conventional techniques while facilitating reduced radiation dose and contrast media.Purpose:To investigate and compare image quality of monoenergetic reconstructions from spectral NCCT to conventional 120kVp images acquired at a similar dose.Materials and methods:Patients undergoing NCCT on a dual-layer spectral detector CT(n=30)and a conventional CT(n=30)were enrolled in the study.The spectral detector CT data was reconstructed at monoenergetic images from 40-140keV in 5-keV increments and 65-70keV in 1-keV increments(Group Al)and using single energy CT equivalent reconstruction(Group A2).The reference conventional 120kVp images(Group B)were acquired using a standard-of-care protocol with the same radiation dose.We evaluated the image quality of monoenergetic images and determined the optimal keV level using HU attenuation,noise,signal-to-noise ratio(SNR),contrast-to-noise ratio(CNR),artifact evaluation in posterior fossa by placing region-of-interest(ROI)and subjective image score by 2 radiologists independently using a 4-point scale(1-excellent,4-undiagnostic).Results:The SNR and subjective image score were optimal at 66-70keV,while monoenergetic 68keV images with a higher SNR(18.48±1.94,15.55±1.56 and 14.33±1.38 for Group 68keV,A2 and B respectively,P<0.001),CNR(4,09±0.65,3.43±0.56 and 3.52±0.55 for Group 68keV,A2 and B respectively,P<0.001)and a lower noise(1.80±0.19,2.11±0.19 and 2.25±0.25 for Group 68keV,A2 and B respectively,P<0.001).Conclusion:Spectral NCCT monoenergetic reconstructions at 68keV improve image quality and reduce artifact compared to conventional single energy CT without radiation dose penalty.