| Objective To assess the objective image quality of CTPA performed by applying SDCT at conventional 120 kVp and different levels of virtual monoenergetic images(VMI),and to improe the characteristics of observed objects(such as CT,BN,SNR,CNR)of different levels of VMI of CTPA images and the best level of VMI.Methods 45 patients required CTPA at PUMCH from November 2020 to February 2021 were included,and all patients were scanned with CTPA using SDCT from the thoracic inlet to the level of the diaphragm,and 17 single-energy spectral images were reconstructed at 10 keV spacing for 40,50,60,70,80,90,100,110,120,130 140,150,160,170,180,190 and 200 keV images.A 30 mm2 area of interest was outlined in the PA?RPA?LPA?URPA?MRPA?LRPA?ULPA?LLPA,and CT values and adipose tissue were recorded for each area of interest and for the lumen of the main airways,the latissimus dorsal muscle The CT and SD values of each area of interest and the main tracheal lumen,dorsalis muscle and adipose tissue were recorded,SNR and CNR of the different levels VMI images were computed.One-way ANO VA was used to compare the CT values,SNR and CNR of different single-energy spectral classes.Results The CT values of pulmonary artery trunk,RP,LP,URP,MRPA,LRP,ULP,and LLP at 40 keV of VMI were significantly higher than those of the conventional 120 kVp,50-200 keV groups,all P<0.05.SNR and CNR of PA,LPA,and LRPA at 40 keV VMI were higher than those of the 120kVp,50-200keV VMI groups,all P<0.05,statistically different.Conclusion The use of SDCT in CTPA can provide high contrast,high SNR images with an optimal monoenergetic spectral class of 40 keV.The use of SDCT can compensate for poor pulmonary artery enhancement leading to non-diagnosis and reduce the occurrence of the adverse contrast medium events,which is suitable of wide clinical application.Objective To evaluate the application of dual-layer SDCT in decreasing contrast beam hardening artifacts around subclavian and axillary veins.Methods 35 patients who underwent chest enhancement in our hospital were collected continuously,and the spectral base image were reconstructed into 18 sequences,including conventional 120kVp and 40-200 keV images of single energy spectrum,with the grading interval of 10keV.The ROI was sketched on each group of images,and the CT value and SD value of high-density artifact area,low-density artifact area and contralateral no-artifact control tissue were recorded respectively.Objective evaluation includes CT value of high and low density artifact area,CT value of artifact true,artifact coefficient AI.2 physicians evaluated quality ofimage subjectively by double-blind method,and the consistency of the image quality evaluation of 2 physicians was evaluated by non-parametric test.Results As the grade of single energy spectrum increase,the artifacts of sclerotic bundles of contrast agents around subclavian vein and axillary vein decrease rapidly,and the images of single energy spectrum from 90 to 150keV could meet the requirements of clinical diagnosis.The CT value of the high-density artifacts around the subclavicular vein[(50.12±29.47)HU]and the CT value of the contralateral no-artifact area[(52.01±6.46)HU]is the smallest,and the artifact coefficient AI(27.26±14.23)is the smallest.Low density artifact CT value[(93.49±41.21)HU]and contralateral artifact free area CT value[(-88.68±6.79)HU]difference[(-4.81±39.75)HU]is the smallest.When the single-energy spectrum is 100keV,the subjective score of the two doctors on the image quality is 4.01 10.65,which is significantly higher than that of the other energy level group and the conventional 120kVp group.The consistency of the two doctors' subjective evaluation on the image quality is very good.Conclusion 90-150keV can significantly reduce the perivenous contrast hardening bundle artifacts and improve the image quality by applying double-layer detector spectral CT.The best single-energy spectrum level is 100keV.Objective To evaluate the value of spectral detector CT in indirect lower extremity venography(CTV)imaging.Methods A total of 44 patients who underwent indirect lower extremity CTV were enrolled in our hospital,and CTV images were reconstructed into 8 sequences,including conventional 120kVp and single-energy spectrum images of 40,50,60,70,80,90 and 100 keV.Interest area was sketched on each group of images,CT value and SD value of each area of interest and uniform adipose tissue and muscle were recorded,signal-to-noise ratio(SNR)and contrast noise ratio(CNR)were calculated.Objective Evaluation includes image noise,CT value,SNR and CNR.The image quality was assessed by two physicians using a double-blind,non-parametric test,and Kappa value was calculated to evaluate the consistency of the image quality analysis.Results At 40 keV,the average CT value of the right popliteus ventral lumen was(216.65±48.72)HU,SNR:19.26±9.63,and CNR:6.99±3.88,all of which were significantly higher than the 50?100keV level group and the conventional 120kVp group[CT value:(100.91 ± 15.70)HU;SNR:8.81 ±3.57;CNR:2.10± 1.06](P<0.05).At 40keV,the average subjective score of the two doctors on image quality was 4.76±0.48,which was significantly higher than that of the 50-120KeV energy level group and the conventional 120kVp group(3.84±0.68).The consistency of the two doctors' subjective evaluation on image quality was very good.(k=0.723,P=0.000).Conclusion The lower extremity vein imaging using spectral detector CT indirect method can show the lower extremity vein well,and the best single energy spectrum level is 40 keV. |
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