| ObjectiveTo discuss the diagnostic value of monochromatic energy image and iodine-basedimage spectral CT in active small bowel bleeding and to screen the optimal energy levelthat indicates the active bleeding of the gastrointestinal tract.MethodsThe bleeding model was established using the small intestines of pigs in vitro.Seven blood flow rates were simulated:0.5ml/min,0.4ml/min,0.3ml/min,0.2ml/min,0.1ml/min,0.05ml/min and0.025ml/min, respectively. For each rate, GE DiscoveryHD750CT scanner was used in GSI scan mode and64-layer CT, with a delay of15sand40s, respectively. GSI reconstruction platform was employed to obtain seven40keV~100keV monochromatic energy images with the interval of10keV and a set ofiodine-based images.In addition,a set of polychromatic energyimages was obtained byordinary scan. The detection rates of the contrast agent exudation regions using the twoscanning methods were compared. The contrast noise ratio for the contrast agentexudation regions were measured. The iodine base figure of iodine containing (IC)and spectal CT attenuation curve slope (K) was measured, and then the correlationbetween the bleeding rate was analysed, and the statistics difference between the arterialphase and portal phase was compared. Randomized block analysis of variance wasperformed to compare the differences in CNR between energy levels. c2test was usedto compare the detection rates obtained from two scanning methods. Iodine content and attenuation curve slope correlation analysis with the blood flow rate, arterial phase andportal phase comparison adopted the matched t-test.ResultsThe detection rates by energy spectral CT and64-slice CT in the arterial phase were88.57%(31/35) and65.71%(23/35), respectively; the difference was of statisticalsignificance (c2=5.185P=0.023). The total detection rates of portal venous phase were100.00%(35/35) and91.4%(32/35), respectively, and the difference was of nostatistical significance (c2=1.393P=0.238). Compared with the CNR of the contrastagent exudation regions (3.58±2.09) on mixed-energy image, those on the single-energyCT images at50keV and60keV in the arterial phase were8.78±7.21and8.83±6.75,respectively, and the difference was statistically significant (p<0.05). In the portalvenous phase, the CNR values on the monochromatic energy images at40keV,50keV,60keV and70keV were19.35±10.89,20.82±11.26,20.63±10.07and15.65±8.17,respectively; that of the polychromatic energy images was11.68±6.38, and thedifference was of statistical significance (P<0.05). The CNR values at different energylevels for arterial phase and portal venous phase were statistically different (t=-2.415,-2.380,-2.575,-2.762,-2.945,-3.157,-3.996and-3.189, p<0.05). The IC (P=0.003)and K (P=0.006) between arterial phase and portal phase showed statistical difference,that in portal-phase was higher. The IC and K of arterial phase with bleeding rate werepositively correlated （r=0.968，P<0.001；r=0.965，P<0.001）, which of portal phasewith bleeding rate were positively correlated （r=0.964，P<0.001；r=0.956，P=0.001）.ConclusionMonochromatic energy image and iodine-based image spectral CT demonstratessuperiority polychromatic energy image in detecting active bleeding of thegastrointestinal tract. The optimal monochromatic energy value for detection wasbetween50keV and60keV, and the detection was easier in portal venous phase than in the arterial phase. |
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