Evaluation of monochromatic imaging spectal CT for intestinal bleeding using an experimental pig intestine model / 中华放射学杂志

ABSTRACT

Objective To discuss the diagnostic value of monochromatic energy image spectral CT in active small bowel bleeding and to screen the optimal energy level that indicates active bleeding of the gastrointestinal tract.Methods The bleeding model was established using the small intestines of pigs in vitro.Seven blood flow rates were simulated0.500,0.400,0.300,0.200,0.100,0.050,0.025 ml/min,respectively.For each rate,a GE Discovery HD750 CT scanner was used in GSI scan mode and 64 slice CT was performed,with a delay of 15 s and 40 s simulated the arterial phase and portal venous phase,respectively.Each out of the blood flow rate in the 2 modes was respectively scanned 5 times.The GSI reconstruction platform was employed to obtain 7 monochromatic energy images(40,50,60,70,80,90,100 keV).A set of polychromatic energy images was obtained from an ordinary scan.The detection rates of the contrast agent exudation regions using the two scanning methods were compared.The contrast to noise ratios(CNR) for the contrast agent exudation regions were measured.Randomized block analysis of Variance was performed to compare the differences in CNR between energy levels.The x2 test was used to compare the detection rates obtained from the 2 scanning methods.Results The detection rates for energy spectral CT and 64 slice CT in the arterial phase were 31/35 and 23/35,respectively; there was significant difference(x2=5.185,P=0.023).The total detection rates of portal venous phase were 35/35 and 32/35,respectively,there was no significant difference(x2=l.393,P=0.238).On the ordinary scan mode,the detection rates of arterial and portal venous phase difference was statistically significant(x2 =6.873,P =0.009);but on the GSI scan mode,there was no significant difference(x2=2.386,P=0.122). The CNR values at 8 group energy levels for arterial phase and portal venous phase were statistically different(respectively P＜ 0.05),the CNR value of the contrast agent exudation regions at 50 keV and 60 keV monochromatic energy images on the GSI scan mode higher than that of polychromatic energy images,the difference was statistically significant(respectively P＜0.05),the CNR in portal venous phase images were higher than that of arterial at all energy groups,differences were statistically significant(t=-3.996 to-2.380,respectively P＜ 0.05).Conclusions Monochromatic energy image spectral CT demonstrates superiority over polychromatic energy images in detecting active bleeding of the gastrointestinal tract.The optimal monochromatic energy value for detection was between 50 keV and 60 keV,and the detection was easier in the portal venous phase than in the arterial phase.