| Objectives 1 To explore the feasibility of low-voltage combined low-concentration contrast agent scanning technique in the diagnosis of bleeding in the gastrointestinal bleeding model,and to seek the optimal solution and the optimal scanning layer thickness.2 To explore the diagnostic value of different scanning combinations on the active hemorrhage of digestive tract model.Methods Part 1:To collected 30 patients who were diagnosed by MSCT enhancement in our hospital and confirmed the operation of the gastrointestinal tract,and measured the CT value of the bleeding point.The average value was 212.13±64.54 HU.With measured bleeder CT value for reference,the nonionic contrast medium iodine fo alcohol(320 mgI/ml)diluted with 0.9% saline into seven different concentrations iodine solution,followed by 6.4,6.08,5.76,5.44,5.12,4.8,4.48,mgI/ml.Under the condition of 120 kV,the mean CT value of 6.4 mgI/ml was 214.73±1.63 HU,and there was no significant difference between the CT value and the measured mean value of the iodine solution above 5.12 mgI/ml(P>0.05).The producted model of gastrointestinal bleeding: 2 pieces of fresh pig rib plate joining together,into the middle period of vertebrae,2 pieces of pig between floor filled with fresh animal fat,kidney and intestine,gas filling the moderate and small intestine.The intravenous indwelling needle(20G)was placed into the intestinal canal and connected with the microinjection pump through the connecting tube.The scaning pardmeters of conventional group: was 120 kV,300mAs,scanning layer thickness 1mm;The experimental group consisted of four parts:(group A: 100 kV,300mAs;Group B: 100 kV,400mAs;Group C: 80 kV,400mAs;Group D: 80 kV,465mAs,scanning layer thickness 1,1.5,2,2.5,3mm;Contrast agent injection rate was 0.5,0.4,0.3ml/min.The contrast concentration corresponded to 7 iodine solutions.Scan each parameter 15 times.The CT volume dose index(CTDIvol)and dose length product(DLP)were recorded and the effective dose(ED)was calculated.The objective noise value of the image was measured,the signal-to-noise ratio was calculated and the number and detection rate of bleeding points using MSCT scanner were recorded to detect the bleeding of the model,and the CT value of the bleeding point was measured.Part 2:At a rate of about 0.5 ml/min injection,respectively,the following six different concentrations iodine solution: 6.4,6.08,5.76,5.44,5.12,4.8,4.48,mgI/ml,after the iodine solution injected 10 s,30s,60 s of the digestive tract hemorrhage model routine dose MSCT scanning.Record 10s+30s,10s+30s+60s CT volume dose index(CTDIvol),dose length product(DLP),calculate effective dose(ED);The detection of model hemorrhage was detected in 10 s,10s+30s and 10s+30s+60s after the scanning,and the CT value of the model was measured,and the optimal combination scanning scheme was evaluated.Results 1 Routine dose group CTDIvol: was 19.63 mGy,DLP : was 691.60±13.98mGy*cm,ED : was 10.37±0.21 mSv,experimental dose group A CTDIvol:was 12.36 mGy,DLP:was 445.53±21.02mGy*cm,ED:was 6.68±0.32 mSv,experimental dose group B CTDIvol:was 16.49 mGy,DLP:was 588.90±25.04mGy*cm,ED:was 8.83±0.38 mSv,experimental dose group C CTDIvol:was 8.19 mGy,DLP:was 287.63±17.82mGy*cm,ED : was 4.31±0.27 mSv,experimental dose group D CTDIvol:was 9.52 mGy,DLP:was 332.97±19.25mGy*cm,ED:was 4.99±0.29 mSv.There were statistically significant differences between the conventional group DLP and ED and the experimental groups(P<0.05).Noise: experimental group A-2.5mm: 17.43±2.96,experimental group A-3mm: 15.90 ±1.19,experimental group B-1.5mm: 14.66±0.86,experimental group B-2mm: 13.60±1.33 and the conventional group showed no statistical significance(P>0.05);Signal to noise ratio: experimental group B-1mm: 2.60±0.41,experimental group B-1.5mm: 3.15±0.14,experimental group B-2mm: 3.45±0.45 and conventional group comparison showed no statistical significance(P>0.05).Subjective image quality score: the experimental group A-2mm: 4.07±1.03,the experimental group A-2.5mm: 4.39±0.61,the experimental group A-3mm: 4.63±0.50,the experimental group B-1mm: 4.07±1.03,the experimental group B-1.5mm:4.61±0.50,the experimental group B-2mm: 4.70±0.47,the experimental group B-2.5 mm: 4.74 ±0.45,the experimental group B-3mm: 4.77±0.43,the experimental group D-3mm: 4.22±0.73,there was no statistically significant difference compared with normal group(P>0.05);Experimental group B-1.5mm-6.08mgI/ml,5.76mgI/ml had no statistical significance(P>0.05)compared with the experimental group B-1.5mm-6.4mgI/ml.In the experimental group B-1.5mm-5.76mgI/ml,the detection rate of the bleeding rate of 0.4ml/min was lower than 0.5ml/min,but the difference was no statistically significant(P>0.05).2 10s+30s CTDIvol:was 39.26 mGy,DLP:was 1446.02±80.43 mGy*cm,ED:was 21.69±1.21 mSv;10s+30s+60s CTDIvol:was 58.89 mGy,DLP:was 2169.03±120.64 mGy*cm,ED:was 32.54±1.81 mSv,The difference between 10s+30s DLP,ED and 10s+30s+60s was statistically significant(P<0.05).The CT value of the hemorrhagic point in 10s+30s was higher than that of 10 s and 10s+30s+60s.There was no significant difference between the CT value of 10s+30s and 10s+30s+60s.(P>0.05).10 s of model bleeding detection rate is 61.1%,less than 10s+30s to the model of bleeding detection rate 79.6% and 10s+30s+60s hemorrhage 85.2% detection rate of the model,and the difference was statistically significant(P<0.05),10s+30s and 10s+30s+60s bleeding detection rate of the model comparison difference was no statistical significance(P>0.05).Conclusions 1 MSCT low voltage combined with low concentration contrast agent is feasible to diagnose hemorrhage in the gastrointestinal bleeding model.2 At the same time of lower tube voltage,in order to reach the image quality of routine dose level,100 kV,400 mAs,1.5mm is the optimal scanning layer thickness,1.5mm is the optimal scanning layer thickness,this condition can check out the bleeder of 0.4ml/min.3 10s+30s is the best combination for the best scan period of the model's bleeding point. |
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