| Objective: The objective of this experimental study was to study the ability of CT virtual colonography by 64 multislice spiral CT using low X-ray dose scanning technique in the diction of polyps under ideal imaging conditions. The different dose scanning to the different size's pig colon simulation polyp's detection rate, and appraises two dimensional, the three dimensional reconstruction and two dimensional and the three dimensional union observation to simulates the sensitivity which the polyp picks out.Methods: fifteen segments of 25cm-long porcine colon were explanted and thoroughly cleaned. 6 stimulated polyps(2 lesions,2-4.9mm; 2 lesions,5-9.9mm; 2 lesions,10-15mm)were placed in every segment of 25cm-long thoroughly cleaned porcine colon that was distended with air and submerged in a water phantom.15 segments were scanned with 64 detector-row MSCT scanner using 50mA,20mA,12mA parameters, and the same time tracked record the CT dose index(CTDIw) 3.83mGy,1.53mGy,0.93mGy respectively. The data were reviewed using axial+MPR,CTC,combined 2D/3D approach. Statistically, Adopted a number of design group Samples of the rank and number of samples tested and compared the February 2 rank and test evaluation of image quality. After dealing with different doses of various methods to simulate the polyp detection rate and after the treatment of three different doses of simulated polyps detection rate, the number of card-related samples to test.Results:1.There were statistical differences in image quality between the axial images with 1mm slice thickness and MPR acquired by using different X-ray dose techniques. There were no statistical differences in image quality the images of CTC acquired by using various X-ray dose acquisition techniques respectively.2.The detection rates of 50mA,20mA,12mA CTC images for stimulated polyps with different dimensions were as follows:100% for the ones with diameters of≥10mm,with all three dose,96.7%,96.7%,93.3% for the ones of 5-9.9mm in diameter and 86.7%,83.3%,80% for those of <5mm in diameter by using 50mA,20mA,12mA.There was no statistical differences in detection rates to stimulated polyps in same group with different X-ray dose. Different from the current 50mA,20mA,12mA its axial + MPR imaging≥10mm stimulated polyp detection rate was 100 percent, the simulation of 5-9.9mm polyp detection rate was 93.3%,66.7%,60%, to the <5mm simulation polyp detection rate is 70%,50%,36.7%, different doses of≥10mm group simulated polyps detection rate was not significant, 5-9.9 mm group, <5mm group simulated polyps there are significant. Different tube electric current 50mA, 20mA, 12mA its 2D+3D union observation to≥10mm the simulation polyp detection rate is 100%, to the 5-9.9mm simulation polyp detection rate respectively is 96.7%,96.7%,93.3%, to the <5mm simulation polyp detection rate is 86.7%,83.3%,80%. With tube current declining, comparing to 50mA, the CTDIw(mGy) of 20mA,12mA was decreased by 60.1%,75.7%.3. Using the 50mA tube electric current gather the image, axial +MPR, CTC, the 2D+3D different observation method for≥10mm the polyp detection rate is 100%, to the 5-9.9mm polyp detection rate respectively is 93.3%,96.7%,96.7%, <5mm polyp detection rate of 70%,86.7%,90%, 2D+3D observation methods were the most sensitive technique for showing polyps of different size, while CTC was in the second place. MPR is less sensitive for demonstrating polyps with less than 5mm in diameter.conclusion:1.Under ideal imaging conditions, sensitivity was higher for detecting polyps using 64 detector-row MSCT colonography scan technology with 12mA low X-ray dose, to simulated polyps showed no obvious effects, and X-ray radiation dose than 50mA dose decreased by about 4/5.2. Various methods of observation, two dimensional and the three dimensional image union observation may raise the polyp detection rate, the CTC detection rate is slightly low, axial + MPR small polyp detection rate decreased significantly. Low-dose simulation colonoscopy for colon lesions census provided broad prospects. |
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