| Objective Explore the optima scan parameters of screening colorectal cancer using low dose with 64-slice spiral CT in order to make it more consummate in clinical application.Materials and Methods 42 artificial polypoid diseases were placed with glue in a thoroughly cleaned porcine colon(overall length,150 cm) that was distented with air and submerged in a water phantom and scanned on a 64-MSCT (GE Lightspeed VCT) under auto tube current modality mode with various combinations of serval parameters [tube voltage(TV):140/120/100 /8 0 kV , noise index(NI):8/12/15/18/21/24/27/30/33, rotation time(RT):0.4/0.5s]. The datas were reconstructioned every 0.625mm and reviewed by two radiologists with more than 10 years work experience respectively using 2D images, navigation, MPR and 3D volume-rendered images on GE ADW4.2 workstation. Image quality score (IQS) were count considering the conditions contain computed tomography virtual coloscopy(CTVC), multiplanar reconstruction (MPR), Raysum & virtual dissection(VD).Dose-length-products(DLP) and IQS were recorded.The relations between DLP and NI/TV/RT and the relations between IQS and NI/TV/RT/DLP were analyzed with partial correlation.Results Coefficient of partial correlation between DLP and NI was -0.895,P O.O5; Coefficient of partial correlation between DLP and RT was -0.078,P >O.O5; Coefficient of partial correlation between IQS and NI was -0.948,P <0.001; Coefficient of partial correlation between IQS and TV was 0.642, P<0.01; Coefficient of partial correlation between IQS and RT was 0.25,P >0.05;Coefficient of partial correlation between IQS and DLP was -0.186,P>0.05.Conclusion The optima parameters of 64-slice spiral CT colonography is a combination of 120kV(TV),12(NI),0.5s(RT)under the auto tube current modality mode.The dose of screening colorectal cancer with 64-slice spiral CT using this scan parameters combination lower to approximate 16.8% dose of fixed tube current scan CT colonography.
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