The Clinical Research Of Gemstone CT With Low Dose Scanning Technology And Low Concentration Agent In CT Portal Venogroaphy

ObjectiveThe main purpose of this research was to evaluate the clinical probability of the Gemstone "double low" CT scan protocal(the low radiation dose and low concentration agent) by comparing the radiation dose and image quality in CT Portal Venography.MethodsData were collected from patients with suspected liver disease diagnosed during November 2013 to January 2015 in the First Affiliated Hospital of Guangzhou University of Chinese Medicine.60 patients who met the criteria were randomly arranged into two group to receive liver CT enhanced scan.30 patients (the "double group") received three-phasic enhanced CT scans with GSI (Gemstone Spectral imaging) protocol using 270mgI/ml Indianola. The other 30 patients (the conventional group) received three-phasic enhanced CT with conventional 120KVP protocol using 350mgI/ml Oversold. The images of portal phase from two imaging modes were retrospectively compared. The images of "double-low" group were used to choose the monochromatic images for obtaining the highest contrast to noise ratio (CNR) for main portal veins and 70kev monochromatic images using the GSI-viewer software. The highest CNR for main portal veins is about 50 Kev, which were reconstructed using different percentage of Adaptive Statistical Integrative Reconstruction(ASIR) (30%、 50%、80%). The images of conventional group were reconstructed using filtered back projection (FBP). Volume Rendering (VR) and Maximum intensity projection (MIP) on portal veins in each image was rated in five ranks using Quantitative Grading System by two experienced radiologists. Image quality was evaluated by comparing the Signal-to-noise-Ratio (SNR)、CNR and image noise of main liver portal veins at 70 Kev and 50 Kev. The CT dose index volume (CTDIvol) and dose length product(DLP) were generated by computers. Record of CTDIvol and DLP was made and calculation of the Effective dose (ED) was then conducted. All data above were statistically analyzed using spssl7.0 software.Results1.The general situationThere was no significant difference in age、sex、weigh、height and BMI between the "double low" group and conventional group.2. The radiation doseThere was a statistically significant difference in CTDIvol、DLP and ED (P<0.01). The effective radiation dose in the "double low"group was obviously lower than the conventional group(3.57±1.14 mSv vs 4.26±0.57mSv, p< 0.001)3.ASIRAs with the increasing of ASIR%, the CNR、SNR gradually increased, while the SD decreased, there was significant differences between different ASIR%(30%、50%、80%) in the subjective scores(p<0.01). Reconstruction using 50% ASIR had the highest subjective scores, display the best imaging quality for CTPV.4. In the "double low" group, the SNR、CNR and objective scores of the monochromatic images at 70kev and 50kev were significantly different (p< 0.05).SNR and CNR of 50kev monochromatic images was higher than that of 70 Kev, as well as the image quality of VR and MIP on portal vein.5. There was a statistically significant difference in the CNR、SNR between the FBP of the conventional group and the 50% ASIR of the 50kev monochromatic images. SNR and CNR of 50% ASIR of the 50kev monochromatic images was higher than that of conventional group. But the subjective image quality has no significant difference.ConclusionThe image qualities of the "double low "group are able to reach the same level with the conventional group. The research shows that it is available to use Gemstone Computed Tomography Angiography joint with "double low" protocol(low dose radiation and low dose contrast medium in CT Portal...