Objective To investigate the feasibility of reduced radiation dose for CT pulmonary angiography (CTPA) and the possible lowest radiation threshold by a phantom study.Methods The CT value difference between air within the trachea and the extracorporeal background region was measured in132 consecutive patients.A noise-measurement phantom and a pulmonary embolism (PE) phantom were made of phenol-formaldehyde, and both phantoms and a water phantom were scanned with standard and lower radiation doses as follow: 280, 200, 160, 100, 90, 80, 70, 60, 50, 40, 30, 20, 15, and 10 mA respectively, at a fixed voltage of 120 kVp.Standard and soft tissue algorithms were used to reconstruct the images.Three experienced doctors independendy evaluate the image quality and the efficiency of detecting PE of the images with various doses.The Pearson correlation analysis, two-tailed paired t test, ANOVA, and Kappa test were employed for the statistical analysis.Results The CT value difference between air within the trachea and the extracorpereal background region in 132 consecutive patients ranged from 20.00 to 55.00 HU, which had a positive correlation with weight[(64.99±11.86) kg], weight-height ratio [(38.71±6.13) kg/m], and BMI[(23.11±3.38) kg/m2](r=0.228,0.374,0.449 respectively; P <0.01).The image noise level with soft-tissue reconstruction algorithm[(16.55±9.08), (16.42±9.40) HU]was significantly lower than that of the image with standard reconstruction algorithm[(22.43±11.25),(21.99±11.67) HU](F=4.316, P < 0.05).The image noise level with soft-tissue reconstruction algorithm at 100 mA was similar to that of the images with standard reconstruction algorithm at 280 mA, and the signal-w-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the image of PE phantom was 23.05 and 20.52 respectively, without any impairment in detectability of embolus.The image noise level with soft-tissue reconstruction algorithm at 60 mA was similar to that of the image with standard reconstruction algorithm at 160 mA, while the SNR and CNR was 18.01 and 15.97 respectively, also with acceptable detectability of embolus.When the tube current was reduced below 30 mA, the image quality decreased significantly, with the SNR and CNR was lower than 12.36 and 10.95 respectively, and the detectability of embolus was degraded.The consistency of the image quality grading by 3 observers was excellent(K=0.807,0.712,0.904 ,respectively; P < 0.01).Conclusions The 100 mA may potentially be the ideal low dose tube current setting, with radiation dose only equal to 36% of 280 mA (standard dose).The 30 mA may possibly be a minimum radiation dose for detecting PE.The soft-tiasue reconstruction algorithm was favorable in preserving the SNR when the radiation dose was reduced.

10.3969/j.issn.1008-9691.2013.03.018

ObjectiveTo investigate the effects of tirofiban on microvascular flow in infarction zone after coronary reperfusion in pigs with acute myocardial infarction (AMI),and to explore its mechanism of decreasing microvessel obstruction (MO) and the relationship with inflammatory factors. MethodsChinese mini pigs were randomized into control group and tirofiban treatment group.Acute myocardial infarction was induced by balloon occluding the medium segment of the left anterior descending artery for 90 min,and then reperfusion was created by withdrawing the balloon.The infarct myocardium and MO area were detected with delayed enhancement multi-slice spiral CT (DE-MSCT),the serum levels of IL-6 and IL-10 were measured with enzyme linked immunosorbent assay (ELISA).The pigs were killed, the heartwere excised and stained with 2, 3, 5-triphenyltetrazolium chloride (TTC). Results6 pig models were successfully established in each group.4 pigs in control group and 3 pigs in tirofiban treating group experienced MO.The MO volume was increased at every time after reperfusion in both groups,while the MO volume was significantly reduced in tirofiban treatment group compared with control group at 1 h [(9.6 ± 3.1) ％ vs.(4.8 ±0.7)％],24 h[(13.4±3.3) ％ vs.(5.8±-1.2)％],48 h[(15.1±3.8)％ vs.(6.4±1.2)％] and 72 h [(15.9±4.6) ％ vs.(6.6±0.8)％ after reperfusion (t=6.99,13.76,14.21,11.38,all P＜0.05).Compared with the baseline,the levels of serum IL-6 and IL-10 in both groups were increased at 30 min after AMI.In tirofiban treatment group,the level of serum IL-6 was significantly lower and serum IL-10 was higher than those in control group (P＜0.05 and P＜0.01) from 10 min to 72 h after reperfusion. Conclusions Tirofiban may lessen the MO area in infarction zone of AMI after reperfusion,which may be ascribed to its anti-inflammation besides anti-platelets.

Objective To evaluate magnetic resonance angiography(MRA) and diffusion weighted imaging(DWI) features of transient ischemic attacks(TIA).Methods 40 patients with TIA were chosen as study subjects,and 34 healthy adults and 36 cases with brain infarction were randomly chosen as control subjects.MRA and DWI was performed with a superconductive GE 1.5T system.The relationship between TIA and the degree and distribution of stenosis of cranial and cervical arteries,the development of the vessels,DWI findings of the brain was analyzed.Results There were significant differences among the three groups in the number and the degree of stenosis of cranial and cervical arteries(P=0.006).The stenosis and occlusion of arteries were severe in the patients with TIA and brain infarctions than that in healthy adults(P=0.004,0.015),but there were no significant differences between TIA and brain infarctions(P=0.148).The incidence of dysplasia of unilateral vertebral arteries(VA) in TIA was higher than that in the normal subjects(P=0.039).The internal carotid artery(ICA)system supplying to the regions of brain tended to show more ischemic focus on DWI(4/8,50%) in the cases with TIA.Conclusion Severe stenosis or occlusion and irregular filling defects of cervical and cranial arteries in patients with TIA might be one of the risk factors for severe ischemia stroke.The hypoplastic VA was one of predisposing factor for TIA.

Objective To assess the effect of intracoronary attenuation,slice thickness,and window setting on CT attenuation measurement of non -calcified coronary plaque in ex vivo specimen.Methods Twenty adult cadaver heart specimens were used.Five solutions of contrast medium diluted with saline were prepared as follows:1/200,1/50,1/40,1/30,and 1/20.CT scans were performed after intracoronary iniection of each solution.The solution of 1/200 was used to measure baseline values of plaques.and the other four solutions were used to imitate the different intracoronary attenuation.The plaque attenuations were measured with region of interest under four intracoronary attenuations,two slice thickness (0.625 mm and 1.250 mm),and two window settings(WW 1000 HU,WL 150 HU and wW 500 HU,WL 200 HU),respectively.The result was compared with factor analysis and partial correlation analysis.Results Twenty four plaques met the study criteria.The baseline CT attenuation of plaques under two window settings were(23.90±6.87)HU(setting 1)and(29.00±7.26)HU(setting 2)respectively.Intracoronary attenuation and window settings had significant effect on CT attenuation measurement of non-calcified plaques(F=45.674 and 79.094,P＜0.01),whereas slice thickness of 0.625 mm and 1.250 mm showed no significant effect on CT attenuation measurement(F=1.033,P＞0.05).Comparing with baseline vslues.plaque attenuations on 1/40 and 1/30 solutions that can imitate lumen attenuation in clinical practice were increased.Conclusions Intraeoronary attenuation and window settings had significant effeet on CT attenuation measurement of non-calcified plaques,while slice thickness of 0.625 mm and 1.250 mm had no significant effect.Plaque attenuation would increase with the increase of intracoronary attenuation.

Objective To compare radiation dose and image quality between prospective and retrospective ECG gating CT coronary angiography (CTCA) with 64-slice CT scanner. Methods Sixty patients with suspected coronary artery disease were selected, and randomly devided into two groups. Thirty patients in research group (average body-mass index [BMI]:[25.30±3.15] kg/m~2, heart rate ≤65 beats per minute [bpm]) underwent CTCA using prospective ECG-gating (120 kV, mA tailored to weight), while the rest 30 patients in control group (average BMI:[25.40±3.00] kg/m~2, heart rate ≤65 bpm) underwent CTCA using retrospective ECG-gating (120 kV, 650 mA). The average effective dose (ED) and standardizing radiation dose (ED_(Sd)) which was standardized by 12 cm length were respectively calculated, and statistical analysis was then conducted, meanwhile image quality was evaluated. Results The average ED of research group and control group was (5.97±1.04) mSv and (26.25±2.36) mSv, respectively (t_(A,B)=43.13, P<0.05). The ED_(Sd) of two groups was (5.49±0.45) mSv and (23.77±1.64) mSv (t_(Sd)=59.00, P<0.05). ED_(Sd) decreased by 76.62% in research group compared with that of control group. No significant difference of image quality was found between two groups (χ~2=4.26, P=0.235). Conclusion Prospective ECG-gating CTCA can effectively reduce radiation dose without compromising image quality.

Objective To compare the displayed inner diameter of coronary stent by high definition(HD)and gem?stone spectral imaging(GSI)using dynamic cardiac and coronary artery phantom. Methods Five different types of coro?nary stents(internal diameter, 3.10 mm±0.55 mm;strut thickness, 0.12 mm±0.04 mm)were placed into a pulsating cardiac phantom(ALPHA 1-VT PC, Fuyo Corporation, Japan). The stent phantom was scanned by 3 systems, gemstone spectral im?aging(GSI), spiral scan(S)and HD. All the spectral imaging data were analyzed using GSI viewer to reconstruct the VMS (monochromic spectral) images(60-140 keV). Image noise(N), signal-to-noise ratio(SNR), contrast-to-noise ratio(CNR) and inner diameter were compared between images acquired through these 3 systems. Results SNRs in images of S and HD were higher than that of GSI(P<0.05),while there were no significant differences in CNRs among images of GSI, S and HD(P>0.05). The visible diameter(%)measurements of HD(0.85 ± 0.06)was significant higher than that of the other 2 scan systems and most close to the width of those stent’s actual size.(GSI:0.40±0.16, 0.48±0.13, 0.50±0.14, 0.51±0.13, 0.45±0.05,0.52±0.13, 0.53±0.13, 0.53±0.13, 0.53±0.13, S:0.53±0.14, P<0.05). Conclusion There was no significant dif?ferences in image quality among the images acquired by these 3 systems when the heart rate was set to 60 beats per min. Comparing to GSI and S, HD can produce best represent images to the known inner diameter of coronary stent.

Objective To evaluate the diagnosis accuracy for coronary stenosis from diameter measurements of differ?ent severities of stenosis by using gemstone spectral imaging (GSI). Methods Totally 3 different coronary artery models(in?ternal diameter:3.00 mm) that with different severities of stenosis (residual lumen diameter ratio:75%, 50%and 25%) were placed in a pulsating cardiac phantom (ALPHA 1-VT PC, Fuyo Corporation, Japan). The coronary phantom was scanned in two models:gemstone spectral imaging (GSI) and axial scan model(AXIAL). All the spectral imaging data were analyzed by using GSI viewer to reconstruct the VMS images (40-140 keV by 10 keV interval) and AXIAL. CT values (HU) of the re?mained lumen from all different stenosis lumens were measured. The residual rate (%) was calculated by dividing the diame?ters of the remained lumen to normal lumen on the reformatted short axial images. One-way ANOVA was used to compare the measurement difference of residual rates between VMS images. Student t-test was used to compare the measurement dif?ference of residual rate between VMS and AXIAL. Bland-Altman test was used to compare the measured residual rates and the gold standard. Results There were no significant differences in measured residual rate betweeb VMS images (P>0.05). From student t-test, only significant difference was found on 50%stenosis between 70 keV VMS and AXIAL(t=4.617,P<0.042). From the Bland-Altman test, measurement of residual rate was more accurate from 70 keV VMS than that of AXIAL by taking the stenosis rate of real model as gold standard(t=14.560,P<0.001). Conclusion VMS image (70 keV) shows more accurate rate than AXIAL images on both diameter measurement and evaluation of the coronary stenosis.

Objective To evaluate the CT findings of invasive pulmonary aspergillosis(IPA) in patients with leukemia.Methods Plain CT scanning of chest was performed in 9 cases of leukemia in company with IPA proved by sputum culture.5 of them underwent over twice CT re-scanning,CT findings of IPA were analysed.Results The lesions were seen more common in the bilateral upper lobe and dorsal segment of lower lobe,mainly located in the peripheral and sub-pleural lung field.Of the 9 cases,the lesions appeared as multi-nodular shadows in 5,single nodule in 2 and sub-pleural consolidation with ground-glass opacity around them in 2,of these 2 cases,one accompanied by multi-nodules.Halo-sign around the nodules in 6 cases and air cresent sign or cavity in 6 were seen.There were scattered ground-glass opacities and patchy attenuations in the bilateral lung in 4 cases.The adjacent pleura of lesion was slightly thinkened in 5 cases.Conclusion The incidence of IPA in leukemia patients is rather high,and CT features of IPA are of certainly characteristics.

Objective To evaluate the effcets of tirofihan on myocardial no-reflow after acute myocardial infarction and reperfusion by delayed enhancement-multi-slice CT(DE-MSCT).Methods Chinese mini pigs were randomized into control group and firofiban treatment group. Acute myocardial infarction was induced by balloon occlusion of the medium segment of the left anterior descending artery for 90 minutes. Repeffusion was created by withdrawing the balloon during angiography. All successful models received DE-MSCT examinatons at 1 h, 24 h, 48 h, and 72 h after reperfusion to observe the myocardial noreflow area. Data were analyzed with Spearman rank correlation and Wilcoxon Rank Sum test. Results Six pigs were successfully induced as acute reperfusion myocardial infarction in each group. Furthermore,4 pigs in control group and 3 pigs in firofiban treatment group had no-reflow phenomenon. The no-reflow volume percent increased from 1 h to 72 h in both groups. The no-reflow volume percent was significantly reduced in tirofiban treatment group compared with control group after reperfusion at 1 h, 24 h, 48 h and 72 h respectively[(4.78±0.66)% and (9.62±3.05)%, t =6.000, P＜0.05; (5.84 ± 1.19)% and (13.44±3.33)% ,t=6.000,P＜0. 05;(6.41± 1.24)% and (15.10±3.76)%,t =6.000,P ＜0.05;(6.63 ±0. 82)% and (15.94 ±4.62)% ,t =6.000,P ＜0.05] ,as well as the infarct myocardium volume percent was significantly reduced in tirofiban treatment group compared with control group at 24 h, 48 h and 72 h after reperfusion [ (19.74± 2. 94) % and ( 25.08 ± 4.68) %, t = 25.000, P ＜ 0.05;(20.34±2.46) % and (27.07 ±5.44)%, t =26. 000,P ＜0.05; (20.72 ±2.10)% and (26.17 ±5.19)% ,t = 24.000,P ＜0.05]. Conclusions DE-MSCT can be used to detect the extent of no-reflow phenomenon. Tirofiban can reduce the volume of myocardial infarct and no-reflow area after reperfusion.