Objective To assess the influence of tube current and tube voltage on the CT attenuation,radiation dose,and image quality.Methods A total of 113 saline solutions with decreasing dilution of contrast medium (370 mg I/ml) was produced.MDCT scan was performed with 15 series of different settings of tube current and tube voltage.CT attenuations with 15 series of different settings were all measured,and influence of tube current and tube voltage on CT attenuations was analyzed.CT dose index (CTDIvol) was recorded.The CT attenuations with different tube voltage and current were compared with one-way ANOVA and Kruskal-Wallis rank sum test.The correlation of CT attenuation with different tube voltage and the influence of tube voltage and current on radiation dose and image quality were tested by correlation analysis.Results Tube current (250,200,150,100,and 50 mA) had no significant effect on CT attenuation (F =0.001,0.008,0.075,P ＞ 0.05),while tube voltage (120,100,and 80 kV) had significant effect (H =17.906,17.906,13.527,20.124,23.563,P ＜ 0.05).The correlation between CT attenuation and tube voltage was determined with equation:CT attenuatio N100 kV =1.561 × CT attenuatio N120kv + 4.0818,CT attenuatio N80kV =1.2131 × CT attenuatio N120kv + 0.9283.The influence of tube voltage on radiation dose and image quality was also analyzed,and equations were also obtained:N120 kV =-5.9771Ln(D120 kV) + 25.412,N100 kV =--10.544Ln (D100 kV) + 36.262,N80 kV =-25.326Ln(D80kv) +62.816.According to the results of relationship among CT attenuation,radiation dose,and image quality,lower tube voltage with higher tube current can reduce the radiation dose.Conclusions Lower tube voltage can reduce the radiation dose.However,CT attenuation was influenced,and correction should be done with the equations.

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 prospectively assess the diagnostic accuracy of MR inflow inversion recovery (IFIR) fast imaging employing steady-state acquisition (FIESTA) for detection of renal artery stenosis (RAS),as compared with renal artery CT angiography (CTA) performed as the reference standard.Methods Thirty patients [18 males,12 females; mean age (65.0±12.1) years] with arterial hypertension and suspected RAS were examined by 3.0-T 3D MR IFIR-FIESTA and renal artery CTA within a week.The IFIR-FIESTA image quality,the IFIR-FIESTA and CTA in display of second-order and third-order branches of renal artery were assessed by two experienced readers.The sensitivity,specificity,accuracy,and negative predictive value (NPV) of IFIR-FIESTA were calculated on artery-by-artery and patient-by-patient bases by the two readers.The inter-observer agreement between the two readers in determining the presence and grade of renal artery stenosis was assessed.Results The scores of qualification of IFIR-FIESTA image quality by reader A and B were (2.16±1.02) and (2.00 ± 0.14),there was no significant difference between them (Z=-0.037,P=0.971).IFIR-FIESTA and CTA in display of second-order and third-order branches of renal artery had no significant difference (x2 =0.298,P=0.585).In the assessment of all 64 main renal arteries by reader A,IFIR FIESTA on artery-by-artery basis had sensitivity,specificity,accuracy,and NPV of 100％,96％,97％,and 100％,respectively; the above parameters assessed by reader B were 100％,90％,93％,and 100％,respectively.There was excellent inter-observer agreement (Kappa=0.803) with the presence or absence of hemodynamically significant RAS.In the assessment of all 30 patients by reader A,IFIR-FIESTA on patient-by-patient basis had sensitivity,specificity,accuracy,and NPV of 100％,95％,97％,and 100％; the above parameters assessed by reader B were 100％,85％,90％,and 100％,respectively; there was good inter observer agreement (Kappa=0.724) with the presence or absence of hemodynamically significant RAS.Conclusions Compared with CTA,MR IFIR-FIESTA can excellently assess RAS without contrast material and radiation exposure,therefore,it can be used for screening of RAS,especially should be widely applied to elderly patients with arterial hypertension.

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 investigate the feasibility and clinical application value of 3D arterial spin labeling (3DASL) technique in diagnosis of ischemic cerebrovascular disease.Methods Experiment 1:Controlgroup (n=30) and brain infarction group (n=20) were established.All patients were routinely examined including 3DASL and dynamic susceptibility contrast (DSC) enhanced series.The analysis of the control group was performed using signal intensity measurement in three paired regions of interest (ROI) which were selected in left hemisphere centrum semiovale and the opposite hemisphere mirror regions respectively.The ROIs of brain infarction group were selected in the lesion areas and their mirror region.The cerebral blood flow (CBF) of each ROI was measured with 3DASL and DSC respectively.The CBF ratio to each ROI and its mirror ROI were calculated.Data were compared using paired-t test.Experiment 2:Acute cerebral infarction (n=30) and transient ischemic attack (TIA) group (n=30) were established.All patients were routinely examined including 3DASL and diffusion weighted imaging (DWI).The positive rate and the area of the lesions were calculated respectively with 3DASL and DWI and compared.Results Experiment 1:Both the control and brain infarction group demonstrated agreement between 3DASL and DSC.The CBF ratios of the control group were 1.02±0.18 and 1.06±0.24 respectively and revealed no statistically significant between that of 3DASL and DSC (P＞0.05).The CBF ratios of brain infarction group were 0.50±0.12 and 0.48±0.18 respectively,and also revealed no statistically significant between two methods (P＞0.05).Experiment 2:The positive rate of acute cerebral infarction were 100％ with both DWI and 3DASL.The areas of the lesion detected by both methods were:SDwI＜S3DASL,n=22; SDWI ≈-S3DASL,n=8; SDWI＞S3DASL,n=0.The positive rate of TIA by DWI was 0％,and 70％ by 3DASL.Conclusion The noninvasive,safe and repeatable 3DASL technique is almost as sensitive as DSC in the measurement of CBF.However,and it is more sensitive than DWI in diagnosis of TIA.Combining 3DASL and DWI will be helpful in early diagnosis of TIA,finding ischemic penumbra and estimating the blood perfusion of ischemic cerebrovascular disease.

Objective:To implement rapid acquisition gradient echo(RAGE)pulse sequence in clinical MRI scaner.Methods:Pascal language is engaged to edit source code.Number of slice excited,order of phase encoded,phase recycle of RF pulse,NEX,on/off of the gradients,and so on are all controlled by sequence parameters.SI×N_(phase)×N_(slice) data of 32 bctys were allocated to restore the k space.Source code of sequence was compiled with executable file and is loaded to RINMR software.Image of human brain are acquired.The experiment has been conducted on 0.36T permanent MRI system.Resuits:In the case of 256×256 matrix acquisition,time of single slice is 4 seconds.The resolution and SNR of the image are all adquately satisfy the clinical application.

Objective To investigate the characteristics of cerebral vascular imaging and risk factors of stroke in popu?lation with family history of stroke in rural areas of Ji County, Tianjin. Methods The volunteers with family history of stroke were recruited in the study to undergo computed tomography and computed tomography angiography (CTA) of head as well as physical and laboratory examinations. A total of 281 subjects, including 153 male and 128 female, underwent exami?nation, and were divided into stroke group and non-stroke group. Results The detection rates were significantly higher in male subjects than those of female subjects, including smoking rate, drinking rate, educational level, and decreased level of high density lipoprotein cholesterol (HDL-C), whereas the detection rate of high level of triacylglycerol (TG) was significant?ly higher in female than that of male subjects (P<0.05). There were 38 subjects in stroke group. The age, internal carotid ar?tery calcification rate (ICAC) and internal carotid artery tortuosity (ICAT) rate were significantly higher in stroke group than those of non-stroke group (P<0.05) . The results of multivariate Logistic regression analysis indicated that age, hyperten?sion, ICAC, and ICAT were independent risk factors for stroke. Conclusion For population with family history of stroke, age, hypertension, ICAC and ICAT were risk factors of stroke.

Objective To explore the characteristics of blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI) in healthy native kidneys. To investigate the relationship between BOLD-MRI and common physiological in-dexes. Methods GE 3.0T MRI scanner and Torsopa phased-array coil were employed to acquire renal coronal T1WI and BOLD image. Ninety patients who were ruled out chronic kidney diseases underwent BOLD-MRI with T2*-spoiled gradient recalled echo (T2*SPGR) sequence. BOLD images were analyzed on R2*map software. Cortical and medullary R2*values were analyzed in bilateral kidneys and in different gender. Different regional R2*values in cortex and medulla were also ana-lyzed. Physiological indices including age, body height and weight, body mass index (BMI), body surface area (BSA), estimat-ed glomerular filtration rate (eGFR) were recorded. Correlation between R2*value and physiological indices were analyzed. Results Bilateral renal cortical R2*values [left (16.56±1.40) Hz and right (16.66±1.28)Hz, respectively] were less than val-ues in medulla [left (28.82±3.71)Hz and right (28.36±3.72)Hz, respectively]. Female and male cortical R2*values [female (16.55±1.30Hz) and male (16.66±1.38)Hz, respectively] were also less than corresponding values in medulla [female (28.46± 3.64) Hz and male (28.70±3.78) Hz, respectively]. In bilateral renal medullary region, R2*values in low pole (27.29±3.05) Hz was less than values in middle (29.32±3.47) Hz and upper pole (29.16±4.21)Hz (F=15.184, P<0.001). Age was positive-ly correlated with R2* values in medulla (r =0.284, P =0.002). However, eGFR was negatively correlated with medullary R2*value (r=-0.232, P=0.007). Conclusion R2*values reflected the levels of renal partial pressure of oxygen and as-sessed the degree of renal ischemia. BOLD MRI could offer a simple, convenient and noninvasive method for to evaluate renal oxygen metabolism in cortex and medulla.

Objective To investigate the feasibility of discriminating different solutions and solutions with different concentrations using gemstone spectral imaging (GSI).Methods Glucose solutions (GSs)with different concentrations (5%,10%,15%,20% g/mL)and 0.9% normal saline(NS)were scanned at a CT scanner with GSI model.Spectral analysis software was used to generate spectral curves of different solutions,representing as CT values on monochromatic images(40~140keV).The same procedure was repeated 3 days later.Reliability analysis with intra-class correlation coefficient (ICC)was used to evaluate the agreement between the twice CT scans.Nonlinear regression analysis was used to generate the regression equation of spectral curves of each solution.One-way ANO-VA was performed to compare the slopes,asymptotes and intercepts of each solution.Results Reliability analysis showed excellent agreements between the twice CT scans for each solution (ICC>0.9).The regression equation was expressed as:f(keV-40)=α-(α-β)×e [-(keV-40)×ρ],where f(keV-40)represented CT values on each monochromatic images,αrepresented asymptotes,βrepre-sented intercepts,ρrepresented slopes of each solution.Statistical differences were found among the slopes of NS and those of GSs with different concentrations (P <0.05),while no statistical differences were found among the slopes of different GSs (P >0.05). The result was highly suggestive that different ingredient solutions demonstrated different shapes of spectral curves.The asymptotes and intercepts of GSs with different concentrations were statistically different (P <0.05).The heights of the spectral curves of GSs elevated with the increase of the concentration.Conclusion Spectral curve with GSI model can be used to discriminate between NS and GSs,or even GSs with different concentrations.It provided a promising potential for in vivo body fluid analyses.

Objective:To explore the feasibility of using Double FLASH coronary CTA (CCTA) to evaluate myocardial blood perfusion based on the original Patlak Plots.Methods:A total of 50 subjects with non-ischemic heart disease were prospectively included in the study who received dynamic myocardial CT perfusion (CTP) and Double FLASH CTA scans in General Hospital of Tianjin Medical University from January 2018 to January 2020 due to coronary heart disease or suspected coronary heart disease. The age of the enrolled patients was at least 18 years old and there was no moderate or above stenosis on CTA. The dynamic CTP images were analyzed by using CTP analysis software on FRONTIER platform to calculate the CTP derived MBF (MBF CTP). While the CTA derived MBF (MBF CTA) was calculated from the CT attenuation values of both aorta and myocardium segments on two scanning time set of Double FLASH CTA which were measured by two independent radiologists. Pearson correlation and Bland-Altman analysis were used to compare the results of MBF CTP and MBF CTA. Results:There was a strong linear correlation between MBF CTP and MBF CTA measurements. In the mid anteroseptal level: MBF CTA=0.936MBF CTP-11.999, r2=0.600, P<0.01. In the mid anterolateral level: MBF CTA=1.010MBF CTP-9.206, r2=0.448, P<0.01. In the apex: MBF CTA=0.822MBF CTP+16.904, r2=0.375, P<0.01. Bland-Altman analysis also showed there were no significant differences between MBF CTP and MBF CTA measurements. Compared with dynamic CTP scan, Double FLASH CTA mode significantly reduced the radiation dose [(4.33±1.89) mSv vs. (1.38±0.19) mSv, t=4.378, P=0.030]. Conclusions:This study validated the feasibility and accuracy of the MBF CTA measurement based on the theory of Patlak Plots only using Double FLASH CTA images. This method might have the potential to expand the clinical application of one-stop CTP examination for simultaneously evaluating coronary artery and myocardial ischemia in the clinic.