| PartiThe die body experiment research for dual-source stellar high-pitch pulmonary computer tomography angiography scanning techniqueObjectiveThrough different tube voltages on the same die bodies of scanning, conclude dual the regular between the radiation dose and image quality of dual-source stellar CT big pitch pulmonary scan mode under the different tube voltage to provide the basis for the pulmonary artery scanning.Materials and MethodsUsing the big pitch pulmonary mode of Siemens dual-source stellar CT scan the Catphan500 die bodies respectively in 120kv, 100kv,80kv,70kv and intelligent tube voltage regulation. Open automatic tube current control technology, of which reference tube current is 456mAs. Scanning length is 18cm. After the scan complete, record each does length product (DLP) and weighted CT dose index (CTDIvol), reconstruct data with filter back projection (FBP) and iterative algorithm (SAFIR), and analysis the impact on the quality of image from scanning condition and reconstruction algorithm (CT value, image noise, SNR, spatial resolution, contrast resolution), As while summarize the relationship between image quality and radiation dose.ResultsEach actual scanning time is 0.6s. With the decline of tube voltage level, the CT values of air plug-in, propylene plug-in and low density polyethylene plug-in have a decreasing trend and Teflon one has increasing trend, but all no statistical significance between groups (P>0.05). The FBP and SAFIR for each plug-in CT values have no statistical significance (P>0.05). With the decline of tube voltage, space resolution is no obvious change, but contrast resolution gradually decreases. More tube voltage has less noise. Reducing a tube voltage level will averagely increase noise value about 43.9%. SAFIR can significantly reduce the image noise in the same tube voltage and have statistically significant between groups (P<0.05). SFAIR algorithm image is better than FBP one and the low contrast resolution of 120kv SFAIR is the best in different tube voltage. The higher tube voltages have the greater effective radiation dose. The ED of 120kv, 100kv,80kv,70kv and intelligent tube voltage regulation are respectively 2.58,1.25,0.28, and 2.35.ConclusionTube voltage and radiation dose, contrast resolution or signal-to-noise is positively related and the noise value into negative correlation. SFAIR can significantly reduce noise and improve image quality. Through anglicizing comprehensive the image quality and radiation dose, the 100kv SFIR is the well scanning.Part2The small doses contrast medium experiment of a high-pitch stellar dual-source technique in pulmonary computed tomography angiographyObjectiveFrom the perspective of basic research, through comparing the low dose contrast medium schemes with the different amount and same concentration to affect on blood vessels time density curve (TDC), provide a basis for the use of contrast medium in the pulmonary artery scanning.Materials and Methods60 patients with check of pulmonary artery were randomly divided into three groups A, B, C, who all accepted by test blot in 100kv. A group use non-ionic contrast medium 350mg I/ml,30ml. B group use non-ionic contrast medium 350mg/ml,20ml. C group use non-ionic contrast medium 350mg I/ml,15ml. Three sets of injection flow rate is 4.5ml/s. After injecting contrast medium, inject 20ml saline at the same flow rate. Record peak value (PV), peak time, beginning time of more than 200Hu and duration time by TDC.ResultsAge, sex, weight and heart rate have no statistical significance (P>0.05). The PV and PT of A group are highest and have statistical significance with B/C group (P<0.05), but have no statistical significance between B and C group (P>0.05). Tb200 among three groups have no statistical significance (P>0.05). T200 among three groups have statistical significance (P<0.05).ConclusionThe greater contrast medium dosage, the.higher PV and the longer PT and T200, but Tb200 has no statistical significant. Combined with dual-source big pitch pulmonary stellar CT and TDC in pulmonary artery, as the result the three groups of contrast medium injection schemes are feasible theoretically.Part3A contrast optimization injection protocol study of a high-pitch stellar dual-source technique in pulmonary computed tomography angiographyObjectiveStudy the feasibility of "double low" pulmonary artery scanning under a high-pitch stellar dual-source CT.Materials and Methods90 consecutive patients with regular checks on the pulmonary artery were randomly divided into A, B, C groups, which all chosed 100kv high-pitch pulmonary mode scanning. Using non-ionic contrast medium (350mg I/ml), dose of group A was 30ml, group B was 20ml, and group C was 15ml. Injection flow rate was 4.5ml/s, 40ml saline was injected in the same injection velocity. Then, recorded each age, heart rate, body, body mass index (BMI), length (LEN), dose length product (DLP) and so on, measured the CT value of pulmonary artery trunk, left pulmonary artery and right pulmonary artery, calculated the contrast to noise ratio (CNR), and evaluated all images by two radiologists.ResultsAge, gender, heart rate, scaning length and radiation dose had no statisitical significant among the three groups (P>0.05), and pulmonary artery trunk and branches showed clearly. CT values had no statisitical significant among pulmonary artery trunk, left pulmonary artery and right pulmonary artery. The CT values of group A were higher than those of group B, C, and had statisitical significant (P<0.05). Most cases met the requirements of diagnosis, and had no statisitical significant (P>0.05). The CNR and pulmonary score of group A respectively was 30.63±10.84, 4.05±0.61, group B respectively was 18.34±7.75,3.80±0.95 and group C was 18.18±8.77,3.47±1.02, and CNR had statistical significance between A and B,C (p<0.05),but score had no statistical significance among three groups (p>0.05). Superior vena cava pseudo score of group C was better than those of group A and B, and had statistical significant (P<0.05). Kappa value was 0.832, hading good consistency between two reiewers.ConclusionThree groups of "double low" scanning solutios for most of patients were feasible, it was recommended to use 20ml. |
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