| Computer tomography pulmonary angiography(CTPA) has been accepted as the first-line imaging modality to exclude pulmonary embolism(PE). compared with Digital subtraction angiography(DSA) CTPA was noninvasive and achieved high sensitivity and specificity. The wide availability and high diagnostic performance have led to increasingly frequent use of CTPA to exclude PE, with a subsequent increase in radiation exposure to patients. Radiation dose related to CT angiography exams have raised concerns. Additionally, Contrast medium nephropathy is increased with higher doses of iodinated contrast medium. Spectrum computed tomography(CT)is widely applied in clinical in recent years, which can get 40-140 kev monochromatic energy images. By adjusting the kev to optimize image quality, reduce the image noise and improve the anatomical and pathological changes the details of the display.Adaptive statistical iterative reconstruction(ASIR)technology can reduce radiation dose without damage the quality of imaging.The purpose is to lower radiation dose and contrast volume in CTPA with the technology of monochromatic image and ASIR of spectral CT.Part one Preliminary study of 80 kvp CT pulmonary angiography with ASIR using 20 ml of contrast agentObject: To evaluate the feasibility of 80 kvp and 20 ml of contrast agent in CT pulmonary angiography(CTPA) with spectral CT using ASIR reconstruction.Methods: A total of 60 patients with suspected pulmonary embolism(PE) underwent CTPA. They were randomly divided into 2 groups. Group A received 60ml(370mg/ml)lopamidol at 120 k Vp and FBP reconstruction. Group B were scanned with 80 kvp after injecting 20ml(370mg/ml) lopamidol and 50% ASIR reconstruction.Independent t-test was used to compare the CT values, image noise, signal-to-noise ratio(SNR), contrast-to-noise ratio(CNR), volume CT dose index(CTDIvol), dose length product(DLP) and effective dose(ED). Mann-Whitney U test was used to compare the image quality score of the two groups..Results: The CT values of pulmonary arteries, SNR, CNR in group B were higher than those of group A(all P<0.05). The CT CTDIvol, DLP, ED in group B were lower than those of group A(all P<0.05). There was no significant difference in image noise,subjective image quality between two groups(P>0.05).Conclusion: 80 kvp and 20 ml of contrast agent in CTPA with spectral CT using ASIR reconstruction can provide high quality image, which can meet clinical diagnostic need, the radiation dose and contrast medium volume could be decreased.Part two Preliminary study of spectrum gemstone CT with low-dose, low concentrations contrast media in CT pulmonary angiographyObject: To evaluate the feasibility of spectral CT monochromatic images with 20 ml of low concentration contrast media in CT pulmonary angiography(CTPA).Methods: A total of 60 patients with suspected pulmonary embolism(PE) underwent CTPA. They were randomly divided into 2 groups. Group A received 60ml(370mg/ml)lopamidol at 120 k Vp. Group B were scanned with GSI mode after injecting 20ml(300mg/ml) lopamidol. The optimal ke V monochromatic energy images were selected by GSI software. Independent t-test was used to compare the CT values, image noise,signal-to-noise ratio(SNR), contrast-to-noise ratio(CNR), volume CT dose index(CTDIvol), dose length product(DLP) and effective dose(ED). Mann-Whitney U test was used to compare the image quality score of the two groups.Results: The monochromatic images at 63~68ke V were demonstrated to have the highest CNR for the CTPA. The total amount of iodine in group B was lower than that of group A(7.5vs24.0g),there was statistically significant difference between two groups(P<0.05). No statistical difference between two groups was found for the CT values of pulmonary arteries, SNR, CNR, image noise, DLP, ED and subjective image quality.Conclusion: Spectral CT monochromatic imaging with low concentration and low load contrast media can provide the same good image quality as the conventional120 k Vp CTPA, the radiation dose couldn’t increased. |
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