The Application Values Of Using Dual-energy Scan In Diagnosis Of Pancreatic Neoplasm With Dual-Source CT

Part IThe clinical values of using virtual non-contrasted technique in diagnosis of pancreatic neoplasm with dual-energy scanning modeObjectiveTo evaluate the feasibility of using virtual non-contrasted images in diagnosis of pancreatic neoplasm with dual-energy scanning mode.Materials and MethodsThe preoperative true non-contrast (TNC) and dual-energy scanning mode in their pancreatic parenchyma phase images of30patients with pathologically and clinically proved pancreatic neoplasm by pathology were retrospectively analyzed. Image of Sn140kVp and80kVp were acquired by dual-energy scanning mode in their pancreatic parenchyma phase. Two groups of images were disposed by "Liver VNC" software, and virtual non-contrasted (VNC) images were received. The difference in the mean CT values, Signal-to-noise ratio (SNR) of normal pancreatic parenchyma tissue, pancreatic parenchyma neoplasm tissue, abdominal aortic and the muscles of posterior spine between two groups of images was compared. The difference in contrast-to-noise ratio (CNR), image quality, the display of lesion and radiation dose between two groups of images was compared.ResultsThere was no statistical in the mean CT values of normal pancreatic parenchyma tissue, pancreatic parenchyma neoplasm tissue, abdominal aortic and the muscles of posterior spine between two groups of images (P>0.05).And the mean CT value in VNC images was higher than TNC images, which the difference was statistically significant between two groups of images (P<0.05).The SNR of normal pancreatic parenchyma tissue, pancreatic parenchyma neoplasm tissue, abdominal aortic and the muscles of posterior spine in VNC images was higher than TNC images, which the difference was statistically significant between two groups of images (P<0.05). The CNR in VNC images was higher than TNC images, which the difference was statistically significant between two groups of images (P<0.05). There was no statistical in image quality between two groups of images (P>0.05), and all images received a score of more than3. Two groups of images had a similar detection performance in lesion, such as necrosis and calcification of pancreatic neoplasm, but the area of calcification in VNC images was reduced than TNC images. The radiation dose of dual-energy scanning mode reduced of about24%than conventional scanning mode.ConclusionThe image quality of VNC images was lower than TNC images, but it could meet the demand of clinical diagnosis. And VNC image is expected to replace TNC image, so as to reduce the radiation dose of patient. Part ⅡThe application of using iterative reconstruction technique in diagnosis of pancreatic neoplasm with dual-energy scanning ModeObjectiveComparing with regular filtered back projection (FBP), to investigate the application value of using sinogram affirmed iterative reconstruction (SAFIRE) and dual-energy scanning mode in diagnosis of pancreatic neoplasm.Materials and MethodsThe research object was the same as the part one. Images of Sn140kVp,80kVp and the linear fusion were acquired. Group A (Sn140kVp, FBP), group B (100kVp, FBP) and group C (linear fusion image, FBP) were obtained by using regular FBP technique.100kVp and linear fusion images were reconstructed by using SAFIRE technique to get group D (100kVp, SAFIRE) and group E (linear fusion image, SAFIRE) respectively. The mean CT values and images noises of normal pancreatic parenchyma tissue, pancreatic parenchyma neoplasm tissue and portal vein were measured in five groups. The CNR in normal tissue of pancreatic parenchyma, the difference of CT value between the normal and lesion pancreatic parenchyma, and the ratio of CT value and contrast to noise for normal to lesion pancreatic parenchyma were calculated and compared. And the image quality of5groups was subjective evaluation.ResultsThere were significant differences among five groups in the mean CT values and images noise of normal, lesion tissue and portal vein (P<0.05). The maximum mean CT values of normal, lesion tissue and portal vein was group D, while the minimum images noise of them was group E. There were significant differences in CNR of normal tissue among five groups (P<0.05), while the maximum CNR was group D (5.27±0.89). There were significant differences among five groups in the difference of CT value, ratio of CT value and contrast to noise for normal to lesion tissue (P<0.05). Group B showed the largest difference in CT value [(49.94±15.45) HU], while group D showed the lowest ratio of CT value (0.47±0.11) and largest contrast to noise (4.78±1.33) for normal to lesion tissue. Among the image quality of 5groups was subjective evaluation, In addition to there was no statistical in image quality between group C and D (P>0.05), and the rest were significant differences between any two groups (P<0.05). All images received a score of more than3, while the maximum scores was group E (4.12±0.50), the minimum scores was group A (3.44±0.51).ConclusionThe lower tube voltage (100kVp) of dual-energy scanning mode combined with SAFIRE technique can significantly reduce image noise, increase the contrast to noise ratio of the images of patients with pancreatic neoplasm and further improve the resolution of pancreatic neoplasm. It can improve image quality while have the potential advantage to reduce radiation dose. Part ⅢThe diagnostic value of using dual-energy scanning mode for pancreatic neoplasm with dual-source CTObjectiveTo analyze the diagnostic value of multiple sequences derived from dual-energy scanning mode with dual-source computed tomography in detecting pancreatic neoplasm. Study with the spectrum characteristics of the normal pancreatic parenchyma tissue, the parenchyma tissue of pancreatic cancer, the cystic tissue of cystadenoma of pancreas and the parenchyma tissue of islet cell tumor. And analyze the diagnostic value of using spectrum curve for pancreatic neoplasm.Materials and MethodsThe research object was the same as the part one. Images of Sn140kVp,80kVp and the linear fusion were acquired by dual-energy scanning mode in their pancreatic parenchyma phase. Iodine image, non-linear fusion image and mono-energetic74keV image were acquired by dual-energy scanning mode in their pancreatic parenchyma phase. The mean CT values of normal pancreatic parenchyma tissue and pancreatic parenchyma neoplasm tissue were measured in linear fusion image, TNC image and iodine image. The difference of CT values between the added CT value (linear fusion image-TNC image) and iodine image were compared. The mean CT values of normal pancreatic parenchyma tissue, pancreatic parenchyma neoplasm tissue were measured and calculated in linear fusion image, non-linear fusion image, iodine image and mono-energetic74keV image. And the standard deviation of midline abdominal subcutaneous fat were measured and calculated in four images. The difference of CT value between the normal and lesion pancreatic parenchyma, and the ratio of CT value and contrast to noise for normal to lesion pancreatic parenchyma were calculated and compared. To analyze the diagnostic value of above four derived sequences images for pancreatic neoplasm. The spectrum curve of the normal pancreatic parenchyma tissue, the parenchyma tissue of pancreatic cancer, the cystic tissue of cystadenoma of pancreas and the parenchyma tissue of islet cell tumor in different proportions were measured and analyzed from40to190keV by using dual energy mono-energetic software. And the CT values of different mono-energetic (40-140keV, units of ten) were received. The mean CT values of four tissues were acquired and spectrum curve were drawn. The rake ratio of spectrum curve were calculated and to evaluate the trend of attenuation.ResultsThere was no statistical in CT value between the added CT value (linear fusion image-TNC image) and iodine image of normal pancreatic parenchyma tissue and pancreatic parenchyma neoplasm tissue were compared (P>0.05). Iodine image was more to directly measure the tissue of added CT value. There were significant differences among four derived sequences images in difference of CT value, ratio of CT value and contrast to noise for normal to lesion tissue (.P<0.05). Non-linear fusion image showed the largest difference in CT value, while iodine image showed the lowest ratio of CT value and largest contrast to noise for normal to lesion tissue. Among the image quality of four images was subjective evaluation, In addition to there were significant differences in image quality between iodine image and others (P<0.05), and the rest were no statistical differences between any two groups (P>0.05).While the minimum score was iodine image. The spectrum curve of the normal pancreatic parenchyma tissue and different pancreatic neoplasm tissue had the same rules. With the increase of mono-energetic keV value, the CT value of lesion reduced. The CT value reduced speedy during40-80keV, and the spectrum curve of four tissues had great difference, the running trend was not parallel. The CT value reduced slowly during100-190keV, and the spectrum curve of four tissues had not obviously difference, the running trend was plateau. The attenuation degree of the normal pancreatic parenchyma tissue and different pancreatic neoplasm tissue were different during40-100keV. The rake ratios of spectrum curve were different. The largest decline of rake ratios of spectrum curve was the parenchyma tissue; the rest followed was the normal pancreatic parenchyma tissue, pancreatic cancer, and the cystadenoma of pancreas. There were significant differences among four tissues in the rake ratio between any two tissues.(P<0.05)ConclusionMultiple sequences can be derived from dual-energy scanning mode with DSCT via multiple post-processing methods. Integration of these sequences may further improve the sensitivity of DSCT in the diagnosis of pancreatic neoplasm. And using the dual-energy spectrum curve is helpful to identify of different pathological types of pancreatic neoplasm.