Application Of Low-dose Whole Pancreas CT Perfusion Combined With Dual-energy CT Scanning In The Diagnosis Of Pancreatic Adenocarcinoma

Part Ⅰ Clinical application of low-dose whole pancreas CT perfusion in diagnosis of pancreatic adenocarcinomaPurpose:To evaluate the perfusion characteristics of pancreatic panrenchyma and pancreatic adenocarcinoma by using low-dose whole pancreas CT perfusion, and to investigate the role of perfusion characteristics in diagnosis of pancreatic adenocarcinoma.Materials and Methords:Ninety-seven patients with suspected pancreatic disease underwent low-dose whole pancreas CT perfusion and 37 cases with pancreatic disease other than pancreatic adenocarcinoma or with pancreatic adenocarcinoma but with no nontumoerous pancreatic parenchyma left were excluded. Thirty cases with pancreatic adenocarcinoma and 30 cases without pancreatic disease were enrolled in this study. Thirty cases with pancreatic adenocarcinoma, including 18 male,12 female, with a mean age of 60.00 ± 10.50 (range,41-81) years old, were proven by clinical diagnosis and pathological results. Thirty cases without pancreas disease, including 14 male,16 female, with a mean age of 53.17 ± 11.18 (range,32-77) years old, were proven by clinical diagnosis and follow-up results. A radiologist with more than 5 years of experience in abdominal CT diagnosis gave the CT diagnosis blinded to clinical diagnosis. Software named "VPCT-Body" was used for perfusion data analysis. The time attenuation curves (TACs) of both normal pancreatic parenchyma and pancreatic adenocarcinoma were drawn and the peak values of TACs were analyzed. Time to peak (TTP) of normal pancreatic parenchyma were recorded. Perfusion parameters, such as blood flow (BF), blood volume (BV) and permeability (PMB), were measured for three times, and the mean values were obtained for statistical analysis. Volume computed tomographic dose index (CTDIvol) and dose length product (DLP) of the whole pancreas CT perfusion were recorded and the effective radiation dose (ED) was calculated. Independent t-test from SPSS 19.0 was used to compare the age, weight, peak value of TAC and perfusion parameters between normal pancreatic parenchyma and pancreatic adenocarcinoma. Statistical significance was established at a P value of<0.05.Results:There was no statistical difference about age and weight between the two groups.1. TAC analysis:The TTP from TAC of normal pancreatic parenchyma was distributed from 23 s to 38 s (30.15 ± 4.24s averagely). The mean peak value of TACs of pancreatic adenocarcinoma was 47.23 ± 9.33 HU, and that of normal pancreatic parenchyma was 104.33 ± 5.28 HU. The peak value of TACs of pancreatic adenocarcinoma was lower than that of normal pancreatic parenchyma (P<0.05). The TACs (30/30 cases,100%) of normal pancreatic parenchyma were rapid rise followed by rapid decline to plateau. The majority (22/30 cases,73.3%) TACs of pancreatic adenocarcinoma were rapid rise followed by plateau, or slow and gradually ascend. Other (8/30 cases,26.7%) TACs of adenocarcinoma were rapid rise followed by slight decline to plateau. TACs were different between normal pancreatic parenchyma and pancreatic adenocarcinoma.2. The perfusion parameters, such as BF, BV and PMB, of normal pancreatic parenchyma were 90.46 ± 14.29 mL/100mL/min,20.38 ± 7.73 mL/100mL and 29.49 ± 10.85 mL/100mL/min; and those of pancreatic adenocarcinoma were 34.88 ± 12.34 mL/100mL/min,4.65 ± 2.73 mL/100mL and 29.59 ± 9.29 mL/100mL/min. Both BF and BV had statistical difference between the normal pancreatic parenchyma and pancreatic adenocarcinoma (P<0.05), whereas PMB had no statistical difference (P >0.05).3. Radiation dose:The CTDIvol of whole pancreas CT perfusion was 36.76 mGy, and the DLP was 325 mGy*cm, resulting in an ED of 4.88 mSv.Conclusion:The low-dose whole pancreas CT perfusion can provide functional information and quantitative analysis of hemodynamic changes with a relatively low radiation dose, and confirm the TTP of pancreatic parenchyma, which could be used to guide the individualized pancreatic CT scan. It has great value in the clinical practice on pancreatic adenocarcinoma diagnosis.Part Ⅱ Individualized dual-energy CT scan and single-energy CT scan of pancreas in pancreatic adenocarcinoma diagnosis: comparison of image quality and radiation dosePurpose:To compare the image quality and radiation dose of individualized dual-energy enhanced CT scan and single-energy enhanced CT scan of pancreas in patients with pancreatic adenocarcinoma.Materials and Methods:We evaluated enhanced CT images of 60 patients with pancreatic adenocarcinoma that were obtained by using two different scan protocols. Group one:sixty-three patients with suspected pancreatic cancer underwent individualized dual-energy CT (DECT) scan and 33 cases without pancreatic adenocarcinoma or with pancreatic adenocarcinoma but with no nontumoerous pancreatic parenchyma left were excluded. Thirty cases with pancreatic adenocarcinoma, which were proven by clinical diagnosis and pathological results, were enrolled. There are 16 male and 14 female, with a mean age of 58.08 ±10.23 (range,41-74) years old. Scan time of individualized pancreatic phase was set based on TAC, which was draw after low-dose whole pancreas CT perfusion. Monoenergetic images were reconstructed and the spectral curve of contrast noise ratio (CNR) of pancreas-to-tumor was draw. The optimal monoenergetic images with the highest CNR of pancreas-to-tumor were selected. Group two:Retrospectively evaluated the 30 cases of pancreatic adenocarcinoma underwent individualized single-energy CT (SECT) scan in Part I. CNRs of pancreas-to-tumor in individualized pancreatic phase were calculated. Dose length product (DLP) of enhanced CT scan was recorded and the effective radiation dose (ED) was calculated. Independent t-test from SPSS 19.0 was used to compare the age, weight, CNR and ED between the two groups. Statistical significance was established at a P value of<0.05.Results:There was no statistical difference about age and weight between the two groups.1. CNR:For Group one, there are only one peak for each spectral curve of CNR in all 30 cases, and the optimal monoenergetic sets were ranged from 60 keV to 75 keV in pancreatic phase. The mean CNR of pancreas-to-tumor of individualized pancreatic phase was 3.935 ± 0.726 in the optimal monoenergrtic images. For Group two, the mean CNR of pancreas-to-tumor of individualized pancreatic phase was 2.933 ± 0.864. The mean CNR of pancreas-to-tumor in Group one was higher than that in Group two (P<0.05).2. Radiation dose:The mean DLP of DECT scan in Group one was 375.11 ± 67.70 mGy*cm (range,271-460 mGy*cm), resulting in a mean ED of 5.63 ± 1.02 mSv (range,4.07-6.90 mSv); The mean DLP of SECT scan in Group two was 309.95 ± 57.33 mGy*cm (range,189-396 mGy*cm), resulting in a mean ED of 4.64 ± 0.86 mSv (range,2.84-5.94 mSv). Radiation dose of Group one is higher than that of Group two (P<0.05).Conclusion:DECT scan provided a higher CNR of pancreas-to-tumor, which makes it the effective method for detecting pancreatic adenocarcinoma. Although radiation dose of DECT was slightly higher than that of SECT, the DECT scan has great value in the application on pancreatic adenocarcinomas detection and diagnosis.