Résumé
Objective:To investigate the features of median arcuate ligament syndrome (MALS) in computed tomography angiography (CTA).Methods:The retrospective and descriptive study was conducted. The clinical and imaging data of 56 patients with MALS who were admitted to Ruijin Hospital, Shanghai JiaoTong University School of Medicine from November 2019 to October 2020 were collected. There were 30 males and 26 females, aged from 19 to 78 years, with a median age of 54 years. All 56 patients underwent CTA. Observation indicators: (1) CTA examination; (2) correlation analysis; (3) surgical situations. Measurement data with normal distribution were represented as Mean± SD. Count data were described as absolute numbers or percentages. Spearman correlation analysis with test level of 0.05 was used to analyze the correlation between celiac trunk stenosis and the distance between the original location of celiac trunk and original location of superior mesenteric artery and the minimum distance of celiac trunk and superior mesenteric artery. Results:(1) CTA examination. ① Celiac trunk stenosis: results of cross sectional examina-tion of CTA showed that of 56 patients, there were 2 cases of celiac trunk occlusion, 10 cases of severe stenosis, 9 cases of moderate stenosis and 35 cases of mild stenosis. Results of sagittal examination of CTA showed that of 56 patients, there were 2 cases of celiac trunk occlusion, 21 cases of severe stenosis, 15 cases of moderate stenosis and 18 cases of mild stenosis. ② Examination of patients with different degree of vascular stenosis: according to the results of sagittal examination of CTA, the 2 cases with celiac trunk occlusion were negative for aneurysms, aortic dissection or vascular variations but positive for compensated varix of the anterior and posterior pancreatico-duodenal arches. Of the 21 cases with celiac trunk severe stenosis, 2 cases were positive for aneurysms, 1 case was positive for aortic dissection, 7 cases were positive for compensated varix of the anterior and posterior pancreaticoduodenal arches, 8 cases were positive for collateral circula-tions of anterior and posterior pancreaticoduodenal archs and 8 cases were positive for vascular variation. Of the 15 cases with celiac trunk moderate stenosis, 2 cases were positive for aneurysms, 3 cases were positive for aortic dissection, 2 cases were positive for compensated varix of the anterior and posterior pancreaticoduodenal arches, 4 cases were positive for collateral circulations of anterior and posterior pancreaticoduodenal archs and 7 cases were positive for vascular variation. Of the 18 cases with celiac trunk mild stenosis, 1 case was positive for aneurysms, 2 cases were positive for aortic dissection, 7 cases were positive for collateral circulations of the anterior and posterior pancreaticoduodenal arches, 6 cases were positive for vascular variation. All 56 patients were negative for ischemia of liver, spleen and stomach. ③ Original location of celiac trunk: of 56 patients, there were 43 cases had celiac trunk originated horizontally from the lower edge of T12 vertebral body, 2 cases had celiac trunk originated from the middle of T12 vertebral body, 1 case had celiac trunk originated from the upper part of T12 vertebral body, 7 cases had celiac trunk originated from the upper part of L1 vertebral body, 1 case had celiac trunk originated from the middle of L1 vertebral body and 2 cases had occluding celiac trunk. (2) Correlation analysis: results of sagittal observation on CTA examination showed the distance between the original location of celiac trunk and original location of superior mesenteric artery of the 56 patients was (6.0±4.0) mm. The distance between the original location of celiac trunk and original location of superior mesenteric artery of patients with celiac trunk mild, moderate or severe stenosis were (6.2±2.8)mm, (8.1±4.4)mm and (5.3±3.2)mm respectively. There were 23 cases of the 56 patients had the distance between the original location of celiac trunk and original location of superior mesenteric artery <5 mm. Results of correlation analysis showed that the degree of celiac trunk stenosis was not related to the distance between the original location of celiac trunk and original location of superior mesenteric artery ( r=?0.205, P>0.05). Results of sagittal observation on CTA examination showed the shortest distance between celiac trunk and superior mesenteric artery of the 56 patients was (3.8±2.4)mm. The shortest distance between celiac trunk and superior mesenteric artery of patients with celiac trunk mild, moderate or severe stenosis were (4.2±2.0)mm, (4.4±3.3)mm and (3.0±1.9)mm, respectively. There were 45 cases of the 56 patients had the shortest distance between celiac trunk and superior mesenteric artery <5 mm. Results of correlation analysis showed that the degree of celiac trunk stenosis was not related to the shortest distance between celiac trunk and superior mesenteric artery ( r=?0.249, P>0.05). (3) Surgical situations: of 56 patients, 2 cases were positive for clinical symptoms of abdominal pain, 54 cases were negative for clinical symptoms, 4 cases under-went surgical treatment and 52 cases not underwent surgical treatment. Of the 4 cases undergoing surgical treatment, 2 cases with abdominal pain were diagnosed as MALS by upper abdominal CTA. Celiac trunk of the 2 cases were severe stenosis and stents implantation under celiac arteriography were performed. Results of postoperative CTA showed celiac trunk was negative for obvious stenosis. The other 2 cases who were negative for clinical symptoms of MALS were planed to pancreaticoduo-denectomy for pancreatic head tumor. Results of preoperative CTA showed severe stenosis of celiac trunk and arterial bypass grafting was performed for the 2 cases during pancreaticoduodenectomy to alleviate liver ischemia caused by gastroduodenal artery ligation which would avoid the incidence of postoperative MALS associated complications. Result of postoperative CTA three-dimensional reconstruction showed the bypass vessel was unobstructed. Conclusion:Based on sagittal result of CTA examination, the stenosis of celiac trunk, the anatomical relationship between celiac trunk and arcuate ligament and the original location of celiac trunk of MALS patients can be evaluated.
Résumé
Objective:To explore the image quality of 40 keV virtual monoenergetic images (VMI) derived from dual-layer spectral detector CT （DLCT） pancreas dynamic enhanced scanning and its optimal window setting.Methods:From January to July 2019, 28 patients who underwent pancreas enhanced DLCT scan within one week before surgery and pathologically confirmed of pancreatic neuroendocrine tumors (pNETs) were retrospectively enrolled. Conventional polyenergetic images (PI) and 40 keV virtual monoenergetic images （VMI 40 keV） were generated after scanning.CT value of normal pancreatic parenchyma, lesion, abdominal subcutaneous fat, abdominal aorta and portal vein were measured in PI and VMI 40 keV. The contrast-to-noise ratio (CNR) of the pNETs lesion was calculated. All these objective results were compared between VMI 40 keV and PI using paired ttest. Individual window settings （W-Ind, including window width and window level） of VMI 40 keVwere recorded. Calculated window settings （W-Calc） were mathematically calculated via regression analysis and optimized window settings （W-Opt） were obtained.Subjective image quality was assessed with a 5-point scale and compared among VMI 40 keV with different window settings (W-Std, W-Ind, W-Calc and W-Opt) using Friedman test, and compared PI with standard abdominal window setting (W-Std) and VMI 40keV with W-Opt settings using Wilcoxon test.The maximum diameter of lesion was measured and compared with one-way ANOVA analysis among PI and VMI 40 keV with different windows settings. Results:For VMI 40 keV in both arterial phase and portal vein phase, the CT attenuation [(464.0±136.7), (375.4±79.2) HU] of pNETs lesion were statistically significantly higher than those in PI [（168.8±38.0), (140.5±23.5) HU] （ t=-16.107,-22.225, P<0.001）, CNR （16.5±11.1, 10.9±6.1） were also statistically significantly higher than those in PI （4.5±2.9, 3.0±1.9） （ t=-7.838, -9.781， P<0.001）,while with lower image noise in VMI 40 keV[（11.8±1.5),(11.8±1.4) HU] than PI （13.1±1.5,12.9±1.3 HU）（ t=6.356,3.891， P<0.001）. The subjective score for PI with W-Std and VMI 40 keV with W-Std, W-Ind, W-Calc, W-Opt in arterial phase were 4（1）, 1（0）, 5（0）, 5（0.75）, 5（1）, and which in portal vein phase were 3.5（1）, 1（0）, 5（0）, 5（0）, 5（1）.The subjective score of VMI 40 keV with different window settings had statistical differences （χ 2=76.143,76.000， P<0.001）. Compared to the image quality of PI with W-Std settings, VMI 40 keV with W-Opt settings have higher objective score （ Z=4.685, 4.235， P<0.001）. The maximum diameter of lesion has no statistical difference among PI and VMI 40 keV with different window settings （ F=0.008, 0.004， P>0.999） in both arterial phase and portal vein phase. Conclusions:The VMI 40 keV in pancreas dynamic enhancement scanning derived from dual-layer spectral detector CT have higher image quality than PI. Due to changes of CT value of tissue in VMI 40 keV, it is recommended to optimize window settings （window width/window level， 880/230 HU for arterial phase and 840/260 HU for portal vein phase） to obtain the best image quality.
Résumé
Objective:To investigate the clinical value of iodine density map and low keV virtual monoenergetic images (VMI) derived from dual-layer spectral detector CT (DLCT) for the pancreatic neuroendocrine tumors (pNETs) detection.Methods:From January to June 2019, data of 23 pathologically confirmed patients of pNETs were retrospectively analyzed. All of the patients underwent pancreas enhanced DLCT scanning within 1 week before surgery. The conventional polyenergetic images (PI), iodine density map and 40, 50, 60, 70 keV VMI were generated. One resident radiologist with 3 years’ experience and one senior radiologist with over 10 years’ experience interpreted the images for the lesion detection independently using the following image series: PI, VMI (40-70 keV), PI combined with iodine density map. Lesion detection rates were recorded and compared among different image series. The CT value and noise of lesion, normal pancreatic parenchyma, and abdominal subcutaneous fat were measured in PI and VMI in both arterial and portal vein phases. The contrast-to-noise ratio (CNR) of lesion was calculated. The CT value of lesion and normal pancreatic parenchyma, CNR of lesion, and image noise were compared using repeated one-way ANOVA test. Subjective image quality was assessed with a 5-point scale and compared with Friedman test.Results:A total of 26 lesions were confirmed from 23 patients. For resident radiologist and senior radiologist, the detection rates of pNETs lesion using PI were 76.9% (20/26) and 84.6% (22/26) respectively, and both improved to 92.3% (24/26) using image series of 40 and 50 keV VMI. For senior radiologist, the pNETs lesion detection rate was further improved to 96.2% (25/26) using image series of PI with iodine map. The CT value of lesion and normal pancreatic parenchyma, CNR, and image noise had statistical differences among PI and VMI (40-70 keV) in both arterial and portal vein phase ( P<0.001). The mean CT attenuation and CNR of lesion in VMI increased significantly as the energy level decreased.The CNR of lesion in all VMI (40-70 keV) was significantly higher than that in PI. The median of subjective scores of image quality in PI and VMI (40-70 keV) were 3, 3, 4, 4, and 5 respectively, and the difference was statistically significant (χ2=66.393, P<0.001). Conclusions:The low keV VMI derived from DLCT can increase the CT value and CNR of pNETs, and the lesion detection rate can be improved combined with iodine density map. The CNR of pNETs is the highest in 40 keV VMI, and image noise is still lower than that of PI, so 40 keV VMI is recommended for clinical application.
Résumé
Objective To explore the feasibility of the virtual non-contrast images derived from dual-layer spectral detector CT (SDCT) substitute for true non-contrast images.Methods From July 2017 to September 2017,40 patients under-went pre-and arterial-venous dual-phase post-contrast abdominal imagining on a SDCT in Shanghai Jiaotong University School of Medicine Affiliated Ruijin Hospital.The images were retrospectively analyzed.The arterial VNC images (VNC-a) and venous VNC images (VNC-v)were derived from spectral based image (SBI) datasets of arterial and portal venous phase using a dedicated software respectively.Then mean CT attenuation,mean image noise,signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were compared with one-way ANOVA analysis among TNC,VNC-a,VNC-v images in liver,spleen,pancreas,abdominal aorta,inferior vena cava,psoas muscle,L4 vertebra and perirenal fat.And Bland-Altman plots was used to analyze the CT attenuation equivalence between TNC and VNC.Subjective image quality was assessed with a 5-point scale and compared with Friedman H test.The dose length product (DLP) of pre-and post-contrast scans were recorded.Results The CT attenuation of abdominal aorta,perirenal fat,L4.vertebra among three kinds of images had significant differences (P＜0.05)which overestimated the CT attenuation of perirenal fat and underestimated CT attenuation of abdominal aorta and vertebra compared to TNC,VNC.Except for pancreas,the image noise of all other tissues among three kinds of images had significant differences,images noise of VNC images were lower than TNC images (P＜0.05).The SNR of liver,spleen,psoas muscle and inferior vena cava and CNR of pancreas,abdominal aorta,inferior vena cava,L4 vertebra and perirenal fat were statistically significant among the three images (P＜0.05).Except for vertebra and perirenal fat,good equivalence between VNC and TNC images were observed in all relevant tissues with Bland-Altman analysis.Image quality subjective scoring of TNC,VNC-a,and VNC-v were 5.00(1.00),5.00(0.75),5.00(1.00) respectively which had no significant differences (P=0.20).The DLP of TNC,arterial and venous phase scan were (255.2±62.0),(258.9±62.9),(252.0±61.2)mGy·cm,and the total DLP of dual-phase contrast enhanced scan was (766.2± 185.3) mGy· cm.The DLP of TNC accounted for 33.3％(255.2/766.2) of the total DLP,and effective dose of TNC was (3.83±0.90)mSv.Conclusions CT attenuation in VNC image which exhibited lower image noise was identical to TNC images in the majority of abdomen tissues except for vertebra and perirenal fat.and the VNC image.The VNC image which reduces radiation dosage derives from SDCT enhanced image might be used as a substitute for the TNC image.