Objective:To investigate the effect of 253 lymph node dissection on postoperative recovery and prognosis of rectal cancer patients in different stages undergoing radical resection.Methods:A total of 232 rectal cancer patients undergoing radical resection in the Fourth Hospital of Hebei Medical University between January 2013 and December 2014 were enrolled and divided into the 253 lymph node dissection group(all cases underwent surgery in 2014)and the non-dissection group(all cases underwent surgery in 2013). Differences in age, sex, tumor differentiation and depth of invasion was analyzed between the two groups.Based on clinicopathological data, each group was further divided into three subgroups(Ⅰ, Ⅱ, Ⅲ). Postoperative recovery assessment included the time of the earliest flatulence, the time of first feeding, the duration of hospitalization and anastomotic leakage.In addition, postoperative survival parameters were also analyzed.Results:Compared with non-dissection group, patients in the 253 lymph node dissection group had similar overall postoperative recovery and rates of complications( P>0.05), but significantly longer survival( P=0.012). Besides, 253 lymph node dissection had a beneficial effect on prognosis for those in the stage Ⅲ subgroup( P=0.039), and did not affect the prognosis for those in the stage Ⅰ and Ⅱ subgroups( P>0.05). Conclusions:For rectal cancer patients undergoing radical resection, 253 lymph node dissection does not affect postoperative recovery, but offers improved prognosis for stage Ⅲ patients.We should perform 253 lymph node dissections on all rectal cancer patients when the clinicopathological staging is unknown.

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.

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.