A Study Of Low-dose Volume Perfusion CT In The Pancreas

Objectives To evaluate image quality and the reliability of CT perfusion parameters measured by low-dose pancreatic perfusion.Materials and methods This study was approved by the local Institutional Review Board and all patients provided written informed consent.One hundred patients were enrolled with suspected pancreatic lesions and had low-dose volume perfusion computed tomography(VPCT)examinations.5 protocols with different combination of Ttube voltage and tube current were used:group A,tube voltage 80Kv and tube current 120mAs(weight ? 80Kg),group B,tube voltage 80Kv and tube current 100mAs(weight ? 70Kg),group C,tube voltage 70Kv and tube current 189mAs(weight,60Kg),group D,tube voltage 70Kv and tube current 130mAs(weight?50Kg),group E,tube voltage 80Kv and tube current 55mAs(weight<50Kg).One experienced radiologists recorded dose parameters CDTI and DLP automatically generated by scan protocol.Mean blood flow(BF),blood volume(BV)and permeability(PMB)were determined with deconvolutional method.The non-contrast scan,arterial phase,portal venous phase perfusion images were selected for assessment of image quality,including subjective and objective image quality(image background noise,signal to noise ratio,contrast noise ratio).Differences between groups were compared using one-way ANOVA analysis.Results The radiation dose was significantly lower in low-dose groups than our conventional group(80Kv,150mAs).The image quality of low-dose groups(A-D)is equivalent(P>0.05).The image quality of E group was higher than other low dose groups(P<0.05).The perfusion parameters of normal pancreatic parenchyma were no significantly different between low-dose groups(All P>0.05).Conclusion The low dose volume perfusion in ensuring the image quality,can effectively reduce the radiation dose.The measured perfusion parameters of normal pancreas parenchyma from low-dose perfusion scans are true and reliable.Objectives To evaluate the image quality of three-dimensional reconstruction of low-dose perfusion CT.Materials and methods According to the time density curve formed by perfusion,we select the best enhancement of abdominal aorta and portal to do the three-dimensional image reconstruction(VRT and MIP).The arterial phase of Perfusion and multi-phase enhanced was used to do VRT reconstruction.The portal phase of Perfusion and multi-phase enhanced was used to do MIP reconstruction.Two radiologists evaluated their image quality,including subjective and objective(background noise,signal-to-noise ratio).Using nonparametric test of paired samples to compare the three-dimensional reconstruction image quality of perfusion images with multi-phase enhanced images.Results The VRT and MIP of perfusion images,the degree of vascular smoothness and vascular branch display are better than conventional multi-phase enhancement,and the image noise is higher than the conventional enhancement,But no statistically significant.There was no significant difference in the overall image quality between the two.Conclusion The perfusion phases selected by the time-density curve can replace the conventional multi-phase enhancement to do three-dimensional reconstruction.The blood vessels can show well.Objectives To explore the possibility for tumor grading(G1,G2 and G3)before operation based on functional parameters of pancreatic volume perfusion CT.Materials and methods Perfusion-CT imaging was performed in 77 consecutive patients with pancreatic neuroendocrine tumors(pNETs)in our center(The Peking Union Medical Hospital)from December 2015 to February 2017.Among them,37 patients with pancreatic neuroendocrine tumors were carried out surgical resection and confirmed by pathology in our hospital.Pathological results showed tumor grading was available(19/G1,17/G2,1/G3).G1-G3 grading tumors can be divided into A,B two groups,group A for G1 stage tumors,group B for G2 + G3 grading tumors.All the patients adopted a standardized pancreatic perfusion scan protocol.One experienced radiologists measured and recorded the perfusion parameters,blood flow(BF),blood volume(BV)and permeability(PMB)in Siemens post-processing workstation.The measurement results showed by mean ± standard deviation.Spearman correlation analyzed the correlation.Perfusion parameters were compared using independent samples T test in A,B two groups.Receiver operating characteristic(ROC)analysis was drawn.Results Whether G1 or G2/3,BF value was significant different between tumors and normal pancreatic parenchyma(p =0.000,p =0.018).PMB had no statistical difference(p =0.569,p =0.174).Nevertheless,BV was significant different in G1 tumor grading(p =0.000),and no obvious difference in G2/3(p =0.763).Spearman correlation analysis results showed that the perfusion parameters BF and PMB had no correlation with tumor pathologic grading(r =-0.230,P =0.177;r =-0.134,P =0.437),and there was a low negative correlation between BV and G1-G3 grading(r =-0.444,p=0.007).The lower BV value was,the higher tumor grading was.Independent sample T test showed the perfusion parameters of BF and PMB had no significant difference in two groups(p =0.155,p =0.646),while BV had obvious difference between the two groups(p =0.023).The BV value of tumors was lower in group B than group A.The area under curve was 0.756.The optimal cutoff of BV to distinguish tumor grading was 23.0,at this point the sensitivity and specificity was 72.0%and 77.8%.Conclusion The perfusion parameter BV was obvious different in different tumors grading in patients with pancreatic neuroendocrine tumors.There was a negative correlation between tumor grading and BV value.To some extent,BV could predict tumor pathologic grading pre-operation.The lower BV value was,the higher tumor grading was.