Application Of Energy Spectrum CT MMD Algorithm In Liver Fat Fraction Quantification

Objective(1)To evaluate the accuracy of the Multimaterial Decomposition(MMD)algorithm for determining the fat content of liver at different levels.(2)To evaluate the Multimaterial Decomposition(MMD)algorithm for determining the fat content of liver at different levels.(3)Using the proton density fat fraction(PDFF)measured by MRI IDEAL-IQ gradient echo as the reference standard,to evaluate and compare the accuracy of the MMD-fat algorithm of energy spectrum CT in the measurement of fat fraction in patients with fatty liver.And to assess the consistency of fat content measurements between MRI IDEAL-IQ and Energy spectrum CT MMD-fat.Methods(1)Part 1:the pig liver and fat(lard)were mixed to simulate fatty liver,0%5%10%15%20%25%30%and 100%fat fraction were placed in test tubes and placed in the phantom.Energy spectrum CT was used for scanning,and CT plain scan images were obtained Fat(blood)images and LFQ images of MMD were measured by IDEAL-IQ scan using MR,and the mean value and standard deviation of each internal value of ROI were calculated to compare the quantitative accuracy of the algorithm.(2)Part 2:Pig liver phantom of iron overload fatty liver including pig liver lard,distilled water and iron.A total of 9 test tubes were prepared,which were mixed with three kinds of fat concentration(10%,20%,30%)and three kinds of iron concentration(25.25-25.97mg/100g,50.38-51.55mg/100g,75.57-77.72 mg/100g)respectively.The GE Revolution CT scanner was used to scan solid cylindrical modules with 9 holes and perform GSI Energy spectrum scanning to obtain 120k VP-like images(Hounsfield as unit)and MMD-fat images(measurement results recorded as FF_CT).Parallel GE Discovery CT750 HD repetitive GSI spectroscopy.Then 3.0T MRI(GE Discovery W750)IDEAL-IQ scan sequence was performed to obtain fat fraction images(the measured results were denoted as FF_MR).Spearman was used to analyze the correlation between CT(MMD-fat and 120k VP-like)and MR measured values and reference values FFref,as well as the scanning measurement consistency of CT phantoms with different energy spectra,to compare whether the difference was statistically significant(P<0.05 was considered statistically significant).Univariate ANOVA and single sample T test were used to analyze the coincidence of MMD-fat and MR IDEAL-IQ measurements with the actual fat fraction of dual-energy CT.A multiple linear regression phantom was established to explore the difference of measured values of different iron concentrations under the same fat concentration.Test level?=0.05.(3)Part 3:A total of 21 patients who volunteered to participate in fatty liver examination from 2021 to 2022 were collected and received GSI Energy spectrum CT upper abdomen examination and MRI IDEAL-IQ examination successively.Three ROIs(areas of the right anterior lobe,right posterior lobe and left lobe)were placed in liver parenchyma at portal vein level on MMD-fat images and fat fraction images of IDEAL-IQ.63 ROIs were measured at corresponding locations,and fat fraction FF_CTand FF_MRwere recorded.In addition,CT value of liver parenchyma was measured on120kv P-like image of Energy spectrum CT,and the fourth ROI was selected from spleen parenchyma at the same level to calculate the ratio of CT value of liver and spleen as a comparative method for CT examination of fatty liver.In addition,14patients with fatty liver were selected,and all of them underwent upper abdomen enhanced GSI scan.ROI was calculated on the corresponding positions of liver on the plain scan of MMD-fat image and enhanced scan of phase 3 of Energy spectrum CT,and 3 ROI(right anterior lobe,right posterior lobe and left lobe region)were placed to measure FF_CT.The measured values FF_CTand FF_MRwere plotted into histogram,and their mean value and standard deviation were calculated respectively.Scatter plots and bland-Altman plots were drawn to test the relationship between measured FF_CTand FF_MR.The ROC curve was established,and FF_MRwas taken as the reference standard to determine the diagnostic accuracy of FF_CT,and the area under the ROC curve was calculated.Sensitivity,specificity and Youden index were calculated.The correlation between liver and spleen CT values and FF_MRwas analyzed.P<0.05 was considered statistically significant.Paired sample T test was used to analyze the MMD-fat measurements of plain and three-phase scanning,and P<0.05 was considered statistically significant.Results(1)Part 1:There was a negative correlation between CT value and reference value of fatty liver volume fraction,and a significant positive correlation between CT value and reference value of fat(blood).There was no statistical difference between MMD-fat and IDEAL-IQ PDFF measurement results and reference value.(2)Part 2:FF_CTof Energy spectrum CT measurement and FF_MRof MRI IDEAL-IQ measurement are positively correlated with the reference value FFref,while the CT value of single-energy CT image is negatively correlated with it.There was statistical difference between the two scanning methods(F=310.017,P<0.01),and the mean measured value of MR IDEAL-IQ was 5.700 higher than that of CT MMD-fat(P<0.01).CT measurements were consistent with FFref(t=1.313,P=0.191).The latter has poor consistency with FFref(t=22.833,P<0.01),and there is good consistency between Energy spectrum Discovery 750 CT MMD-fat and Revolution CT MMD-fat,with correlation coefficient R~2=0.994.There was no statistical significance between the two(t=-1.454,P=0.184).(3)Part 3:There was a positive correlation between FF_CTand FF_MR(R~2=0.971;P<0.001),the two methods have good consistency.When average liver fat was less than10%,FF_CTof quantitative fatty liver was lower than FF_MR,MMD was lower than IDEAL-IQ for normal and mild fatty liver,and sensitivity was lower than IDEAL-IQ.The measured values of IDEAL-IQ and MMD-fat were correlated with the ratio of liver CT value to spleen CT value,with high correlation coefficients(0.958 and 0.943,respectively).Paired sample T test analysis of 14 patients with fatty liver showed no statistically significant difference between FF_CTmeasurements of upper abdominal CT plain scan and 3 phase CT scan(t=-1.597,P=0.118;t=-1.847,P=0.074;t=-0.642,P=0.524).Conclusion(1)In the phantom of fatty liver,MMD-fat measurement can accurately quantify the liver fat content in percentage directly,and it is less affected by iron concentration.The measurement results of different Energy spectrum phantoms are consistent.(2)In the clinical application of patients with fatty liver,Energy spectrum CT MMD-fat can accurately measure liver fat fraction,and has a good correlation and accuracy with MRI IDEAL-IQ proton density fat fraction,and is not affected by enhanced scanning contrast agent,which can provide a new method for clinical examination.