Quantitative Evaluation Of Lumbar Vertebral Body Fat Content By Magnetic Resonance Fat Quantitative Technology(IDEAL-IQ And 3D MDixon Quant)

Objective:(1)To evaluate the MRI fat quantification efficiency for lumbar vertebra under different field strength using the iterative decomposition of water and fat with echo asymmetry and least-squares estimation-iron sequence(IDEAL-IQ);(2)To investigate the effects of different acceleration factors(AF)on lumbar vertebra fat quantification using 3D m Dixon Quant sequence accelerated by sensitivity coding(SENSE)and Compressed SENSE(CS-SENSE);(3)To investigate the relationship among lumbar body fat content,age,sex and body mass index(BMI).Materials and methods: We recruited healthy volunteers in our hospital from April to June 2018,with the following enrollment criteria:(1)No contraindications to MRI examinations,such as pacemakers,stents,metal implants,and claustrophobia;(2)No history of vertebral or pelvic malignant tumors,metastases,and radiotherapy and chemotherapy;(3)No history of metabolic diseases,those who did not use glucocorticoids and affected bone metabolism;(4)No history of lumbar fractures or other trauma.Exclusion criteria:(1)Poor image quality;(2)Lumbar vertebral body lesions.Finally,21 volunteers were enrolled,all of whom were women and aged 21 to 50 years,with an average age of 27.95±9.92 years.All volunteers underwent routine lumbar spine MRI scan and IDEAL-IQ examination at 1.5T MRI and 3.0T(Signa HDxt,GE Medical System,Inc.,Waukesha,WI,USA).The examination of the same patient is completed within 4-6 hours.The fat fraction(FF)(%)of L1 to L5 vertebral body was measured at the GE AW4.6 workstation and compared between the two field strengths.From January to February 2020,36 healthy volunteers were recruited according to the same inclusion and exclusion criteria,including 18 males and 18 females,from 16 to 79 years old,with an average age of 42.33 ± 19.64 years.Volunteers were divided into three groups according to age: young group(<40 years old),middle-aged group(40～60 years old),and elderly group(>60 years old).All volunteers were imaged at 3.0T(Ingenia CX 3;Philips Healthcare,Best,the Netherlands)with a fat quantification sequence(3D m Dixon Quant)for the entire lumbar spine,and the sequence was accelerated at different folds with either SENSE(acceleration factor S = 2,4)or CS-SENSE(acceleration factor CS =2,3,4,5,6).FF,signal-noise-ratio(SNR),and contrast-noise-ration(CNR)were measured for the L1-L5 vertebra by two radiologists independently with a double-blind method,measurement carried out on a Intelli Space Portal workstation(ISP version 7.0;Philips Healthcare,Best,the Netherlands).The measured parameters were compared among different AFs.All data were analyzed on SPSS 19.0.The normality of the data was analyzed using the Shapiro-Wilk test.The intra-class correlation coefficients(ICC)were used to check the consistency of the measurement between the two observers,and the consistency of FF values measured at 1.5T and 3.0T was analyzed using the Bland-Altman test.The paired sample t test and Pearson correlation analysis were also used to compare and analyze the FF values of lumbar vertebrae under different field strengths.The non-parametric Friedman test was used to analyze the differences in FF,SNR and CNR measured at different AFs.The independent sample t test was used to compare and analyze the lumbar vertebra FF values between different gender groups.Comparison of lumbar vertebra body fat content values between different age groups was performed via analysis of variance(ANOVA),and the least-significant difference(LSD)method was used to perform pair-wise comparisons.Spearman’s test was used to analyze the correlation between lumbar vertebra fat content and BMI.The difference was considered statistically significant when P<0.05.Results:(1)FF values measured with IDEAL-IQ at different field strengths had no significant statistical difference(P>0.05),and the lumbar vertebrae FF values measured under two field strengths were significantly correlated(r=0.978,P<0.01)and consistent(95% consistency limit;lower limit-1.3403,1.5689);(2)The two observers had good agreement on the measurement of lumbar vertebra FF for all the 3D m Dixon Quant sequence scans(ICC value> 0.75).FF,SNR and CNR at different AF were not statistically significant(P=0.769,0.110,0.349)as measured with 3D m Dixon Quant,while CS=6 reduced the imaging time by 60.66% compared to the S=2;(3)FF values were significantly different between the three age groups(F = 19.712,P<0.01).Among them,the FF value of the young group was significantly lower(P<0.01)than that of the middle-aged and the elderly groups,while the difference between the middle-aged and the elderly groups was not statistically significant(P=0.189).In the young group,the lumbar vertebra FF of the male was higher than that of the female(P<0.05),while in the middle-aged group and the elderly group,the FF of the male was slightly lower than that of the female,albeit not significantly(P>0.05);(4)The FF value of lumbar vertebrae in men was moderately positively correlated with BMI(r = 0.668,P=0.005),while in females such correlation was not observed(r = 0.214,P=0.395).Conclusion:(1)The magnetic resonance IDEAL-IQ technology can accurately quantify the lumbar vertebra body fat content,and the results have high consistency and reliability under 1.5T and 3.0T field strength.(2)The 3D m Dixon Quant sequence combined with SENSE and CS technology is reliable for assessing the lumbar vertebral body fat content.When the AF of CS was selected to 6,the image quality and the measurement accuracy were maintained while the imaging time dramatically reduced.(3)Age,gender,and BMI are all factors that may affect the lumbar vertebra fat content.These factors should be considered in the analysis and evaluation of lumbar vertebra fat content in different individuals.