Measuring Lumbar Paraspinal Muscle Fat Content Using MRI Combined with CT
Objective To investigate the accuracy and feasibility of MRI combined with CT scanner and manually defined gray threshold method in measuring lumbar paraspinal muscle fat content.Methods According to the inclusion and exclusion criteria,30 patients with lumbar degeneration were enrolled in this study,including 15 males and 15 females,aged(57.18±10.52)years(29-74 years).Lumbar CT and MRI images were obtained,to investigate the paraspinal muscles(multifidus and erector spinae)in the horizontal position of the L5 endplate,define muscle boundaries using MRI combined with CT scanning(CT+MRI group)and MRI scanning alone(MRI group),respectively.T2-STIR images of the same level were selected as positive control.ImageJ software was used to measure the total muscle area and functional muscle area,and the differences between the methods were compared.Furthermore,the fat replacement area and fat infiltration rate of paraspinal muscle were measured,and the effects of automatic gray level threshold(automatic threshold group)and manual gray level threshold(manual threshold group)on the measurement of paraspinal muscle fat infiltration on T2-weighted images were compared.Results The total area and functional area of each paravertebral muscle in CT+MRI group were larger than those in MRI group,and the difference was statistically significant(P＜0.05).The total area and functional area of paraspinal muscles in the CT+MRI group were similar to those in the positive control group,and the measurement results in the MRI group were significantly smaller than those in the positive control group,and the difference was statistically significant(P＜0.05).In the assessment of paraspinal muscle fat infiltration,the functional area of each paraspinal muscle in the manual threshold group was larger,the fat replacement area was smaller,and the fat infiltration rate was lower,with the difference being statistically significant(P＜0.05).The results of the positive control group were more similar to those of the manual threshold group,while the results of the positive control group were significantly different from those of the automatic threshold group(P＜0.05).Conclusion The method of MRI combined with CT tracing muscle boundary and manually defining gray threshold can effectively improve the accuracy of the evaluation of paravertebral muscle fat infiltration.
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