| Background:All newborns are red bone marrow,which gradually converts to yellow bone marrow without hematopoietic function with age,and reaches a relatively stable state until they are about 25 years old,that is,most of the bone marrow in the body is yellow bone marrow.The largest component of yellow bone marrow was fat,which showed high signal on MRI T1WI.In most common blood diseases,the fat content in the normal bone marrow cavity is lost in different forms,and the bone marrow signal on T1WI is reduced.Objective:Based on the research background,this study aims to establish the normal reference value range of T1WI signal intensity ratio between 30-50 years old cross-sectional slope and fat adjacent to the same plane,and initially explore its diagnostic value in AL,so as to provide imaging basis for early detection and diagnosis of diseases.Methods:(1)Strictly according to the inclusion and exclusion criteria,671 healthy young adults aged 30-50 years who underwent head MRI examination in the First Affiliated Hospital of Gannan Medical University from December 2017 to December 2022 were retrospectively collected as the healthy group,including 433 males and 238 females.The average age was 42.1±5.9 years.At the same time,102 patients aged 30-50 years who received MRI examination at the same time and were diagnosed as AL by bone marrow examination were retrospectively collected as AL group,including 59 males and 43 females.The average age was 43.5±5.5 years,ranging from 30 to 50 years.(2)The T1WI images of the patient’s head MRI cross-section were collected,and the plane with the best slope display was selected for quantitative and qualitative imaging evaluation.Quantitative and qualitative assessments were performed independently by a junior physician and a physician with more than 10 years of experience in radiology without knowing the results of all laboratory tests.Quantitative assessment included measurement of T1WI signal intensity of the slope and adjacent fat.Two physicians placed ROI on the slope bone marrow and adjacent fat respectively,with the range of 0.3-0.5cm2.The bone marrow and fat of the slope at the same level were measured three times respectively,and the mean value was recorded.For qualitative assessment,the signals of fat and muscle at the same level were relatively fixed as reference,and the T1WI signals of bone marrow in the slope were set as equal(T1WI signals on the slope were similar to those of fat),low(T1WI signals on the slope were lower than those of fat but higher than those of muscle),and very low(T1WI signals on the slope were similar to or even lower than muscle signals).ICC was used to evaluate the difference between the two physicians in measuring the signal intensity ratio of T1WI and the evaluation of the bone marrow signal on the slope.In case of difference in quantitative or qualitative evaluation results,the two physicians shall make a joint decision after consultation.(3)SPSS 26.0 was used for statistical analysis.For the normality test of measurement data,continuous variables subject to normal distribution were represented by mean ± standard deviation(X±S),and inter-group comparison was evaluated by independent sample t test or one-way analysis of variance according to the number of groups.Continuous variables with non-normal distribution were represented by median and percentile,and comparison between groups was tested by non-parametric test.The classified data is expressed in frequency and rate and compared using chi-square tests or Fisher exact tests depending on the size of the data cell.P<0.05 was defined as statistically significant.Combined with ROC curve and area under curve,the diagnostic value of T1WI signal intensity ratio between slope and adjacent fat in AL was further analyzed.Results:(1)There was no significant difference in T1WI signal intensity ratio between different GE machine health groups and AL groups(P>0.05).(2)The T1WI signal intensity ratio of cranic slope and adjacent fat in AL group and healthy group did not follow normal distribution,and the reference ranges were determined by the 5th and 95th percentiles,ranging from 0.63 to 0.98.(3)The T1WI signal intensity ratio of bone marrow and adjacent fat in slope between AL group and healthy group was significantly different(P<0.05).(4)There was no statistical significance in T1WI signal intensity ratio between male and female in healthy group,male in different age groups and female in different age groups in slope bone marrow and adjacent fat(P>0.05).(5)There was a significant difference in T1WI signal reduction between ALL and ANLL cranial MRI slopes(P<0.05).(6)ROC curve was used to analyze the diagnostic value of AL in the signal intensity ratio between the cranial MRI cross-sectional slope and the adjacent fat T1WI.The results showed that the sensitivity was 0.961,the specificity was 0.791,the area under ROC curve was 0.947,and the optimal diagnostic cut-off value was 0.61.(7)ICC was used to evaluate the consistency of the T1WI signal intensity ratio measured by two physicians and the evaluation results of the bone marrow signal on the slope,and the results showed good consistency.Conclusion:(1)The difference in T1WI signal intensity of slope caused by different machines and different scanning parameters can be eliminated by calculating the T1WI signal intensity ratio between slope and adjacent fat.(2)In this study,the reference value range of T1WI signal intensity ratio between 30-50 years old cranial MRI sectional slope and adjacent fat was initially established,ranging from 0.63 to 0.98.(3)The T1WI signal intensity ratio of cranial slope and adjacent fat in AL patients aged 30-50 years was significantly lower than that in healthy people of the same age group.(4)The ratio of T1WI signal intensity between cranial slope and adjacent fat was independent of sex and age in healthy individuals aged 30-50 years.(5)T1WI signal reduction of AL cranial MRI slope was different in different types,and the signal of ALL T1WI was lower than that of ANLL T1WI.(6)The ratio of skull MRI slope and adjacent fat T1WI diagnostic AL sensitivity reached 0.96,specificity of 0.79,and the optimal cut-off value of 0.61. |
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