Bone marrow is the fourth largest organ of the human body, which consists of two main types-red (cellular) and yellow (fatty)[1].Magnetic resonance imaging (MRI) has become preferred over other imaging modalities in evaluating marrow compositions . Although the routine MRI can evaluate the cellularity of marrow according to signal intensity, it is not quantitative analysis [2]. IVIM provides both diffusion and perfusion quantification using a single imaging study at the same time, without the need for intravenous contrast injection [3]. The purpose of this study is using the parameters of IVIM to assess the microstructure of marrow ,and then to investigate the gender-related cellular and capillary network in marrow of healthy young adults.This study was approved by the ethics committee of performing site. 60 healthy volunteers were recruited, comprising 30 males and 30 females (age range: 22 to 25years; average age:23 years). The inclusion criteria were: (a) no lesions in the spine (such as spinal deformity, spinal tuberculosis, et al). (b) no disease of hematology(such as leukemia, anemia, aplastic anemia, et al). MR imaging of the lumbar vertebral bone marrow was performed on a GE Signa 1.5-Tesla MRI scanner (GE Healthcare, Waukesha, Wisconsin) using a 8-channel phased-array body coil. The imaging protocol included routine fast spin echo sagittal T1-weighted (TR 400.0ms; TE 9.3ms; section thickness 5.0mm; spacing 0.0mm; NEX 4; FOV 36cm×36cm; matrix 320×192; acquisition time was 2min29s), conventional DWI ( b=0,500s/mm²; TR 4000.0ms; TE 66.5ms; section thickness 5.0mm; NEX 4; FOV 36cm×28.8cm; matrix 128×96; acquisition time was 2min 12s) and IVIM DWI (b= 0,10,25,50,100,200,400,600,800,1000, 1200s/mm², TR 2000ms, TE 91ms,other parameters are the same as the DWI sequence, the acquisition time was 8min 45s).The image data were analyzed on an Advantage Windows Workstation 4.4 (GE Healthcare). Regions of interest (ROIs) were selected centrally in the lumbar vertebral cancellous bone (L2–L4) [4], which was intended to minimize the effect of vertebral end-plate changes, vertebral venous plexus and cerebrospinal fluid. The results were presented as the mean ± standard deviation (𝑥̅±𝑠). An independent t-test was performed to detect significant difference in the ADC value and parameters of IVIM between males and females. Comparison of the parameters of IVIM in L2, L3 and L4 vertebraes were made using analysis of variance (ANOVA). Statistical analyses were performed using SPSS software (IBM Corporation, Armonk, New York). A P values less than 0.05 were considered to indicate a significant difference.The ADC value (0.60±0.04)×10^-3mm²/s in females was higher than that (0.58±0.07)×10^-3mm²/s in males, the difference was not statistically significant (t =-1.337, p =0.186). The D value of IVIM represented tissue water diffusivity, the D value was lower than ADC value in females and males. The D value (0.28±0.04) ×10^-3mm²/s in females was higher than that (0.20±0.04) ×10^-3mm²/s in males, the difference was statistically significant (t =-8.653, p=0.001). In the perfusion-related parameters, f was significantly higher in females (31.70±3.65 ) compared with males (28.94±5.52; t =-2.286, p=0.026). However, D* was significantly lower in females (46.72±12.90)×10^-3mm²/s than that (91.78±30.83)×10^-3mm²/s in males (t=7.387, p=0.001) (Table 1, Fig1).The logarithmic plot of signal-intensity decay and biexponential fitting curves showed the difference between that representative female (red line) and male (green line), which was shown in Fig2. ROI was in the fourth vertebral bone marrow. The signal intensity decays more quickly in males than in the females within b<200 s/mm².The signal attenuation in male was more slowly than that in females when b＞200s / mm². As a result, the biexponential fitting curves for the females and male are cross instead of parallel (Fig2).The D, f and D* value were not significant difference among second, third and fourth lumbar vertebras in females (t = 0.022,p=0.978; t=0.445,p=0.642; t = 0.942, p =0.397 respectively; Table2).The result suggested that the D value was more faithfully than ADC value in reflecting the variety of cellularity in bone marrow.The f (perfusion related IVIM parameters) value in bone marrow of younger females was significantly increased compared to males of the similar age in our study. The younger female menstrual cycle and sex hormones were important factors of more bone marrow perfusion, the blood loss from menstruation may activate the hematopoietic marrow and promoting red marrow. We assumed that f value could be a biological marker which can assess the characteristics of marrow perfusion.In conclusion, IVIM parameters can discriminate the microstructure of marrow in younger females from males compared with the ADC values. It may provide noninvasive methods for evaluating cellularity, vascular volume and blood velocity of bone marrow.