Age and gender dependence of liver diffusion parameters and the evidence of intravoxel incoherent motion modelling of perfusion component is constrained by diffusion component.

Abstract

ObjectivesTo establish reference values for middle aged subjects and investigate age and gender dependence of liver diffusion MRI parameters. MethodsThe IVIM type of liver diffusion scan was based on a single-shot spin-echo type echo-planar sequence using a 1.5-T magnet with 16 b-values. DDVD (diffusion-derived vessel density) was the signal difference between b=0 and b=2 s/mm2 images after removing visible vessels. IVIM analysis was performed with full-fitting and segmented-fitting, and with threshold b-value of 60 or 200 s/mm2, and fitting started from b=2 s/mm2. 32 men (age range: 25-71 years) and 26 men (age: 22-69 years) had DDVD and IVIM analysis respectively, while 36 women (age: 20-71 years) had DDVD and IVIM analysis. ResultsDDVD had an age-related reduction noted for women. IVIM results of full fitting had good agreement with segmented fitting with threshold b of 60 s/mm2 results, but less so with results of threshold b of 200 s/mm2. As age increases, female subjects Dslow measure had significant reduction, and PF and Dfast measure had significant increase. For the age group of 40-55 years, DDVD, Dslow, PF, and Dfast were 12.27{+/-}3.90, 1.072{+/-}0.067 (10-3mm2/s), 0.141{+/-}0.025, 61.0{+/-}14.0 (10-3mm2/s), and 13.4{+/-}3.6, 1.069{+/-}0.074 mm2/s, 0.119{+/-}0.014, 57.1{+/-}13.2 mm2/s, for men and women, respectively. ConclusionDDVD measure suggest that aging may be associated with reduction in liver perfusion. Lower Dslow measurement can lead to artificial higher PF and Dfast measurement, providing the evidence of IVIM modeling of perfusion component is constrained by diffusion component.