Age-and gender-related variations of liver diffusion metrics apparent diffusion coefficient (ADC) and diffusion derived vessel density (DDVD), and explanations with the known physiological T2 relaxation time variations among different volunteers' groups.

Abstract

Background: Age-related liver diffusion metrics changes have been described. We aim to further clarify these questions: 1) whether an age-related reduction of liver perfusion can be observed by DDVD (diffusion derived vessel density) in older males; 2) whether there is a male female difference in liver perfusion; 3) whether liver ADC values and spleen ADC values are correlated. It is known that, physiologically, males' liver has a higher iron level (thus a shorter T2) than females' liver; pre-menopausal females have a lower liver iron level (thus a longer T2) than post-menopausal females. The observations of this study will be interpreted with the recently gained knowledge of the T2 contribution to diffusion metrics.

Methods: Included in this healthy volunteer's study were 68 males (mean age:50.22 years, range: 25-70 years) and 43 females (mean age 45.56 years, range:20-71 years). DWI images with b-values of 0, 2, 10, 20, 60, and 600 s/mm² were acquired at 1.5T. DDVD were calculated with b = 0, b = 2, b = 10, and b = 20 s/mm² images. ADC were calculated with b = 0, b = 2, b = 60 and b = 600 s/mm² images.

Results: There was a statistically significant age-related decline of liver DDVD values for females (p = 0.024). A similar trend was observed for males, though statistical significance was not achieved (p = 0.113). Liver DDVD values were all higher in females than in males (p < 0.001). There was a statistically significant age-related decline of liver ADC values both for males (ADC_(b0b600), p = 0.009) and for females (ADC_(b0b600), p = 0.016). Liver ADC values and spleen ADC values were positively correlated (ADC_(b0b600), r = 0.33 for males and 0.31 for females, p < 0.05). When the spleen ADC was used to normalize the liver ADC, then the age-related trend was largely removed, both for males and for females (p > 0.05).

Conclusion: Females have a larger liver perfusion volume than males. There is an age-related decrease of DDVD and ADC, both for males and females. Liver ADC values and spleen ADC values are positively correlated. These gender and age-related changes are unlikely mainly caused by the liver T2 relaxation time variations.

Clinical trial number: Not applicable.