Effect of body mass index (BMI) on image contrast in the hepatobiliary phase of Gd-EOB-DTPA-enhanced-MRI and the feasibility of the application of half-dose Gd-EOB-DTPA to hepatobiliary phase imaging in patients with a BMI less than 24: a comparative study.

BACKGROUND: Gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) can detect more lesions through the image contrast of hepatobiliary phase. Body mass index (BMI) reflects the composition ratio of human tissue, which is an influencing factor of magnetic resonance image contrast. Meanwhile, Gd-EOB-DTPA is recommended to use the minimum dose when the diagnosis demands could be met. The aim of this paper was to investigate the effect of BMI on hepatobiliary phase image contrast and explore the feasibility of using low-dose Gd-EOB-DTPA to obtain good hepatobiliary phase image contrast in patients with normal and lean BMI.

METHODS: Eighty-two patients who had previously undergone Gd-EOB-DTPA-enhanced MRI (0.025 mmol/kg) were collected and divided into group A (BMI <24 kg/m2 ) and group B (BMI ≥24 kg/m2 ) according to Chinese BMI standards. Liver-to-portal vein contrast ratio (LPC20) and liver-to-spleen contrast ratio (LSC20) in hepatobiliary phase (20 min after injection) were calculated. Thirty patients with a BMI <24 kg/m2 who were about to receive Gd-EOB-DTPA-enhanced MRI were randomly divided into group C (0.0125 mmol/kg) and group D (0.025 mmol/kg). Image acquisition was performed at 10, 15, and 20 min after injection. LPC10, LPC15, LPC20 and LSC10, LSC15, LSC20 in corresponding phases were calculated.

RESULTS: In retrospective grouping study, compared with group B, group A's LPC20 was significantly higher [2.63 (2.42-3.00) vs. 2.22 (1.97-2.67); P<0.01]. In prospective grouping study, there were no differences in LPC15, LSC15, LPC20 and LSC20 between group C and group D. Intragroup comparison in each group showed that LPC15 (group C: 2.67±0.33; group D: 2.61±0.21) and LPC20 (group C: 2.74±0.37; group D: 2.72±0.27) were higher than LPC10 (group C: 2.19±0.18; group D: 1.94±0.17) (all P<0.01), while there were no changes between LPC15 and LPC20.

CONCLUSIONS: Under conventional dose, hepatobiliary phase image contrast in patients with a BMI <24 was higher, which was mainly manifested in the high LPC. For patients with a BMI <24 kg/m2 , using a half conventional dose (0.0125 mmol/kg), good hepatobiliary phase image contrast can still be obtained at 15-20 min after administration.