Hepatic Enhancement at Computed Tomography: is There a Dependence on Body Weight Past Institutional Contrast Dosing Limits?

Background Although described in product monographs, the maximum contrast media (CM) dose at computed tomography (CT) varies among institutions. Purpose To investigate whether an upper limit of 40 g of iodine in women and 50 g in men is sufficient or if there is a body weight (BW) dependence of mean hepatic enhancement (MHE) beyond those thresholds. Material and Methods At our institution, CM injection duration is fixed to 30 s and dosed 600 mg iodine/kg up to 40 g in women and 50 g in men. Pre- and post-contrast hepatic attenuation values (HU) were retrospectively obtained in 200 women and 200 men with glomerular filtration rate >45 mL/min undergoing 18-flurodeoxyglucose PET-CT (18F-FDG PET-CT) of which half weighed below and half above those dose thresholds using iodixanol 320 mg iodine/mL or iomeprol 400 mg iodine/mL. The correlation between BW and MHE was assessed by simple linear regression. Results Weight range was 41–120 kg in women and 47–137 kg in men. There was no significant relationship between MHE and BW in women receiving <40 g (r = −0.05, P = 0.63) or in men receiving <50 g (r = 0.18, P = 0.07). Above those thresholds there was an inverse relationship (r = −0.64, P<0.001 in women and r = −0.30, P<0.002 in men). There was no apparent upper limit where the dependence of hepatic MHE on BW decreased. Hepatosteatosis limited MHE. Conclusion Adjusting CM to BW diminishes the dependence of MHE on BW. There was no apparent upper limit for the relationship between BW and MHE in heavier patients at CM-enhanced CT.