Variations in the disappearance rate of indocyanine grenn

Abstract

Time-associated changes in the disappearance rate of indocyanine green from the blood (K.ICG) as an index of liver function, were studied. Blood was drawn 5 times at 3-minute intervals from 32 patients. Early, intermediate, and late K.ICG values were 0.087 +/- 0.040, 0.082 +/- 0.038, and 0.076 +/- 0.033 min-1, respectively, showing serial decreases. When blood was drawn 8 times at 2-minute intervals from 22 other patients, the means of the K.ICG values at 11 time points showed a nearly linear relationship (r = -0.986). These findings indicated that K.ICG is approximated by a linear function of time, K(t) = -K'.t + K0. According to this function, K.ICG is considered to decrease by 1.96% every minute. The K.ICG value determined by the conventional method is, therefore, a mean disappearance rate of 15 minutes, and K0 is considered to reflect the initial reaction speed.

Liver functional assessment using time-associated change in the liver-to-spleen signal intensity ratio on enhanced magnetic resonance imaging: a retrospective study

“…Previous basic and clinical reports have suggested that dynamic quantitative liver function tests provide more accurate assessment of the specific aspects of liver function than passive assessments [ 23 – 25 ]. Some researchers have classified ICGR15 as a dynamic liver function test, but ICGR15 does not strictly reflect time-associated changes in the concentration of ICG, because evaluation is only made from two time points, before and 15 min after injection [ 18 , 23 – 25 ]. Yokoyama et al reported preoperative liver functional assessment using ICG-K as a more useful parameter for predicting PHLF than ICGR15 [ 25 ].…”

“…Preoperative assessment of liver function by ICGR15 similarly involves timing bias in blood sampling and should be evaluated accurately at 15 min after ICG injection. Conversely, ICG-K, which is calculated by multiple blood samplings after injection, reflects changes in ICG concentration over time and is known to provide functional assessment of the liver with minimal timing bias for blood sampling [ 18 ]. Kumasawa et al reported that ICG-K calculated using blood samples at 3-min intervals after injection correlated closely with results calculated from values at 2-min intervals [ 18 ].…”

“…Conversely, ICG-K, which is calculated by multiple blood samplings after injection, reflects changes in ICG concentration over time and is known to provide functional assessment of the liver with minimal timing bias for blood sampling [ 18 ]. Kumasawa et al reported that ICG-K calculated using blood samples at 3-min intervals after injection correlated closely with results calculated from values at 2-min intervals [ 18 ]. The present study revealed high correlations between LSRi calculated using four time points and LSRi calculated using three time points.…”

“…ICGR15 should therefore be performed under accurate injection with an appropriate amount of ICG and accurate blood sampling at 15 min after ICG injection. On the other hand, the ICG disappearance rate (ICG-K), which is calculated from the serum ICG concentration at multiple time points, reflects changes in ICG concentration over time without the dose bias of ICG or the timing bias of blood sampling [ 18 , 19 ]. We expected this quantitative evaluation, which analyzed information on infused compounds at multiple time points, would exclude limitations such as the timing bias from imaging and protocol bias from MRI acquisition settings, and would facilitate the development of widely available radiological assessments of liver function.…”