Authors
Derwent, E. N. J., Risbey, C. W. G., Niu, A., Yousif, P., Fonseka, N., Curry, S., Seow, C., Ng, I., McCaughan, G. W., Crawford, M., Pulitano, C., Babekuhl, D.
Abstract
Liver transplantation remains the only curative treatment for end-stage liver failure, yet its impact is constrained by organ shortages and graft non-utilisation. Machine perfusion (MP) enables ex-vivo assessment of donated livers; however, existing viability criteria rely on intermittent sampling, reducing temporal resolution and accuracy. Indocyanine green (ICG), a clinically validated dye cleared exclusively by hepatocytes, provides a continuous index of hepatic function beyond initial injury. Accordingly, we present a non-invasive, clamp-on optical sensor that enables continuous, real-time quantification of ICG clearance during MP. The sensor consists of a clamp-on module with an 808 nm laser and phototransistor connected to a microcontroller-based unit and computer for real-time plotting. The raw phototransistor signal was linearised to a unitless absorbance signal proportional to perfusate ICG; bi-exponential fitting yielded plasma disappearance rate (PDRbi, %/min) and the 15-minute residual fraction (R15). Across 10 whole and 3 split human livers (45 boluses; 13 paired with spectrophotometry), the sensor closely matched spectrophotometric measurements (mean R2 = 0.994; range 0.983-0.999). The sensor resolved expected physiological trends: ICG clearance increased with temperature (PDRbi: 8.2%/min (subnormothermic MP) to 22.6%/min (normothermic MP) (n=4); 9.3%/min (32{degrees}C) to 11.9%/min (36{degrees}C) (n=1)). The sensor's continuous signal traces also revealed early mixing dynamics and medication-related effects that are missed by intermittent sampling. This optical sensor enables accurate, real-time monitoring of ICG clearance during ex-vivo perfusion. The ex-vivo setting is uniquely positioned to validate ICG clearance models and enhance clinical interpretation.
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bioRxiv
The authors list and abstract were imported from bioRxiv on 07 Nov 2025.
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