T-1 relaxation times for viability evaluation of the engrafted and the native liver in a rat model of heterotopic auxiliary liver transplantation: a pilot study

Following a heterotopic auxiliary liver transplantation, commonly used meas urements are either invasive or non-indicative of individual viability of t he coexisting engrafted and native livers. Magnetic resonance imaging (MRI) was therefore tested for its potential to monitor the post-transplant hepa tic viability in a rat model. Thirteen Wistar rats were systematically eval uated with MRI and serum biochemical liver parameters. Post-transplant comp lications and the causes of animal death were identified by autopsy and his to-pathological examinations. The data of the healthy survivors were compar ed with those of the rats that developed complications. On MRI, the hepatic complications could be depicted in the individual livers. A specific patte rn of signal evolution was found in the livers of the healthy survivors: th e mean T-1 relaxation times of the engrafted livers increased immediately a fter transplantation (476 +/- 64 ms, mean +/- standard deviation, pre-opera tive; 730 +/- 48 ms, week 1) and then declined steadily to a 3 month value of 489 +/- 246 ms, while, following a transient first rise (476 +/- 64 ms, pre-operative; 589 +/- 28 ms, week 1), the mean T-1 value of the native liv ers increased again 4 weeks after surgery and reached a 3 month value of 85 9 +/- 43 rns. However, in the rats with various complications, the mean T-1 relaxation times of the engrafted livers continued to increase throughout the first post-operative month (760 +/- 48 ms, week 1; 922 +/- 76 ms, week 4), while that of the native liver only varied mildly (546 +/- 25 ms, week 1; 473 +/- 25 ms, week 4). After the first post-transplant week, the health y engrafted livers could already be distinguished from those with complicat ions by a significant decrease in T-1 relaxation times. These data suggest that, besides demonstrating major complications, MRI may allow one to monit or the viability of each liver by analysing the relative signal intensity a nd T-1 relaxation times after a heterotopic auxiliary liver transplantation . Copyright (C) 2001 John Wiley & Sons, Ltd.