Fig. 6.

Potential role of molecular optical imaging to guide thrombolytic therapy in acute stroke patients. Currently there is no established clinical tool for characterizing the resistance of a thrombus to thrombolytic drugs. One of the key determinants of thrombolytic resistance is fibrin cross-linking resulting from the activity of FXIII. FXIII activity or the density of cross-linked fibrin mesh cannot be measured in vivo (A). One patient (who was later found to have had a highly cross-linked clot) had received a urokinase infusion in the setting of acute stroke. It took a long time to lyse the thrombus occluding (red circle in B) the left middle cerebral artery (MCA). This resistant thrombus was associated with not only delayed recanalization but also with high doses of thrombolytic drug delivered into MCA perforating arteries or collateral arteries (blue arrows in B and C). The patient exhibited post-thrombolysis hemorrhage in the basal ganglia and corona radiata (red arrow in D). In the near future, the thrombolytic resistance of a thrombus is likely to become measurable in vivo and in real time using a fluorescence-sensing fiber-optic catheter and molecular imaging probes to characterize the nature of the thrombus (E). This could be of great benefit in triaging patients to appropriate treatments (F and G).