The optimization of fluorescence imaging of brain tumor tissue differentiated from brain edema--in vivo kinetic study of 5-aminolevulinic acid and talaporfin sodium.

OBJECTIVE We aimed to clarify the optimal timing for the fluorescence imaging of brain tumor tissue differentiated from brain edema after the administration of photosensitizers. METHODS We have performed an in vivo study of the kinetics of 5-aminolevulinic acid (5-ALA) in comparison with talaporfin sodium using the rat brain tumor model and rat vasogenic edema model produced by cold injury. The in vivo kinetics of 5-ALA and talaporfin sodium in brain tumor model and the vasogenic edema model was determined by a fluorescence macroscope and a microplate reader. RESULTS The in vivo kinetic study of 5-ALA showed mild fluorescence intensity of protoporphyrin IX (PpIX) in brain tumor differentiated from vasogenic edema. The mean lesion-to-normal-brain ratio (L/N ratio) in the group of brain tumor model 2h after the administration of 5-ALA was 7.78+/-4.61, which was significantly higher (P<0.01) than that of the vasogenic edema 2h after the administration of 5-ALA (2.75+/-1.12). In vivo kinetic study of talaporfin sodium showed high fluorescence intensity and retention in brain tumor differentiated from vasogenic edema. The mean L/N ratio of the fluorescence intensity in the group of brain tumor model 12h after the administration of talaporfin sodium was 23.1+/-11.9, which was significantly higher (P<0.01) than that of the vasogenic edema 12h after the administration (8.93+/-8.03). CONCLUSIONS The optimization of fluorescence imaging of brain tumors differentiated from brain edema is possible in the case of 5-ALA within 6h, and also possible in the case of talaporfin sodium beyond 12h.