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R. Brinkmann, E. Poerksen, H. Elsner, G. Schuele, D. Theisen–Kunde, J. Roider, R. Birngruber; On–line dosimetry for selective retina treatment (SRT) . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2032.
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Purpose:Selective retina therapy (SRT) is a new approach to treat diseases associated with a decreased function of the RPE. By applying a train of µs laser pulses, irradiated RPE cells are selectively disrupted by microbubbles forming around the strong absorbing melanosomes. The adjacent photoreceptors and the neural retina are spared. Due to the ophthalmological invisibility of the RPE damage, we developed and investigated an optoacoustic on–line dosimetry system (OAD), which detects the onset of microvaporisation. In vitro and first clinical results comparing OAD to standard FL and ICG angiography are presented. Methods:Using a frequency doubled Q–switched Nd:YLF laser (527 nm), a train of 30 pulses, each 1.7 µs in duration, at a repetition rate of 100 Hz was applied. Freshly enucleated porcine RPE–samples were irradiated, while optoacoustic transients were recorded with a hydrophone. Cell vitality was proved by calcein–am. Patients with diabetic maculopathy and branch vein occlusion were treated. OA data were received with a modified contact lens and were analyzed with mathematical algorithms on PC. Results:Optoacoustic bipolar transients were recorded. The transients significantly differ when exceeding the irradiation damage thresholds of porcine RPE. In patient treatment a high correlation was found between OA–transient changes and RPE leakage proved by angiography one hour post treatment. Conclusions:The optoacoustics method seems to have the potential to accurately detect induced RPE–damage on–line and non invasively. It may serve as a realtime dosimetry control and feedback–system, thus additional angiography post treatment to confirm the desired RPE–damage can be avoided.
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