Mariam Alaverdashvili1, Phyllis G Paterson2, Michael P Bradley3. 1. Neuroscience Research Group, University of Saskatchewan, Saskatoon, SK, Canada S7N 5E5; College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, SK, Canada S7N 5E5. Electronic address: mariam.alaverdashvili@usask.ca. 2. Neuroscience Research Group, University of Saskatchewan, Saskatoon, SK, Canada S7N 5E5; College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, SK, Canada S7N 5E5. 3. Department of Physics, University of Saskatchewan, Saskatoon, SK, Canada S7N 5E2. Electronic address: michael.bradley@usask.ca.
Abstract
BACKGROUND: The rat photothrombotic stroke model can induce brain infarcts with reasonable biological variability. Nevertheless, we observed unexplained high inter-individual variability despite using a rigorous protocol. Of the three major determinants of infarct volume, photosensitive dye concentration and illumination period were strictly controlled, whereas undetected fluctuation in laser power output was suspected to account for the variability. NEW METHOD: The frequently utilized Diode Pumped Solid State (DPSS) lasers emitting 532 nm (green) light can exhibit fluctuations in output power due to temperature and input power alterations. The polarization properties of the Nd:YAG and Nd:YVO4 crystals commonly used in these lasers are another potential source of fluctuation, since one means of controlling output power uses a polarizer with a variable transmission axis. Thus, the properties of DPSS lasers and the relationship between power output and infarct size were explored. RESULTS: DPSS laser beam intensity showed considerable variation. Either a polarizer or a variable neutral density filter allowed adjustment of a polarized laser beam to the desired intensity. When the beam was unpolarized, the experimenter was restricted to using a variable neutral density filter. COMPARISON WITH EXISTING METHOD(S): Our refined approach includes continuous monitoring of DPSS laser intensity via beam sampling using a pellicle beamsplitter and photodiode sensor. This guarantees the desired beam intensity at the targeted brain area during stroke induction, with the intensity controlled either through a polarizer or variable neutral density filter. CONCLUSIONS: Continuous monitoring and control of laser beam intensity is critical for ensuring consistent infarct size.
BACKGROUND: The ratphotothrombotic stroke model can induce brain infarcts with reasonable biological variability. Nevertheless, we observed unexplained high inter-individual variability despite using a rigorous protocol. Of the three major determinants of infarct volume, photosensitive dye concentration and illumination period were strictly controlled, whereas undetected fluctuation in laser power output was suspected to account for the variability. NEW METHOD: The frequently utilized Diode Pumped Solid State (DPSS) lasers emitting 532 nm (green) light can exhibit fluctuations in output power due to temperature and input power alterations. The polarization properties of the Nd:YAG and Nd:YVO4 crystals commonly used in these lasers are another potential source of fluctuation, since one means of controlling output power uses a polarizer with a variable transmission axis. Thus, the properties of DPSS lasers and the relationship between power output and infarct size were explored. RESULTS: DPSS laser beam intensity showed considerable variation. Either a polarizer or a variable neutral density filter allowed adjustment of a polarized laser beam to the desired intensity. When the beam was unpolarized, the experimenter was restricted to using a variable neutral density filter. COMPARISON WITH EXISTING METHOD(S): Our refined approach includes continuous monitoring of DPSS laser intensity via beam sampling using a pellicle beamsplitter and photodiode sensor. This guarantees the desired beam intensity at the targeted brain area during stroke induction, with the intensity controlled either through a polarizer or variable neutral density filter. CONCLUSIONS: Continuous monitoring and control of laser beam intensity is critical for ensuring consistent infarct size.
Authors: John W Krakauer; S Thomas Carmichael; Dale Corbett; George F Wittenberg Journal: Neurorehabil Neural Repair Date: 2012-03-30 Impact factor: 3.919
Authors: Mariam Alaverdashvili; Sally Caine; Xue Li; Mark J Hackett; Michael P Bradley; Helen Nichol; Phyllis G Paterson Journal: Transl Stroke Res Date: 2018-02-03 Impact factor: 6.829
Authors: Nathalie Percie du Sert; Alessio Alfieri; Stuart M Allan; Hilary Vo Carswell; Graeme A Deuchar; Tracy D Farr; Paul Flecknell; Lindsay Gallagher; Claire L Gibson; Michael J Haley; Malcolm R Macleod; Barry W McColl; Christopher McCabe; Anna Morancho; Lawrence Df Moon; Michael J O'Neill; Isabel Pérez de Puig; Anna Planas; C Ian Ragan; Anna Rosell; Lisa A Roy; Kathryn O Ryder; Alba Simats; Emily S Sena; Brad A Sutherland; Mark D Tricklebank; Rebecca C Trueman; Lucy Whitfield; Raymond Wong; I Mhairi Macrae Journal: J Cereb Blood Flow Metab Date: 2017-08-11 Impact factor: 6.200
Authors: Sarah S J Rewell; Leonid Churilov; T Kate Sidon; Elena Aleksoska; Susan F Cox; Malcolm R Macleod; David W Howells Journal: PLoS One Date: 2017-02-09 Impact factor: 3.240