optimization fixes, and improvements
optimization fixes, and improvements

sdimoudi/bart,Takishima/bart,sidward/bart,mrirecon/bart,sidward/bart,Takishima/bart,mrirecon/bart,sidward/bart,Takishima/bart,mjacob75/bart,mrirecon/bart,sdimoudi/bart,Takishima/bart,mjacob75/bart,Takishima/bart,mrirecon/bart,sidward/bart,sdimoudi/bart,mjacob75/bart,sdimoudi/bart,mrirecon/bart,mjacob75/bart,sdimoudi/bart,mjacob75/bart,sidward/bart