双筛孔式准直器
dual sieve-mesh collimator
筛孔配置
arrangement of sieve holes
筛孔
Sieve
mesh
aperture
SIEVES
sieve pore
aperture of screen
screen aperture
screen opening
sieve mesh
cribriform foramina
ethmoid foramen
ethmoidal foramen
screen mesh
Foramina ethmoidea
MESA
mercury penetration method
sieve opening