A method of fabricating a collimator assembly includes attaching a first layer to a second layer and forming channels through the attached first layer and second layer. Openings are disposed in the first and second layers before attaching the first and second layers. The openings of the first and second layers are aligned before forming the channels. Forming channels includes removing material of the first layer, the second layer or both layers. The attachment of the first and second layers defines an overall thickness of the collimator assembly. A thickness of the first layer ranges from about 5% to about 10% of the overall thickness.