Filtered collimator for dual isotope medical imaging

An X-ray collimator is provided to permit diagnostic medical imaging of two or more radioactive isotopes emitting spectrically close gamma rays. The collimator includes a filter plate at one or both ends of the collimator's tubular passageways with the filter plate having a plurality of openings extending therethrough which are aligned and coincident with the tubular passageways. The openings in the filter provide a thin filtering edge adjacent the collimator passageway ends which interact with and remove substantially most of the unwanted secondary and scattered radiation produced by photons striking septa within the collimator's passageways.