Densitometers

Claim 1

A densitometer for diagnostic use to indicate density variations due to respiratory and cardiac cycle movements in a human subject, comprising: a. a trolley platform; b. a column upstanding from said platform; c. a support mounted on said column for axial adjustment therealong; d. a U-shaped member having a first U-arm, a U-base, and second U-arm, disposed with its medial axis substantially horizontal, and mounted at its U-base on said support for rotation about said medial axis; e. a screened radiation unit housing a gamma -ray isotope source, which unit is mounted on the free end of said first Uarm and is formed with a collimation channel outlet directed towards the free end of said second U-arm; f. a mechanism selectively operable between first and second conditions in which said source is respectively wholly screened in said unit from said outlet and exposed to said outlet to emit a gamma -ray beam therefrom; g. a detector unit mounted on the free end of said second U-arm, which unit includes a fluorescent scintillation detector device aligned with said collimation channel outlet for response to said beam, and a photomultiplier operably related with said detector device to generate electrical signals in response to scintillation events in said device; h. a discriminator and pulse forming circuit connected with said photomultiplier to form electrical output pulses in response to said signals representing absorption of gamma -rays of a predetermined energy level in said detector device; i. a ratemeter connected with said circuit to form a D.C. voltage representation of said pulses; j. a potential divider network connected with said ratemeter to balance said D.C. voltage; k. an operational amplifier connected with said ratemeter and said network to provide a difference signal output therebetween; l. at least two low pass filters having different, but overlapping bandwidths representing respective components of respiratory and vascular cycle movements, and switches to selectively connect said filters with said amplifier for response to said difference signal output; and m. indicator means connected with said filters to display or record the signal components passed thereby.