Computed tomography detection method and apparatus

Claim 3

The method of Claim 1 wherein said detectors comprise a stationary ring of solid state photodiodes (212) and where said cooling step is performed by blowing cool air in the region of said photodiodes (212).

Claim 4

Apparatus comprising: a source of x-radiation (40) mounted to rotate about a subject position to irradiate a subject with radiation from a plurality of positions; a stationary ring of detectors (98) fixed about said subject to detect x-radiation intensity once it passes through the subject, each of said detectors including a crystal (210) for converting x-radiation to visible light and a photo diode (212) for converting visible light from said crystal into a current proportional to x-radiation intensity impinging on said crystal (212); and means (96, 94, 17, 16) for analyzing the output from said ring of detectors as said source (40) rotates about said subject position to image a cross-section of said patient by backprojecting modified intensity readings to multiple pixel locations corresponding to said cross-section; characterised in that there is provided means (156, 112) for routing cool air across the detectors (98) comprised in said ring of detectors to reduce the temperature of said photodiodes (212) below the temperature ambient to the apparatus and thereby enhance the signal to noise of the photodiode current output from said detectors (98).

Claim 5

Apparatus comprising: a source of x-radiation (40) mounted to rotate about a subject position to irradiate a subject with radiation from a plurality of positions; a stationary ring of detectors (98) fixed about said subject to detect x-radiation intensity once it passes through the subject, each of said detectors including a crystal (210) for converting x-radiation to visible light and a photo diode (212) for converting visible light from said crystal into a current proportional to x-radiation intensity impinging on said crystal (212); and means (96, 94, 17, 16) for analyzing the output from said ring of detectors as said source (40) rotates about said subject position to image a cross-section of said patient by backprojecting modified intensity readings to multiple pixel locations corresponding to said cross-section; characterised in that there is provided means (156, 112) for routing cool air across the detectors (98) comprised in said ring of detectors to reduce the temperature of said photodiodes (212) below the temperature ambient to the apparatus and thereby enhance the signal to noise of the photodiode current output from said detectors (98).

Claim 6

Apparatus according to Claim 3 wherein said means for routing includes means (128) for maintaining said detectors at a temperature above the dewpoint of ambient air.

Claim 7

Apparatus according to Claim 3 or Claim 4 wherein said means for routing (156,112) cools both the detector ring and also cools at least a portion (94,96) of the means for analyzing.

Claim 8

Apparatus for cooling an array of x-radiation stationary detectors (98) when used in a computed tomography scanner (10), the apparatus being characterised in that it comprises: means (114) for compressing a refrigerant in a gas state to an elevated pressure; means (116) for allowing said gas to expand and cool as it condenses to a liquid state; means (118,120) for directing air into thermal contact with said refrigerant to cool said air and warm said refrigerant back to the gaseous state; means (156,112,168,170) for routing said cool air past said array of detectors to lower the temperature of said detectors below ambient, and means (146,149) for returning said refrigerant back to said means for compressing (114) to be recycled.

Claim 9

Apparatus for cooling an array of x-radiation stationary detectors (98) when used in a computed tomography scanner (10), the apparatus being characterised in that it comprises: means (114) for compressing a refrigerant in a gas state to an elevated pressure; means (116) for allowing said gas to expand and cool as it condenses to a liquid state; means (118,120) for directing air into thermal contact with said refrigerant to cool said air and warm said refrigerant back to the gaseous state; means (156,112,168,170) for routing said cool air past said array of detectors to lower the temperature of said detectors below ambient, and means (146,149) for returning said refrigerant back to said means for compressing (114) to be recycled.

Claim 10

Apparatus according to Claim 6 wherein said means for routing cool air past said detector array comprises a plurality of abutting detector mounting modules (50) which combine to form passageways (112,168,170) for said air.

Claim 11

Apparatus according to Claim 7 wherein said modules (50) each supports electronics (94,96) for converting analog outputs from said detectors (98) into digital signals and wherein said passageways (112,168,170) direct cool air to both said detectors (98) and to said electronics (94,96).