Simultaneous transmission and emission converging tomography

A gamma camera system in which a subject in an examination region is injected with a radionuclide of at least a first energy level, the gamma camera system comprising:

• three gamma camera heads disposed for movement around and facing the examination region;
• each gamma camera head receiving radiation from the examination region and producing output signals indicative thereof;
• a transmission radiation source disposed opposite one of the heads across the examination region, the radiation source generating radiation of a second energy level;
• each gamma camera head providing first and second energy level output signals;
• and
• a second energy level correcting means for correcting the second energy level signal from the head opposite the radiation source in accordance with other photopeak emission photons received by the other two camera heads, the second energy level output signal from each of the camera heads being connected with the second energy correction means.

A gamma camera head system comprising:

• a plurality of gamma camera heads facing an examination region for receiving emission radiation emitted from a subject in the examination region;
• a radiation source disposed across the examination region opposite one but not all of the heads such that the one head further receives transmitted radiation from the source which has traversed the examination region and at least one other head is positioned not across the examination region from a radiation source;
• a circumferential moving means for moving the heads and the source circumferentially around the examination region;
• a radial moving means for moving the heads toward and away from the examination region during the circumferential rotation;
• a reconstruction means for processing concurrently received transmission radiation data from the one head and emission radiation data from the heads into an attenuation corrected image representation of emission radiation distribution in the examination region.

A method of reconstructing emission projection signals from a three head gamma camera system to produce a pixelized image of a distribution of emission sources in an attenuating medium, the method comprising:

• rotating the heads around the medium;
• as the heads are rotated, simultaneously (i) transmitting radiation through the medium to one of the heads and (ii) receiving emission radiation from the emission sources distributed in the medium with the three heads and simultaneously collecting transmission and emission projection data;
• determining cross-talk corrections from the simultaneously collected transmission and emission projection data to correct for transmission radiation contributions to the emission projection data and emission radiation contributions to the transmission projection data;
• correcting the transmission and emission projection data with the cross-talk corrections;
• generating attenuation coefficients from the transmission data for the pixelized space;
• from the emission projection data set and the attenuation coefficient set, reconstructing an image space representation of the distribution of emission sources in the medium.

A method of simultaneously measuring transmission and emission projection data, the method comprising:

• transmitting transmission radiation photons of a first energy from a radiation source on one side of an attenuating medium to a first gamma camera head disposed across the medium from the transmission radiation source;
• concurrently detecting the transmission radiation photons and emission radiation photons of a second energy from emission radiation sources distributed within the attenuating medium with the first camera head and concurrently detecting the emission radiation photons and scattered transmission radiation photons with at least one additional camera head;
• separating first and second energy photons received by the detector heads to generate first energy transmission projection data and second energy emission projection data;
• correcting the transmission projection data from the first detector head in accordance with the transmission projection data from the at least one additional camera head to correct for scatter;
• correcting the emission projection data in accordance with the corrected transmission projection data generated by the first head.

A method of simultaneously measuring transmission and emission photons from a subject, the method comprising:

• directing transmission radiation photons through the subject from a transmission radiation photon source;
• concurrently detecting transmission photons which have passed through the subject and emission photons emanating from emission sources distributed within the subject with a first camera head;
• concurrently detecting emission photons and scattered transmission photons with additional camera heads;
• correcting output data from (1) the first head with output data from the other heads and (2) the output data from the other heads with the output data from the first head.

A method of determining an emission source distribution within a subject, the method comprising:

• transmitting radiation photons through the subject;
• detecting only transmission radiation photons which have passed through a central portion of the subject such that transmission radiation photons passing through edge portions of the subject are not detected;
• determining radiation attenuation properties of the subject from the detected transmission radiation photons;
• concurrently with the detecting of transmission radiation photons, detecting emission radiation photons emitted by emission sources distributed within the central and edge portions of the subject;
• correcting (i) the determined radiation attenuation properties for contributions of the emission radiation photons and (ii) the detected emission radiation photons for contributions of the transmission radiation photons;
• from the corrected emission radiation photons, reconstructing a representation of the emission source distribution in the subject.

A gamma camera system for examining a subject in an examination region who has been injected with a radiopharmaceutical having a first characteristic energy level, the gamma camera system comprising:

• a transmission radiation source for generating radiation having a second characteristic energy level, the radiation source being disposed adjacent the examination region;
• a first gamma camera head disposed across the examination region from the radiation source such that the first gamma camera head receives radiation from the examination region of the first and second characteristic energy levels, the first gamma camera head generating first energy level and second energy level signals corresponding to a location on a face of the first gamma camera head at which radiation of the first and second energy levels, respectively, is received;
• at least a second gamma camera head mounted adjacent the examination region, the second gamma camera head being mounted with a face thereof facing toward the examination region and away from the transmission radiation source such that the second camera head receives radiation of the first characteristic energy level directly from the examination region and receives radiation of the second characteristic energy level from the examination region attributable to secondary photopeaks of the emission source and only scattered radiation from the transmission source and produces first energy level and second energy level signals indicative of a location on the second gamma camera head face at which radiation of the first and second energy levels, respectively, is received;
• a means for rotating the first and second gamma camera heads and the transmission radiation source concurrently around the examination region;
• a transmission radiation correction means for correcting the second energy level output signal of the first gamma camera head in accordance with the second energy level output signal of the second gamma camera head in order to correct for scatter and secondary photopeaks in the second characteristic energy range;
• an emission radiation correcting means for correcting the first energy level signal from the first and second gamma camera heads in accordance with the corrected second energy level output signal;
• and
• a reconstruction means for concurrently processing corrected first and second energy level signals from the first and second gamma camera heads into at least an attenuation corrected image representation of emission radiation distribution in the examination region.