Event localization and fall-off correction by distance-dependent weighting

A nuclear camera system comprising:

• a detector for receiving radiation from a subject in an exam region, the detector including:
• a scintillation crystal that converts radiation events into flashes of light;
• an array of sensors arranged to receive the light flashes from the scintillation crystal, a plurality of the sensors generating a respective sensor output value in response to each received light flash;
• and
• a look-up table for storing weighting values which are determined in accordance with respective distances from a position of each event to each of the sensors that detects the event, the look-up table being multi-dimensional and indexed as a function of at least one of time, temperature, count-rate, depth of interaction, and energy;
• a processor for determining at least one of an initial position and an energy of each of the detected radiation events in accordance with respective distances from a position of the detected event to the sensors, weighting the sensor output values with the weighting values from the look-up table to determine corrected positions and energies of the events, and generating an image representation from the corrected positions and the energies.

A method of generating an image representation from detected radiation events, the method comprising:

• converting radiation from a subject in an examination region into flashes of light;
• receiving the flashes of light with an array of sensors;
• generating respective sensor output values in response to each received light flash;
• determining for each flash of light (i) at least one of an initial position and an energy and (ii) distances from the determined initial position to each sensor which received the flash of light;
• generating weighting values as a function of the energy of the radiation;
• weighting each of the sensor output values in accordance with a corresponding weighting value;
• determining the corrected position and a corrected energy in conjunction with the weighted sensor output values;
• generating an image representation from the corrected positions.

A method of generating an image representation from detected radiation events, the method comprising:

• converting radiation from a subject in an examination region into flashes of light;
• receiving the flashes of light with an array of sensors;
• generating respective sensor output values in response to each received light flash;
• determining for each flash of light (i) at least one of an initial position and an energy and (ii) distances from the determined initial position to each sensor which received the flash of light;
• indexing a look-up table with the distances to retrieve a weighting value that is a function of at least one of time, temperature, count-rate, depth of interaction, and radiation energy;
• weighting each of the sensor output values in accordance with the retrieved weighting value;
• determining the corrected position and a corrected energy in conjunction with the weighted sensor output values;
• and
• generating an image representation from the corrected positions.

A method of determining a position and an energy of an event detected by a medical imaging device, the method comprising:

• determining weighting values wiE and wix from pre-correction curves as a function of a respective distance |xi−x0| and energy of an event where xi represents sensor location and x0 represents an initial position of an event;
• transforming each received radiation event into a light energy event;
• with an array of sensors, converting each light energy event into a plurality of output pulses Si;
• determining when a radiation event occurs from the sensor output pulses;
• determining the initial position x0 of the event as a function of the respective distances of the sensors from the position of the event;
• determining a corrected position x of the event as:
• x = ∑ i ⁢ ⁢ w i x ⁢ S i ⁢ x i ∑ i ⁢ ⁢ w i x ⁢ S i ;
• calculating the energy E of the event as:
• E = ∑ i ⁢ ⁢ w i E ⁢ S i .

A method of diagnostic imaging, the method comprising:

• generating a plurality of fall-off curves, each of the fall-off curves corresponding to a respective one of a plurality of energies;
• creating a plurality of energy ratio curves as a function of the fall-off curves, each of the energy ratio curves representing a relationship between a selected pairs of the energies;
• determining weighting values from the energy ratio curves for scaling the fall-off curve associated with each of a plurality of energies;
• storing the weighting values in a memory;
• converting radiation from a subject in an examination region into flashes of light;
• receiving the flashes of light with an array of sensors;
• generating respective sensor output values in response to each received light flash;
• determining for each flash of light (i) an initial position and an energy and (ii) distances from the determined initial position to each sensor which received the flash of light;
• correcting each initial position in accordance with the determined distances and the determined weighting values;
• and
• generating an image representation from the corrected positions.

An apparatus for generating diagnostic images comprising:

• a scintillation crystal that converts radiation into flashes of light;
• an array of sensors mounted adjacent the scintillation crystal such that a subset of the sensors closest to a flash of light each generate output pulses which are combined to provide an indication of position on the scintillation crystal and energy of the radiation event;
• with weighting values which are a function of the energy of the sensed radiation event, correcting the position on the scintillation crystal at which each radiation event is received;
• and
• reconstructing the corrected positions into an image representation.